ISBN Flashcards
An investigator wishes to perform a randomized clinical trial to evaluate a new B-blocker as a treatment for hypertension. To be eligible for the study, subjects must have a resting diastolic blood pressure of at least 90 mm Hg. One hundred patients seen at the screening clinic with this level of HPN are recruited for the study and make appointments with the study nurse. When the nurse obtains their BP 2wks later, only 65 of them have diastolic blood pressures of 90 mm Hg or more. The most likely explanation for this is
a. Spontaneous resolution
b. Regression toward the mean
c. Baseline drift
d. Measurement error
e. Hawthorne effect
b. Regression toward the mean
Although hypertension can resolve spontaneously, this is an unlikely explanation for resolution over a 2-wk period in 35% of the subjects. A much more likely explanation is regression toward the mean. Because of random fluctuations, any one measurement of blood pressure may be far from a persons normal BP. By referring patients for the study based on a single measurement, those in whom the measurement was high (which proved later not to reflect the actual BP) are much more likely to be referred than those in whom the measurement was too low. Thus, in any group selected based on a characteristic with substantial day-to-day variation, many will have values closer to the population mean when the measurement is repeated and the worst patients will improve.
Neither baseline drift (which occurs with measurements on certain machines that require frequent calibration) nor measurement error is as likely an explanation.
The Hawthorne effect refers to a tendency among study subjects to change simply because they are being studied. It is much more likely to affect studies of behavior or attitudes than a study of blood pressure.
Which of the following measures is used frequently as a denominator to calculate the incidence rate of a disease?
a. Number of cases observed
b. Number of new cases observed
c. Number of asymptomatic cases
d. Person-years of observation
e. Persons lost to follow-up
d. Person-years of observation
Person-years of observation are frequently used in the denominator of incidence rates and provide a method of dealing with variable follow-up periods. Person-years of observation simultaneously take into account the number of persons under observation and the duration of observation of each person. For example, if eight new cases of diabetes occurred among 1000 people followed for two years, the incidence would be 8 cases per 2000 person-years, or 4 per 1000 person-years of follow-up. The distinction between rates and proportions is not well maintained in standard epidemiologic terminology. Rates should have units of inverse time and will vary depending on the units of measurement of time; they can vary from 0 to infinity. However, such terms as case fatality rate, attack rate, and prevalence rate are in wide- spread usage even though technically they are all proportions; that is, they vary between 0 and 1 and are unitless.
Among women aged 18 to 34 in a community, weight is normally distributed with a mean of 52 kg and a standard deviation of 7.5 kg. What percentage of women will have a weight over 59.5 kg?
a. 2% b. 5%
c. 10% d. 16% e. 32%
d. 16%
For any normal distribution, 68% of the population values are contained within the interval of the mean +/-1 standard deviation (16% will be higher and 16% will be lower), 95% within the mean +/-2 standard deviations (2.5% will be higher and 2.5% will be lower), and 99% within the mean +/-3 standard deviations (0.5% will be higher and 0.5% will be lower). In this case, 59.5 kg is equal to the mean +/-1 standard deviation, which means 16% of women will be heavier.
A randomized clinical trial is undertaken to examine the effect of a new combination of antiretroviral drugs on HIV viral load compared to usual therapy. Randomization is used for allocation of subjects to either treatment or control (usual care) groups in experimental studies. Randomization ensures that
a. Assignment occurs by chance
b. Treatment and control (usual care) groups are alike in all respects
except treatment
c. Bias in observations is eliminated
d. Placebo effects are eliminated
e. An equal number of persons will be followed in the treatment and control group
a. Assignment occurs by chance
Randomization is the use of a predetermined plan of allocation or assignment of subjects to treatment groups such that assignment occurs solely by chance. It is used to eliminate bias on the part of the investigator and the subject in the choice of treatment group. The goal of randomization is to allow chance to distribute unknown sources of biologic variability equally to the treatment and control groups. However, because chance does determine assignment, significant differences between the groups may arise, especially if the number of subjects is small. Therefore, whenever randomization is used, the comparability of the treatment groups should be assessed to determine whether or not balance was achieved
A research team wishes to investigate a possible association between smokeless tobacco and oral lesions among professional baseball players. At spring training camp, they ask each baseball player about current and past use of smokeless tobacco, cigarettes, and alcohol, and a dentist notes the type and extent of the lesions in the mouth. What type of study is this?
a. Case-control
b. Cross-sectional
c. Prospective cohort
d. Clinical trial
e. Retrospective cohort
b. Cross-sectional
Because the association between the risk factor (use of smokeless tobacco) and the disease (oral lesions) is measured at a single point in time in a whole group of subjects, this is a cross-sectional study. A case-control study might be performed over a similar time period, but the sampling would be different: one sample would be selected from among those baseball players found to have oral lesions (the cases) and a separate sample would be selected from among those players whose mouths were normal (the controls). In a cohort study, the habits of a group of players initially free of the disease would be measured, and these players would be followed over time to see how many develop the lesions. A clinical trial involves allocation of the subjects by the investigator (usually randomly) to one of two or more treatment groups.
A 6-y/o child is brought to the emergency room by her parents on a Friday night because they are concerned about rabies. A bat was present in the child s bedroom when they arrived at their country home that evening. It started flying around the head of the girl when she entered her room and it ruffled her hair. The parents heard her scream, ran up to her room, and shooed the bat out the window. Upon examination, there is no visible bite or scratch marks. Which is the most appropriate intervention at this time?
a. Reassure the parents that there is no risk of rabies given the history and examination
b. Consult public health authorities to determine the epidemiology of rabies in that area
c. Administer rabies vaccine and rabies immunoglobulin (RIG)
d. Administer rabies immunoglobulin (RIG) only
e. Administer rabies vaccine only
c. Administer rabies vaccine and rabies immunoglobulin (RIG)
Postexposure prophylaxis is recommended for any physical contact with bats. Bites or scratches may be too small to be visible to the naked eye. Both human rabies immunoglobulin (RIG) and vaccine should be administered to persons who have not been previously vaccinated. RIG is never recommended as only prophylaxis. It provides rapid passive protection with a half-life of 21 days. Active immunization induces response after 7 to 10 days and persists for at least 2 years. Only the vaccine is necessary if the person has a history of previous vaccination with documented antibody response. Consulting public health authorities before an intervention may be appropriate if the contact did not involve animals known to be a reservoir for rabies. Animals known to be reservoirs are the bat, skunk, raccoon, fox, coyote, and other wild carnivores, and prophylaxis is indicated regardless of the region.
