Comparison between RF and ACPA positive and negative patients
| Variable | RF positive (n=11) | RF negative (n=110) | P value (RF) | ACPA positive (n=6) | ACPA negative(n=115) | P values (ACPA) |
| Age (years; mean±SEM) | 68 (±3.8) | 58 (±1.4) | 0.44 | 62 (±6.3) | 58 (±1.4) | 1.00 |
| Gender (male; n, %) | 4 (36) | 47 (43) | 1.00 | 3 (50) | 48 (42) | 1.00 |
| ACPA (≥ 7 U/mL) (n, %) | 3 (27) | 3 (3) | 0.21 | |||
| RF (≥ 40 IU/mL) (n, %) | 3 (50) | 8 (7) | 0.21 | |||
| Gamma globulins (8–13.5 g/L; mean±SEM) | 14 (±1.8) | 12 (±0.5) | 1.00 | 12 (±2.8) | 12 (±0.5) | 1.00 |
| CRP at diagnosis (< 5 mg/L; mean±SEM) | 53 (±18.8) | 19 (±3.9) | 1.00 | 37 (±25.6) | 23 (±4.3) | 1.00 |
| ESR at diagnosis (< 15 mm/hour; mean±SEM) | 53 (±11.5) | 30 (±2.8) | 1.00 | 57 (±14.2) | 31 (±2.8) | 1.00 |
| CK at diagnosis (< 190 U/L; mean±SEM) | 2127 (±1036) | 3274 (±880) | 1.00 | 552 (±248) | 3308 (±844) | 1.00 |
| Smoking (n, %) | 5 (45) | 48 (48) | 1.00 | 4 (67) | 49 (47) | 1.00 |
| Dyspnoea (n, %) | 8 (73) | 55 (50) | 1.00 | 4 (67) | 59 (51) | 1.00 |
| FEV1 (%, mean±SEM) | 72 (±5.6) | 88 (±2.1) | 0.23 | 76 (±7.8) | 87 (±2.1) | 1.00 |
| FVC (%, mean±SEM) | 79 (±6.4) | 94 (±2.1) | 0.63 | 83 (±5.8) | 93 (±2.2) | 1.00 |
| DLCO (%, mean±SEM) | 67 (±8.2) | 67 (±2.1) | 1.00 | 51 (±10.2) | 68 (±2.1) | 1.00 |
| TLC (%, mean±SEM) | 80 (±4.4) | 90 (±1.9) | 1.00 | 78 (±4.6) | 90 (±1.8) | 1.00 |
| ILD (n, %) | 5 (45) | 31 (28) | 1.00 | 3 (50) | 33 (29) | 1.00 |
| Arthralgia (n, %) | 8 (73) | 68 (62) | 1.00 | 5 (83) | 71 (62) | 1.00 |
| Arthritis (n, %) | 5 (45) | 31 (28) | 1.00 | 2 (33) | 34 (30) | 1.00 |
| Erosion on RX (n=44, n, %) | 1 (20) | 6 (15) | 1.00 | 0 (0) | 7 (17) | 1.00 |
| MSA (n, %) | 2 (18) | 23 (21) | 1.00 | 0 (0) | 27 (23) | 1.00 |
| MAA (n, %) | 6 (55) | 33 (30) | 1.00 | 3 (50) | 36 (31) | 1.00 |
| ARS (n, %) | 3 (27) | 34 (31) | 1.00 | 3 (50) | 34 (30) | 1.00 |
ACPAs, anticitrullinated protein antibodies; ARS, antiaminoacyl-tRNA synthetase antibodies; CK, creatinine kinase; CRP, C reactive protein; DLCO, diffusing capacity of the lungs for carbon monoxide; ESR, erythrocyte sedimentation rate; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; ILD, interstitial lung disease; MAA, myositis-associated antibodies; MSA, myositis-specific antibodies; RF, rheumatoid factor; TLC, total lung capacity.