Re-evaluation of sputum staining for the diagnosis of pulmonary tuberculosis

Data were collected at 2 teaching institutions, University Hospital, University of Michigan (UMH) and University of California at Los Angeles (UCLA) Hospital, to evaluate the usefulness of the auramine-rhodamine fluorochrome stain in the diagnosis of pulmonary tuberculosis in hospitalized patients. The patients studied had received no prior therapy, and their sputum specimens were positive for a pathogenic Mycobacterium by microscopy or culture or both. The true-positive smear rate was 0.88 at UMH and 0.83 at UCLA; the relative false-positive smear rate was 0.12 at UMH and 0.17 at UCLA. The sensitivities at UMH and UCLA were 0.78 and 0.51, respectively, and the specificity was greater than 0.99 at both. The data suggest that sputum stained by the fluorochrome method is useful and reliable for the diagnosis of pulmonary tuberculosis, because the false-positive rates are acceptably low in hospitalized patients.