Comparison of Xpert MTB/RIF Assay and the Conventional Sputum Microscopy in Detecting Mycobacterium tuberculosis in Northern Thailand

Table 2

Two by two contingency tables showing true positive, false positive, true negative, and false negative comparing Xpert assay (a) and sputum acid-fast smear (b) with the reference standard.

(a)

	Positive Xpert assay	Negative Xpert assay	Total
Culture grew M. tuberculosis	41	2	43
Culture grew NTM or no growth	9	57	66
Total	50	59	109

NTM: nontuberculous mycobacteria, 4 in positive Xpert assay and 6 in negative Xpert assay.

(b)

	Positive sputum acid-fast smear	Negative sputum acid-fast smear	Total
Culture grew; M. tuberculosis	26	17	43
Culture grew NTM or no growth	1	65	66
Total	27	82	109

NTM: nontuberculous mycobacteria, 10 in negative sputum acid-fast smear.