Poster Presentation Women's Health Forum 2021

Estimating the true prevalence of rheumatoid arthritis in Australian women (#30)

Louise Koller-Smith 1 2 , Ahmed Medhi 1 , Lyn March 3 4 , Gita Mishra 5 , Leigh Tooth 5 , Ranjeny Thomas 1
  1. The University of Queensland Frazer Institute, Woolloongabba, Queensland
  2. Rheumatology, John Hunter Hospital, Newcastle, New South Wales
  3. Florance and Cope Professorial Department of Rheumatology, Royal North Shore Hospital, Sydney, New South Wales
  4. Institute of Bone and Joint Research, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales
  5. University of Queensland, School of Public Health, University of Queensland, Brisbane, Queensland

Introduction: Currently, all estimates of rheumatoid arthritis (RA) prevalence in Australia are through self-report. Overseas validation studies have found that self-report substantially overestimates true RA, but addition of self-reported medications to case-finding definitions improves validity. Best validated global estimates suggest a prevalence of RA of around 0.5% overall and around 0.7% in women. No studies have been done in an Australian context.

 

Aim: To examine the prevalence of RA in Australian women using self-reported cases alone versus self-reported cases and compatible self-reported medications.

 

Methods: We used prospectively collected data from the Australian Longitudinal Study on Women’s Health (ALSWH), collected between 2005 and 2015. RA cases were identified based on positive self-report. Medication self-report was used to develop three medication case-finding definitions; a ‘liberal’ definition that included patients on any of disease modifying anti-rheumatic drugs (DMARDs), prednisone and/or non-steroidal anti-inflammatories (NSAIDs), a ‘mid’ definition that included patients reporting DMARDs and/or prednisone, and a ‘strict’ definition that included patients reporting DMARDs only. Prevalence of RA according to each of the case finding definitions was calculated.

 

Results: A total of 34 993 responses from participants aged 79-84 years, 59-64 years, 56-61 years and 37-42 years were identified from questions on self-reported RA and medications. Self-reported prevalence was 4.5% (1576 / 34 993). In respondents with self-reported RA, 434 fulfilled the ‘liberal’ medication definition for RA (prevalence 1.24%), 194 fulfilled the ‘mid’ medication definition (prevalence 0.55%) and 103 fulfilled the ‘strict’ medication definition (prevalence 0.29%). 

 

Conclusion: A combination of self-reported RA and self-reported use of DMARDs or prednisone is likely acceptable to capture true RA cases. This combination estimates a prevalence for RA in Australian women that is consistent with currently published global figures. Accuracy should be improved by linkage of self-reported RA with data from prescriptions and health service use.