Evaluation of a new multi-parallel line immunoassay for systemic sclerosis-associated antibodies in an Asian population

Objectives. To compare the SSc-line immunoassay (LIA) with conventional techniques of antibody detection, to evaluate its diagnostic utility and to describe clinical associations of antibodies in Asian SSc patients. Methods. Stored sera from patients with SSc (n = 68), SLE (n = 49), OA (n = 41) and normal controls (NCs, n = 32) were evaluated. Cohen's kappa and Bland-Altman plots were used to evaluate agreement. Results. There was good agreement between LIA and ELISA for anti-Scl-70 (kappa = 0.97), anti-CENPA (kappa = 0.83), anti-CENPB (kappa = 0.96) and anti-PmScl100 (kappa = 1.00) (5.48-8.22% of values outside the 95% limits of agreement using Bland-Altman plots), and between LIA and IIF for anti-CENPA (kappa = 0.81) and anti-CENPB (kappa = 0.77) (P < 0.001). Using LIA, of 32 (32/68, 47%) SSc patients negative for anti-Scl-70 and anti-CENPA/B, 5 (5/32, 15%) were positive for anti-Ku, -Nor90, -fibrillarin and -RP155. Specificity of each antibody for SSc was at least 97% (vs OA/NC) and 94% (vs SLE), except for anti-Ro52 (63%). Anti-CENPB was associated with joint pain [odds ratio (OR) 0.17], interstitial lung disease (OR 0.24) and telangiectasia (OR 4.00) (P < 0.05). Anti-Ro60 was associated with pulmonary arterial hypertension (OR 3.89, P = 0.041). Conclusion. The SSc-LIA has good agreement with conventional techniques for selected antibodies and has good diagnostic utility.