Immunology CH 3.3 Infectious Diseases Flashcards
which serum antibody response usually characterizes the primary (early stage) syphillis?
ab against syphillis are undetectable
detected 1 to 3 wk after appearance of the primary chancre
detected in 50% of cases before the primary chanchre disappears
detected within 2 weeks after infection
B, 90% of people develope ab between 1-3 wk after primary chancre
what substance is detected in the sample bu RPR and veneral diease reasearch lab VDRL tests for syphillis?
cardiolipin
anticardiolipin antibody ACA
anti-trepronema pallidum antibody
T. pallidum
ACA or Reagin
what type of antigen is used in the RPR card test?
live treponema organisms
killed suspension of treponemal organisms
cardiolipin
tanned sheep cells
cardiolipin
which of the following is the most sensitive test to detect congenital syphillis?
VDRL
RPR
T. pallidujm agglut (TP-PA)
PCR
PCR will amplify very small amount of DNA to allow detection
a biological false positive rxn is least likely with which test for syphillis?
VDRL
TP-PA
RPR
All results are equally likely to result a false positive
TP-PA is most specific for syphillis
a 12yr old girl has sympt of fatigue and localized lymphadenopathy. Tests reveal peripheral blood lymphocytosis, positive RPR and positive spot test for IM. what test should be preformed next?
HIV screen
VDRL
EBV - specific antigen test
TP-PA test
TP-PA
which test is most likely to be positive in the tertiary stage of syphillis?
trep-specific antibody
RPR
VDRL
RST (reagin screen test)
A: treponemal specific antibody
what is the most likely interpretation of the following syphillis serological results?
RPR reactive; TP-PA nonreactive
neurosyphillis
secondary syphillis
syphillis that has been sucessfully treated
bio false positive
D bio false positive
which specimen is the sample of choice to evaluate latent or tertiary syphillis?
serum sample
chancre fluid
CSF
joint fluid
CSF
Interpret the following
RPR titer: weak reactive- 1:4 reactive 1:8 to 1:64
excess antibody: prozone
excess antigen: post zone
equivalence
impossible to interpret
excess antibody, prozone
tests to ID infection with HIV fall into which three general classification types of tests?
tissue cultures, antigen and antibody tests
tests for antigens, antibodies and nucleic acid
DNA probe, DNA amp and western blot
ELISA, western blot and southern blot
tests for antigens, antibodies and nucleic acid
which tests are considered screening tests for HIV?
ELISA, chemilum, and rapid antibody tests
IFA, western blot, radioimmunoprecip assay
culture, antigen capture, DNA amp
Reverse transcript and mRNA assay
A
which tests are recommended confirmitory for HIV?
ELISA and rapid antibody test
HIV, 1-2 antibody ssay and qualitative PCR
Culture, antigen capture, quant PCR
Reverse transcript and mRNA assay
B. HIV 1-2 antibody assay and qual PCR
how do fourth and fifth gen HIV tests reduce the time from infection to the test becoming positive?
they are PCR tests detecting viral RNA
they detect p24 ag in addition to HIV antigen
they detect proviral DNA
they detect ab to more ag than earlier HIV tests
B, p24 ag in addition to HIV ag
a woman who has had five pregnancies test pos for HIV on fourth gen assay, and is negative on 1-2. Initial reactivity may be due to?
poss corss rxn with herpes/EBV
interference w medications
cross rxn of pregnancy antibodies
possible technical error, repeat specimen
cross rxn of pregnancy antibodies
Interpret the following results for HIV testing:
Fourth Gen ELISA pos; repeat ELISA pos; HIV 1,2 assay negative; qual HIV RNA rt PCR pos
False pos fourth gen assay
false neg antibody diff assay
indeterminante, more testing needed
HIV p24 antigen detected on fourth gen ELISA
D, fourth gen HIV p24 antigen detected
What is the most likely explanation when antibody tests for HIV are negative but the PCR test is positive?
probably not HIV infection
pt is in the “window phase” before ab production
tests were preformed incorectly
clinical signs misinterpreted
B, pt may be in the window phase and ab may not be produced yet
what criteria constitutes the classification system for HIV infections?
