Norovirus Assays Compared In Acute Gastroenteritis Patients

Noroviruses (NoVs) are the most common cause of acute viral gastroenteritis worldwide and they affect all age group and are frequently involved in outbreaks in communal facilities, such as hospitals, schools, prisons, cruise ships.

Norovirus infections mainly cause nausea, vomiting, diarrhea and fever, the symptoms are generally of a relatively short duration and they usually resolve within 2 to 6 days. The virus affects approximately 267 million people and causes over 200,000 deaths each year. NoVs include six distinct genogroups, and NoV GI and GII are the most frequently detected in human infections, while NoV GIV is also implicated in human gastroenteritis.

Scientists at the Fondazione IRCCS Policlinico San Matteo (Pavia, Italy) and their colleagues collected 173 stool samples during the period February 2012 to April 2014 from 173 adult patients hospitalized with acute gastrointestinal syndromes, patient age ranged from 29 years to 101 years (median age 79 years). Acute gastroenteritis was defined as the rapid onset of two or more of the following symptoms: diarrhea, vomiting, nausea, fever or abdominal pain.185 (5)

The stool samples were tested in parallel with a laboratory developed (LD) real-time reverse transcription-polymerase chain reaction (RT-PCR) assay and with Xpert Norovirus Assay (Cepheid, Sunnyvale, CA, USA). Both the LD real-time RT-PCR assays and the new molecular “on demand” test Xpert Norovirus Assay are designed to detect NoV GI and GII. Stored archival samples volumes were tested with two specific NoV real-time RT PCR assays, one targeting a portion of NoV GI capsid gene and the other targeting a portion of NoV GII ORF1-ORF2 junction gene.

When the scientists used the Xpert Norovirus Assay, 62/173 (36.0%) samples were positive: one for NoV GI and 61 for NoV GII, while 111/173 (64.0%) samples were negative. The laboratory real-time RT-PCR assays detected NoV in 65/173 (37.5%) samples: one NoV GI and 64 NoV GII, while 108/173 (62.5%) were negative. The Xpert Norovirus Assay results were concordant with results obtained using LD real time RT-PCR in 62/65 (95.4%) samples tested, while in 3/65 (4.6%) samples were discordant.

The authors concluded that the Xpert Norovirus Assay results could be obtained in 90 minutes and with a simpler sample handling. The LD NoV real-time RT-PCR assays has an high sensitivity and includes two separated steps, extraction and amplification, thus requiring more time to get the results, but it is less expensive than the commercial assay. In conclusion, high-level concordance (95.4%) was observed between Xpert Norovirus Assay and the LD real-time RT-PCR assays. The study was published online on May 4, 2016, in the journal Diagnostic Microbiology and Infectious Disease.

Related Links:
Fondazione IRCCS Policlinico San Matteo
Cepheid