Arthritis Case Definitions

Overview

Having a standard case definition of a condition is important for surveillance and other public health research. CDC, the National Arthritis Data Workgroup, and others have developed public health case definitions for general arthritis or related rheumatologic conditions (e.g., lupus). The public health definitions are broader than those used by clinicians. We include arthritis-related conditions that would otherwise be left out, which is important when making comparisons of the burden and impact of arthritis and other major medical conditions. We exclude musculoskeletal conditions that are major public health problems in their own right (e.g., osteoporosis, chronic back conditions) but are unlikely to include a high proportion of what is considered to be arthritis.

Because arthritis in children is generally different from that in adults, there are separate case definitions for these groups. In addition, there are two definitions for adults that include self-reported and healthcare system data.

Adult Arthritis Case Definition

Estimating Population Prevalence

There are two case definitions for adult arthritis: one for information that people report themselves (self-reported or “doctor-diagnosed arthritis”) and one for coded information available from healthcare system encounters (the ICD-based “arthritis and other rheumatic conditions” or AORC).

Self-reported data

For estimating how common arthritis is in the general population, we recommend using self-reported data as the data source and using doctor-diagnosed arthritis as the case definition. Both the state-based Behavioral Risk Factor Surveillance System (BRFSS) and National Health Interview Survey (NHIS) are self-reported data surveys. A “case” of doctor-diagnosed arthritis in these surveys is defined as a “yes” answer to the following question; “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?”

NHIS starting using this case definition question annually in 2002.  BRFSS started using this case definition question as part of a 4-question Arthritis Burden module in odd-numbered years starting in 2003.  In 2011 the BRFSS case finding question for doctor-diagnosed arthritis was moved out of the Arthritis Burden module to a general chronic disease module.  An optional, 4-question BRFSS Arthritis Management Module is used by some states in the odd-numbered years. Get more information about self-reported adult case definitions.

Healthcare system data

For assessing the burden of arthritis using healthcare system data (e.g. hospital discharge data, ambulatory care, death.) a “case” of arthritis is defined by the National Arthritis Data Workgroup definition using arthritis related ICD-9-CM codes and is labeled “arthritis and other rheumatic conditions”.

Be aware that other studies (e.g., clinical trials), including some statistics and studies cited elsewhere on this website, have different data sources and use different arthritis case definitions, and some surveys choose to code their self-report data using ICD-9 codes.

Pediatric Arthritis Case Definition

Pediatric Arthritis Case Definition for Surveillance

In the Arthritis Prevention Control and Cure Act of 2004, Congress directed CDC to estimate the prevalence of childhood arthritis.

The CDC Arthritis Program finalized a standardized case definition for ongoing monitoring of pediatric arthritis and other rheumatologic conditions after consulting with key constituents and partners.¹ The definition is based on selected pediatric arthritis and other rheumatologic conditions ICD-9-CM codes used in health care and other data sources. Researchers apply these codes to national ambulatory care surveys to estimate both the number of ambulatory health care encounters and the number of children with pediatric arthritis and other rheumatologic conditions.

Reference

1. 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. abstract