Is Detection of IgM Antibodies againstRSV and Type A Influenza an Alternative Rapid Diagnostic Method for Determining the Etiologyof the Disease?

Overview

The authors elaborated an ELISA system enabling specific detection of IgM antibodies againsttype A influenza and RSV. The aim of the study was to verify the practicability of this methodfor rapid diagnosis, particularly in those cases where it was not possible to take a nasopharyn-geal smear during the acute phase of the disease.Detection of RSV antibodies was tested in a cohort of 25 patients where the aetiology wasdemonstrated by isolation of viruses and a marked decline of IgG antibody titres. IgM antibodiesin the first or second serum samples were detected in 23 cases (92 %). The 34 negative pairedsera, serving as controls, gave negative results only. IgM antibodies against type A influenzawere tested on a set of 40 paired sera with confirmed seroconversion; positive IgM titres weredetected in a convalescent serum samples only in 35 examined cases (87.7 %). Of 15 controlnegative paired sera, none had a positive IgM titre.Our results show that IgM antibodies against RSV and type A influenza virus appear relativelylate following onset of disease and last for 4-10 weeks in the case of RSV and up to 3 monthsfor influenza. Therefore, detection of IgM cannot be accepted as proof of acute infection withthese viruses.

Key words:
IgM antibodies - RSV - influenza - diagnosis.