CD4 positive t cell count and clinical symptoms
clinical symptoms, condition, durnation, and strength of reactivity on fourth gen HIV test
presence/absence of lymphadenopathy
strong fourth gen HIV test reactivity and CD8 positive T cell count
A, CD4 positive t cell count and clinical symptoms
what is the main difficulty associated with the development of an HIV vaccine?
the virus has been diff. to culture, antigen extraction and concentration are laborious
human trials cannot be preformed
different strains of the virus are genetically diverse
anti-idiotype antibodies cannot be developed
C, different strains of the virus are genetically diverse
which CD4:CD8 ratio is most likely in a patient with AIDS?
2:1
3:1
2:3
1:3
inverted ratio is common, D is correct 1:3 ratio with more CD8
what is the advantage of fourth gen rapid HIV tests over earlier rapid HIV tests?
they use recombinant antigens
they detect mult strains of HIV
they detect p24 antigen
they are quantitative
C, they detect p24 antigen
which method is used to test for HIV infection in infants who are born to HIV pos mothers?
ELISA
western blot
PCR
viral culture
PCR is used, uses small amount of blood and do not rely on antibody response
what is the most likely cause when a fourth gen HIV assay is pos for all the controls and samples?
improper pippetting
improper washing
improper addition of sample
improper reading
improper washing may not remove unbound Ig
what constitutes a diagnosis of viral hepatitis?
abn tests for liver enzymes
clinical signs and sympt
pos results for hepatitis markers
all of these options
all of these options
which of the following statements regarding infection with Hep D (HDV) is true?
occurs in pts with HIV infections
does not progress to chronic hepatitis
occurs in pts with HBV infection
is not spread through the blood or sexual contact
HDV can only infect if it is cross reacted/coinfected with HBV, option C
all of the following hepatitis viruses are spread through blood or blood products except?
Hepatitis A virus: HAV
HBV
HCV
HDV
HAV is spread through fecal oral route, short incubation period
which hepatitis B marker is the best indicator of early acute infections?
hep B surface ag (HBsAg)
hep B e-antigen (HBeAg)
hep B core antigen (HBcAg)
hep B surface antibody (Anti-HBs)
HBsAg is the first to appear in HBV infections
which is the first antibody detected in serum after infection with HBV?
Anti-HBs
Anti-HBc IgM
Anti-HBe
all are detectable at the same time
HBcAg is the first detectable antibody , it presists for years after infection and is found in asymptomatic carriers
which antibody persists in low level carriers of HBV?
IgM anti-HBc
IgG anti-HBc
IgM anti-HBe
IgG anti-HBs
IgG anti HBc can be detected in carriers who are negative
what is the most likely explanation when a patient has clinical signs of viral hepatitis but tests negative for HAV IgM, HBsAg, and HCV antibody?
tests were preformed improperly
pt does not have hepatitis
the patient may be in the core window
clinical eval was improper
the pt may be in the core window when surface ag and ab are undetectable
which hepatitis marker should be preformed on blood products?
HBsAg and Anti-HBc
Anti-HBs and anti-HBc
HBeAg and HBcAg
Anti-HBs and HBeAg
HBsAg and Anti-HBc blood products are early indicators
which hepatitis antibody confers immunity against reinfection with HBV?
Anti HBc IgM
Anti HBc IgG
Anti HBe
Anti HBs
D, anti HBs used as a marker for immunity after infection or vaccination
which test, other than serological markers, is most consistently elevated in viral hepatitis?
antinuclear ab
alanine aminotransferase (ALT)
absolute lymph count
lactate dehydrogenase
ALT may be increased in hepatic disease, with highest in the acute viral
if only anti-HBs is positive, which of the following can be ruled out?
HBV vaccination
distant past infection with HBV
hep B Ig injection (HBIG)
chronic HBV infection
D, persons with chronic infection show a negative anti- HBs
interpret the following results for EBV infection:
IgG and IgM antibodies to viral capsid antigen (VCA) are positive
infection in the past
infection with a mutual enhancer virus, such as HIV
current infection
impossible to interpret, need more info
current infection, igM will disappear after 4 months of infection resolving
rapid mono tests use latex particles coated with which of the following?
guinea pig ag
beef proteins
horse proteins
sheep proteins
heterophile antibody directed against beef proteins
Blood products are tested for which virus before being transfused to new borns?
