A new predictive model for an improved respiratory isolation strategy in HIV-infected patients with PTB

SETTING: Luigi Sacco Hospital, Milan, Italy, 1 January 2000-31 December 2010. OBJECTIVES: To develop a predictive score for identifying human immunodeficiency virus (HIV) infected patients with pulmonary tuberculosis (PTB). DESIGN: Retrospective study based on the medical charts of HIV-infected patients admitted consecutively on presumption of PTB. Patients with culture-positive TB were included in the TB group. Culture-negative subjects formed the non-TB group. Risk factors for PTB were identified and a predictive model was developed. The diagnostic test accuracy of the derived score and that of previously developed scores were analysed. RESULTS: A total of 65 patients were included in the TB group and 505 subjects in the non-TB group. An eight-variable model (age, origin, alcohol use, respiratory rate, weight loss, haemoglobin, white blood cell count, typical chest X-ray) was derived. When compared with the different scores, this model showed the greatest area under the receiver operating characteristic curve (0.880). This score was the only one to present a negative likelihood ratio of <0.2, which is the threshold for giving strong diagnostic evidence against TB. CONCLUSIONS: This model may be useful in predicting PTB in HIV patients in low-endemic countries. A validation study is necessary.