einstein (São Paulo). 22/Jan/2020;18:eAO5132.
Comparison between enzyme-linked immunosorbent assay and indirect immunofluorescence for detection of antineutrophil cytoplasmic antibodies
DOI: 10.31744/einstein_journal/2020AO5132
ABSTRACT
Objective
To evaluate the performance of enzyme-linked immunosorbent assay and indirect immunofluorescence methods for the detection of antineutrophil cytoplasmic antibodies in a routine clinical laboratory setting.
Methods
A total of 227 samples were tested by indirect immunofluorescence and enzyme-linked immunosorbent assay with antigen specificity for antiproteinase 3 and antimyeloperoxidase. The proportions of positive samples were compared by McNemar hypotheses and agreement was described by Cohen’s Kappa coefficient.
Results
The agreement of the tests was 96.5%, and the Kappa coefficient obtained was 0.70 (95%CI: 0.50-0.90; p<0.001). Considering indirect immunofluorescence as the gold standard, the sensitivity of the enzyme-linked immunosorbent assay was 0.62 and the specificity was 0.99, with diagnostic accuracy in 96% of cases. Some samples were negative in enzyme-linked immunosorbent assay and positive in indirect immunofluorescence. This situation occurred in all immunofluorescence patterns, but particularly in atypical patterns. Two samples with antiproteinase 3 positivity were considered negative in indirect immunofluorescence.
Conclusion
The enzyme-linked immunosorbent assay had high specificity but lower sensitivity. The performance of indirect immunofluorescence increases diagnostic sensitivity, while the search for antiproteinase 3 by enzyme-linked immunosorbent assay may also add diagnostic power.
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