Use of a disposable water filter for prevention of false-positive results due to nontuberculosis mycobacteria in a clinical laboratory performing routine acid-fast staining for tuberculosis.

A point-of-use 0.2-microm filter was evaluated for elimination of nontuberculosis mycobacteria in laboratory water to reduce false-positive acid-fast bacillus staining results. Use of the point-of-use filter can significantly reduce the false-positive rate to 1.2% compared to samples treated with tap water (10.7%) and deionized water (8.7%).