Clinical evaluation of highly sensitive silver amplification immunochromatography systems for rapid diagnosis of influenza

•We evaluated the clinical usefulness of SAI system, which employed a photographic development technology to increase the sensitivity of the conventional immunochromatographic assay.•The sensitivity of SAI was higher than conventional rapid influenza diagnostic kits.•SAI was able to detect influenza viruses even within 6h after the disease onset with 90% sensitivity. In this study, the clinical usefulness of silver amplification immunochromatography (SAI) influenza virus detection kits, which employed a photographic development technology to increase the sensitivity of the conventional immunochromatographic assay was evaluated. Influenza A and B virus strains of nasopharyngeal aspirates obtained from influenza patients were tested at different dilutions on the SAI system and conventional immunochromatographic assay kit (ESPLINE Influenza A & B-N), and detection limits were calculated for comparison. The detection ability of the SAI system was 8 times higher for Influenza A viruses and 32–64 times higher for Influenza B viruses. Then 1118 respiratory specimens were obtained from patients who presented with influenza-like symptoms between 2009 and 2012. The sensitivities of the SAI system were 91.2% for type A and 94.4% for type B viruses and higher than those of the conventional kit. The SAI system also showed excellent specificities, 95.8% for type A and 98.0% for type B viruses, and was able to detect influenza viruses even within 6h after the disease onset with 90% sensitivity. In conclusion, the SAI system is useful for diagnosis of influenza from early stages of the illness.