EBV
Human T lymphotropic virus II (HTLV-II)
CMV
HDV
CMV can be life threatening to newborns in blood products
what is the end point for the antistreptolysin O (ASO) latex agg assay?
highest serum dilution that shows no agglut
highest serum dilution that shows agglt
lowest serum dilution that shows agglut
lowest serum dilution that shows no agglut
highets dilution showing agglutination
A streptozyme test was preformed but the result was negative, even though the pt showed clinical signs of a strep throat infection. what should be done next?
ASO or anti-deoxyrib B (anti-DNase B) test
another test but diluted
antihyaluronidase test
wait for 3 - 5 days and repeat the test
A, ASO or Anti-DNase B test
rapid assays for influenza that utilize specimens obtained from nasopharyngeal swabs detect:
IgM anti-Influenza
IgA anti-influenza
IgA - influenza antigen immune complexes
influenza nucleoprotein antigens
D, influenza nucleoprotein antigens
how can interferring cold agglut be removed from a test sample?
centrifuge the serum and remove the top layer
incubate the clot at 1deg to 4 deg for several hours then remove the serum
incubate at 56deg in water bath for 30 min
use an anticoag sample
B, incubate the clot at 1deg to 4deg for several hours then remove the serum
all tubes (dilutions) except the negative controls are positive for cold agglutinins. this indicates:
contaminanted RBCs
a rare antibody against RBC antigens
the sample was stored at 4deg prior to separating serum and cells
further serial dilution is neccessary
D, further serial dilution is neccessary
all pos cold agglut tubes remain positive after 37deg incubation except the positive control. what is the most likely explination for this situation?
high titer cold agglut
contamination of test system
antibody other than cold agglut
faulty bath water
C, antibody such as warm auto or allo antibody is present
which of the following positive antibody tests may be indicated of recent vaccination or early primary infection for rubella in patients with no clinical symptoms?
Only IgG antibodies positive
only IgM antibodies positive
Both IgM and IgG positive
fourfold rise in titer for IgG antibodies
B, only IgM
which increase in antibody titer (dilution) best indicates an acute infection?
from 1:2 to 1:8
1:4 to 1:16
1:16 to 1:256
1:64 to 1:128
C, shows a 16 fold rise in titer and is most difinitive
why is laboratory diagnosis difficult in cases of lyme disease?
clinical respose may not be apparent upon initial infection: IgM antibody may not be detected until 3 to 6wk after infection
lab tests may be designed to detect whole B. bordoferii, not flagellar antigen found in early detection
most labs are technically demanding and lack specificity
antibodies formed initially to b.bugdorferi may cross rxn in antigen tests for autoimmune diseases
A, IgM antibody may not be detected until 3-6wk after infection/bite from tick
serological tests for which disease may give a false pos result if the pt has lyme disease?
HIV
Syphillis
EBV
Hep C
B, may test pos with some treponemal antibody tests with syphillis
in monitoring HIV infections, which parameter may be expected to be the most sensitive indicator of the effectiveness of the antiretroviral treatment?
HIV antibody titer
CD4:CD8 ratio
HIV viral lode
absolute total t cell count
C, HIV viral load, will rise and fall
a renal transplant is found to have a rising creatinine level and reduce urine output. Dr orders a Urine PCR assay. when you call out which organism the dr wants to ID, you are told:
HCV
Legionella pneumophila
EBV
BK virus
BK virus can cause renal and urinary tract infections
A newborn is tested for vertically transmitted HIV. which of the following test is most useful?
HIV PCR
CD4 count
rapid HIV antibody test
HIV IgM antibody test
A neonatal test HIV PCR
which of the following fungal organisms is best diagnosed by antigen detection as opposed to antibody detection?
Histoplasma
cryptococcus
candida
aspergillus
B, cryptococcus
you are referred a papanicolaou smear specimen for you to assay to detect the presence of a virus associated with cervical cancer: you preform:
an ELISA for anti-huma simplex virus 2 antibodies
a molecular assay for HSV-2
an ELISA for HPV antibodies
a molecular assay for HPV
D a molecular assay for HPV
a pt has unexplained anemia.m Dr suspects a parvovirus B19 Infection. the parvovirus IgM test result is negative. next steps is:
the pt does not have parvovirus
a convelecent sample is recommend in 4wk to determine if fourfold titer rise has occured
a parvovirus PCR is reccom
a recent transfusion for pt anemia may have resulted the false neg result and the pt should be retested in 4 wks
C a parvovirus PCR is recommended
