The detection of autoantibodies on HEp-2 cells using an indirect immunoperoxidase kit (Colorzyme)

An indirect immunoenzyme (IIE) kit to detect autoantibodies in the sera of patients with systemic rheumatic diseases has been evaluated and compared to a conventional indirect immunofluorescence (IIF) assay. Both IIF and IIE were performed on a human epithelial cell line (HEp-2) using sera categorized on the basis of their autoantibody specificity. The correlation coefficient between the two assays was greater than 0.77 for all autoantibodies except antimitochondrial antibodies, which had higher end-point titers with the IIE kit. The inter- and intratest variability of IIE and IIF was comparable, differing by no more than one tube dilution. The IIE test had less background staining, allowing for better resolution and easier interpretation of staining patterns. IIE assay in the form of a commercially available kit is a reliable alternative to IIF.