Table 1.
Demographic, clinical and laboratory features of patients with knee effusion and controls
| PsA (n = 23) | RA (n = 30) | OA (n = 20) | HC (n = 20) | P | |
|---|---|---|---|---|---|
| Sex (male/female) | 16/7 | 8/22 | 13/7 | 8/12 | PsA versus RA 0·001; RA versus OA 0·007 |
| Age (years) | 44/40–56 | 53·5/45·7–65 | 59/47·5–78 | 51/44·3–65 | PsA versus OA 0·005 |
| Disease duration (months) | 96/25·5–156 | 96/21–171 | 66/12–186 | n.a. | n.s. |
| Tender joints (0–28) | 1·5/1–3·5 | 3/1–6·5 | 1/1–1 | n.a. | RA versus OA 0·01 |
| Swollen joints (0–28) | 1/1–2 | 1/1–3·5 | 1/1–1·5 | n.a. | n.s. |
| ESR (mm/h) | 16/9–33 | 32/20–40 | 12/5–24 | – | PsA versus RA 0·01; RA versus OA 0·005 |
| CRP (mg/l) | 6·5/2·25–13·5 | 10/6–40 | 2/0–4 | – | PsA versus OA 0·02; RA versus OA 0·0002 |
| DAS28 | 3·2/2·7–3·8 | 3·7/3–5 | n.a. | n.a. | n.s. |
| RF (n/%) | 0/0 | 23/76·6 | 0/0 | – | PsA versus RA < 0·0001; RA versus OA < 0·0001 |
| ACPA (n/%) | 0/0 | 25/83·3 | 0/0 | – | PsA versus RA < 0·0001; RA versus OA < 0·0001 |
| Synovial fluid | |||||
| WBC (cell/ml) | 6 750/3 238–10 180 | 7350/5450–11 650 | 550/200–2550 | n.a. | PsA versus OA < 0·0001; RA versus OA < 0·0001 |
| PMN (%) | 68/29·5–80 | 68/50–78·75 | 7·5/0–27·5 | n.a. | PsA versus OA 0·002; RA versus OA 0·0001 |
| Therapy (n/%) | |||||
| NSAIDs | 11/47·8 | 12/42·8 | 10/50 | n.a. | n.s. |
| Prednisone | 3/13·04 | 11/39·3 | 0/0 | n.a. | RA versus OA 0·001 |
| DMARDs | 10/43·4 | 16/57·1 | 0/0 | n.a. | RA versus OA < 0·0001; PsA versus OA 0·0007 |
Data are expressed as median and 25th–75th percentiles. Statistical comparisons between groups of patients and healthy controls were performed by Kruskal–Wallis analysis of variance (anova) with Dunn's post-test. Univariate comparisons between nominal variables were performed by Fisher's exact test. ACPA = anti-citrullinated protein/peptide antibodies; CRP = C-reactive protein; DAS28 = disease activity score (28 joint count, four variables, erythrocyte sedimentation rate-based); DMARDs = disease-modifying anti-rheumatic drugs; ESR = erythrocyte sedimentation rate; HC = healthy controls; n.a. = not applicable; n.s. = not significant; NSAIDs = non-steroidal anti-inflammatory drugs; OA = osteoarthritis; PMN = polymorphonuclear cells; PsA = psoriatic arthritis; RA = rheumatoid arthritis; RF = rheumatoid factor; WBC = white blood cells.