A clinical trial for a new fertility treatment was provided to 1000 women for a

Question

A clinical trial for a new fertility treatment was provided to 1000 women for a 5 year study period. Investigators were interested in noting when women became pregnant for the first time (subsequent pregnancies were not an outcome of interest, only first pregnancies). Every year, they came in for a follow-up visit and were asked if they were pregnant (outcome). Project coordinators also took note at these visits if any of the women had been loss-to-follow-up. Of the 1000 women at the beginning of the study, 203 became pregnant by the first visit. During visits 2 and 3, an additional 112 women became pregnant by each visit. Another 65 women became pregnant by the 4th visit, and a final 27 women became pregnant by the last visit. There were also 8 women lost to follow-up at visit 1, 6 women LTFU in visit 2, 12 women LTFU in visit 3, and 17 women LTFU in visit 4. What was the incidence density of pregnancies for the study, in 100 person-years? Select one: a. 14.9 b. 12.3 c. 9.6 d. 33.1

Explanation / Answer

Incidence density: = no. of cases of pregnant women/ length of time for each individual.

this length of time for each individual is known as person year

for 1st year

incidence density= 203/1000*1

for 100 person year = 20.3

for 2nd and 3rd year

incidence density = 112/1000*3

for 100 person years = 3.7

for fourth year

incidence density = 65/1000*4

for 100 person years = 1.62

for 5th year

incidence density = 27/1000*5

= 0.54

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