Interval between onset of psoriasis and psoriatic arthritis: comparing UK Clinical Practice Research Datalink with a hospital-based cohort.

PROMPT Study Group

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Background: The benefits of early diagnosis of psoriatic arthritis (PsA) are being increasingly recognized. A greater understanding of the time interval between the presentation of psoriasis and arthritis could help inform future screening strategies in patients with psoriasis.

Methods: Patients aged 18–89 years with incident psoriasis and/or PsA between 1998 and 2014 were identified in the Clinical Practice Research Datalink (CPRD) based on Read codes and prescription records. The incidence of psoriasis and PsA in the general population was calculated and the incidence of PsA within the incident psoriasis cohort. For incident PsA patients the time interval between their first psoriasis record and their PsA diagnosis was calculated. Comparison of the interval between psoriasis and PsA in the CPRD was made with the Royal National Hospital for Rheumatic Diseases Bath PsA observational cohort.

Results: Within the CPRD 88,858 incident psoriasis (48.6% male) and 6783 incident PsA patients (49.0% male) were identified. The incidence of psoriasis and PsA was 182.8 (95% CI 181.6,184.0) and 13.4 (95% CI 13.1,13.8) per 100,000 person-years respectively. The average duration of follow-up was 5.8 years. Within the incident psoriasis cohort, the incidence of PsA was 270.7/100,000 person-years (95% CI 256.9, 285.0). Of the CPRD PsA patients, 5,272 (77.7%; 2,652 males) had a record of psoriasis. The Bath cohort included 815 patients with data on both the year of psoriasis and PsA diagnosis. The mean age at PsA diagnosis was 49.2 years in the CPRD and 42.0 years in the Bath cohort. In the CPRD, the majority of patients had a psoriasis diagnosis before their PsA diagnosis (82.3%) or synchronously within the same calendar year (10.5%), with only a minority receiving their PsA diagnosis code first (7.1%). In the Bath cohort, 61.3% presented with psoriasis before their PsA, 23.8% presented within the same calendar year and 14.8% presented with arthritis first. Excluding those who presented with arthritis before their psoriasis, the mean time interval between diagnoses was 10.8 years [SD 10.9; median 8 (IQR 2–15)] in the CPRD and 11.8 years [SD 13.2; median 7 (IQR 0–20)] in the Bath cohort. Among the CPRD patients, 60.1% received their PsA diagnosis within the 10 years after their psoriasis diagnosis and 75.1% within 15 years. This was comparable with the Bath cohort at 57.2% within 10 years and 67.7% within 15 years.

Conclusion: The larger proportion of patients receiving their PsA diagnosis before or synchronous with their psoriasis diagnosis in the Bath hospital-based cohort reflects in part the differences in recording and the nature of the healthcare settings. Although the majority in both cohorts receives a diagnosis of PsA within 10 years of the diagnosis of psoriasis, there was a significant proportion who did not, which may have implications for screening strategies.
Original languageEnglish
Title of host publicationRheumatology
EditionSuppl 2
Publication statusPublished - Apr 2017


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