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Timothy S.H. Kwok, MD, on Bone Mineral Density in Psoriatic Arthritis

Research on the effect of psoriatic arthritis (PsA) on bone mineral density (BMD) is inconsistent. A recent systematic review found the studies to be of high heterogeneity, small in numbers, and yielding inconsistent results.1 There is also insufficient guidance on BMD testing in patients with PsA as per recent major clinical practice guidelines.

In a new retrospective study, Timothy S.H. Kwok, MD, a resident in internal medicine in the Department of Medicine at the University of Toronto, and colleagues sought to determine BMD in the PsA population, factors associated with undergoing BMD testing, and the effect of PsA clinical activity on BMD.2

Rheumatology Consultant caught up with Dr Kwok at the 2019 American College of Rheumatology (ACR)/Association of Rheumatology Professionals (ARP) Annual Meeting, where he presented the research.

Rheumatology Consultant: What prompted you to conduct your study?

Timothy Kwok: First and foremost, I think there is a knowledge gap in this area. The disease process in PsA inherently features the combination of new bone formation and bone destruction, but yet BMD and osteoporosis as a whole are not really prominent in the major clinical guidelines published by the ACR and the European League Against Rheumatism. We decided to use the longitudinal cohort we had at the Psoriatic Arthritis Clinic at Toronto Western Hospital to conduct this study to help describe BMD in the PsA population to help guide clinicians on how to treat these patients. Our study had several objectives. We first wanted to describe the BMD characteristics in our population. The second objective was to determine what clinical and laboratory variables clinicians are using to select patients for BMD testing.  Lastly, we wanted to determine clinical factors associated with BMD changes and BMD changes over time.

RHEUM CON: What are the key findings from your study?

TK: The first conclusion is that, contrary to previous studies, BMD in the PsA population is not vastly different than in the general population, at least compared with Canadian reference standards. Secondly, rheumatologists and other clinicians are currently using a combination of traditional BMD risk factors for osteoporosis in addition to markers for disease severity to select patients for BMD testing. Lastly, and most importantly, there appears to be certain disease characteristics that portend worsening BMDs over time. One of the characteristics that is most interesting is polyarticular disease at onset, which we know independently leads to worse disease outcomes in PsA.

RHEUM CON: What was the biggest limitation of the study?

TK: We did not have a control group (ie, persons without PsA or persons with psoriasis only) to determine and compare BMD between the groups. Secondly, we selected patients who already had a BMD regardless of clinical indication, which might have led to a selection bias. However, despite this possible selection bias, we did not find that BMDs in our patient population are worse than those in the general population.

RHEUM CON: What are the key takeaways of the study for rheumatologists?

TK: I think that despite our preliminary data showing that there is no worse BMD in our cohort compared with the general population, there are certain disease features that we would like to highlight that might suggest to clinicians that the patient in front of them might have poor bone health or worsening BMDs over time. Perhaps clinicians can be prompted to select these high‑risk patients for BMD testing at an early stage and, of course, in shorter intervals.

 

References:

  1. Chandran S, Aldei A, Johnson SR, Cheung AM, Salonen D, Gladman DD. Prevalence and risk factors of low bone mineral density in psoriatic arthritis: a systematic review. Semin Arthritis Rheum. 2016;46(2):174-182. doi:10.1016/j.semarthrit.2016.05.005.
  2. Kwok T, Ye JY, Pereira D, Gladman D. Bone mineral density in psoriatic arthritis: results from a longitudinal study [abstract 2440]. Arthritis Rheumatol. 2019;71(suppl 10). Presented at: 2019 ACR/ARP Annual Meeting; November 8-13, 2019; Atlanta, GA. https://acrabstracts.org/abstract/bone-mineral-density-in-psoriatic-arthritis-results-from-a-longitudinal-study/. Accessed November 26, 2019.

 

For more on PsA, visit the Center of Excellence.