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National Center for Chronic Disease Prevention and Health Promotion
Arthritis
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National Center for Chronic Disease Prevention and Health Promotion Arthritis Home | About Us | Contact Us |
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Note: These questions refer to both NHIS and BRFSS surveys, unless otherwise indicated.
How is the new 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.”
[Note: People with chronic joint symptoms but no doctor-diagnosed arthritis, are now called “possible arthritis.” Estimates for “possible arthritis” should not be added to estimates for doctor-diagnosed arthritis. See more about “possible arthritis.”]
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:
Would be
easier to adapt to a smaller BRFSS survey being considered for the future,
because it requires only one question.
What 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 2010 also recommends using NHIS data for national estimates.
Using NHIS data (2003-2005), we estimate that 46.4 million (21.6%)
adults had doctor-diagnosed arthritis.
There are differences in the national arthritis prevalence estimates between 2001 to 2002. Why?
There are three main reasons account for the differences.
Change in the data source. In 2001, BRFSS was used to
produce a national estimate. In 2002, the National Health Interview Survey (NHIS)
was used. NHIS will be used for
future estimates.
Why did CDC add 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.
Why are the neck and back excluded from the survey question addressing joint symptoms: “The next questions refer to your joints. Please do NOT include the back or neck. DURING THE PAST 30 DAYS, have you had any symptoms of pain, aching, or stiffness in or around a joint?”
Although many types of arthritis can affect the neck and back,
many neck and back symptoms are due to
other conditions. Experts recommended we exclude those with neck or back
symptoms to assure a conservative estimate of doctor-diagnosed arthritis.
Should people with doctor-diagnosed arthritis but no chronic joint symptoms be excluded from the prevalence estimate?
No, they should not be excluded from prevalence estimates.
It is not unusual for joint symptoms to come
and go as the condition worsens and improves. Moreover, the use of medications
can affect the occurrence of joint symptoms. Accordingly, we would not
exclude these persons when making estimates of the prevalence of arthritis.
State prevalence estimates should be for all persons with doctor-diagnosed
arthritis regardless of whether they have symptoms at the time they are surveyed.
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, lupus) because self-reported condition data have been shown to be inaccurate based on studies done by the program and other researchers. For example, the CDC Arthritis Program compared how frequently the arthritis condition type reported by participants in the Medical Expenditure Panel Survey1 (MEPS) agreed with each of the participants’ doctor’s diagnosis. This study found that among persons whose doctor had diagnosed them with osteoarthritis, only 9% 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.
1 The Medical Expenditure Panel Survey is a nationally
representative survey of the U.S. civilian non-institutionalized population.
What is CDC doing to learn more about the people with possible arthritis?
Analyses are under way to further
characterize this group. Four states
collected additional information through the 2005 BRFSS on this specific
population. Two of the questions are: 1) “Earlier you said you had never seen
a doctor about your joint symptoms. Please tell me why you did not see a
doctor about your joint symptoms?” 2) “Earlier you said you had seen a doctor
for your joint symptoms. What did the doctor say was the cause of your joint
symptoms?” The responses to these questions should give us additional insight
about this group. We will share results of this work as it
becomes available. Additionally, CDC will be analyzing data for people with
possible arthritis from a national sample collected in 2005-2006 through the
Arthritis Conditions Health Effects Survey (ACHES).
See note.
What changes are expected for future BRFSS surveys?
We expect BRFSS will continue to put arthritis questions on the core in odd
numbered years, although the number of questions allotted for arthritis may
decrease in future years. We are proposing a new arthritis questions for the
BRFSS Core in 2009. A list of BRFSS
Arthritis Core (Burden Questions) by year is available.
How often are the Arthritis Burden Questions on the BRFSS survey?
Starting in 2003, the BRFSS Arthritis Core
(Burden Questions) are offered on the core survey in odd
numbered years. State programs are encouraged to add the optional module
known as the
BRFSS Arthritis Optional Module (Management
Questions) in the same odd-numbered year. Although states may be
interested in using the questions every year, CDC will NOT financially or
analytically support the use of any arthritis questions in even numbered
years. States may add them as state-added questions.
What does the CDC Arthritis Program recommend state arthritis programs do regarding the BRFSS survey in even years?
CDC is not supporting the use of arthritis questions in even years. This means
we are not funding the BRFSS to put the questions on the survey nor are we
providing our standard analytic tables, as we
do for all states using odd number year data. Any use of
these questions in even years would have to be as state-added questions. We do
not feel it is necessary to have the data each year, as the prevalence is
unlikely to change rapidly and with lots of programs competing for space on the
questionnaire, one can quickly wear their welcome out with the BRFSS
coordinator. In infrequent instances, when a state feels it is imperative for
its program to make substate prevalence estimates (e.g., for large cities),
it may choose to use the arthritis questions in even years. CDC is unable to
provide any support for doing this and we don’t recommend it.
Is there more than one way to define a “case” of arthritis?
Yes, the purpose (e.g., estimating prevalence or assessing burden) and source of the data determine the arthritis case definition to be used. In general, data used in arthritis surveillance falls into two broad categories, self-reported data and health care system data.
For the purpose of estimating the population prevalence of arthritis, 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, and use doctor-diagnosed arthritis as the case definition. 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?” Further information on the CDC arthritis case definition is available.
For assessing the burden of arthritis using
health care 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
(PDF-73K) and
is labeled “arthritis and other rheumatic conditions”. The CDC discourages
states from pursuing these assessments unless there is a direct link to program
activity that is consistent with the state arthritis plan.
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.
Some documents on this page are available in Portable Document Format (PDF). Learn more
about viewing and printing PDF documents with
Acrobat Reader.
A note about “possible arthritis”
“Possible arthritis” is another variant of self-reported data. It is defined
as a person without doctor-diagnosed arthritis who answers “yes” to both
of the following questions: “During the past 30 days, have you had any symptoms
of pain, aching or stiffness in or around a joint?” and “Did your joint symptoms
first begin more than 3 months ago?” The state-based Behavioral Risk Factor
Surveillance System (BRFSS) and National Health Interview Survey (NHIS) can
identify persons with “possible arthritis.” Analysis of BRFSS data on
“possible arthritis” indicates
the group has a different demographic profile than those with doctor
diagnosed arthritis. Unlike doctor-diagnosed arthritis,
“possible arthritis” decreases
with age and is more common in men than women. A smaller proportion of
people with possible arthritis report activity limitation due to joint
symptoms compared to those with doctor-diagnosed arthritis. CDC is currently
analyzing data from 4 states collected in 2005 to learn more about people
with “possible arthritis.” Additionally, CDC will be analyzing data for people
with possible arthritis from a national sample collected in 2005 through the
Arthritis Conditions Health Effects Survey (ACHES). We are still learning
who these people are and whether or not they fit into the larger arthritis
picture.
Page last reviewed: June 15, 2007
Page last modified: June 13, 2007
Content Source: Division of
Adult and Community Health,
National Center for Chronic Disease Prevention and Health Promotion
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