Diagnostic strategy for pulmonary tuberculosis in a low-incidence country: results of chest X-ray and sputum cultured for Mycobacterium tuberculosis.

The referral centre of tuberculosis in the municipality of Copenhagen, Denmark was the setting for this study, which aimed to assess the diagnostic strategy (chest X-ray and clinical mycobacteriology) in pulmonary tuberculosis. Patient records and chest X-rays were examined for all patients who had sputum or gastric lavage examined for Mycobacterium tuberculosis (Mtb) from 1 January 1992 to 30 April 1994. All chest X-rays were re-evaluated by a trained lung specialist, who did not know the results of sputum culture. Evaluation was referred to one of seven X-ray categories, and compared to the results of culture. Culture of sputum or gastric lavage were positive for Mtb in 54 (14%) of 392 patients; in 61% of 59 patients with X-ray changes thought to be due to tuberculosis (TB); in 20% of 51 patients with X-ray changes compatible with TB; in 14% of 35 patients with previous TB and radiographically active TB; in 2% of 103 patients with previous TB, but not radiographically active TB; in 1% of 112 patients with X-ray changes thought to be due to other disease; and none out of 32 patients with normal X-ray. Even in this highly selected material, it is relatively expensive to find the very few cases of active TB in patients with chest X-ray changes not suspected to be due to TB. It is recommended that: (1) examination of sputum for Mtb should always be preceded by X-ray of the chest in a low-prevalence country; (2) routine culture of sputum for Mtb is restricted to patients with X-ray changes typical or compatible with active TB; and (3) exceptions to this general rule should be made on the basis of the individual's clinical history.