Comparison of anti-agalactosyl IgG antibodies, rheumatoid factors, and anti-cyclic citrullinated peptide antibodies in the differential diagnosis of rheumatoid arthritis and its mimics

CER3139
2007 Vol.25, N°5
PI 0716, PF 0721
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PMID: 18078619 [PubMed]

Abstract

OBJECTIVES:
Anti-agalactosyl IgG antibodies [anti-Gal(0) IgG] have been regarded as a useful serological marker for rheumatoid arthritis (RA). Our aim was to evaluate the clinical usefulness of anti-Gal(0) IgG in the differential diagnosis of rheumatic disorders that mimic RA compared to rheumatoid factors (RF) and anti-cyclic citrullinated peptide antibodies (anti-CCP).
METHODS:
Sera were collected from 39 patients with RA, 49 patients with primary Sjögren`s syndrome (pSjS), 47 patients with systemic lupus erythematosus (SLE), 65 patients with chronic hepatitis B viral infection (HBV), 68 patients with chronic hepatitis C viral infection (HCV) and 19 normal individuals. RF-IgM was measured by the nephelometeric method, and RF-IgA, anti-Gal(0) IgG and anti-CCP were measured by the respective ELISA assays.
RESULTS:
Anti-Gal(0) IgG titers were remarkably elevated in patients with RA (191.0 ± 250.8 AU/ml) compared to pSjS (37.9 ± 42.6 AU/ml), SLE (10.3 ± 13.6 AU/ml), chronic HBV with (36.1 ± 38.4 AU/ml) or without rheumatic symptoms (9.6 ± 19.4 AU/ml), RF(+) chronic HCV without rheumatic symptoms (19.0 ± 14.8 AU/ml), chronic HCV with rheumatic symptoms (15.2 ± 17.4 AU/ml) and healthy individuals (2.6 ± 0.7 AU/ml). The specificity of anti-Gal(0) IgG could be greatly enhanced by elevating the cut-off value from 12 AU/ml to 40 AU/ml (68.6% vs. 85.6%, p < 0.001) without significantly compromising its sensitivity (76.9% vs. 61.5%, p > 0.05).
CONCLUSIONS:
The serum titer of anti-Gal(0) IgG is much higher in rheumatoid arthritis than in mimicking diseases. The specificity of anti-Gal(0) IgG is enhanced when the cut-off value is raised. However, anti-CCP remains the most specific biomarker for RA.