Detection of serum M2 anti-mitochondrial antibodies by enzyme-linked immunosorbent assay is potentially less specific than by immunofluorescence.

AIM: To compare the predictive values of enzyme-linked immunosorbent assays (ELISAs) and indirect immunofluorescence (IIF) techniques for the detection of M2 anti-mitochondrial antibodies.

METHODS

Commercial ELISAs are widely available for the detection of anti-mitochondrial antibody subtypes in primary biliary cirrhosis (PBC). We compared the results from two ELISAs (one recombinant, one purified antigen) with those from two IIF methods in a well-defined cohort of PBC patients and in patients with systemic lupus erythematosus, Sjögren's syndrome, sicca syndrome, systemic sclerosis, rheumatoid arthritis and blood donor controls.

RESULTS

There was good correlation between a rodent substrate IIF and ELISA A (r=0.9134), but poor correlation with ELISA B (r=0.5999), which produced many false-positive results in the control population. We show that rodent IIF alone or human epithelial cell (HEp-2000) screening with confirmation by ELISA produce similar predictive values for PBC and require lesser degrees of skilled interpretation of IIF patterns.

CONCLUSIONS

We conclude that the specificities of IIF are greater than the ELISA methods (99% versus 85-97%), although the ELISAs are slightly more sensitive in biopsy-proven PBC. Careful in-house validation of all new ELISA technologies is mandatory for good laboratory practice, but IIF in experienced hands remains an effective and specific assay.