Which of the following conditions has been associated with a false-positive Fluorescent Treponemal Antibody Absorption ( FTA- ABS) test?
a. Tuberculosis
b. Mononucleosis
c. Lyme disease
d. Viral pneumonia
e. HIV infection
c. Lyme disease
Lyme disease (caused by Borrelia burgdorferi, a spirochete) has been associated with false-positive treponemal FTA-ABS (Fluorescent Treponemal Antibody Absorption) tests which are designed for the diagnosis of Treponema pallidum infections (i.e., syphilis).
The nontreponemal test is often negative in this disease. Other conditions associated with false-positive treponemal tests include yaws, pinta, leptospirosis, and lupus.
Biological false-positive nontreponemal tests VDRL (Venereal Disease Research Laboratory), and RPR (Rapid Plasma Reagin) are classified as acute (reverting back to negative in six months) or chronic.
Acute reactions can occur with recent immunization, mononucleosis, viral pneumonia, tuberculosis, malaria, and a variety of viral diseases.
Chronic reactions can occur in users of intravenous drugs, with aging, and in autoimmune diseases, such as systemic lupus erythematosus.
A positive nontreponemal test must always be confirmed by a treponemal test: the TP-PA (Treponemal Particle Absorption test) or the FTA-ABS.
Nontreponemal and treponemal tests are reliable indicators of syphilis in HIV-infected persons. Although no false-positives are associated with the disease, some false-negatives may occur during end-stage disease because of severe immunosuppression.
One of your patients, a 30y/o developer, tells you he is planning a trip to the Dominican Republic the following month. He will need to travel in rural areas. Which is the most appropriate intervention for malaria prophylaxis for this patient?
a. No prophylaxis
b. Chloroquine
c. Mefloquine
d. Doxycycline
e. Primaquine
b. Chloroquine
The Dominican Republic is one area of high risk for malaria where no chloroquine-resistant strains of Plasmodium falciparum have been identified. Other areas include Central America west of the Panama Canal Zone, Haiti, Egypt, and most of the Middle East. Almost all other countries with a high risk for malaria have resistant strains.
The drug of choice for prophylaxis in these areas is mefloquine or doxycycline. Primaquine is given to prevent relapses due to P. vivax or P. ovale. Current information on the foci of drug-resistant P. falciparum is available through the Centers for Disease Control (CDC) travel Web site or the annual publication of the World Health Organization (WHO).
A 20 mo old child presents to your office with a mild viral infection. The results of examination are normal except for a temperature of 37.2°C (99°F) and clear nasal discharge. Review of her vaccination records reveals that she received only two doses of polio vaccine and diphtheria-tetanus-pertussis (DTaP) vaccine, and that she did not receive the measles-mumps-rubella (MMR) vaccine. The mother is 20 weeks pregnant. Her brother is undergoing chemotherapy for leukemia. Which of the following is the most appropriate intervention?
a. Schedule a visit in two weeks for DTaP
b. Administer inactivated polio vaccine (IPV) and DTaP
c. Administer DTaP, oral polio vaccine (OPV), and MMR
d. Administer DTaP, IPV, and MMR
e. Administer DTaP and OPV and schedule a visit in three months for
MMR
e. Administer DTaP and OPV and schedule a visit in three months for
MMR
Children who are late in their immunization schedule should be vaccinated when the opportunity arises. Mild acute illness or antibiotic use is not a contraindication to immuniza- tion. MMR is not contraindicated in children of pregnant women. OPV, but not MMR, is contraindicated in any household contact of a severely immunocompromised person. In fact, in an effort to reduce vaccine-associated paralytic polio (VAPP), OPV is no longer recommended for the first two doses of polio immunizations in infants since 1997, and effective January 2000, the CDC recommendations are to give 4 doses of IPV at 2 months, 4 months, 618 months, and then at 68 years. OPV can be considered only under a few specific circumstances. If the parents refuse the schedule, OPV could be given only for the third or fourth dose and parents should be counseled about the possible occurrence of VAPP. In this case scenario, however, OPV would not be acceptable given the sibling situation. Live and inactivated vaccines can be given at the same time.
Prevention of human brucellosis depends primarily on
a. Pasteurization of dairy products derived from goats, sheep, or cows
b. Treatment of human cases
c. Control of the insect vector
d. Immunization of farmers and slaughterhouse workers
e. Destruction of infected animals
a. Pasteurization of dairy products derived from goats, sheep, or cows
Prevention of human brucellosis depends on pasteurization of dairy products from cows, goats, and sheep; education of farmers and workers in the live-stock industry as to the dangers of infected animals; and care in handling products from aborted animals. There is no insect vector. No vaccine for human use is available. Since person-to-person transmission does not occur, treatment of individual cases will not control spread of brucellosis. Destruction of infected animals will prevent transmission to other animals and is a method to control an outbreak in animals. Vaccine is available for livestock, for prevention but not control of outbreak. Vaccines have been used for workers in the meat and dairy industries in the former Soviet Union and Europe, but it is not used in the United States. Immunity from the vaccine lasts only two years.
Which of the following vaccines is CONTRAINDICATED during pregnancy?
a. Hepatitis B vaccine
b. Varicella vaccine
c. Influenza vaccine
d. Tetanus toxoid
e. Rabies vaccine
b. Varicella vaccine
Varicella-zoster vaccine is a live attenuated vac- cine. In general, live attenuated vaccines, such as the MMR, should be avoided during pregnancy because of the potential of infecting the fetus, which may result in congenital malformation. If a susceptible pregnant woman comes in contact with varicella, the administration of varicella- zoster immunoglobulin (VZIG) should be strongly considered because the disease can be very severe for women during pregnancy. However, there is no assurance that VZIG may prevent congenital infection and malformation, a relatively rare event (risk 0.7% if acquired early in pregnancy and 2% if acquired between 12 and 20 weeks of gestation). Because neonates are at risk of developing severe generalized varicella, VZIG is also indicated for newborns of mothers who develop chicken pox 5 days prior to or within 48 hours after delivery. Hepatitis B and influenza vaccines are inactivated and should be administered to women at risk of infection. Both vaccines available for the prophylaxis of rabies are inactivated and should be given to pregnant women when indicated. Tetanus toxoid and diphtheria toxoid are the only immunobiological agents routinely indicated for susceptible pregnant women. Previously vaccinated pregnant women who have not received a Td vaccination within the last 10 years should receive a booster dose.
