G18.3

Cytomegalovirus infection and coronary restenosis. Table 18.8 contains results from the cytomegalovirus (CMV) and restenosis study considered as an illustrative example of naturalistic samples in section 18.1. The occurrence of coronary restenosis within 6 months of surgery is cross tabulated according to CMV status.

Table 18.8:

	Restenosed	Did not restenose	(Total)
CMV+	21	28	49
CMV-	2	24	26
(Total)	23	52	75

1. Calculate the prevalence of CMV in the patient population as a whole.
2. Calculate the incidence of restenosis in the patient population as a whole.
3. What percent of CMV+ patients experienced restenosis? What percent of CMV- patients restenosed? What type of conditional percents are these?
4. Calculate the relative risk of restenosis associated with CMV.
5. Calculate the odds ratio of restenosis associated with CMV exposure. Why is this OR larger than the RR calculated in (d)?