Early identification and isolation of inpatients at high risk for tuberculosis

Although it has been recommended that all patients suspected of having tuberculosis be placed in isolation, the feasibility of this recommendation has not been investigated.

Forty-three patients with pulmonary tuberculosis were compared with 43 control subjects. The control subjects had submitted expectorated sputum, and were culture negative. Variables included chest roentgenogram results, and risk factors used by the Centers for Disease Control and Prevention (Atlanta, Ga) to identify patients at increased risk for tuberculosis.

Potential control subjects outnumbered patients by 92:1. Although a positive tuberculin skin test, foreign birth, and weight loss were more common in the patients, 86% of the control subjects had at least one risk factor for tuberculosis. Chest roentgenograms consistent with tuberculosis (cavities or apical or nodular infiltrates) were found in 86% of the patients, but in only 16% of the control subjects (odds ratio, 31.7; 95% confidence interval, 8.6 to 127.7). The positive and negative predictive values of a consistent chest roentgenogram were 6% and 99.8%, respectively. The sensitivity of testing a single sputum specimen was 81%, yet almost half of the control subjects had only one specimen submitted. Of the inpatient cases, 58% were not identified on admission with a median delay of 13 days before isolation.

Isolating all the patients at the time sputum is submitted for testing is not practical and would have resulted in a 92-fold overuse of isolation rooms. The chest roentgenogram was of great value in identifying patients who did not require isolation and was the best available means of identifying inpatients at high risk for active pulmonary tuberculosis.