01/27/15 - Study Types, Statistics & Diagnostic Tests Flashcards
A study splits a student population by their grade point averages into three groups, and then watches to see who develops a related syndrome. What type of study is this?
A. Case-control study
B. Clinical treatment trial
C. Cross-sectional study
D. Prospective cohort study
E. Retrospective cohort study
D. Prospective cohort study
No treatment is being applied, and the students were enrolled prior to the development of the syndrome.
Under what circumstances is the prevalence of a disease much higher than its incidence?
A. If the patients recover from the disease in 1 day
B. If the disease is fatal in <4 hours
C. If the disease lasts for more than 1 year
D. If having the disease confers benefits to the sufferer
C. If the disease lasts for more than 1 year
The incidence of a disease is the number of cases in a given time interval, generally 1 year. The prevalence is the incidence rate times the disease duration (ie How many people in the population currently suffer).
A. (1x38)/(159x2) = 0.119
B. [1/(1+159)]/[2/(2+38)] = 0.125
C. Cannot be calculated
B. [1/(1+159)]/[2/(2+38)] = 0.125
Relative risk is the probability of getting a disease following an exposure divided by the probability of disease in the unexposed group.
Which of the following is true of a retrospective cohort study?
A. If relative risk is <1, an exposure is actually protective.
B. Number needed to harm is equal to the number of needed exposures for one person to develop disease.
C. When the prevalence of disease is low, the odds ratio approximates the relative risk.
D. All of the above.
D. All of the above
A retrospective cohort study reports that an exposure has a relative risk of developing a certain disease of 2.7; if true, what does this signify?
A. The incidence rate of the disease is 2.7 times greater in the exposed than the non-exposed
B. The odds of the disease developing is 2.7 times higher in those not exposed
C. It took 2.7 times longer for the non-exposed to develop the disease
A. The incidence rate of the disease is 2.7 times greater in the exposed than the non-exposed
Which of the following study types and objectives is tacitly matched?
A. Case series to report prevalence of a disease
B. Cross-sectional study to publish the causes of a disease
C. Case-control study because a disease is rare
D. Crossover study because the disease is irreversible
C. Case-control study because a disease is rare
A. (13x206)/(1x190) = 14.1
B. (13/203)/(1/207) = 13.3
C. 13/13+1 = 0.93
D. 206/206+190 = 0.52
A. (13x206)/(1x190) = 14.1
Note: ODDS ratio. Weird way to calculate it though.
Which of the following statements are accurate with regard to disease prevention?
A. Primary prevention prevents complication of a disease.
B. Secondary prevention strategies take less than a minute to implement.
C. Diagnostic tests used to screen for secondary prevention should have high sensitivity.
D. Tertiary disease prevention reduces the spread of a disease from one person to another.
C. Diagnostic tests used to screen for secondary prevention should have high sensitivity.
Primary prevention prevents the initial development of disease. Secondary refers to early detection to prevent morbidity & mortality. Tertiary prevention reduces the severity of that morbidity.
A test designed to screen for a disease examines the level of a certain salivary hormone. Why may this not have 100% specificity and 100% sensitivity?
A. An unrelated process may elevate (or decrease) the level of this hormone
B. A student with the disease may not be able to provide a saliva sample
C. The normal level of salivary hormone is a bell-curve, so some will naturally exceed the levels required (false positive)
D. All of the above.
D. All of the above
A test screens for salivary hormone elevation in a certain disease. Which of the following could cause a false positive?
A. Elevation in response to non-disease factors
B. Improper test administration
C. Instrument miscalibration
D. All of the above
D. All of the above
What is the prevalence?
A. 2/(2+1) = 0.667
B. 90/(90+7) = 0.927
C. 2/(2+7) = 0.22
D. 90/(90+1) = 0.989
E. 2+1/(1+2+7+90) = 0.03
E. 2+1/(1+2+7+90) = 0.03
Prevalence = Number afflicted compared to total population
What is the sensitivity of the test?
A. 2/(2+1) = 0.667
B. 90/(90+7) = 0.927
C. 2/(2+7) = 0.22
D. 90/(90+1) = 0.989
E. 2+1/(1+2+7+90) = 0.03
A. 2/(2+1) = 0.667
Sensitivity = “If you have the disease, how likely are you to test positive”
What is the specificity of the test?
A. 2/(2+1) = 0.667
B. 90/(90+7) = 0.927
C. 2/(2+7) = 0.22
D. 90/(90+1) = 0.989
E. 2+1/(1+2+7+90) = 0.03
B. 90/(90+7) = 0.927
Specificity = “If you don’t have the disease, how likely are you to test negative”
What is the PPV of the test?
A. 2/(2+1) = 0.667
B. 90/(90+7) = 0.927
C. 2/(2+7) = 0.22
D. 90/(90+1) = 0.989
E. 2+1/(1+2+7+90) = 0.03
C. 2/(2+7) = 0.22
PPV = “If you test positive, how likely are you to have the disease”
What is the NPV of the test?
A. 2/(2+1) = 0.667
B. 90/(90+7) = 0.927
C. 2/(2+7) = 0.22
D. 90/(90+1) = 0.989
E. 2+1/(1+2+7+90) = 0.03
D. 90/(90+1) = 0.989
NPV = “If you test negative, how likely are you to not have the disease”
