Evaluation of a new immunochromatography test for the detection of Norovirus

Abstract number: P782

Kato D., Nakayama Y., Tajiri H., Tanaka T., Hirayama Y., Kamata K., Sekine S.

Objectives: Norovirus is one of the most common pathogens causing gastroenteritis and belongs to the family Caliciviridae, which is a non-enveloped, positive-sense, single-stranded RNA virus. RT-PCR and ELISA are widely used detection methods, which have drawbacks such as long turnaround times, relatively high cost, need for specialised equipment and trained technicians. The newly developed Quick Ex-Norovirus "SEIKEN" assay is based on immunochromatography (IC) method, which is easier to perform, rapid, cost efficient and offers true clinical value.

Materials and Methods: A total of 163 faecal specimens obtained from adults, children and infants in Japan, who showed acute gastroenteritis symptoms during period May 2006 to March 2007, were collected and stored in a public laboratory and two hospitals in Japan.

The reactivity of this test was evaluated against Virus-like particles (VLPs), containing 6 genotypes of genogroup 1 (G1) and 13 genotypes of genogroup 2 (GII).

The test was performed according to the instruction manual. In summary, 0.1 g of faecal specimen (or 100 mL of VLPs) was added to the specimen preparation tube, containing 0.9 mL of specimen buffer, then mixed with a tube mixer for 30 sec. and centrifuged at 2000xg for 5 min. An aliquot of 300 mL of supernatant was transferred to a sample tube and after capping this tube with a specimen filter, filtrate is collected into a reaction tube. The IC test strip was inserted into this tube and interpretation was done after 15 min. incubation time at room temp. All clinical specimens were also tested by RT-PCR, as described by Yan et al. (2003). A primer set of G1-SKF and G1-SKR was chosen for G1 and a set of G2-GKF and G2-SKR for GII identification.

Results: Fifty three (53) of 163 samples (32.5%) were positive by the IC test. Sensitivity, specificity and overall agreement were 73.6%, 98.9% and 87.7% respectively, when compared with RT-PCR. Nineteen (19) specimens were negative by the IC test, but positive by RT-PCR. These discrepancies might be due to low viral load in these specimens. The IC test showed positive against all VLPs, including GI types 1, 2, 3, 4 & 6 and GII types 1 to 8, 12 to 15 and 17.

Conclusion: The sensitivity and specificity of the IC test for clinical specimens were comparable with current Norovirus detection methods, hence the Quick Ex-Norovirus "SEIKEN" assay might be a valuable attribute in the clinical setting.