[Two selected commercially based nucleic acid amplification tests for the diagnosis of tuberculosis]

Abstract

Introduction: This is the retrospective study on diagnostic effectiveness of two nucleic acid amplification tests: AMPLICOR Mycobacterium tuberculosis (MTB) and Xpert MTB/RIF. The first one was included into diagnostic procedure for tuberculosis from 1999 to 2009 and the second one has been used from November 2009.

Material and methods: Study groups comprised 1875 samples for AMPLICOR MTB (104 were inhibited), and 213 samples for Xpert MTB/RIF.

Results: The assay sensitivity was 81.9% for AMPLICOR MTB and 81.8% for Xpert MTB/RIF, and specificity was 97.2% and 99.5% respectively, as compared to the culture on Loewenstein-Jensen medium. However, sensitivity of each test correlated with Ziehl-Neelsen staining. For AFB+ samples, assay sensitivity was 97.8% for AMPLICOR MTB and 100% for Xpert MTB/RIF and for AFB- samples it was 58.1% and 50% respectively.

Conclusions: The reported results show a high diagnostic usefulness of Xpert MTB/RIF test for samples, which are positive for Ziehl-Neelsen staining.