biostats

Question 1

new treatment but not cure, how does this affect prevalence and incidence?

Answer 1

-incidence of a disease is not changed by any kind of treatment, because the disease has already developed when the treatment is started. any treatment that prolongs survival does not cure the disease will increase prevalence due to an increase in the number of afflicted (but still alive) individuals over time

Question 2

Relative risk reduction

Answer 2

RRR = 1-RR
or
RRR = absolute risk control - absolute risk treatment
/absolute risk control

Question 3

Attrition bias - selection bias

Answer 3

Loss of follow up occurs disproportionately between the exposed and unexposed groups –> attrition bias –> underestimate or overestimate the association between the exposure and the outcome

Question 4

Case series study

Answer 4

A case series study collects detailed information about people who are believed to have the same disease or condition. This information allows a clear description of the common elements that define the dieases. There is no control group of non disease people in the same. Case series studies are critical first steps to generating a profile by which a new disease can be recognized

Question 5

Lowers a tests upper limit of normal increases the tests sensitivity

Answer 5

Increased sensitivity, will decrease FN thus decrease NPV
recall NPV =TN/TN+FN

Increase sensitivity decreases a tests specificity. Decreasing a tests specificity increases the FP rate, increased FP will increase PPV

recall: ppv = TP/TP+FP

Question 6

High specificity

Answer 6

A positive test in a high specificity tests means that there is a high probability that the patient has the disease since specific tests are good at ruling in disease.