Abstract: 【Abstract】 Objective To detect serum levels of fibroblast growth factor （FGF）-23 in patients with psoriatic arthritis （PsA）, and to explore its correlation with inflammatory markers and disease severity. Methods Twenty-five PsA patients and 25 healthy controls were retrospectively enrolled from the First Affiliated Hospital of Xiamen University between January and December 2020. Serum levels of FGF23 and 25-hydroxyvitamin D （25［OH］VitD） were detected in all participants. In PsA patients, C-reactive protein （CRP） and erythrocyte sedimentation rate （ESR） were also measured, and disease activity was assessed using the disease activity index for psoriatic arthritis （DAPSA）. Differences in the serum levels of FGF23 and 25（OH）VitD were analyzed between high CRP （> 3 mg/L） and normal CRP （≤ 3 mg/L） subgroups, between high ESR （> 15 mm/1 h） and normal ESR （≤ 15 mm/1 h） subgroups, as well as between moderate-to-high disease activity （DAPSA > 14 points） and low disease activity （DAPSA ≤ 14 points） subgroups. Correlations of FGF23 with CRP, ESR, DAPSA, and 25（OH）VitD were analyzed. Statistical analyses were carried out by two-independent-sample t test and Spearman correlation analysis. Results Serum FGF23 levels were significantly higher in the PsA patients （224.30 ± 25.83 pg/ml） than in the healthy controls （123.80 ± 11.76 pg/ml, t = 3.54, P < 0.05）, while no significant difference was observed in serum 25（OH）VitD levels between the two groups （P > 0.05）. Among the PsA patients, the serum FGF23 levels were significantly higher in the high CRP group than in the normal CRP group, significantly higher in the high ESR group than in the normal ESR group, and significantly higher in the moderate-to-high disease activity group than in the low disease activity group （all P < 0.05）; however, there were no significant differences in the 25（OH）VitD levels between these subgroups （all P > 0.05）. In the PsA patients, the serum FGF23 levels showed positive correlations with the levels of CRP and ESR, as well as with DAPSA （all P < 0.05）, but no significant correlation with serum 25（OH）VitD levels （P = 0.914）. Conclusions Serum FGF23 levels were significantly higher in PsA patients than in healthy individuals, and were positively correlated with CRP, ESR, and DAPSA.

Key words: Arthritis, psoriatic, Fibroblast growth factor 23, Calcifediol, Blood sedimentation, C-Reactive protein, Disease activity