Ultrasonographic Measurement of the Tuberculin Skin Test

Purpose: The aim of this study is to define the ultrasonographic (US) findings of the tuberculin skin test and to compare them with the results of the manual reading. Methods: Sixty-eight consecutive patients were enrolled in this study. Tuberculin skin test was applied to the left forearm. Two independent readers measuered the induration at 24, 48 and 72 hours. High-resolution US examinations were performed at the same data points. Comparison was made using paired-samples t test and analysis of variance with kappa. A difference with P < 0.05 was considered significant. Results: Twenty-two patients had no induration measurable either manually or by US at 72 hours. At 24, 48, and 72 hours, 34, 28, and 26 patients were reported with zero induration by the first reader and 36, 27, and 26 patients had zero induration as reported the second reader. On US, 25 patients showed zero mm reaction at 24 hours. Two patients that had zero mm induration at both 24 and 48 hours showed 7.4 and 8.1 mm indurations at 72 hours. Conclusions: The TST can be simply and objectively measured in patients who should start on tuberculosis treatment immediately and whose tuberculin skin test results around cutoff points.