Clinical evaluation of rapid diagnostic kit detecting separately influenza A and B viruses

The Directigen Flu A + B kit, a rapid diagnostic device for influenza virus A and B was evaluated. The nasopharyngeal aspirates were obtained from 239 patients who visited our hospital, between January and March, 2000, presenting flu-like symptoms. Influenza virus AH1: 77 and AH3: 51 were isolated from 128 specimens and none from 111 specimens. Directigen Flu A + B showed 115 specimens positive and 106 specimens negative. The sensitivity and specificity of this kit were 89.8% (115/128) and 95.5% (106/111) compared with viral isolation. Agreement on positive and negative interpretations between Direction Flu A and this kit was 97.9% (234/239). In the evaluation of this kit for influenza B virus, 60 frozen nasopharyngeal aspirates collected from February to April, 1999 were used. The sensitivity and specificity of this kit were 88.9% (16/18) and 88.1% (37/42) compared with viral isolation. Agreement on positive and negative interpretations between FLU OIA and this kit was 91.7% (55/60). The Directigen A + B demonstrated sensitivity and specificity equivalent to the conventional kits in nasopharingeal aspirates. This kit can also differentiate influenza A and B viruses, a feature which is useful for treatment using anti-viral agents such as amantadine and neuraminidase inhibitor. To date, the kit is the most effective tool for the rapid diagnosis of influenza.