Evaluation of clinical parameters to predict Mycobacterium tuberculosis ininpatients

Background: Respiratory isolation has been recommended for all patients wit h suspected tuberculosis (TB) to avoid transmission to other patients and h ealth care personnel. In implementing these guidelines, patients with and w ithout TB are frequently isolated, significantly increasing hospital costs. The objective of this study was to derive a clinical rule to predict the n eed for respiratory isolation of patients with suspected TB. Methods: To identify potential predictors of the need for isolation, 56 inp atients with sputum cultures positive for TB were retrospectively compared with 56 controls who were isolated on admission to the hospital based on cl inically suspected TB but whose sputum cultures tested negative for TB. Var iables analyzed included TB risk factors, clinical symptoms, and findings f rom physical examination and chest radiography. Results: Multivariate analysis revealed that the following factors were sig nificantly associated with a culture positive for TB: presence of TB risk f actors or symptoms (odds ratio [OR],7.9 [95% confidence interval (CI),4.4-2 4.2]), a positive purified protein derivative tuberculin test result (OR, 1 3.2 [95% CI, 4.4-40.7]), high temperature (OR, 2.8 [95% CI, 1.1-8.3]), and upper-lobe disease on chest radiograph (OR, 14.6 [95% CI, 3.7-57.5]). Short ness of breath (OR, 0.2 [95% CI, 0.12-0.53]) and crackles noted during the physical examination (OR, 0.29 [95% CI, 0.15-0.57]) were negative predictor s of TB. A scoring system was developed using these variables. A patient's total score of 1 or higher indicated the need for respiratory isolation, ac curately predicting a culture positive for TB (98% sensitivity [95% CI, 95% -100%]; 46% specificity [95% Ci, 33%-59%]). Conclusion: Among inpatients with suspected active pulmonary TB, a predicti on rule based on clinical and chest radiographic findings accurately identi fied patients requiring respiratory isolation.