Performance certification of gelatin particle agglutination assay for anti-HTLV-1 antibody: inconclusive positive results.

In order to test the performance of particle agglutination assay (PA), 800 preselected PA-positive sera at 8 blood centers in the Kyushu area were tested in various assays. Most blood centers should improve their PA technique, since a third of the samples were PA-negative in our hands. A third of our PA high-titer sera were negative in indirect immunofluorescence and enzyme immunoassay, the results of which were consistent with each other. Western blots did not detect every positive serum. PA inhibition positivity was not consistent with PA titer. Most IgM antibody-positive sera also contained IgG antibody. PA should be used in combination with other methods before notifying the results to positive testees.