Extent of pulmonary tuberculosis in patients diagnosed by active compared to passive case finding

To compare the extent of pulmonary tuberculosis amongst patients detected by screening (active case finding) with that in patients detected by symptoms (passive case finding), and to identify early symptoms of pulmonary tuberculosis.

In this cross-sectional study, Tuberculosis Control Program records were reviewed for method of detection and extent of disease in Canadian Plains Aborigines between 1 January 1991 and 30 June 1999.

Among 903 cases, method of detection was active in 450 (49.8%) and passive in 453 (50.2%). Cough and fever were the most common symptoms in both methods of detection, and were significantly more frequent in passive detection (P < 0.05). Cough was present in 59% and fever in 19% of actively detected cases compared to 84% and 47%, respectively, of passively detected cases. Age was significantly different between the two methods of detection. Hemoptysis, weight loss and method of detection were associated with increased risk of infectiousness among those < or = 19 years, while cough, hemoptysis and weight loss were associated among those >19 years.

Method of detection rather than age contributed to infectiousness in children and adolescents. Daily cough for more than 1 month and unexplained fever for more than 1 week should raise the suspicion for TB.