The influence of epidemiologic factors on drug resistance rates in tuberculosis

We evaluated the relationship between drug resistance rates and various epidemiologic factors in 376 hospitalized adults with culture-proved tuberculosis, studying 356 cases prospectively, 20 retrospectively. The patient was interviewed in 332 cases. Patients born in the United States, Canada, or Europe were considered to belong to Group I. Group II consisted of patients born in Latin America, Asia, or Africa and was subdivided into II(a), immigrants living in the United States for more than 10 yr, and II(b), those living here less than 10 yr. Of the 70 patients who had received antituberculosis therapy in the past, resistance rates in Group II (n = 31) to isoniazid (INH), streptomycin (SM), and rifampin (RIF) were extremely high: 39, 29, and 19%, respectively. Nineteen percent showed resistance to both INH and RIF. In Group I (n = 39), INH, SM, and RIF resistance rates were 8, 5, and 8%, respectively. Of 283 patients who gave no history of prior antituberculosis therapy, those in Groups I and II(a) (n = 170) rarely showed INH or RIF resistance. Among recent immigrants from Latin America or Asia [Group II(b), n = 113], 11.5% showed INH or RIF resistance and 14% harbored organisms resistant to SM. Thus, the 3 variables that are most helpful in estimating the likelihood of drug resistance are a history of prior antituberculosis therapy, country of origin, and duration of residence in the United States.