Comparative characteristics of early psoriatic arthritis with and without axial skeleton injury (a subanalysis of the all-Russian registry of patients with psoriatic arthritis)

Abstract

Objective: to compare the clinical features of two groups of patients with early psoriatic arthritis (PsA): with the involvement of the axial skeleton and without axial lesion.Subjects and methods. Examinations were made in 95 patients (47 men and 48 women) with early PsA from the Russian registry, the diagnosis met the CASPAR criteria; their mean age was 36.5+10.7 years; the duration of arthritis was 12.1 + 10.3 months. In addition to the standard examination, all the patients underwent evaluation of inflammatory back pain (IBP) (ASAS criteria), pelvic radiography, and determination of HLA-B27; 79 patients had additionally magnetic resonance imaging (MRI) of the sacroiliac joints (SIJ). Active sacroiliitis (SI) detected on MRI (MRI-SI) was identified as bone marrow edema (osteitis) in the STIR mode. Radiographic SI on (rSI) was recorded if there were bilateral or unilateral changes (Kellgren grades >II or >III, respectively). The results of radiography and MRI were assessed by an independent radiologist. The disease activity in patients with IBP was evaluated by BASDAI. patients’ global assessment of disease activity (GADA) and assessment of pain intensity (PI) were made using a 100 mm visual analogue scale (VAS). The patients were divided into two groups: 1) those with axial lesion (axPsA), who had IBP, and/or rSI, and/or MRI-SI; 2) those without axial lesion, who had only peripheral PsA (pPsA).Results and discussion. IBP was found in 63 (66.3%) patients; it was transient, episodic in 35 (60.3%) from them. MRI-SI was detected in 28 (35.4%) from the 79 patients; rSI — in 29 (30.5%). The axPsA group included 65 (68.4%) patients and the pPsA group consisted of 30 (31.6%) patients. There was a preponderance of males in the axPsA group (60%) and that of females in the pPsA group (73.3%) (р=0.003). The patients with axPsA were younger than those with pPsA (33.9+9.6 and 41.7+10.6 years, respectively; p=0.0007). They were more frequently HLA-B27 positive than pPSA patients: 47.6% (n=30) and 23.3% (n=7) (p=0.02); and had shorter duration of arthritis: 10.3+8.7 and 16.1 + 11.7 months, respectively (p = 0.008).In the axPsA group, of PI was worse than that in the pPsA group: GADA averaged 58.4+17.3 and 49.8+16.7 mm (p=0.02); PI >50 mm was observed in 44 (67.7%) and 13 (43.3%) patients, respectively [odds ratio (OR), 2.74; 95% confidence interval (CI), 1.13-6.67; p=0.026]. More severe skin lesions were seen in patients with axPsA than in those with pPsA: BSA >3% was detected in 24 (40.7%) and 4 (14.8%) patients (OR, 3.94; 95% CI, 1.21-12.86; p=0.023); the median PASI was 9.7 [6.6; 21.5] and 5.0 [0.0; 6.4] respectively (p=0.005). The patients with axPsA showed higher C-reactive protein (CRP) values than those with pPsA: CRP >5 mg/L was found in 58 (89.3%) and 19 (63.3%) patients, respectively (OR, 4.80; 95% CI, 1.63-14.13; p=0.004).Conclusion. The targeted examination of PsA patients revealed axial lesion in 68% from them; delayed diagnosis was generally associated with the inconsistent character of IBP. Among the patients with axPsA, there are significantly more males, younger adults, and HLA-B27 carriers. With the involvement of the axial skeleton, there was a more severe course of the disease: worse PI, a greater severity of skin lesions, and higher CRP levels. Considering the need for early diagnosis of axPsA for the timely use of biological agents, studies of this problem should be continued using large patient cohorts.

Keywords

• axial psoriatic arthritis
• inflammatory back pain
• magnetic resonance imaging of the sacroiliac joints