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Diagnosing autoimmune hepatitis (AIH) should be improved with a standardised assay using a cloned marker antigen to detect telltale antibodies in patients. The results of the assay using recombinant soluble liver antigen/liver pancreas antigen (SLA/LP) (rELISA) were impressive when compared with confirmatory western blots and an inhibition ELISA (iELISA) test. Among 454 serum samples from 419 patients with AIH from four different countries only one false positive result was recorded with the new test. Twenty one were borderline positive (13 positive by western blotting; therefore considered positive by rELISA) and eight were negative (also by western blotting; therefore considered negative by rELISA). Sixty seven were positive by rELISA and western blotting, of which 61 were positive by iELISA.
Overall specificity of rELISA, when results from this cohort were combined with those for 1026 sera used to validate the test, was 99% and sensitivity 87% at the upper limit of borderline reactivity. Combining results for rELISA and western blotting on borderline sera gave 99% specificity, 100% sensitivity. Positive results were obtained at similar rates in patients from different countries and races.
The test was standardised against a high titre SLA/LP serum. It was calibrated with serum from 200 healthy blood donors and 195 patients with AIH and validated against 1026 non-selected sera from patients with liver disease.
Antibodies to SLA/LP are specific for AIH. Until now a reliable test, suitable for general testing for AIH has not been available.