New immunochromatographic rapid test for diagnosis of acute Puumala virus infection

A new immunochromatographic rapid test, POC PUUMALA (Erilab Ltd., Kuopio, F inland), for detection of acute-phase Puumala virus (PUUV) infection was de veloped based on a highly purified baculovirus-expressed PUUV nucleocapsid protein antigen and lateral immunodiffusion techniques. After addition of s ample (5 mul of serum, plasma, or fingertip blood) and buffer, PUUV-specifi c immunoglobulin M (IgM) antibodies, if present, together with the gold-con jugated anti-human IgM, formed a specific colored line in 5 min. The sensit ivity and specificity of the test were evaluated with 200 serum samples and 30 fingertip blood samples, The reference method for the serum samples was a mu -capture enzyme immunoassay (EIA) for IgM and an immunofluorescence a ssay (IFA) for IgG antibodies. The analytical sensitivity and specificity o f the rapid test were 100 and 99%, respectively, for unfrozen serum samples (n = 103; 12 PUUV IgM-positive samples). When freeze-thawed serum samples were used, the sensitivity and specificity were each 97.1% (n = 70; 35 PUUV IgM-positive samples). The specificity of the test was 96.2% for 27 serum samples with nonspecific IgM antibodies or rheumatoid factor (RF), The fing ertip blood samples (n = 30) were negative, but they gave clear positive re sults when spiked with IgM-positive sera (n = 20), The results were in good agreement with the standard diagnostic methods. The rapid performance, the lack of need for refined laboratory equipment, and the high specificity wi th fresh serum and fingertip blood samples indicate that the developed POC PUUMALA rapid test is a useful tool for fast diagnosis of acute PUUV infect ion.