A 32y/o farmer presents to the emergency room with a crushing injury of the index finger and thumb that occurred while he was working with machinery in his barn. Records show that he received three doses of Td in the past, and that his last dose was given when he was 25 years old. In addition to proper wound cleaning and management, which of the following is the most appropriate prevention intervention?
a. No additional prophylaxis
b. Administration of tetanus toxoid
c. Administration of tetanus immunoglobulin only
d. Administration of tetanus toxoid and immunoglobulin
e. Administration of tetanus and diphtheria toxoid
e. Administration of tetanus and diphtheria toxoid
If a person has received three doses or more of the Td, and the last dose was given more than five years before an injury, a tetanus and diphtheria booster should be given if the wound is contaminated, such as the one described. It is prefer- able to administer the combined diphtheria and tetanus booster (Td). You are then also using the opportunity to provide primary prevention for diphtheria. If the last dose of Td was given in the preceding five years, then no further action would be necessary. Td and tetanus immunoglobulin (TIG) are recommended for prophylaxis of contaminated wounds when the history of tetanus toxoid is unknown or the person received less than three doses. TIG is never recommended as sole prophylaxis as prolonged immunity is desired.
Epidemics of typhus fever have been associated with war and famine for several centuries. What factor was most important in the control of such epidemics following the end of World War II? a. Eradication of Anopheles mosquitoes b. Improved sanitation practices c. Improved methods for handling food supplies d. Disinfestation by use of DDT e. Mass therapy with antibiotics
d. Disinfestation by use of DDT
The infectious agent for epidemic forms of typhus fever is Rickettsia prowazekii, which is transmitted from person to person by the human body louse, Pediculus humanus corporis. Disruptions of social and economic institutions by war, famine, or natural catastrophes are associated with declining standards of personal hygiene and spread of lice. Even before social and economic recovery after World War II, epidemic typhus was controlled by mass application of DDT powder. This insecticide killed the body lice; thus, the transmission cycle was interrupted. Widespread resistance to DDT and lindane now exists, and other products such as permethrin should be used. Effective antibiotic therapy with chloramphenicol and tetracycline was not available until the early 1950s. Anopheles mosquitoes are vectors in the transmission of malaria, not typhus.
Immunization of preschool children with diphtheria toxoid results in
a. Protection against the diphtheria carrier state
b. Lifelong immunity against diphtheria
c. Detectable antitoxin or immunologic memory for about 10 years
d. Frequent adverse reactions
e. Protection against infection of the respiratory tract by Corynebacterium diphtheria
c. Detectable antitoxin or immunologic memory for about 10 years
Diphtheria toxoid, alone or in combination with pertussis vaccine and tetanus toxoid (DTaP), induces protective levels of antitoxin that persist for about 10 years. Boost- ers are required every 10 years after completion of primary immunization in order to maintain protective concentration of antibody. Antitoxin antibodies do not prevent infection of the respiratory tract with C. diphtheriae and do not prevent the development of the carrier state. The antibodies are directed against the exotoxin produced by the bacteria, not against the bac- teria themselves. Adverse reactions from the toxoid are very infrequent in infants and young children but are more common in adults; therefore, the administration of a reduced dose of toxoid is recommended for children after their seventh birthday and for adults. The reduced dose is symbolized by a lowercase d. It is usually combined with tetanus toxoid as a Td.
What is the recommended interval in months between the administration of whole blood transfusion and the measles-mumps-rubella (MMR) vaccine?
a. 0
b. 1
c. 3
d. 6
e. 10
d. 6
Whats important here is to remember the concept that passively acquired measles antibody can interfere with the immune response of the measles vaccine. The intervals suggested by CDC are extrapolated from an estimated half-life of 30 days for passively acquired antibody and an observed interference with the immune response to measles vaccine for five months after a dose of 80 mg IgG/kg. The intervals vary according to the amount of plasma (containing the anti- bodies) or immunoglobulins present in the preparations. The recommended interval is 0 months for washed red cell transfusion; 3 months for adenine- saline RBC transfusion; 6 months for packed RBCs or whole blood; and 7 months for plasma/platelet transfusion. An interval of 3 months is recom- mended between the administration of tetanus immunoglobulin (TIG), hepatitis A prophylaxis with serum immunoglobulin (IG), and hepatitis B immunoglobulin (HBIG), and the MMR vaccine; 4 months between human rabies immunoglobulin (HRIG) and the MMR vaccine; and 5 months between varicella zoster immunoglobulin (VZIG) and MMR.
Professional organizations recommend that all pregnant women be routinely counseled about HIV infection and be encouraged to be tested. What is the most important reason for early identification of HIV infection in pregnant women?
a. A cesarean section can be planned to reduce HIV transmission to the newborn
b. Breast feeding can be discouraged to reduce transmission to the newborn
c. Early identification of a newborn at risk of HIV infection will improve survival
d. Counseling on pregnancy options, such as termination, can be offered
e. Antiretroviral therapy can be offered to reduce the chance of transmission of HIV to the newborn
e. Antiretroviral therapy can be offered to reduce the chance of transmission of HIV to the newborn
The landmark randomized placebo controlled trial ACTG 076 demonstrated that zidovudine (ZDV) given at the beginning of the second trimester, during labor and delivery, and to the newborn for 6 weeks, significantly reduced the transmission of HIV to the newborn from 25.5% in the control group to 8.3% in the treatment group. Thus, ZDV can be highly effective for primary prevention in the newborn. Other promising treatment schedules with ZDV and other antiretrovirals are under study. Recent data demonstrates that a cesarean section can reduce vertical transmission, but it should not supersede antiretroviral therapy.
