Preventive therapy for tuberculosis in Western Australia.

Setting: State Tuberculosis Control Programme, Western Australia.
Objective: To ascertain baseline information, applicability and efficacy of preventive therapy for tuberculosis (TB) under indirectly supervised treatment in Western Australia.
Design: Retrospective analyses of records of persons with TB infection who were prescribed preventive therapy for the period 1993-1996 inclusive, using simple descriptive statistics.
Results: Preventive therapy was given to 411 persons after screening for TB due to on-arrival migrant surveillance (269), contact tracing (59), tuberculin surveys (59) and other reasons (24). Six-month isoniazid monotherapy (HMT) was prescribed for 403 and multidrug regimens for the remaining eight. Excepting 34 whose compliance was unknown, varying degrees of treatment non-adherence were found in 90 (24%) of the remaining 369 persons given HMT, including 36 (10%) with under five months of total medication. Minor adverse drug effects occurred in 32 (9%) subjects and contributed to the non-adherence in 23 of these. One person has since developed active TB.
Conclusions: Preventive therapy in Western Australia conformed to generally accepted guidelines. Varying degrees of non-adherence to HMT occurred in 24% of persons, but 90% completed adequate therapy under indirect supervision. Non-adherence is significantly related to adverse drug effects.