Evaluation of a multiplex flow cytometric immunoassay to detect PR3- and MPO-ANCA in active and treated vasculitis, and in inflammatory bowel disease (IBD)

The immunoassay specificity was 88% compared with 96% for IIF and 94% (median, range 91-96%) for both ELISAs. Its sensitivity in treated disease was 82% compared with 84% for IIF and 69% (median, range 57-82%) for the ELISAs. The immunoassay's specificity was 88% which was the same as the median for both ELISAs (range 84-95%). The PR3- and MPO-ANCA immunoassay was almost as sensitive as IIF, and more sensitive than, but just as specific as, most ELISAs, in detecting ANCA in active and treated vasculitis. A major advantage of this assay is its ability to be further modified to simultaneously screen for a panel of autoantibodies relevant to vasculitis.