Drug-resistant tuberculosis in a southern California hospital. Trends from 1969 to 1984

Resistance to one or more antituberculosis drugs was found in 98 of 281 (35%) patients hospitalized at Harbor-UCLA with culture-positive tuberculosis between 1980 and 1984. Resistance to antituberculosis drugs occurred in 23% of patients who had not been previously treated, whereas previously treated patients had a 59% rate of resistance. The overall rates of drug resistance had not significantly changed from prior studies at this hospital. Drug resistance was also found in patients with extrapulmonary disease, but tended to be less frequent than in patients with pulmonary disease. An analysis of risk factors for drug resistance rates revealed no significant differences between Hispanics, blacks, Caucasians, and Asians. Age was not found to be a significant factor to predict resistance rates. Resistance rates were higher if cavitary disease was present on radiographs. Furthermore, cavitary disease seems to be additive to prior antituberculosis treatment as a risk factor for drug resistance. Patients who had both of these risk factors present had 71% incidence of drug resistance rates.