Rheumatoid arthritis, psoriatic arthritis, and axial spondyloarthritis epidemiology in England from 2004 to 2020: An observational study using primary care electronic health record data

Abstract

Background: Contemporary data on rheumatoid arthritis (RA), psoriatic arthritis (PsA) and axial spondyloarthritits (SpA) epidemiology in England are lacking. This knowledge is crucial to planning healthcare services. We updated algorithms defining patients with diagnoses of RA, PsA, and axial SpA in primary care and applied them to describe their incidence and prevalence in the Clinical Practice Research Datalink Aurum, an electronic health record (EHR) database covering ∼20% of England.

Methods: Algorithms for ascertaining patients with RA, axial SpA, and PsA diagnoses validated in primary care EHR databases using Read codes were updated (to account for the English NHS change to SNOMED CT diagnosis coding) and applied. Updated diagnosis and synthetic disease-modifying anti-rheumatic drug code lists were devised by rheumatologists and general practitioners. Annual incidence/point-prevalence of RA, PsA, and axial SpA diagnoses were calculated from 2004 to 2020 and stratified by age/sex.

Findings: Point-prevalence of RA/PsA diagnoses increased annually, peaking in 2019 (RA 0·779% [95% confidence interval (CI) 0·773, 0·784]; PsA 0·287% [95% CI 0·284, 0·291]) then falling slightly. Point-prevalence of axial SpA diagnoses increased annually (except in 2018/2019), peaking in 2020 (0·113% [95% CI 0·111, 0·115]). RA diagnosis annual incidence was higher between 2013-2019 (after inclusion in the Quality and Outcomes Framework, range 49·1 [95% CI 47·7, 50·5] to 52·1 [95% CI 50·6, 53·6]/100,000 person-years) than 2004-2012 (range 34·5 [95% CI 33·2, 35·7] to 40·0 [95% CI 38·6, 41·4]/100,000 person-years). Increases in the annual incidence of PsA/axial SpA diagnosis occurred following new classification criteria publication. Annual incidence of RA, PsA and axial SpA diagnoses fell by 40·1%, 67·4%, and 38·1%, respectively between 2019 and 2020, likely reflecting the COVID-19 pandemic's impact on their diagnosis.

Interpretation: Recorded RA, PsA, and axial SpA diagnoses are increasingly prevalent in England, underlining the importance of organising healthcare services to provide timely, treat-to-target care to optimise the health of >1% of adults in England.

Funding: National Institute for Health and Care Research (NIHR300826).

Keywords: Axial spondyloarthritis; Incidence; Prevalence; Psoriatic arthritis; Rheumatoid arthritis.

Figure 1

Percentage of patients with at least 1 Read/SNOMED code for RA who meet the diagnosis algorithm. Panel A = percentage of patients ever receiving an RA Read/SNOMED code that meet the algorithm and each of its criteria in each calendar-year; panel B = percentage of patients ever receiving an RA Read/SNOMED code that meet each criteria 2 component in each calendar-year; 2+ Read/SNOMED codes = having ≥2 Read/SNOMED codes (on different dates); no alternative diagnosis = no Read/SNOMED code for an alternative form of IA after the final RA Read/SNOMED code; Read/SNOMED code from groups 1/2 = having a Read/SNOMED code from strength of evidence code groups 1 (“strong” evidence) or 2 (“fairly strong” evidence) as opposed to 3 (“fairly weak” evidence) or 4 (“weak” evidence).

Figure 2

Annual incidence and point-prevalence of rheumatoid arthritis diagnoses. Panel A = annual incidence; Panel B = incidence stratified by sex (<5 patients had indeterminate sex recorded and were excluded from this analysis); Panel C = incidence stratified by age-bands (<25: < 25 years; 25-35: ≥25 to <35 years; 35-45: ≥35 to <45 years; 45-55: ≥45 to <55 years; 55-65: ≥55 to <65 years; 65-75: ≥65 to <75 years; >75: ≥75 years); Panel D = overall prevalence; Panel E = prevalence stratified by sex (<5 patients had indeterminate sex recorded and were excluded from this analysis); Panel F = prevalence stratified by age-bands (<25: < 25 years; 25-35: ≥25 to <35 years; 35-45: ≥35 to <45 years; 45-55: ≥45 to <55 years; 55–65: ≥55 to <65 years; 65-75: ≥65 to <75 years; >75: ≥75 years); py = person-years; CI = confidence interval.

Figure 3

Annual incidence and point-prevalence of psoriatic arthritis diagnoses. Panel A = incidence; Panel B = incidence stratified by sex (<5 patients had indeterminate sex recorded and were excluded from this analysis); Panel C = incidence stratified by age-bands (<25: < 25 years; 25-35: ≥25 to <35 years; 35-45: ≥35 to <45 years; 45-55: ≥45 to <55 years; 55-65: ≥55 to <65 years; 65-75: ≥65 to <75 years; >75: ≥75 years); Panel D = overall prevalence; Panel E = prevalence stratified by sex (<5 patients had indeterminate sex recorded and were excluded from this analysis); Panel F = prevalence stratified by age-bands (<25: < 25 years; 25-35: ≥25 to <35 years; 35-45: ≥35 to <45 years; 45-55: ≥45 to <55 years; 55-65: ≥55 to <65 years; 65-75: ≥65 to <75 years; >75: ≥75 years); py = person-years; CI = confidence interval.

Figure 4

Annual incidence and point-prevalence of axial spondyloarthritis diagnoses. Panel A = incidence; Panel B = incidence stratified by sex; Panel C = incidence stratified by age-bands (<25: < 25 years; 25-35: ≥25 to <35 years; 35-45: ≥35 to <45 years; 45-55: ≥45 to <55 years; 55-65: ≥55 to <65 years; 65-75: ≥65 to <75 years; >75: ≥75 years); Panel D = overall prevalence; Panel E = prevalence stratified by sex; Panel F = prevalence stratified by age-bands (<25: < 25 years; 25-35: ≥25 to <35 years; 35-45: ≥35 to <45 years; 45-55: ≥45 to <55 years; 55-65: ≥55 to <65 years; 65-75: ≥65 to <75 years; >75: ≥75 years); py = person-years; CI = confidence interval.

Figure 5

Annual crude versus age and sex standardised incidence and point-prevalence of inflammatory arthritis diagnoses. Panel A = rheumatoid arthritis incidence; Panel B = psoriatic arthritis incidence; Panel C = axial spondyloarthritis incidence; Panel D = rheumatoid arthritis prevalence; Panel E = psoriatic arthritis prevalence; Panel F = axial spondyloarthritis prevalence.