Arthritis Case Definitions
Using a standard case definition for a condition is important when conducting surveillance and public health research. Below are the arthritis case definitions that CDC uses for calculating the prevalence and impact of arthritis in the general population.
Defining Arthritis for Surveillance and Public Health Research
A surveillance case definition is a set of standard criteria used to define a disease for public health surveillance. Public health officials use case definitions to classify and count cases consistently across geographic areas or time.
CDC uses an arthritis case definition that includes arthritis and other rheumatic conditions. Some other rheumatic conditions may not technically be considered to be arthritis by health care providers but they are close enough to include in a simplified term “arthritis.” Clinical and public health experts recommend that the arthritis case definition include other rheumatic conditions because these are conditions frequently seen by rheumatologists who are doctors who treat arthritis (for example, fibromyalgia).
Health care providers use very specific clinical definitions to ensure they correctly diagnose and treat their individual patients’ conditions. They do not use surveillance case definitions to diagnose or treat individual patients. These clinical definitions distinguish specific arthritis conditions and other conditions closely related to arthritis.
Health care providers usually diagnose arthritis using the patient’s medical history, physical examination, X-rays, and tests that include bloodwork.
Defining Arthritis in Adults
Population-based surveillance and public health research uses two approaches for defining arthritis:
- Self-reported “doctor-diagnosed arthritis.”
- ICD-9-CM based arthritis.
Self-Reported Doctor-Diagnosed Arthritis
CDC recommends using self-reported doctor-diagnosed arthritis as the case definition for estimating the prevalence of arthritis. Individuals are considered to have self-reported doctor-diagnosed arthritis if they respond “yes” to: “Have you EVER been told by a doctor or other health professional that you have some form of arthritis, rheumatoid arthritis, gout, lupus, or fibromyalgia?” This case definition question appears annually on both the state-based Behavioral Risk Factor Surveillance System (BRFSS) (as of 2010) and National Health Interview Survey (NHIS) (as of 2002).
Learn more about the case definition for self-reported doctor diagnosed arthritis and related data sources on the FAQs about Case Definitions page.
ICD-9-CM Based Arthritis
Some data sources, such as health care utilization and mortality, report conditions as ICD-9-CM codes. When analyzing ICD-9-CM based data, CDC defines a “case” of arthritis as the presence of at least one arthritis related ICD-9-CM code.
CDC frequently uses the ICD-9-CM based “arthritis and other rheumatic conditions” definition that was developed by an expert panel (National Arthritis Data Workgroup).1 For more information about these definitions, see our FAQs-Self-Reported Case Definition.2
Increasingly, health systems in the United States use the ICD-10-CM. CDC will be working with other leaders in the field of arthritis public health surveillance to develop a standard list of ICD-10-CM codes that will be used to define arthritis.
Be aware that some of the statistics and studies cited elsewhere on this website are based on different arthritis case definitions.
Defining Arthritis in Children
Pediatric Arthritis Case Definition for Surveillance
The CDC Arthritis Program recommends using a standardized case definition for estimating the prevalence of childhood arthritis.2 The definition is based on selected pediatric arthritis and other rheumatologic conditions ICD-9-CM codes used in health care and other data sources. Pediatric rheumatologists developed the definition for ongoing monitoring of pediatric arthritis and other rheumatologic conditions as directed by Congress in the Arthritis Prevention Control and Cure Act of 2004.
Why Are There Separate Definitions for Adults and Children?
The pediatric case definition is a modified subset of the National Arthritis Data Workgroup ICD-9-CM definition used for adults. The definition for children includes conditions (for example, juvenile rheumatoid arthritis) that are the most prevalent among children and likely represent a substantial percentage of pediatric arthritis cases. The pediatric definition also includes conditions that are recommended for surveillance by experts including the American College of Rheumatology Section on Pediatric Rheumatology and the American Academy of Pediatrics Section on Rheumatology,
Learn more about childhood arthritis.
- Helmick CG, Lawrence RC, Pollard RA, Lloyd E, Heyse SP. Arthritis and other rheumatic conditions: who is affected now, who will be affected later? National Arthritis Data Workgroup. Arthritis Care Res. 1995;8(4):203–211. PubMed PMID: 8605258.
- Murphy LB, Cisternas MG, Greenlund KJ, et al. Defining arthritis for public health surveillance: Methods and estimates in four US population health surveys. Arthritis Care Res (Hoboken). 2017;69(3):356–367. doi: 10.1002/acr.22943. PubMed PMID: 27214851.
- Sacks JJ, Helmick CG, Luo YH, Ilowite NT, Bowyer S. Prevalence of and annual ambulatory health care visits for pediatric arthritis and other rheumatologic conditions in the United States in 2001–2004. Arthritis Care Res. 2007;57(8):1439–1445. PubMed PMID: 18050185.