Comparison of 44/107L one-step immunocapture enzyme-immunoassay and time-resolved fluoroimmunoassay for influenza A diagnosis

One-step immunocapture enzyme-immunoassay (EIA) was compared with time-resolved fluoroimmunoassay (TR-FIA) for rapid diagnosis of influenza A infection by antigen detection. The high-affinity monoclonal antibodies (MAbs) recognising two independent epitopes on the conservative nucleoprotein were used for capture (MAb 44) and detection (MAb 107L) of antigen by both assays. The detection limit for purified recombinant influenza A virus nucleoprotein was approximately 10 pg by EIA and 5 pg by TR-FIA. The performance of the methods was evaluated by testing 43 known positive and 50 negative clinical specimens (nasopharyngeal washes and aspirates). The sensitivity and specificity was 93% and 92% for EIA and 100% and 98% for TR-FIA, respectively, in comparison to the reference A3/A1 TR-FIA. The relationship of 44/107L immunoassays has been evaluated: in comparison to 44/107L TR-FIA (100%), EIA confirmed 93% of positive and 94% of negative samples. In conclusion, the capture-detector pair of MAbs 44 and 107L can be used for the sensitive detection of influenza A viral antigen in clinical samples by both immunocapture methods. Despite the slightly lower accuracy of the EIA, widespread availability and economy of the EIA methodology makes it an advantageous alternative for the laboratory diagnosis of influenza A virus infections.