Multi-Center Evaluation of the Xpert Norovirus Assay for Detection of Norovirus GI and GII in Fecal Specimens.

Gonzalez MD1, Langley LC2, Buchan BW3, Faron ML3, Maier M4, Templeton K5, Walker K6, Popowitch EB7, Miller MB8, Rao A7, Liebert UG4, Ledeboer NA3,Vinjé J2, Burnham CD9.

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Abstract

Norovirus is the most common cause of sporadic gastroenteritis and outbreaks worldwide. The rapid identification of norovirus has important implications for infection prevention measures, and may reduce the need for additional diagnostic testing. The Xpert Norovirus Assay recently received FDA clearance for the detection and differentiation of norovirus genogroups I and II (GI and GII), which account for the vast majority of infections. In this study, we evaluated the performance of the Xpert Norovirus Assay with both fresh, prospectively collected (n=914) and frozen, archived (n=489) fecal specimens. A Centers for Disease Control (CDC) composite reference method was used as the gold standard for comparison. For both prospective and frozen specimens, the Xpert Norovirus Assay showed a positive percent agreement (PPA) and negative percent agreement (NPA) of 98.3% and 98.1% for GI, and 99.4% and 98.2% for GII, respectively. Norovirus prevalence in the prospective specimens (collected from March to May of 2014) was 9.9% (n=90), with the majority of positives caused by genogroup II (82%, n=74). The positive predictive value (PPV) of the Xpert Norovirus Assay was 75% for GI whereas it was 86.5% for GII positive specimens. The negative predictive value (NPV) for GI and GII was 100% and 99.9%, respectively.