A small group of individuals was followed prospectively from January 1, 1975, to
ID: 3226878 • Letter: A
Question
A small group of individuals was followed prospectively from January 1, 1975, to monitor the incidence of adverse reactions to a drug. The results were: (6 pts)
Patient Date (1975) Outcome Days
1 2/1 no reaction _______
2 2/1 no reaction _______
3 1/9 adverse reaction _______
4 2/1 no reaction _______
5 1/13 dropped from study _______
6 1/15 adverse reaction _______
7 1/18 adverse reaction _______
8 2/1 no reaction _______
9 1/25 dropped from the study _______
10 2/1 no reaction _______
Total _______ person-days
Assuming the two subjects that had dropped out of the study did not have a reaction:
What is the person-time or person-days at risk for this study group?
b. What is the incidence rate of adverse reactions?
c. What is the incidence density for adverse reactions for this drug?
Explanation / Answer
Patient 3, 6 & 7 suffer from adverse recaction for 9 days, 15 days and 18 days respectively.
Therefore Person - time at risk = 9+15+18 days = 42 days
b) The formula incidence rate = No. of new cases during a period of time / person - time at risk= 3/42 = 0.0714 persons a day. By multiplying the numerator and denominator with 100, we get 7.14 ( approx 7 persons ) per hundred.
c) The formula incidence density = (No.of new cases of a disease during a specified period / Sum of length of time at risk for each individual in the population)
Incidence density = 3/42=0.0714
Thank you
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