Introduction

Rheumatoid Arthritis (RA) is a chronic, inflammatory autoimmune disorder that causes the immune system to attack the joints. It is a disabling and painful inflammatory condition, which can lead to substantial loss of mobility due to pain and joint destruction. The disease is also systemic in that it often also affects many extra–articular tissues throughout the body including the skin, blood vessels, heart, lungs, and muscles. (Lix L, et al., 2006).

This concept identifies the data sources and methods that have been used to define RA using administrative data, and describes some of the RA-related research using data from the Manitoba Population Research Data Repository.

Note: Rheumatoid arthritis is a very specific type of arthritis. For a more general definition of arthritis, please read the Arthritis - Measuring Prevalence concept.

Data Sources and Methods for Defining Rheumatoid Arthritis (RA)

The data sources used to define RA in administrative data include:


• diagnosis codes in the Hospital Abstracts data
  
• diagnosis codes in the Medical Services / Medical Claims data, and can also include,
  
• Anatomical Therapeutic Chemical (ATC) codes in the Drug Program Information Network (DPIN) data

The International Classification of Diseases (ICD) codes used to identify RA in the hospital and medical services / medical claims data sources include:


• ICD-9-CM code: 714
  
• ICD-10-CA codes: M05 and M06

Pharmacological treatment of RA is primarily by:


• disease-modifying anti-rheumatic drugs (DMARDS), which include xenobiotic agents and biologic agents,
  
• anti-inflammatory agents including glucocorticoids and non-steroidal anti-inflammatory agents (NSAIDs), and
  
• analgesics such as acetaminophen, opiates, and topical agents. (Lix L et al., 2006).

For specific ATC codes used to identify treatment of RA, please see the individual research information provided below.

Rheumatoid Arthritis Research using Data from the Manitoba Population Research Data Repository

• In Lix L et al., (2006) they investigated the validity of different algorithms for chronic diseases. They identified rheumatoid arthritis (RA) (as part of an investigation into arthritis that also included osteoarthritis) by the presence of ICD-9-CM code 714.x in hospital and/or physician claims data, and/or the presence of relevant prescription drug (DMARDS, NSAIDS, and analgesics) records.
  
  For a list of prescriptions related to RA treatment used in this study, please read APPENDIX B: SUPPLEMENTARY DATA FOR ARTHRITIS ALGORITHMS in the deliverable.
  
  
• In Raymond C et al., (2012) they investigated the use of biologic agents for the treatment of rheumatoid arthritis, ankylosing spondylitis, inflammatory bowel disease, and psoriasis. RA was identified by the presence of ICD-9-CM code: 714 and/or ICD-10-CA codes: M05 and M06 in physician or hospital claims.
  
  For more information on the methods and results related to this investigation, please read Chapter 5: Biologic Agents (PDF) in the deliverable.
  
  
• In Marrie RA et al., (2017) they used the following algorithm:
  
  
  • ICD-9-CM code: 714.0 / ICD-10-CA codes: M05, M06
    For less than 2 years of data, >= 3 hospital abstract records and/or physician visits.
    For 2 or more years of data, >= 5 hospital abstract records and/or physician visits.
  
  For more information, please read the full-text Rising incidence of psychiatric disorders before diagnosis of immune-mediated inflammatory disease (PDF) article.
  
  
• In Hitchon CA et al., (2020) they investigated the validation of the administrative definition for RA in the Manitoba Population Research Data Repository (MPRDR) using the University of Manitoba Rheumatology clinic (UMRC) diagnosis as the criterion standard. As a comparison, they found other administrative definitions available in other studies during the study period, and investigated the following three definitions:
  
  
  • Definition 1: Individuals were identified with RA if they were residents of Manitoba for 2 years or more and had 5 or more physician visits or hospitalizations with ICD-9-CM/ICD-10-CA codes 714/M05, M06. For those who were residents for less than 2 years, this was reduced to 3 or more claims.
    
  • Definition 2: >= 2 physician visits >= 2 months apart with an RA diagnostic code (ICD9 714.X), excluded if for >= 2 visits, after second RA visit, had diagnoses of other inflammatory arthritis (systemic lupus erythematosus, other connective tissue diseases, psoriatic arthritis, ankylosing spondylitis, and other spondyloarthropathies.
    
  • Definition 3: 3a) >= 1 physician visits for 1 year; or 3b): >= 2 physician visits for 1 year.
  
  Validity of the administrative definitions for RA was determined for use in the entire Manitoba population and then estimated separately for First Nations (FN) and non-FN populations. The κ, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) with 95% confidence intervals (95% CIs) and Youden J statistic were calculated to determine the most appropriate definition to use in the MPRDR. They were most interested in specificity to minimize over diagnosis, so they further characterized the “false-positive” RA cases identified by definition 1, by determining the diagnosis assigned in the UMRC database and the use of prescribed arthritis medications (disease-modifying antirheumatic drugs (DMARDS), biologics, or corticosteroids) as identified in the following list:

  Drug claims codes based on the World Health Organization’s Anatomic Therapeutic Chemical (ATC) Classification System: Disease-Modifying Anti-Rheumatic Drugs (DMARDs) and biologics available at time of data extraction:

  A07EC01 sulfasalazine
  J01AA08 minocycline
  L01AA01 cyclophosphamide
  L01BA01 methotrexate
  L04AA01 cyclosporine
  L04AA13 leflunomide
  L04AX01 azathioprine
  L04AX03 methotrexate
  M01CB01 sodium aurothiomalate
  M01CB03 auranofin
  M01CB04 aurothioglucose
  M01CC01 penicillamine
  P01BA02 hydroxychloroquine
  L04AA11 etanercept
  L04AA12 infliximab
  L04AA14 anakinra

  For more information, please read the full-text Prevalence and Incidence of Rheumatoid Arthritis in Canadian First Nations and Non–First Nations People (PDF) article.

Data Cautions / Limitations

• The ICD-9-CM codes do not reflect an updated classification of juvenile chronic arthritis / juvenile idiopathic arthritis (JIA). Therefore, it is assumed that prevalence and incidence in individuals younger than 18 years would be slightly underestimated.
  
• medication lists related to any disease treatment should be reviewed prior to your research to ensure you are using an up to date list of relevant medications.