Specimen Dilution Improves Sensitivity of the Amplified Mycobacterium tuberculosisDirect Test for Smear Microscopy-Positive Respiratory Specimens

ABSTRACTSpecimen dilution has been proposed as a strategy to minimize amplified Mycobacterium tuberculosisdirect (MTD) test inhibition (N. Pollock, J. Westerling, and A. Sloutsky, Am. J. Clin. Pathol. 126:142-147, 2006; A. Sloutsky, L. L. Han, and B. G. Werner, J. Clin. Microbiol. 42:1547-1551, 2004). We evaluated the impact of respiratory specimen dilution on MTD test accuracy in a public health laboratory. The difference in MTD test sensitivity between the dilution and conventional methods was 15.9% (P= 0.001) for smear microscopy-positive specimens and -3.6% (P= 0.38) for smear microscopy-negative specimens.