Detection of pulmonary tuberculosis in patients with a normal chest radiograph

Objectives: To describe the early symptoms of pulmonary tuberculosis (TB) w hen the chest radiograph (CXR) is normal. Setting: Centralized, provincial TB control program. Subjects: Twenty-five patients with culture-positive pulmonary TB and a nor mal CXR were identified from a review of 518 consecutive patients with cult ure-positive pulmonary TB in the province of Saskatchewan from January 1, 1 988 to March 31, 1997. Patients with abnormal CXRs at the time of diagnosis were excluded from the analysis. Results: Twenty-three of the 25 patients (92%) were symptomatic at the time of diagnosis, with cough/sputum (76%) being reported most commonly. Eleven patients were identified because of contact tracing from cases of infectio us pulmonary TB, while the other 14 patients were identified because of an investigation of symptoms. Twenty-four patients (96%) exhibited one or more symptoms of cough for > 1 month, fever for > 1 week, or skin-test conversi on after contact with infectious TB, The sputum smear of only one patient w as positive. Two patients were pregnant at the time of diagnosis, one patie nt was HIV-positive, and one patient demonstrated isoniazid-resistant organ isms on sensitivity testing. Five patients were diagnosed as having primary TB associated with Mantoux skin-test conversion. The incidence of culture- positive pulmonary TB with a normal chest radiograph was < 1% in the period from 1988 to 1989 and steadily increased to 10% in the period from 1996 to 1997. Conclusions: Culture-positive pulmonary TB with a normal CXR is not uncommo n, and the incidence of this presentation is increasing, Patients with this presentation of TB are typically symptomatic and/or are detected by contac t tracing to infectious cases of pulmonary TB. The results suggest that pat ients presenting with a cough for > 1 month, with a fever for > 1 week, or with documented skin-test conversion < 2 years after known exposure to infe ctious TB should have sputum submitted for a Mycobacterium tuberculosis sme ar and culture despite a normal CXR.