FAQs (Data Related) Additional Case Definition

1. Why was the arthritis case definition changed in 2002?
2. How is the current case definition of doctor-diagnosed (used since 2002) different from the old case definition (used 1996–2001)?

1. Why was the arthritis case definition changed in 2002?

   CDC, partners, and outside experts agreed to use a new definition, starting in 2002. The reasons for this were many.

   First, the questions used to determine both doctor-diagnosed arthritis and chronic joint symptoms were changed. A summary of the BRFSS arthritis questions from 1996 on can be found in the following document.

   Because of the change in the questions and the results of validation studies, a new case definition appeared in order. Using doctor-diagnosed arthritis as the definition:

   • Is likely to be more valid than the old definition, in identifying those most likely to have arthritis.
   • Is more compatible with surveillance definitions for other health conditions.
   • Identifies those most likely to be affected by arthritis, and thus more likely to be more receptive to our interventions.
   • Would be easier to adapt to a smaller BRFSS survey being considered for the future, because it requires only one question.
     

2. How is the current case definition of doctor-diagnosed (used since 2002) different from the old case definition (used 1996–2001)?

   From 1996 to 2001, the case definition included those with doctor-diagnosed arthritis and/or those with chronic joint symptoms and labeled them “arthritis or chronic joint symptoms.”

   Since 2002, CDC, partners, and outside experts have agreed on a new case definition of simply “doctor-diagnosed arthritis.”

   As an interim step from 2002 to 2007 people with chronic joint symptoms but no doctor-diagnosed arthritis, were put into a category called “possible arthritis.” CDC advised analysts to keep estimates for “possible arthritis” separate from estimates for doctor-diagnosed arthritis.

   In 2009, the 2 questions on chronic joint symptoms will be dropped and replaced with other questions that address the impact of arthritis.

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