RESUMO
We evaluated the usefulness of ImmunoCatch-Noro (Eiken Chemical Co., Ltd.) (IC-A), a newly developed immunochromatography kit using Au colloid, for the detection of norovirus in stool specimens collected from patients with acute gastroenteritis during the three-year period from 2008-2011. When a total of 316 specimens were tested by RT-PCR and direct sequencing of the PCR products, norovirus was detected in 198 specimens (62.7%), including nine genotypes (GI/2, GI/4, GI/8, GII/1, GII/2, GII/3, GII/4, GII/6 and GII/ 13). The most frequently isolated genotypes were GII/3 (64), GII/2 (59) and GII/4 (58), accounting for about 90% of the positive specimens. As compared to RT-PCR, the sensitivity, specificity and concordance rate of IC-A were 87.4% (173/198), 100% (118/118) and 92.1% (291/316), respectively. Twenty-five positive specimens that were positive by RT-PCR were negative by IC-A, however there were no false-positive results of IC-A. On the other hand, the commercially available immunochromatography kit (IC-B), which was tested for comparison, had a sensitivity, specificity and concordance rate of 59.6% (118/198), 96.6% (114/118) and 73.4% (232/316), respectively, containing 80 false-negative and four false-positive specimens. All of the 118 specimens positive by both IC-B and RT-PCR were also interpreted as positive by IC-A. The detection rates of the predominant genotypes (GII/2, GII/3 and GII/4) by IC-A were 88.1%, 87.5% and 89.7%, respectively. In contrast, those by IC-B were only 32.2%, 67.2% and 81.0%, respectively. These results show that IC-A had adequate sensitivity and cross-reactivity for a wide range of GI and GII genotypes, and also had high specificity. In conclusion, IC-A is a useful rapid-diagnostic kit for the detection of norovirus, however, its current application is limited for stool specimens.
