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FAQs-Self-Reported Case Definition

Note: These questions refer to both NHIS and BRFSS surveys, unless otherwise indicated.

  1. Why does CDC include the four types of arthritis to the end of the survey question addressing doctor-diagnosed arthritis: “Have you ever been told by a doctor or other health professional you have some form of arthritis, rheumatoid arthritis, gout, lupus, or fibromyalgia?
  2. Which estimate best indicates the prevalence of arthritis for the nation?
  3. Is self-reported information on the type of arthritis valid?
  4. What happened with the 2011 BRSS that might alter use of the doctor-diagnosed arthritis case definition?

 

 

  1. Why does CDC include the four types of arthritis to the end of the survey question addressing doctor-diagnosed arthritis: “Have you ever been told by a doctor or other health professional you have some form of arthritis, rheumatoid arthritis, gout, lupus, or fibromyalgia

For public health surveillance, we are trying to capture more than 100 diseases that are considered “arthritis or other rheumatic conditions.” Some of these conditions may not be readily recognized as arthritis by survey respondents. Experts recommended adding these conditions.

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  1. Which estimate best indicates the prevalence of arthritis for the nation?

National estimates should come from a national survey; CDC uses the National Health Interview Survey (NHIS) for such estimates. Healthy People 2020 also recommends using NHIS data for national estimates.

Using NHIS data (2010-2012), we estimate that 52.5 million (22.7%) adults had doctor-diagnosed arthritis.1

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  1. Is self-reported information on the type of arthritis valid?

The CDC Arthritis Program strongly discourages the collection and reporting of self-reported data on arthritis type (e.g., osteoarthritis, rheumatoid arthritis, and lupus) because self-reported condition data have been shown to be inaccurate in studies done by program staff and other researchers. For example, a study conducted by the Agency for Healthcare Research and Quality examined how frequently the arthritis type reported by participants in the Medical Expenditure Panel Survey (MEPS) agreed with each of the participants’ doctor’s diagnosis. This study found that among persons whose doctor had diagnosed them with osteoarthritis, only 12% of survey participants reported that they had osteoarthritis. Since self-reported information on type of arthritis is not valid, the CDC arthritis program discourages states and researchers from measuring and using data on self-reported arthritis condition type.

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  1. What happened with the 2011 BRSS that might alter use of the doctor-diagnosed arthritis case definition?

Two things happened in 2011 with BRFSS.

    1. The case finding question for doctor-diagnosed arthritis was moved out of the Arthritis Burden module and into a new Chronic Health Conditions core section, along with questions for other chronic conditions.  The other 3 questions remain in the Arthritis Burden core section.  Because the sequence and immediate association with the Arthritis Burden questions have been altered, that could affect the respondent answers.
    2. The bigger issue is that BRFSS significantly changed its methods in 2011, so that estimates of doctor-diagnosed arthritis defined in 2011 and subsequent BRFSS surveys CANNOT be compared doctor-diagnosed arthritis defined in BRFSS surveys prior to 2011.  Estimates of trends can run from 1996–2001 or from 2002-2009 or from 2011 forward but not across these periods.  It would be impossible to know if any observed change across these periods is real or due to the changes to the BRFSS survey.

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References

  1. Barbour KE, Helmick CG, Theis KA, Murphy LB, Hootman JM, Brady, Cheng YJ.  Prevalence of doctor-diagnosed arthritis and arthritis-attributable activity limitation—United States, 2010-2012.  MMWR Morb Mortal Wkly Rep. 2013;62(14):869-873. PubMed PMID: 24196662. abstract

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