Comparison of commercial influenza A virus assays in detecting avian influenza H7N9 among poultry cloacal swabs, China.

BACKGROUND Avian H7N9 virus emerged in China in February 2013 and has since spread widely among China's poultry, causing numerous human infections. OBJECTIVES To compare World Health Organization (WHO) and US commercial influenza assays in detecting avian H7N9 virus in poultry cloacal specimens. STUDY DESIGN Between April 6 and July 15, 2013, 261 cloacal swabs were collected from commercial poultry in Nanjing and Wuxi City, Jiangsu Province, China. Swabs were screened with the WHO's influenza A and H7N9 real-time RT-PCR (qRT-PCR) assays. A blinded panel of 97 specimens (27 H7N9-positive and 70 influenza A-negative) was then used to compare 3 antigen based commercial assays (Remel Xpect Flu A&B, Quidel Quickvue influenza, and Quidel Sofia Influenza A+B), and 2 molecular commercial assays (Quidel Molecular Influenza A+B assay and Life Technologies VetMAX™-Gold SIV Detection Kit). None of these commercial assays were approved for use with poultry specimens. RESULTS Considering the WHO H7N9 qRT-PCR assay as the gold standard, all assays except the Quidel Quickvue influenza assay had high specificity (ranging from 96 to 99%). Regarding sensitivity, the Life Technologies VetMAX™-Gold SIV Detection Kit (100%; 95% CI 87-100%) and the Quidel Molecular Influenza A+B assay (85%; 95% CI 66-96%) performed the best. The sensitivities of the non-molecular antigen detection assays were either unable to detect small amounts of H7N9 viral RNA or were inhibited by specimen type. CONCLUSIONS The Life Technologies VetMAX™-Gold SIV Detection Kit and the Quidel Molecular Influenza A+B assay are comparable in performance to the WHO H7N9 qRT-PCR assay in detecting H7N9 from poultry cloacal specimens.