Abstract: Objective To develop a diagnostic scoring model of smear negative active pulmonary tuberculosis(TB). Methods A hospita1-based case-control study was undertaken among a cohort comprised of 119 smear negative active pulmonary TB patients and 79 patients with other respiratory diseases who were hospitalized between Jun,2005 and Dec,2006.All patients were recorded with their symptoms and laboratory examinations.Risk factors and symptoms described in the documents were compared between these two groups.Significant and borderline risk factors and symptoms were selected to undergo multivariate logistic regression.A high risk scoring model was constructed according to the weighted numerical scores of every variable. Results The average score was significantly higher for the smear negative active pulmonary TB patients than for the control patients(mean 21.3±3.0vs15.3±3.4,P<0.01).With a cut-off value of 19 points,the sensitivity and specificity of the scoring model were 84.9%(101/119) and 81.0%(64/79),respectively. Conclusion The diagnostic scoring model provides a simple and feasible way to detect earlier smear negative active pulmonary TB patients in hospitals at all levels,especially for hospitals at low level without sputum culture facility.This screening strategy needs to be demonstrated furtherly.

Key words: pulmonary tuberculosis/diagnosis, case-control studies