Laboratory and imaging characteristics of patients diagnosed with psoriasis with pPsA, axPsA and patients not diagnosed with PsA
| Patient group | |||||
| Patient characteristic | All patients seen at rheumatology (N=100) | pPsA (N=5) | axPsA (N=14) | No PsA (N=81) | P value* |
| HLA-B27 positive—n (%) | 16 (16.0) | 0 | 4 (28.6) | 12 (14.8) | 0.204 |
| CRP (mg/L)—mean (SD) | 3.5 (6.1) | 8.0 (15.4) | 8.0 (10.8) | 2.5 (3.1) | 0.039 |
| Elevated CRP (>5 mg/L)—n (%) | 17 (17.0) | 1 (20.0) | 5 (35.7) | 11 (13.6) | 0.041 |
| Peripheral arthritis, current (last 7 days)—n (%) | 11 (11.0) | 5 (100.0) | 3 (21.4) | 3 (3.7) | 0.012 |
| Radiographic sacroiliitis as per mNY criteria—n (%) | 5 (5.0) | 0 | 4 (28.6) | 1 (1.2)† | <0.001 |
| Radiographic sacroiliitis ≥grade 2 unilaterally—n (%) | 9 (9.0) | 0 | 5 (35.7) | 4 (4.9)† | <0.001 |
| Active inflammation, sacroiliac joint (MRI)—n (%) | 8 (8.0) | 0 | 8 (57.1) | 0 | <0.001 |
| Structural (post)inflammatory changes, sacroiliac joint (MRI)—n (%) | 8 (8.0) | 0 | 8 (57.1) | 0 | <0.001 |
| Active inflammation, spine (MRI)—n (%) | 13 (13.0) | 0 | 13 (92.9) | 0 | <0.001 |
| Structural (post)inflammatory changes, spine (MRI)—n (%) | 8 (8.0) | 0 | 8 (57.1) | 0 | <0.001 |
*Statistically significant differences between the axPsA and noPsA groups of patients were determined by using Mann–Whitney U test for continuous data and χ² test for categorical data
†In those four patients not diagnosed with axPsA suspicious findings by conventional radiography were observed (one of the even fulfilling the mNYc), but those were then judged as not compatible with axPsA after MRI evaluation.
axPsA, axial psoriatic arthritis; CRP, C reactive protein; HLA-B27, human leucocyte antigen B27; mNY, modified New York; N, number; pPsA, peripheral psoriatic arthritis.