[Tuberculosis therapy in canton Zurich 1991-1993: what are the causes for recurrence and therapy failure?].

A retrospective cohort analysis of TB patients in the Canton of Zurich was undertaken to evaluate the effectiveness of a primary care physician-based tuberculosis treatment program in the Canton of Zurich (1991-1993) and compare it with treatment results in selected patient groups in controlled prospective studies. Of the 440 TB patients (62.5% men, 51% foreign born, 9.6% with HIV infection) 65% were initially hospitalized. The total treatment duration was 210 (+/-108) days on average. Only 75% of the patients who were treated by a total of 410 hospital and primary care physicians were treated with standard regimens according to guidelines. 3 patients were treatment failures; 13 relapsed (5.1% of the 257 patients reexamined in 1995). Possible causes for relapses were poor patient compliance due to alcoholism, homelessness, drug addiction, psychiatric disorders; prescription errors with inadequate treatment durations, concurrent AIDS disease, or use of a three-drug combination despite primary drug resistance. In 4 of the relapse patients and in all 3 treatment failures, secondary drug resistance developed under treatment. 5 of these 7 patients were treated initially only with a fixed three-drug regimen (Rifater). The relatively high INH resistance rate (8.6%) and relapse rate (5.1%) in the Canton of Zurich renders the use of a four-drug combination therapy necessary. In the outpatient maintenance phase, more effort must be devoted to ensuring patient compliance and adherence to a proper treatment duration. This should be documented by a standardized questionnaire at 6 or 12 months after initiation of therapy. In high risk patients in particular, home care visits by a TB nurse in addition to consultations by primary care physicians are necessary to ensure directly observed therapy (DOT) in order to prevent relapses and treatment failures.