Diagnostic Immunoassay Evaluated for Influenza A

A low cost colloidal gold immunochromatographic assay (GICA) for the rapid detection of Influenza A virus has been developed.

The GICA is an immunochromatographic technique in which a cellulose membrane is used as the carrier and a colloidal gold-labeled antigen or antibody is used as the tracer.

Scientists at The Military General Hospital (Beijing, China) consecutively enrolled 626 patients from October 2008 to September 2009, for testing for influenza. All patients contributed two pharyngeal swabs, one used for GICA for Influenza A virus immediately after the collection of specimen and one used for real-time reverse transcriptase polymerase chain reaction (RT-PCR) test or virus culture at the influenza network laboratory. The GICA test is a double antibody sandwich immunoassay that includes nuclear protein monoclonal antibody and colloidal gold labeled nuclear protein monoclonal antibody.

The 626 patients enrolled in this study were divided into two groups. The first group included 200 patients who provided two pharyngeal swab samples. Of them, 127 patients were male, 73 were female, mean age was 44.4 years. The second group included 426 patients, 153 were female, 273 were male, and the mean age was 24.5 years. All 626 patients enrolled in the study were tested for Influenza A virus. The reason for 499 outpatient visits was primarily acute upper respiratory infection. The reasons for hospitalizing 127 patients included acute upper respiratory infection, acute bronchitis, pneumonia, and bronchial asthma.

A total of 198 patients (31.6%) tested positive for Influenza A virus, 11 of them were detected by virus culture and 187 of them were detected by RT-PCR. Among these influenza A positive patients, three were inpatients, two cases with acute bronchitis and one case with asthma; and all others were outpatients with acute upper respiratory infection. In reference to viral culture, GICA influenza A test demonstrated a sensitivity of 64%, a specificity of 95% and an overall accuracy of 93%. The agreement between the GICA test and virus culture assay was only moderate. In reference to RT-PCR, GICA test demonstrated considerable high sensitivity of 74% and 86% specificity with overall accuracy at 81%. There was no significant difference between GICA test and virus culture/RT-PCR on the detected positive rates of influenza A cases. The GICA-based Influenza Virus A rapid test kits were developed by ASCLE BioEngineering Company (Beijing, China).

The authors concluded that GICA is a reliable, rapid, convenient, and inexpensive test for the screening and diagnosis of influenza A. The GICA test has the great potential in the management of influenza A in resource-poor countries given its lower cost than other rapid tests. The study was published on September 1, 2011, in the journal Clinical Chemistry and Laboratory Medicine.

Related Links:
The Beijing Military General Hospital
ASCLE BioEngineering Company