Prevalence and clinical predictors of pulmonary tuberculosis among isolated inpatients: a prospective study

Guidelines help to prevent the transmission of Mycobacterium tuberculosis in healthcare settings, but may also result in the unnecessary isolation of many patients. We performed a prospective study to assess the prevalence and identify clinical predictors of culture-proven tuberculosis among inpatients isolated for suspected pulmonary tuberculosis (PTB) at our hospital. We also wished to validate a pre-existing clinical decision rule to improve our isolation policy. From August 2005 to January 2007, 134 patients isolated on admission to the ward for suspicion of PTB were prospectively enrolled. The admitting team made the decision to isolate patients on the basis of clinical and radiological findings, without the use of the clinical decision rule, and graded the overall suspicion of PTB. Twenty-six of the 134 isolated patients had PTB (prevalence: 19.4%), as well as one patient not isolated at admission. Univariate analysis revealed that PTB was significantly associated with young age, lack of human immunodeficiency virus (HIV) infection, weight loss, night sweats, fever, upper lobe disease and, especially, cavitary lesions on chest X-ray (adjusted OR 25.4, p <0.0001). Low suspicion of PTB by the admitting team and low clinical decision rule score had negative predictive values of 98.5% and 95.8% for PTB, respectively. Use of the clinical decision rule in addition to the team assessment would have led to the isolation of the patient with PTB not isolated on admission, and avoided 16 (14.8%) unnecessary isolations. In conclusion, the prevalence of PTB among isolated inpatients was high, and the use of a clinical decision rule in addition to clinical impression might improve isolation decisions.