Specific anti-nuclear antibodies in systemic sclerosis patients with and without skin involvement: an extended methodological approach.

OBJECTIVES: To determine how sensitively SSc-associated ANAs are detected by a standard identification algorithm compared with an extensive panel of ANA identification assays, and to assess the distribution of SSc-associated ANAs and SSc organ system involvement in patients without skin involvement (limited SSc).

METHODS: Serum samples from 145 consecutive monocentric SSc patients fulfilling LeRoy and Medgser's criteria for early SSc were studied. ANAs were detected by IIF on HEp-2000 cells and identified by western blotting, protein radio-immunoprecipitation, RNA immunoprecipitation and line immunoassay (LIA). SSc organ involvement was assessed according to a modification of Medsger's disease severity scale.

RESULTS: At least one specific ANA reactivity was present in 88% of the patients. The standard algorithm (IIF and LIA) found at least one specific ANA in 74% of the patients. The main reactivities missed by this algorithm were anti-RNA polymerase III, anti-PM/Scl and anti-Th/To. Eighty-three percent of the patients with limited SSc had at least one ANA. ACAs and anti-Th/To antibodies were significantly associated with limited SSc, whereas anti-topoisomerase I and anti-RNA polymerase III were observed less frequently. SSc organ system involvement was present in 63% of the patients with limited SSc, most of whom had lung involvement.

CONCLUSIONS: Standard algorithms for ANA identification lack sensitivity for the detection of SSc-associated ANA and should be supplemented with additional assays, especially in a clinical environment that has particular interest in SSc. The spectrum of SSc-associated ANA differs according to the presence or absence of skin involvement.