The impact of repeated NALC/NaOH- decontamination on the performance of Xpert MTB/RIF assay

Abstract

The Xpert MTB/RIF assay detects Mycobacterium tuberculosis in unprocessed or NALC/NaOH- decontaminated sputum. The effect of repeated NALC/NaOH-decontamination on several Xpert performance parameters was assessed in this study. A second NALC/NaOH-decontamination had no effect on the binary Xpert-outcome but increased the value for the quantitative readout (C_Tmin). Repeated decontamination was not associated with PCR-inhibition or invalid results. The C_Tmin of M.tb positive samples was higher in inhibited Xpert runs. Our data indicate that NALC/NaOH-decontamination has an effect on the performance of the Xpert assay, and that C_Tmin readouts of decontaminated sputum samples should be interpreted with caution.

Trial registration: ClinicalTrials.gov NCT00864383.

Keywords: Quantitative PCR; Sputum processing; Xpert-inhibition; Xpert-performance.