Analysis of unsuccessful GeneXpert MTB/RIF tests and the handling experience in Shanghai

Abstract

Abstract The GeneXpert MTB/RIF assay is a widely used technology for detecting Mycobacterium tuberculosis(MTB) in clinical settings. But limited studies have focused on the failure of the GeneXpert MTB/RIF assay during routine implementation. This study investigated the reasons for unsuccessful GeneXpert MTB/RIF tests and verified the stability of GeneXpert testing on clinical samples that had been pretreated at 15 minutes, 3 hours, and 6 hours later, as recommended by the instructions from Cepheid. According to our statistics, the failure rate for GeneXpert assay tests in our laboratory is 2.37% (268 out of 11,241). The main reason for these failures was the occurrence of "Error" reports. In the stability tests of prolonged pretreatment homogenates, 85% (102/120) of the cases yielded the same results as the three treatment timelines in GeneXpert tests. However, 2.5% (3/120) of the paucibacillary samples yielded inconsistent results in MTB and rifampicin resistance detection. To address the unsuccessful tests of GeneXpert MTB/RIF, it would be more effective to "resample" to test rather than conduct additional trials with the remaining samples. Above all, we suggest that understanding the reasons for the failures in GeneXpert tests is essential and meaningful for both laboratory quality control and cost reduction in clinical laboratories.