Frequency of SSc-specific autoantibodies in the different ethnic groups. Values are % (n) unless otherwise specified.
| Autoantibody | Entire Cohort, n = 1000 | African American, n = 228 | White, n = 555 | Hispanic, n = 196 | Other*, n = 21 | p |
|---|---|---|---|---|---|---|
| ACA | 22.0 (220) | 6.6 (15)1,3 | 29.2 (162)1,6 | 19.4 (38)3,6 | 23.8 (5) | < 0.0001 |
| Scl-70** | 21.3 (213) | 26.8 (61)2 | 18.0 (100)2 | 24.0 (47) | 23.8 (5) | 0.04 |
| RNAP III** | 16.8 (168) | 14.0 (32) | 16.6 (92) | 20.9 (41) | 14.3 (3) | NS |
| U3-RNP | 7.8 (78) | 22.8 (52)1,4 | 1.8 (10)1,5 | 6.1 (12) 4,5 | 19.1 (4) | < 0.0001 |
| Th/To | 3.9 (39) | 1.8 (4) | 4.5 (25) | 4.0 (8) | 9.5 (2) | NS |
| PM/Scl | 2.2 (22) | 0.9 (2) | 2.9 (16) | 2.0 (4) | 0 (0) | NS |
| More than 1 | 1.2 (12) | 0.9 (2) | 1.1 (6) | 2.0 (4) | 0 (0) | NS |
| Undefined | 19.7 (197) | 21.9 (50) | 20.0 (111) | 17.9 (35) | 4.8 (1) | NS |
| ANA− | 6.1 (61)*** | 5.7 (13)*** | 6.7 (37)*** | 5.1 (10)*** | 4.8 (1) | NS |
↵* Excluded in statistical analyses.
↵** Includes 4 samples that were negative by immunodiffusion or ELISA, but positive by immunoprecipitation.
↵*** There are 10 overlapping RNAP III and ANA− samples (3 African American, 4 white, and 3 Hispanic). African American versus white:
↵1 p < 0.0001 (ACA and U3-RNP),
↵2 p = 0.008 (Scl-70). African American versus Hispanic:
↵3 p < 0.0001 (ACA),
↵4 p = 0.033 (U3-RNP). White versus Hispanic:
↵5 p < 0.0001 (U3-RNP),
↵6 p = 0.007 (ACA). No other significant differences in antibody prevalence were detected between any 2 ethnic groups. ANA+ samples negative for ACA, Scl-70, RNAP III, U3-RNP, Th/To, and PM/Scl were classified as undefined. SSc: systemic sclerosis; ACA: anticentromere antibodies; RNAP III: RNA polymerase III antibodies; ANA: antinuclear antibodies; NS: not significant.