Rapid influenza antigen test for diagnosis of pandemic (H1N1) 2009

Accuracy of rapid influenza detection test in diagnosis of influenza A and B viruses in children less than 59 months old

Influenza burden among children is underestimated. Rapid influenza diagnostic tests (RIDTs) may be helpful in the early diagnosis of the disease, but their results should be interpreted cautiously. The aim of our study was to estimate the accuracy of the rapid influenza detection test BD Directigen™ EZ Flu A+B (Becton, Dickinson and Company, Sparks, MD) used among children with influenza-like illness (ILI) consulted in the ambulatory care clinics. A total number of 150 patients were enrolled into the study. The inclusion criteria were: age of the child less than 59 months, presentation of ILI according to CDC definition (fever >37.8 °C, cough, and/or sore throat in the absence of another known cause of illness), and duration of symptoms shorter than 96 h. In all patients two nasal and one pharyngeal swab were obtained and tested by RIDT, RT-PCR, and real time RT-PCR. For or influenza A(H1N1)pdm09, virus sensitivity of RIDT was 62.2 % (95 %CI 53.4-66.5 %), specificity 97.1 % (95 %CI 93.4-99 %), positive predictive value (PPV) 90.3 % (95 %CI 77.5-96.5 %), and negative predictive value (NPV) 85.7 % (95 %CI 82.4-87.3 %). For influenza B, virus sensitivity was 36.8 % (95 %CI 23.3-41.1 %), specificity 99.2 % (95 %CI 97.3-99.9 %), PPV 87.5 % (95 %CI 55.4-97.7 %), and NPV 91.5 % (95 % CI 89.7-92.1 %). We conclude that the RIDT immunoassay is a specific, but moderately sensitive, method in the diagnosis of influenza type A and is of low sensitivity in the diagnosis of influenza B infections in infants and children.