Rapid detection and typing of influenza A and B by loop-mediated isothermal amplification: comparison with immunochromatography and virus isolation.

A reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) assay was established for the detection of influenza A virus H1 and H3 subtype strains and influenza B virus strains specifically. The total procedure from RNA extraction to virus typing was completed within 3h. In terms of specificity, the representative AH1, AH3 and B strains were detected only by strain-specific primers respectively. No cross-detection was observed. In terms of sensitivity, virus was detected at a minimum concentration of 10 ffu/ml. Eighty-three nasopharyngeal aspirates obtained from children diagnosed clinically with influenza were tested by the RT-LAMP assay, along with commercially available immunochromatography rapid diagnostic tests and by virus isolation. Virus was isolated from 78 samples (94%) and the subtype was determined by the hemagglutination inhibition test. Although it took at least 3 days, the detection sensitivity was the best of the three methods. With two rapid assays, the detection sensitivity of the RT-LAMP assay (85.5%) was higher than that of immunochromatography tests (75.9%). In addition, the RT-LAMP assay can be used to differentiate emerging influenza virus subtypes by selecting appropriate primer sets.