To the Editor.
—The study reported by Dr Garg and colleagues1 is not a retrospective case-control study. It is a retrospective cohort study. In a case-control study, the investigators select on presence or absence of disease, not presence or absence of exposure, as was done in this case.This letter was shown to Dr Garg, who declined to reply.—Ed.
Roseman J. Oral Contraceptives and Complications From Diabetes. JAMA. 1994;272(14):1104. doi:10.1001/jama.1994.03520140034032