Currently, it appears that it is not a routinely recommended procedure for HIV-infected pregnant women, but this may change in the future. HIV can be transmit- ted by breast feeding, and in some studies, the risk is increased by 14%. However, breast feeding has no impact on the highest risk of transmission, which occurs during gestation, labor, and delivery. Early identification of newborns at risk of HIV infection will guide the medical management and improve outcomes. It has no impact on the primary prevention of the infection to the newborn. Finally, all HIV-infected women should be made aware of the benefit of ZDV so they can make informed choices.
A 35y/o patient comes to your office in early April for a routine examination. In the course of the history, he tells you that he plans to go turkey hunting in Nantucket, Massachusetts, for one week in May. He is concerned about Lyme disease. Which is the most appropriate intervention for preventing Lyme disease?
a. Vaccination
b. Avoidance of bushy areas
c. Tick check at the end of each day
d. Protective clothing and DEET
e. Antibiotic prophylaxis for one week
d. Protective clothing and DEET
Nantucket Island (off the coast of Massachusetts) has one of the highest rates of Lyme disease in the United States. Lyme disease is a tick-borne zoonosis from the spirochete Borelia burgdorferi. Avoidance of bushy areas is the first line of prevention recommendation for patients traveling in endemic areas. Risk is higher in summer and spring. However, it is unrealistic to expect this patient to keep away from bushy areas. His best protection would be wearing appropriate clothing and applying DEET to avoid tick bites. Next, since infection rarely occurs if the tick has been attached for less than 36 hours, daily checks for ticks may be helpful. Antibiotics are used for treatment but not prophylaxis. Optimal protection for the vaccine is obtained after three doses at 0, 1, and 12 months. Vaccine is currently primarily recommended for persons 15 to 70 who engage in activities that result in prolonged exposure to tick-infested habitat in areas of high to moderate risk. Benefit of the vaccine for short exposure beyond that provided by personal protection is uncertain. Furthermore, there would not be enough time to complete the series in this case.
An 18y/o sexually active college student presents with complaints of lower abdominal pain and irregular bleeding for five days. She has no fever. She uses oral contraceptives as method of birth control. Upon examination, the cervix is friable, there is cervical motion tenderness and adnexal tenderness. The pregnancy test is negative. Which is the most likely etiologic agent responsible for these findings?
a. Neisseria gonorrhoeae
b. Chlamydia trachomatis
c. Treponema pallidum
d. Herpes simplex virus type 2
e. Mycoplasma hominis
b. Chlamydia trachomatis
Chlamydia trachomatis is the most frequently reported bacterial sexually transmitted disease (STD) in the United States. Infections of the cervix may present as a friable cervix, but are most often without signs or symptoms.
An 18y/o sexually active college student presents with complaints of lower abdominal pain and irregular bleeding for five days. She has no fever. She uses oral contraceptives as method of birth control. Upon examination, the cervix is friable, there is cervical motion tenderness and adnexal tenderness. The pregnancy test is negative. She tells you that she had a similar episode two years ago. What is her risk of infertility following this second clinical episode of pelvic inflammatory disease?
a. <1% b. 5% c. 10%
d. 20% e. 40%
d. 20%
Pelvic inflammatory disease (PID) caused by chlamydia often presents with milder symptoms than when it is caused by gonorrhea. Prompt treatment reduces the occurrence of long-term sequelae such as infertility, ectopic pregnancy, and chronic pelvic pain. The risk of infertility appears to be higher for chlamydial infections compared to any other STD. Screening women is important to reduce the risk of PID and its sequelae.
In the course of investigating a 24y/o HIV-infected male, the HBsAg is positive. He is currently asymptomatic, his physical examination is essentially normal, and his CD4 cell count is 800. Which of the following tests is most helpful in determining whether the patient is in the acute phase of viral hepatitis?
a. ALT levels
b. HBeAg
c. HBsAg
d. IgG anti-HBcAg
e. IgM anti-HBcAg
d. IgG anti-HBcAg
Currently available laboratory tests for hepatitis B include HBsAg (hepatitis B surface antigen), anti-HBs (antibody to hepatitis B sur- face antigen), IgM anti-HBc, IgG anti-HBc (antibodies to the core antigen), HBeAg, and anti-HBe. Because HBcAg is sequestered within an HBsAg coat, HBcAg is not routinely detected in patients with hepatitis B. IgM anti- HBc appears soon after the onset of infection and the detection of HBsAg, and precedes by many weeks detectable levels of anti-HBsAg. It generally disappears after 6 to 8 months. The presence of IgM is a marker for acute (less than 6 months) hepatitis B. IgG anti-HBc appears somewhat later than the IgM and may persist for years. Elevated ALT may be present both in the early and chronic phases of the disease. HBeAg may persist for years in patients with chronic disease and is associated with high infectivity. HBsAg remains detectable beyond 6 months in chronic hepatitis B.
Which of the following complications has been associated with the recall of rotavirus vaccine?
a. Guillain-Barr syndr ome
b. Hemolytic anemia
c. Febrile seizures
d. Intussusception
e. Neutropenia
d. Intussusception
The rotavirus vaccine was rapidly removed from the market (a few months after the CDC had recommended its use) because of reports of intussusception ocurring in infants within three weeks of vaccination.
Which etiological agent was responsible for most cases of illness due to waterborne-disease outbreaks in the US in the 1990s?
a. Salmonella enteritidis (serotype typhimurium)
b. Giardia lamblia
c. Campylobacter jejuni
d. Cryptosporidium parvum
e. Shigella sonnei
d. Cryptosporidium parvum
Cryptosporidium parvum was responsible for illness in 403,271 persons, the greatest number of cases of illness due to outbreaks of waterborne disease in the US in the 1990s. During an outbreak in Milwaukee in 1993, an estimated 403,000 persons became ill and 4,400 were hospitalized.
Although the actual number of outbreaks as opposed to number of cases is about the same for C. parvum and G. lamblia, outbreaks of G. lamblia caused illness in an estimated 385 persons.
The most important risk factor for heat-related illness is
a. Age over 65
b. Age under 1
c. History of prior heat stroke
d. Low socioeconomic status
e. Obesity
a. Age over 65
Older adults over the age of 65 are particularly at risk of death due to heat-related illness because of decreased response of the cardiovascular system during hot weather.
