Anti-mitochondrial antibodies (AMA) represent serological markers of primary biliary cholangitis (PBC). Investigation of these autoantibodies can be performed by indirect immunofluorescence (IIF) on tissue sections or immunodot using M2 and M2-3E antigens. We aimed to evaluate the concordance of these immunological tests and their performance in PBC diagnosis. We reviewed sera which were tested for autoimmune liver disease anti-bodies by IIF (EUROIMMUN®) and immunodot (EUROIMMUN®). Results of IIF (AMA) and immunodot (anti-M2 and anti-M2-3E) were analyzed. A focus was given on positive results for AMA and/or anti-M2 and/or anti-M2-3E. According to available clinical data, patients were divided into two groups "PBC" and "Non PBC". Three-hundred-nineteen sera were tested by both techniques. Results of AMA, anti-M2 and anti-M2-3E were concordant in 296 cases (92.8%). Indeed, the three biomarkers were negative in 237 cases (74.3%) and positive in 59 cases (18.5%). Eighty-two sera were tested positive for AMA and/or anti-M2 and/or anti-M2-3E. Clinical data were available for 30 patients. In "PBC" group (n = 15), AMA, anti-M2 and anti-M2-3E antibodies were positive in 14/15 cases. PBC diagnosis was made in 12/15 patients without requiring liver biopsy. In "non PBC" group (n = 15), AMA, anti-M2 and antiM2-3E antibodies were positive in 9/15 cases. However, PBC diagnosis was not reached in the absence of other diagnostic criteria. IIF represents a first-line technique for AMA detection while immunodot is useful to confirm antigenic specificity in IIF-AMA positive cases. Anti-M2 and/or anti-M2-3E can be detected in some IIF-AMA negative cases. Interpretation of these tests'results relays mainly on clinical context.
Les anticorps anti-mitochondries (AAM) peuvent être recherchés par immunofluorescence indirecte (IFI) ou immunodot en utilisant les Ag M2 et M2-3E. Afin d’évaluer la concordance de ces tests et leur intérêt dans le diagnostic de cholangite biliaire primitive (CBP), nous avons comparé les résultats de recherche des AAM (IFI), anti-M2 et anti-M2-3E (immunodot) de 319 sérums. Selon les données cliniques disponibles, les patients avec au moins un marqueur positif ont été classés en deux groupes « CBP » et « non CBP ». Les résultats des trois marqueurs étaient concordants dans 296 cas (92,8 %). Au moins un marqueur était positif dans 82 cas. Dans le groupe « CBP » (n = 15), les trois marqueurs étaient positifs dans 14 cas. Dans 12 cas, le diagnostic était retenu sans recours à la biopsie hépatique. Dans le groupe « non CBP » (n = 15), les trois marqueurs étaient positifs dans neuf cas, mais les autres critères de CBP n’étaient pas remplis. L’IFI demeure la technique de première intention pour la recherche des AAM ; l’immunodot permet de confirmer la spécificité antigénique. L’interprétation, notamment des cas discordants, repose surtout sur le contexte clinique.
Keywords: anti-mitochondrial antibodies; indirect immunofluorescence; immunodot; primary biliary cholangitis.