Arthritis Incidence in Psoriasis Higher Than EHR Records Suggest

Alex Rudge

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People with preexisting psoriasis (PsO) had an estimated annual incidence of psoriatic arthritis (PsA) of 2.20 per 100 patient years over a 2-year period, higher than some previous literature based on health records alone has suggested.¹

“Psoriatic arthritis (PsA) is a potentially debilitating form of inflammatory arthritis that affects about 20% of the psoriasis population world-wide. Skin psoriasis usually precedes the development of PsA by several years, affording an opportunity to screen an at-risk group for early detection of PsA. The efficiency and cost benefit of screening strategies are dependent on the incidence of the target condition, and the potential for alleviating that condition by effective treatment,” lead investigator Alex Rudge, PhD candidate, University of Bath, and colleagues wrote.¹ “Studies have shown that delay in diagnosis of psoriatic arthritis is associated with adverse outcome, and a range of newer more effective therapeutic agents for psoriatic arthritis are now available. Hence accurate estimates of the incidence of psoriatic arthritis in populations targeted for screening are highly desirable.”

Rudge and colleagues analyzed data from 511 participants of the multicenter, prospective, 2-arm parallel-group cluster randomized controlled Total Burden of Psoriasis (TUDOR) trial comparing the early identification of PsA by annual rheumatological assessment ("Enhanced Surveillance") with standard care in people with PsO identified in primary care. Of the participants in the enhanced surveillance group, 14 developed PsA over 12 months (2.74/100 patient-years [95% CI, 1.32-4.16]) and 7 of 444 developed PsA over 24 months (1.58/100 patient-years [95% CI, 0.42-2.74]). Altogether, the combined incidence over 24 months was 2.20/100 PYs (95% CI 1.27-3.13).¹

“Estimates of the incidence of PsA in people with psoriasis have varied considerably for many possible reasons, including disease heterogeneity, classification criteria used and study setting. Studies based on primary care records alone tend to find a lower range of incidence of around 0.27 per 100 patient-years. Comparatively, the annual incidence from a prospective cohort study, where individuals with psoriasis were clinically examined, was 2.7 per 100 patient-years… Therefore, more accurate estimates of incidence in primary care require prospective studies accompanied with adequate screening and assessment,” Rudge and colleagues concluded.¹

The investigators noted that limitations of the study include relatively short follow-up time and a lack of power to investigate known risk factors for developing PsA, including psoriasis severity, obesity, or the presence of nail disease, although there was a trend for incident cases to have a higher frequency of psoriatic nail disease. They also noted that there may have been some selection bias in favor of the presence of PsA, although participants were not made aware that the trial’s aim was early identification of PsA. The participants in the TUDOR trial also may not be fully representative of a primary care psoriasis population, as factors including the prior presence of musculoskeletal symptoms, other health-care seeking behaviors, educational background, socioeconomic and employment status, may have influenced trial participation.

REFERENCES

1. Rudge A, Brown ST, Ransom M, et al. Incidence of Psoriatic Arthritis in a Primary Care Psoriasis Population in the United Kingdom. J Rheumatol. 2024; 51(9). doi: 10.3899/jrheum.2024-0556

2. Tillett W, Charlton R, Nightingale A, et al. Interval between onset of psoriasis and psoriatic arthritis comparing the UK Clinical Practice Research Datalink with a hospital-based cohort. Rheumatology 2017;56(12):2109-2113. (In eng). DOI: 10.1093/rheumatology/kex323.