Anti-centromere antibodies in a large cohort of systemic sclerosis patients: comparison between immunofluorescence, CENP-A and CENP-B ELISA

Introduction: Anti-centromere antibodies (ACA) are useful biomarkers in the diagnosis of systemic sclerosis (SSc) where they are found in 20-40% of patients and, albeit with lower prevalence, in patients with other systemic autoimmune rheumatic diseases. Historically, ACA were detected by indirect immunofluorescence (IIF) on HEp-2 cells and confirmed by immunoassays using recombinant CENP-B. During the last few years, to accommodate high throughput diagnostics, a number of laboratories changed from IIF to ELISA assays. The objective of this study was to compare the detection of ACA by IIF to CENP-A and a CENP-B ELISA in a large cohort of SSc patients.

Methods: Sera collected from SSc patients (n=834) were tested for ACA by IIF on HEp-2 cells (ImmunoConcepts, Sacramento, CA) and CENP-A and CENP-B ELISA (both Dr. Fooke Laboratorien GmbH, Neuss, Germany). Furthermore, other autoantibodies were determined by QUANTA-Plex(TM) SLE 8 profile (INOVA, San Diego, CA), QUANTA Lite RNA Pol III (INOVA) and PM1-Alpha ELISA (Dr. Fooke).

Results: The prevalence of ACA was 35.0% by IIF, 41.6% by CENP-A and 57.8% by CENP-B ELISA. When the CENP-A and the CENP-B ELISA results were compared to the IIF, the area under the curve value derived from receiver operating characteristic analysis was 0.98 for both assays. ACA and anti-topoisomerase I antibodies co-occurred in 1.2% (ACA by IIF), in 3.5% (by CENP-A ELISA) and in 7.4% (by CENP-B ELISA). Anti-CENP-A antibodies were negatively associated with anti-Scl-70, anti-RNA Pol III, (both p<0.0001), anti-U1-RNP (p=0.008) and anti-PM1-Alpha antibodies (p=0.0337). The degree of association was dependent on the cut-off value used.

Conclusion: Although we found good agreement between IIF and ELISA for the detection of ACA in SSc, a significant portion of CENP ELISA positive sera did not show the typical ACA staining pattern. Based on these findings, we conclude that an IIF ACA negative result might not rule out the presence of ACA. In addition, new CENP ELISA kits are reliable for the detection of anti-CENP in SSc sera.