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Clinical Decisionmaking

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Certain clinical factors can accurately identify patients at low risk of active TB who don't need respiratory isolation

Transmission of tuberculosis (TB) by hospitalized patients has become a major concern in the United States, especially transmission of drug-resistant strains of TB. Current guidelines recommend respiratory isolation (single-bed, negative-pressure rooms) of all patients with suspected active TB, leading to isolation of patients at low risk for TB and significantly increasing hospital costs. Fortunately, a few clinical factors can accurately identify hospitalized patients at low risk of active TB who don't need to be put in isolation, according to a study supported by the Agency for Healthcare Research and Quality (HS11393).

Juan P. Wisnivesky, M.D., M.P.H., of Mount Sinai Medical Center, and his colleagues developed a decision rule that could have avoided about one-third of the unnecessary episodes of respiratory isolation for TB at two New York city hospitals. The rule assigned point scores to six clinical factors: TB risk factors or symptoms (for example, exposure to an individual with TB, institutionalization in the preceding 3 years, weight loss of 10 percent or more of body weight, and night sweats for 3 or more weeks); positive tuberculin skin test results; shortness of breath; fever of varying degrees (with more points for higher fever); crackles on physical examination, and upper lobe disease on chest x-ray.

The investigators conducted face-to-face interviews to identify the presence of these clinical factors among 516 individuals who were isolated on admission to two New York City hospitals for clinically suspected TB. Nineteen of the patients were found to have TB (3.7 percent). The prediction rule had a sensitivity of 95 percent and a specificity of 35 percent. This means that 35 percent of the TB-negative patients in the study might not have been isolated with use of the rule. The model, however, would have missed 1 of the 19 patients who did have TB.

More details are in "Prospective validation of a prediction model for isolating inpatients with suspected pulmonary tuberculosis," by Dr. Wisnivesky, Claudia Henschke, Ph.D., M.D., Jerry Balentine, D.O., and others, in the February 28, 2005, Archives of Internal Medicine 165, pp. 453-457.

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