Drug-Resistant Tuberculosis in New York City

To the Editor: In their article on drug-resistant tuberculosis in New York City, Frieden et al. (Feb. 25 issue) 1 demonstrate that cases of such disease are cause for serious concern. I wonder, however, whether the authors studied a representative population of patients. The survey population consisted of patients who had a positive culture for Mycobacterium tuberculosis during April 1991. Such a survey represents neither incidence nor prevalence. Like autopsy studies, laboratory-based surveys are subject to selection bias and may oversample patients with severe morbidity. Patients with treatment failure, relapse, or drug resistance are more likely to undergo serial drug-susceptibility testing . . .