A total of 516 patients were enrolled in this study. Of the 516, 19 (3.7%) were found to have culture-proven pulmonary TB. Univariate analyses showed that history of positive PPD, higher (98% vs. 95%) oxygen saturation, upper-lobe consolidation (not upper lobe cavity), and lymphadenopathy (hilar, mediastinal, or paratracheal) were all associated with the presence of pulmonary TB. Shortness of breath was associated with the absence of TB. A total score of 1 or higher in the prediction rule had a sensitivity of 95% for pulmonary TB, and score of less than 1 had a specificity of 35%. The investigators estimated a prevalence of 3.7%, thereby yielding a positive predictive value of 9.6% but a negative predictive value of 99.7%. They estimated that 35% of patients isolated would not have been with this prediction rule.
Though validated scientifically, this tool still has a false-negative rate of 5%. In a less endemic area, the false-negative rate would be correspondingly lower and thus more acceptable from a public health perspective. This is one step closer to a balance of optimal bed utilization and reasoned clinical assessment.