Very young children under the age of 1 are also at risk, but less than older persons.
Heat-related illness is seen more frequently in lower-socioeconomic areas, presumably because of no access to air conditioning and good ventilation and because of higher temperatures in urban areas (heat islands).
Obesity and prior history of heat stroke also increase the risk, but to a much lesser degree than older age. Drugs that inhibit sweat production, cause dehydration, and reduce cutaneous blood flow (atropine, antidepressants, diuretics, etc.) also increase susceptibility to heat.
Following an accident in a nuclear laboratory, some workers were exposed to 300 rem (3 Sievert) of radiation. They are immediately sent to your emergency department. Which of the following effects will most likely occur among the majority of these workers?
a. Bone marrow depression
b. Neurovascular syndrome
c. Gastrointestinal syndrome
d. Cardiovascular syndrome
e. No detectable physiological effect
a. Bone marrow depression
Disturbances begin to occur at exposures above 100 rem. Following an acute exposure to 100 to 200 rem of ionizing radiation, mild hematopoietic disturbances may occur (5% at 100 rem and 50% at 200 rem) after a few wks, which only warrant surveillance. Some patients may have vomiting 3hrs after the exposure. Between 200 and 600 rem, more severe hematopoietic disturbances will occur, with a peak at 4 to 6 wks, requiring transfusions, antibiotics, & hematopoietic GF. Patients will vomit within 2hrs. Extreme disturbances will occur after an acute exposure of 600-1000 rem, with a high case fatality rate (80 - 100% within 2 mos). Vomiting will occur within 1hr. All patients with exposures above 1000 rem will die, with early onset (1-14 days depending on exposure) of GI syndrome (diarrhea, fever, and electrolyte disturbances) and CNS problems dominating the clinical picture.
The Haddon matrix is used for assessing interventions for the prevention of
a. Water pollution
b. Air pollution
c. Radiation exposure
d. Injury
e. Toxic substance exposure
d. Injury
This is a systematic approach to injury prevention developed by William Haddon Jr. of the New York State Department. The matrix categorizes interventions as modifying the host, agent, and environment either before, at the time of, or after the event.
The most effective means of preventing trichinosis in humans is
a. Cooking pork to reach a internal temperature of at least 40°C (104°F)
b. Proper disposal of hog feces
c. Prohibiting feeding garbage to hogs
d. Testing hogs with Trichinella antigen prior to slaughter
e. Freezing pork at 10°F
c. Prohibiting feeding garbage to hogs
Infection of hogs with nematodes of the genus Trichinella can be prevented by ensuring that all garbage and offal fed to the hogs are heat-treated to destroy the cysts or, preferably, by using feed devoid of animal meat, such as grain. Prohibition of marketing of garbage-fed hogs is easier to enforce than inspection to ensure that all garbage is properly cooked. The disease is transmitted by ingestion of larvae in hog skeletal muscle, not by hog feces. Thorough cooking of pork and pork products so that all the meat reaches at least 71°C (160°F) destroys the encysted larvae. Freezing pork also destroys the larvae if adequate time-temperature schedules are followed. In order to be effective, freezing must be done at −15°C (−5°F) for 30 days if the piece of meat is 15cm in thickness or less.
Which engineered water purification system is the most effective for the elimination of Cryptosporidium parvum?
a. Flocculation
b. Sedimentation
c. Disinfection
d. Boiling
e. Filtration
e. Filtration
Slow sand, rapid granular, or membrane filtration is the most effective water treatment method to remove Cryptosporidium cysts, as they are not destroyed by disinfection.
Flocculation is used to help form large floc particles from particulate matter including bacteria which can then can be more easily removed.
Sedimentation, through gravity, makes particulates including bacteria settle to the bottom of a tank.
Flocculation and sedimentation do not effectively remove cysts. It is important to note that high water turbidity may affect the ability of filtration to remove the parasite, and that filtration may not always afford absolute protection.
Boiling is not an engineered water sanitation process, but it is the simplest effective method to prevent Cryptosporidium parvum infections if drinking water is contaminated or has not been treated adequately. The water intended for drinking should be boiled for 1 min. Immunosuppressed persons, such as those with HIV, are particularly at risk of severe infections.
The major environmental source of lead absorbed in the human blood stream in adults is
a. Air
b. Water
c. Lead-based paint
d. Food
e. Soil
a. Air
Although most lead intake in humans is from ingestion of lead-contaminated food (about 0.1 mg of lead is ingested daily per person), the amount of lead that is absorbed after inhalation of lead-contaminated air is of greater significance because up to 50% of inhaled lead, compared with only as much as 10% of ingested lead, is absorbed and circulated through the blood.
Because modern building codes require the replacement of lead domestic water-supply pipes with those made of copper or galvanized iron, drinking water has become a decreasing source of lead poisoning.
The intake of lead through ingestion of lead-based paint is mainly a problem with children.
GI absorption of lead appears to be more efficient in children, while pulmonary absorption is more efficient in adults.
You are asked to evaluate the working environment in a manufacturing plant processing metal parts. In one area of the mill, where such parts are flattened, the sound level is measured at 85dB. The workers responsible for this process are exposed to this sound for the entire 8-hr shift. The most appropriate intervention for this level of sound is
a. None. This level of sound is below the level at which OSHA regulations apply
b. A hearing conservation program
c. A shutdown of the manufacture until the level of sound is reduced
d. A shutdown only of the process area where the sound is 85dB or higher
e. Enforcement of hearing protective devices for all exposed workers
b. A hearing conservation program
Exposures of 85 dB or more for 8 hrs/day or more require the implementation of a hearing conservation program (HCP) under OSHA (Occupational Safety and Health Administration) regulation. This program includes noise monitoring, engineering controls, administrative control, worker education, selection and use of hearing protection devices (HPD), and periodic audiometric evaluations.
Engineering controls where possible are always the preferred method of controlling sound levels.
Administrative controls include reducing the amount of time the worker is exposed to high levels of sound. This is often difficult to achieve and requires constant oversight to ensure implementation.
Hearing devices must be able to bring the level of sound to 90 dB or less, the permissable exposure level for sound. However, workers may not always wear these devices. At levels of sound below 90 dB, OSHA requires that HPD be made available to workers. At level 90 or above, HPD must be provided and proper use must be enforced by the employer.
