Objective: Patients admitted to the pulmonary isolation service to rule out tuberculosis (TB) were prospectively studied to identify predictors of smear-positive TB.
Methods: History of symptoms--cough, sputum production, fever, weight loss, night sweats, hemoptysis, anorexia, and dyspnea; medical history--TB, tuberculin skin test (TST) status, TB contact; and social factors--crowding index, history of incarceration or living in a shelter, and employment status were obtained in face-to-face interviews. Chest x-rays (CXRs) were scored as typical, atypical, or negative. Serial morning sputa were collected.
Results: Complete data were collected on 101 patients; 44 had pulmonary TB; 33 patients were smear positive and considered infectious; 11 patients were smear negative but culture positive. There was no difference between TB and non-TB patients with respect to HIV status and social risk factors. Significant differences were found between patients who were smear positive for TB and smear negative with respect to cough, sputum, and typical CXR (79%, 76%, and 79% sensitivity, respectively). Eleven patients without TB had an atypical CXR and denied cough, sputum, and weight loss. Only one patient with TB presented this way.
Conclusion: Even in high-risk populations, symptoms of cough, sputum, weight loss for less than 2 weeks, and the absence of a typical CXR are strong negative predictors for TB.