POS1085 OSTEOPOROSIS IN PSORIATIC ARTHRITIS: A 5 YEAR PROSPECTIVE STUDY OF AN OUTPATIENT CLINIC COHORT

Abstract

Background:Data addressing whether patients with psoriatic arthritis (PsA) are at increased risk of osteoporosis have been inconclusive (1). Most studies have reported cross sectional data, and there is a lack of longer-term studies. We have previously reported bone density data from an outpatient PsA clinic cohort (2). Herein, we present 5-year follow up data from that same cohort.Objectives:To explore longer-term change in bone mineral density (BMD) at femoral neck and spine (L1-4) in an outpatient PsA cohort.Methods:140 PsA patients were at baseline examined with dual energy x-ray absorptiometry (DXA) with measurements at femoral neck and spine (L1-4). Trained nurses performed the DXA scans. The DXA machines used at baseline (Lunar Prodigy) and at 5 year follow-up (Lunar iDXA) were stable over the measurement periods. Cross calibration using a spine phantom was performed between the two DXA machines (BMD of the old phantom in the new machine and the old phantom in the old machine, with 55 measurement over a time period of 2 weeks) had a difference of less than 1%. Demographic, disease measures and treatment data was collected at the same day or within 14 days to the date of DXA assessment. For group comparison, we used paired student t-test.Results:After 5 years, 114 PsA patients (50.4% women) were re-examined. Baseline mean (SD) was for age 51.4 (9.4) years, BMI 28.1 (3.4) kg/m2, disease duration 9.1 (6.7) years.Disease characteristics at baseline and follow-up presented as mean (SD) were: DAS28 3.05 (1.1) and 2.4 (0.8); CRP 4.3 (6.7) and 5.1 (12.2) mg/dl, ESR 14.9 (11.1) and 10.9 (12.9) mm/hr; mHAQ 0.40 (0.35) and 0.38 (0.37).The proportions of patients as baseline and follow up using conventional synthetic disease modifying anti-rheumatic drugs (DMARD) were 61.4% vs. 46.5%; for biological DMARDs 37.7% vs. 48.2%; for prednisolone 5.3% vs. 10.5%, for targeted osteoporosis medication 0.9% vs. 3.5%; for calcium and vitamin-D 11.4% vs. 26.3%. As shown in the table, no significant change in femoral neck and spine BMD and T-scores was found for the 114 patients. However for Z-scores (age and weight adjusted T-score) a significant increase was found both at femoral neck and lumbar spine. When gender was examined separately no significant reduction in bone density was found in men whereas in women a significant reduction during follow up was only found for right femoral neck BMD.Baseline5 yearsP valueBMD spine L1-41.22 (0.17)1.23 (0.17)0.13T-score spine L1-40.21 (1.42)0.32 (2.01)0.42Z-score spine L1-40.20 (1.32)0.78 (2.05)<0.001BMD Femoral neck L0.98 (0.14)0.97 (0.14)0.09T-score Femoral neck L-0.59 (1.15)-0.50 (1.02)0.14Z-score Femoral neck L-0.06 (1.02)0.37 (1.04)<0.001BMD Femoral neck R0.98 (0.14)0.98 (1.16)0.57T-score Femoral neck R-0.59 (1.10)-0.52 (0.94)0.22Z-score Femoral neck R-0.08 (1.02)0.35 (0.90)<0.001Conclusion:No reduction in BMD at femoral neck and spine was found in our PsA outpatient clinic cohort at baseline or over 5 years follow up. Rather, we found a statistically significant increase in age adjusted bone density (Z-score) both at femoral neck and spine over time. Our data thus adds evidence that PsA patients treated in ordinary clinical practice do not seem to be at an increased risk of developing osteoporosis.