A 42y/o welder is brought in the emergency room complaining of a sore throat, headache, and myalgias. He also started feeling a tightness in the chest and shortness of breath. He works in an electroplating operation brazing and cutting metals. Pulmonary function tests reveal a reduced FEV. The CXR is normal. Which of the following exposures is the most likely cause of the workers symptoms?
a. Lead
b. Mercury
c. Chromium
d. Copper
e. Cadmium
e. Cadmium
Acute exposure to mercury results in cough, inflammation of the oral cavity, and GI symptoms. Renal injury is of particular concern. Neurological symptoms can later occur. Mercury is often used in the manufacturing of control instruments (such as thermometers). Dimercaprol is used for treatment.
Copper toxicity (in the US) is primarily due to accidental ingestion or suicide attempts and leads to intravascular hemolysis and methemoglobinemia. No specific treatment exists. The initial symptoms associated with acute exposure (ingestion or inhalation) of lead are primarily gastrointestinal (abdominal cramps). Encephalopathy can follow.
Lead is used intensively in the production of storage batteries.
Chromium is used in plating. Acute exposure results in irritation of eyes, nose, and throat with epistaxis.
A 42y/o welder is brought in the emergency room complaining of a sore throat, headache, and myalgias. He also started feeling a tightness in the chest and shortness of breath. He works in an electroplating operation brazing and cutting metals. Pulmonary function tests reveal a reduced FEV. The CXR is normal. The most likely source of absorption is
a. Lung
b. Skin
c. Mucous membranes
d. Gastrointestinal
e. Open sores
a. Lung
A 42y/o welder is brought in the emergency room complaining of a sore throat, headache, and myalgias. He also started feeling a tightness in the chest and shortness of breath. He works in an electroplating operation brazing and cutting metals. Pulmonary function tests reveal a reduced FEV. The CXR is normal. Which of the following should be used to treat acute exposure?
a. EDTA
b. Pralidoxime
c. Dimercaprol
d. Acetylcysteine
e. Atropine
a. EDTA
Chromium is a known carcinogen (lung cancer). Dermatologic conditions are common among chromium workers (ulcerations with delayed healing on fingers, knuckles, and forearms) and are treated with 10% CaNa2 EDTA ointment.
Atropine and pralidoxime are used in the treatment of pesticide exposure.
Acetylcysteine is used for acetaminophen poisoning.
Toxicology is the study of adverse effects of chemicals on living organisms. Which of the following occurrences would be indicative of the most important nonthreshold effect in humans?
a. Infertility
b. Paralysis
c. Adenocarcinoma
d. Neutropenia
e. Cirrhosis
c. Adenocarcinoma
Substances causing adverse biological effects in humans can be classified as reproductive, renal, and respiratory toxins; neurotoxins, dermatotoxins, and hepatotox- ins. It is assumed that there may be some form of dose-response relationship and that there is a minimal exposure below which a toxic effect will not occur (the threshold). The absence of threshold is assumed for any substance that is carcinogenic, mutagenic, and/or teratogenic. There is no safe exposure below which no effect exists.
In other words, a nonthreshold
effect exists when there is no safe level of exposure to humans.
What proportion of cancers in humans is estimated to be the result of environmental factors?
a. 10%
b. 25%
c. 50%
d. 75%
e. 90%
e. 90%
Most cancers are caused by one or a combination of exposure(s) due to the environment or lifestyle such as tobacco smoke, radon, chemicals, asbestos, toxins, and ultraviolet light.
A 34y/o woman is brought in from a sporting event complaining of headache, nausea, and weakness. She had been jogging outside in sunny weather where the temperature was 90° F with a relative humidity of 70%. She had started a training program 2wks before. She is hyperventilating, her skin is moist, and her core body temperature is 38.8° C. She most likely suffers from
a. Sunstroke
b. Heat cramps
c. Heat exhaustion
d. Heat stroke
e. Heat syncope
c. Heat exhaustion
Heat stroke is characterized by the presence of mental status changes and a core body temperature of more than 39° C.
*Cardiovascular collapse will occur if not treated immediately as the body temperature may reach up to 41.1° C. This is a medical emergency requiring IV hydra- tion and rapid cooling: cool water or isopropyl alcohol 70% on the body with fanning, sponge baths, ice packs on the groin/axilla/neck, and/or iced gastric lavage until the core body temperature drops to 39° C. Patients should be advised to avoid heat exposure for at least 4 wks because hypersensitivity to heat may persist for a long period of time after an episode of heat stroke.
Heat cramps are characterized by painful muscle cramps along with some nausea and vomiting. The core body temperature is normal. This is caused by sodium depletion due to sweating: the patient should be placed in a cool environment and hydrated with a balanced salt solution. Rest for at least 1 to 3 days is recommended.
Heat syncope is a sudden loss of consciousness due to vasodilation secondary to heat.
A 34y/o woman is brought in from a sporting event complaining of headache, nausea, and weakness. She had been jogging outside in sunny weather where the temperature was 90° F with a relative humidity of 70%. She had started a training program 2wks before. She is hyperventilating, her skin is moist, and her core body temperature is 38.8° C. The most appropriate cooling measure for this patient is
a. Immersion in ice-water bath
b. Iced gastric lavage
c. Ice packs to groin, axilla, & neck
d. Evaporative cooling
e. Cool & shaded environment
e. Cool and shaded environment
She should be placed in a cool and shaded environment.
This patient should also receive hydration and salt replenishment with IV fluids.
Milder cases can be treated with oral hydration.
A 34y/o woman is brought in from a sporting event complaining of headache, nausea, and weakness. She had been jogging outside in sunny weather where the temperature was 90° F with a relative humidity of 70%. She had started a training program 2wks before. She is hyperventilating, her skin is moist, and her core body temperature is 38.8° C. In addition to proper hydration, rest, and attention to heat index guidelines, she should be advised to avoid reexposure to heat for at least
a. 1 day
b. 1 week
c. 2 weeks
d. 3 weeks
e. 4 weeks
a. 1 day
At least 1 day of rest is recommended after heat exhaustion.
Heat index guidelines are developed by the National Weather Service and predict risk of heat-related disorders based on ambient heat and humidity.
