The Use of Selected Commercial Molecular Assays for the Microbiological Diagnosis of Tuberculosis

Introduction: We performed a retrospective assessment of the AMPLICOR Mycobacterium tuberculosis (MTB) assay for the molecular diagnosis of tuberculosis based on our own determinations between 1999 and 2009 and a preliminary assessment of the Xpert MTB/RIF system, which we are currently using. Materials and methods: The study groups comprised 1875 samples (including 104 inhibited samples) and 213 samples, respectively. Results: The sensitivities of the AMPLICOR MTB and the Xpert MTB/RIF assays were 81.9% and 81.8%, respectively, and their specificities were 97.2% and 99.5%, respectively, versus culture on Loewenstein-Jensen medium. Both assays showed a considerable difference in sensitivity depending on whether the test samples were smear-positive (AFB+) or smearnegative (AFB–). The sensitivities of the AMPLICOR MTB and the Xpert MTB/RIF assays were 97.8% and 100.0%, respectively, for AFB+ samples and 58.1% and 50.0%, respectively, for AFB– samples. Conclusions: Our results confirm full usefulness of the Xpert MTB/RIF assay for routine diagnosis in the case of smearpositive clinical samples.