Clinical study of serum fibroblast growth factor 23 levels in patients with rheumatoid arthritis and their association with osteoporosis

Abstract

Objective To explore the serum levels of fibroblast growth factor 23 (FGF23) in patients with rheumatoid arthritis (RA) and to investigate the relationship between FGF23 and RA disease activity and the occurrence of osteoporosis (OP). Methods Serum levels of FGF23 from 174 cases of patients with RA and 88 normal subjects were detected by enzyme linked immunosorbent assay (ELISA). Bone mineral density (BMD) was measured by dual energy X-ray absorptiometry. All the clinical and laboratory indexes of RA patients were recorded in details, disease activity score (DAS28) and health assess questionnaire (HAQ) were also calculated in the meantime. Radiographic changes in both hands of RA patients were assessed by Sharp's method. T test, nonparametric test, χ2 test, correlation analysis and Logistic regressive analysis were used for statistical analysis. Results Serum levels of FGF3 [145.46(67.67, 245.93) pg/ml] in RA patients were higher than the control group [32.64(12.34, 44.70) pg/ml, Z=11.416, P<0.01]. The positive rate of serum levels of FGF23 (≥71.95 pg/ml) in RA was 74.7%(130/174), while the positive rate in control was 4.5%(4/88,χ2=115.16, P<0.01). The threshold of FGF23 serum levels for diagnosing RA was 48.56 pg/ml (AUC=0.932, Youden index=0.743, P<0.01, sensitivity 89.1%, specificity 85.2%). In RA patients with serum FGF23≥48.56 pg/ml, compared with negative FGF23 group, VAS, HAQ, number of joint swelling and BMD at femoral neck,Ward, GT, Total hip, L4 and L1-4 were significantly higher in FGF23 positive group (P<0.05). Linear correlation analysis found that in RA patients with serum FGF23≥48.56 pg/ml, anti-CCP was negatively correlated with serum FGF23 levels (r=-0.171, P=0.035). And DAS28 was positively correlated with serum FGF23 (r=0.163, P=0.045). BMD at femoral neck, Ward, GT, Total hip, L4 and L1-4 were negatively correlated with serum FGF23 (P<0.05). Results of logistic regression analysis showed that sex (OR=8.518, 95%CI (2.636, 27.522), P<0.01, age [OR=1.129, 95%CI (1.079, 1.180), P<0.01] and Sharp score [OR=1.008, 95%CI(1.003, 1.013), P=0.001] were risk factors for OP in RA patients. BMI[OR=0.801, 95%CI(0.707, 0.909), P=0.001] was a protective factor for OP in RA patients. Conclusion Serum FGF23 level is significantly higher in RA patients. Meanwhile, the serum FGF23 level correlates with RA disease activity and BMD. Key words: Arthritis, rheumatoid; Fibroblast growth factor 23; Osteoporosis