Which of the following tests is the most frequently used rapid screening test to assess mutagenicity /carcinogenicity of a chemical substance?
a. Ames test
b. Mammalian mutation assay
c. Unscheduled DNA assay
d. Cell transformation assay
e. Cytogenetic assay
a. Ames test
All the tests listed can be used to screen substances for mutagenesis and carcinogenesis, that is, their ability to interact with genetic material and DNA.
The Ames test is the most commonly used rapid screening test and is a bacterial mutation assay. It tests for the reversion of a histidine-requiring Salmonella typhimurium mutant to the wild type. It is very sensitive to DNA damage.
The other tests are more sophisticated, take more time, and are more expensive.
A migrant farm worker is brought to the clinic at 2:00 P.M. complaining of blurred vision, salivation, nausea, and diarrhea. He had been working in the fields since 6:00 A.M. in hot and humid weather. The examination reveals the following findings: HR 50 bpm, RR 20 cycles/min, profuse perspiration, and miosis. The most effective initial intervention with this worker is
a. Rapid administration of intravenous fluid
b. Evaporative cooling
c. Atropine
d. Observation only
e. Epinephrine
c. Atropine
The clinical signs are not consistent with heat-related illness, but rather poisoning with the commonly used pesticide carbamate.
Symptoms are related to the inhibition of cholinesterase.
Mild symptoms are characterized by muscarinic signs and symptoms.
Atropine blocks the effect of acetylcholine at the muscarinic receptors.
Which of the following waste management methods is the preferred method of waste control?
a. Waste minimization
b. Incineration
c. Recycling
d. Physical treatment
e. Biological treatment
a. Waste minimization
Minimizing waste is the best approach to controlling the problem by reducing the amount of waste generated.
Recycling, when possible, is the next best method, followed by incineration when appropriate (organic compounds can be reduced to water, CO2, and heat).
Physical treatment is most commonly used for water treatment (sedimentation, filtration, flocculation).
Chemical treatment can be used to transform hazardous substances into less-toxic ones.
Biological treatment can be used to treat industrial wastewater, a major source of waste.
Commercial airline pilot shave higher exposures to which type of radiation compared to the general population?
a. Alpha particles
b. Beta particles
c. Gamma rays
d. Cosmic rays
e. X-rays
d. Cosmic rays
Natural background radia- tion (terrestrial and cosmic radiation, naturally occurring radionuclides) is the most important source of radiation exposure for all humans. Radiation from manufactured origins accounts for only 20% of all radiation exposure. Terrestrial radiation, consisting of gamma rays (average exposure: 4050 mr em per year), varies with geography, and cosmic radiation due to cosmic rays (average exposure: 4050 mr em per year) increases with altitude. Air travel increases exposure and aircrews have five times greater exposure than the general population.
Alpha radiation
- very limited penetration because of the large size of the particles and is completely absorbed by the outer layer of the skin;
- hazard occurs when these particles enter the body and irradiate living tissue (radon daughters that are inhaled);
Beta particles are all internal hazards, but external exposure can be stopped by one inch of water.
Cosmic rays are more penetrating than gamma rays.
X-rays are indistinguishable from gamma rays, except for their origin (synthetic versus natural terrestrial).
Radioactive waste is best disposed by
a. Physical treatment
b. Incineration
c. Landfill
d. Injection wells
e. Chemical treatment
c. Landfill
* used to dispose of nonliquid waste only;
* is the only method of disposing of radioactive waste safely;
Other methods are used to dispose of nonradioactive waste.
Which of the following is responsible for the largest proportion of domestic water use?
a. Bathing
b. Drinking
c. Laundry
d. Toilet flushing
e. Dishwashing
d. Toilet flushing
Flushing: 40% Bathing: 30% Laundry: 15% Drinking/Cooking: 5% Dishwashing: 5%
On a hot summer day in a large urban center located in the southwestern US, an emergency room department re- ports an increase in admissions for asthma in children and young adults, but not among patients suffering from chronic bronchitis or ischemic heart disease. The most likely air pollutant responsible for the exacerbation of asthma is
a. CO
b. Ozone
c. Nitrogen dioxide
d. Particulate matter
e. Lead
b. Ozone
The major air pollutants are particulates, sulfur oxides, carbon monoxide, oxides of nitrogen, hydrocarbons, lead, and ozone. The latter is formed by sunlight irradiating an atmosphere containing hydrocarbons and oxides of nitrogen, and has been associated with Southern California smog. It has primarily been linked to an exacerbation of asthma. Hydrocarbons are precursors of smog. Carcinogenicity is debated.
Oxides of nitrogen are also precursors of smog: important sources are automobiles and airplanes. They are primarily mucosal irritants and studies on respiratory effects are conflicting.
CO, although a plentiful pollutant, is quickly transformed into CO2. Increases will aggravate coronary artery disease, precipitate MI, and reduce exercise tolerance. Particulate matter will most severely affect persons with COPD.
Sulfur oxide is the most important air pollutant.
A 42-year-old welder presents to employee health services complaining of tearing eye pain and photophobia. A photokeratoconjunctivitis is diagnosed. The most likely cause of this condition is
a. Infrared radiation
b. Visible radiation
c. Ultraviolet radiation A
d. Magnetic radiation
e. Ultraviolet radiation B
e. Ultraviolet radiation B
Ultraviolet radiation covers the spectrum between visible radiation (light) and ionizing radiation (100400 nm).
Ultraviolet radiation B
- ranges fr om 280 to 315 nm, the range to which the eye is particularly sensitive &where most injuries occur;
- Acute exposure to UV of less than 315 nm results in photokeratoconjunctivitis, with symptoms appearing 6 to 12 hours after exposure;
- Prolonged exposures to UV between 295 and 320 nm can result in cataract formation;
Ultraviolet A
- ranges from 315 to 400 nm. Injuries caused by visible radiation (light);
- covers the spectrum between infrared & UV radiation (400750 nm);
- affect primarily the retina, which is most sensitive to blue light (eclipse blindness);
Infrared light
- covers the spectrum between visible light and radiofrequency (750 to 3 million nm);
- is given off by any material of a temperature greater than absolute zero;
- Thermal injury can occur with intense exposure to infrared light of less than 2000 nm and has been associated with cataract formation.
