Tuberculosis among Aboriginal and Nonaboriginal Persons in British Columbia

Abstract

OBJECTIVE:To compare cases of tuberculosis (TB) diagnosed among aboriginal persons with a random sample of nonaboriginal persons diagnosed with TB, and evaluate the trends in rates of disease between both groups during the same period.DESIGN:A case-control study.SETTING:A provincial TB control program.PATIENTS AND METHODS:All patients with TB diagnosed among aboriginal persons in British Columbia between 1992 and 1996 were compared with control patients diagnosed during the same period. For each patient a control patient was identified.INTERVENTION:The demographic details, type of disease, bacteriology, risk factors for TB, therapy received as well as mode of administration were documented. The number of contacts identified for each patient as well as the number of patients completing chemoprophylaxis were identified. The rates of disease during the same period were also documented.RESULTS:During the study, 202 patients with TB were diagnosed among aboriginal persons and 201 controls were chosen. Apart from age at diagnosis (35.1±20 years versus 45.7±19.7), differences in the prevalence of lymphadenopathy (5.9% versus 16.4%, P=0.0008) and pleural disease (21.3% versus 16.4%, P=0.00008), there were no differences in presentation between aboriginal and nonaboriginal people. Aboriginal people were more likely to have a  history of contact with a patient with TB (53% versus 17.9%, PÃ0.05), to have received directly observed therapy (55% versus 33.8%, P=0.00002) and to have contacts who were purified protein derivative (PPD) positive (4±9 versus 2±3, P=0.002). These contacts were more likely to start isoniazid (2±3 versus 1±1, P=0.002). Overall, there was a significant decline in rates of TB among aboriginal persons compared with the general population, but there was a small increase in rates among all subjects in the final year of the study.CONCLUSIONS:In the present study, significant variations in rates of TB among different population groups in British Columbia were found. During the study period, there was a greater decline in the rates of TB among aboriginal persons. A greater use of directly observed therapy and greater use of chemoprophylaxis occurred among aboriginal persons, which may have contributed to this decline, or alternatively, it simply reflects the natural evolution of the TB epidemic.