Background/Purpose: Evidence thus far on the effect of psoriatic arthritis (PsA) on bone mineral density (BMD) has been inconsistent. There is also insufficient guidance surrounding BMD testing in PsA patients. The purpose of this study was to determine BMD in the PsA population, factors associated with having BMD testing performed, and the effect of PsA clinical activity on BMD.

Methods: : This retrospective cohort study was conducted at the Psoriatic Arthritis Clinic. Patients who had a BMD, irrespective of clinical indication were included. All patients in the cohort fulfilled the 2006 CASPAR criteria. Patients without T-scores reported, those with no visits prior to first BMD and those < 50 years old at the time of BMD were excluded. Descriptive statistics were used to summarize lumbar spine, femoral neck and total hip T-scores. Cox proportional hazard regression was performed on patients with BMDs with visits at the clinic within 2 years of their first BMD to determine covariates that predicted undergoing BMD testing. Subsequently, spearman correlation analysis was used to identify clinical features associated with low bone density. Linear regression analysis was used to model T-scores changes according to different clinical variables.

Results: Of the 214 patients with BMDs, 201 fulfilled inclusion criteria and were included for analysis. Higher age at initial visit (p< 0.001), menopause (p< 0.008), biologic therapy (p< 0.001) and disease-modifying antirheumatic drug (DMARD) use (p< 0.018) were associated with a higher chance of having a BMD when adjusted by age at baseline, PsA disease duration and gender (Table 1). The percentage of patients in the osteopenic and osteoporotic range of BMDs was 45.3% and 12.9% respectively. Mean T-scores at the lumbar spine, femoral neck and total hip were -0.3, -1.1 and -0.45 respectively. Higher body mass index (BMI) was significantly associated with a higher BMD across all measured sites (Table 2). Every unit increased in the Psoriasis Area Severity Index (PASI) was associated with a 0.084 decrease, whereas every unit increased in psoriasis body surface area (BSA) translated to a 0.804 decrease in lumbar spine T-score. For total hip T-scores, every additional damaged joint was associated with a 0.027 decrease in T-score.

Conclusion: : Higher age at initial visit, menopausal status, biologic therapy and DMARD use predicted undergoing BMD testing in our cohort. 45.3% and 12.9% of patients with PsA had osteopenia and osteoporosis respectively, with mean T-scores at the lumbar spine, femoral neck and total hip being -0.3, -1.1 and -0.45 respectively. High BMI was significantly associated with a higher BMD. More research is needed to identify risk factors associated with worsening BMD over time in the PsA population.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/bone-mineral-density-in-psoriatic-arthritis-results-from-a-longitudinal-study/