Patients with osteoarthritis or rheumatoid arthritis have similar severity of pain and functional disability when compared according to the same patient questionnaire measure: data from 1979-2019

Purpose: To review evidence that disease burden in osteoarthritis (OA) is similar to rheumatoid arthritis (RA) in studies between 1979 and 2019, in which the same patient questionnaire measure was used to assess patients with OA or RA, and to analyze some possible reasons for underestimation of OA by the rheumatology community and general public. Methods: All published studies found in the medical literature between 1979 and 2019 were analyzed for scores for pain on a visual analog scale (VAS), physical function on a health assessment questionnaire (HAQ) or derivative multidimensional HAQ (MDHAQ), as well as RAPID3 (routine assessment of patient index data), when available. All scores for pain and functional disability were adjusted to 0-10, and RAPID3 is scored 0-30. Results: Identical measures were used in 8 studies reported between 1979 and 2019 from 8 sites in North America, Europe, and Australia. A pain VAS was higher in OA compared to RA in 11 of 12 reported patient groups, while physical function on a HAQ or derivative MDHAQ and RAPID3 were slightly higher in RA before 2013 and higher in OA in later reports. Furthermore, a study of population-based data from the 1978 US Health Interview Survey indicated similar levels of disability and earnings losses according to surrogate variables for OA and RA. Conclusions: Over the last 40 years, pain and functional disability in OA appeared to be severe and similar to RA. Underestimation of OA may be explained in part by: a. most older individuals have radiographic joint damage, which often is not associated with clinical symptoms; b. abnormal biomarkers have been recognized in RA for more than 70 years, which are regarded as conveying greater significance than symptoms of pain and disability according to a “biomedical model,” the dominant paradigm of modern medicine; c. most reports of OA and RA have emphasized differences between the 2 diseases even beyond laboratory abnormalities in pathogenesis, physical findings, and imaging; d. even pain and functional disability seen in both diseases are assessed using different patient self-report questionnaires, a WOMAC (Western Ontario McMaster Universities osteoarthritis index) in OA, and HAQ (health assessment questionnaire) in RA; e. RA may have been considerably more severe in the (distant) past, prior to effective therapies. These studies were based primarily on retrospective analyses of patients from settings at which a patient questionnaire was collected in routine clinical care from all patients at all visits to inform clinical decisions. These observations also illustrate the potential value of using an identical patient questionnaire in all patients at all visits in routine care settings, analogous to using the same laboratory tests such as erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) in all rheumatic diseases, and maintaining a database of the Results for later analyses.