Which of the following physical characteristics of water is the most important impediment to disinfection?
a. Color
b. Viscosity
c. Turbidity
d. Density
e. Temperature
c. Turbidity
* is a major impediment to disinfection.
Major steps in potable water treatment are sedimentation, coagulation (often alum is added to facilitate floc formation that will settle more readily) and flocculation, which get rid of 90% of the bacterial load and reduce color and turbidity (see question 239). Filtration eliminates particles which cannot be destroyed by other methods, such a cysts from Cryptosporidium, Entamoeba hystolitica, and Giardia lamblia. Finally, the water is disinfected generally with chlorine whose power is greater at lower pH. Residual levels remain in the water as it is distributed to consumers, a major advantage over ozone.
Which of the following residential environmental pollutants is the leading cause of lung cancer?
a. Radon
b. Tobacco smoke
c. Asbestos
d. Formaldehyde
e. Sulfur oxide
c. Asbestos
Tobacco is still a leading cause of lung cancer.
Radon has also been associated with lung cancer, and the combination of radon and tobacco smoke can be synergistic.
Lung cancer is responsible for 20% of all asbestos-related deaths.
Formaldehyde has been associated with nasopharyngeal cancers.
Sulfur oxide is primarily an outdoor pollutant
Which of the following minerals is responsible for hard water?
a. Lead
b. Copper
c. Iron
d. Sulfur
e. Manganese
e. Manganese
So-called hard water is primarily due to high concentrations of calcium or manganese.
Soft water can be corrosive and leach metals from pipes, especially lead.
A 28y/o woman presents with nausea, vomiting, and diarrhea. She has no fever. Her history reveals that she attended a reception about 6hrs ago. She ate roast beef with gravy, salad, and had cream-filled pastries for dessert. Prevention of this food-borne illness could have been achieved by
a. Freezing the food
b. Heating the food to 140° F
c. Proper hand washing by food handlers
d. Proper cleaning of contaminated surfaces
e. Control of flies
c. Proper hand washing by food handlers
The short IP and symptoms are characteristic of food poisoning due to the toxin produced by Staphylococcus aureus. Organisms and toxin are not destroyed by freezing. Although the organisms can be killed by heating food to 66° C (150° F), the preformed toxin generally survives.
Optimum growth of the bacteria occurs at 59° to 99° F (growth is inhibited at below 39° F), with toxin production optimal after 4-6 hrs. The source is human skin, mouth, and nose.
Proper hand washing by food handlers and excluding those with skin infections is the best
way to prevent contamination.
A 50y/o textile worker presents to your office for his periodic health examination. He has no complaints. Review of history reveals that he has been working for over 25 yrs at the same company. His work consists of preparing dyes. Which of the following tests would be appropriate in this setting?
a. A chest x-ray
b. A brain CT scan
c. Liver function tests
d. A complete blood count
e. A urinalysis
e. A urinalysis
Dye workers are susceptible to bladder cancer due to exposure to β-Naphtylamine and benzidine. The most common presenting symptom will be gross hematuria or microscopic hematuria.
Liver cancer has been associated with exposure to vinyl chloride while hematologic cancers are associated with radiation and benzene exposure.
Occupational causes of brain cancer have not been well identified at this time.
A 30y/o patient presents at an evening walk-in clinic after work complaining of chills, fever, and malaise of acute onset. He started coughing and feeling out of breath late in the afternoon. Inspiratory crackles are present on chest auscultation. The CXR is normal. The CBC reveals 12,000 WBC with 70% PMNs. His PMH is benign. No one else in the household is sick. He says some of his coworkers have a cold. He works in a pet shop in the bird section. He is not taking any medication. He states he had a similar episode a few wks ago that resolved after a few days of rest at home. The most appropriate management is to prescribe
a. Rest, fluid, and antipyretics
b. Amantadine
c. Doxycycline
d. Prednisone
e. Erythromycin
a. Rest, fluid, and antipyretics
These symptoms are typical of hypersensitivity pneumonitis, which can often be confused with infectious causes such as influenza or Mycoplasma pneumoniae.
CXR may be completely normal even in symptomatic individuals. However, typically, the CXR may show bilateral reticulonodular infiltrates. The acute form is characterized by the appearance of symptoms a few hours after short-term high exposure, and resolves after a few hours or days. Treatment should primarily consist of avoiding the causative agent or wearing respiratory protective equipment.
Acute episodes resolve on their own without glucocorticosteroids. Prednisone is the treatment for severe or progressive hypersensitivity pneumonitis.
Psittacosis has an incubation period of 7-14 days, can be associated with splenomegaly (10 to 70% of cases), and the x-ray generally shows diffuse patchy infiltrates.
Biological oxygen demand (BOD) measures the total organic content of water-based on the consumption of oxygen in a sample at 20° C over 5 days. A consumption of 10-20 mg of O2 per liter most likely represents a sample from
a. Treated freshwater
b. Untreated freshwater
c. Treated sewage
d. Domestic sewage
e. Industrial wastewater
c. Treated sewage
Biological oxygen demand is a measure of organic content in water. The greater the demand, the greater the load of organic content that can be broken down, reflecting a high bacterial load. (in mg/L BOD)
Untreated freshwater: 25;
Treated sewage: 1020;
Domestic sewage: 200500;
Industrial sewage: >2000
Which of the following factors of air travel is most likely to adversely impact a patient with cardiopulmonary disease?
a. Immobility
b. Cabin air quality
c. Barometric pressure
d. Temperature
e. Humidity
c. Barometric pressure
Lower barometric pressure associated with air travel will lower the tension of oxygen in the inspired air, the alveolar oxygen tension, and arterial oxygen saturation, which could lead to an exacerbation of coronary artery disease deficiency.
Immobilization for long periods of time can increase the risk of thromboembolic disease, which may be more of an issue for pregnant women. Getting up periodically to walk up and down the aisles may help alleviate this problem. The circadian rhythm will be changed due to the change in time zones and peaks of cortisol production will also vary. This can potentially affect the pathophysiology and timing of cardiac events.
Cabin air quality studies have shown that the CO, CO2, and respirable particulate levels are below OSHA standards, and that ozone levels are below the Federal Aviation Administration (FAA) standards.
