Question

Researchers hypothesized that Dengue fever infection is associated with an increased risk of miscarriage. At a hospital in South America, 300 women who have experienced a miscarriage in the last two years were identified. 300 women who had a viable pregnancy at the same hospital during the same time frame were identified as controls. Cases and controls were questioned about recent febrile illness and serum was collected and tested for Dengue fever IgM antibodies. Of the 300 women who experienced miscarriages, 150 had a recent diagnosis of Dengue fever (febrile illness and positive Dengue fever IgM antibody test). Of the 300 women who did not experience a miscarriage (delivered their babies at full term), 50 had a recent diagnosis of Dengue fever a. Construct a 2 x 2 table that appropriately shows the cases and controls by exposure status.

b. Calculate the odds ratio and interpret.

describe one advantage to using patients from the same hospital as controls rather than population-based controls.

Describe one strength and one weakness of using the case control study design. Annotations

Answer 1

Odds ratio = ad/bc

= 150* 250 / 150 * 50

= 5

So the mothers who had miscarriages were 5 times more likely to have suffered from dengue fever than those who hadn't.

The advantage of using the same hospital patients as controls is that the patients are attended by the same doctors and have availed the same facilities.If population based controls had been taken some of then may have got better or worse facilities.

Strength is that it is not time consuming and inexpensive.

Weakness is that recall bias may occur because cases remember history better than controls.

Miscariage 450 150 Devgue 150 250