Extra-pulmonary tuberculosis: a high frequency in the absence of HIV infection

Setting: A tuberculosis centre for the diagnosis, management and control of all tuberculosis in a region in Western Canada with a population of approximately 1.2 million.

Objective: To measure the proportion of cases of extra-pulmonary tuberculosis in relation to country of birth, age and gender of the subject.

Design: A prospective study of all patients with tuberculosis diagnosed during a five-year period, 1990–1994. Information relating to age, country of birth and details relating to their tuberculosis were all gathered and stored on a computerised tuberculosis register.

Results: A total of 351 patients with tuberculosis were diagnosed during the five-year period. Extra-pulmonary tuberculosis, defined as disease which, with the exception of miliary tuberculosis, was not associated with lung involvement, was diagnosed in 160 (46%) of the patients. The incidence of extra-pulmonary tuberculosis, especially lymph node disease, tended to be higher in younger patients but was significantly higher in immigrants from Asia in whom the majority (61%) presented with extra-pulmonary disease. Less than 2% of the subjects in this study were infected with the human immunodeficiency virus (HIV).

Conclusion: Extra-pulmonary tuberculosis accounted for approximately half of the cases of tuberculosis in a western Canadian tuberculosis centre. This high frequency of extra-pulmonary disease was not attributable to HIV infection.