Abstract

The success of therapeutic measures is predicted on the basis of rapid and precise diagnosis of  infection. A comparison of three rapid influenza immunoassay (RIIA) kits, the Directigen Flu A+B test, QuickVue influenza A+B test and the Quick S-INFLU A.B, for detection of pandemic influenza H1N1 (2009) viruses, have been made on 105 patients with flu like syndrome. The sensitivity, specificity and ability to screen influenza type A and B viruses were evaluated. The clinical specimens detected positive by real-time RT-PCR for pandemic influenza H1N1 (2009) viruses and the reference influenza strain [A/PR/8/34 (H1N1)] were cultured in MDCK cells to determine TCID₅₀ and the performance of kits were compared against the current gold standard, real-time RT-PCR. The diagnostic sensitivity of Directigen kit was 10³ TCID₅₀/ml where as the QuickVue and Quick S-INFLU A.B were 10^3.5 TCID₅₀/ml in case of the pandemic H1N1 viruses which was comparable to the reference H1N1 virus (10³ TCID₅₀/ml for QuickVue and Directigen and 10^3.5 TCID₅₀/ml for Quick S-INFLU A.B). Our findings suggest that although RIIA kits are not as sensitive as the conventional and real-time RT-PCR yet they are very useful in preliminary bedside screening of large number of critically ill patients during pandemic situation.

Key words: Pandemic influenza virus (H1N1), Rapid influenza immunoassay (RIIA), Real-time RT-PCR, sensitivity, specificity.