- Last Updated: 30 August 2017 30 August 2017
Differential diagnosis between ME/CFS and fibromyalgia
Fibromyalgia (FM) is a common and chronic disorder characterized by widespread pain, diffuse tenderness, and a number of other symptoms. The pain is widespread, affecting all four quadrants of the body, and can be severe enough to interfere with routine daily activities. It migrates, can be achy, throbbing, shooting, or stabbing, and is worse in areas used most, like the neck or back.
Individuals often say they awaken feeling as if they hadn't slept. A sudden onset of profound fatigue can occur during or following exertion. Many other symptoms are common to fibromyalgia, including stiffness on waking, memory and concentration problems, excessive sensitivity of the senses, headaches, Temporomandibular Joint Syndrome (TMJ), irritable bowel, and bladder and muscle spasm.
Fibrositis, an older name, is still used interchangeably with fibromyalgia.
Although fibromyalgia is often considered an arthritis-related condition and is usually diagnosed and treated by rheumatologists, it is not truly a form of arthritis (a disease of the joints) because it does not cause inflammation or damage to the joints, muscles, or other tissues. It is often associated with the Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and sometimes confused with it.
Research authorities vary in viewpoint as to the relation of FM and ME/CFS, but the best research to date indicates that the two illnesses, while often associated, are different and separable—both in nature of causation and in their pathophysiologies (effects on processes in the body.)
The fact that the two illnesses are the province of separate specialties can also lead to diagnostic problems. As a rheumatologist is trained in rheumatological illnesses, there are occurrences of ME/CFS being diagnosed as FM when the physician is not well versed in the diagnosis of ME/CFS. And an infectious disease specialist may be prone to misdiagnosing FM as ME/CFS.
Therefore, when there is doubt about which illness a patient has, s/he should become familiar with the differences between the two illnesses and seek a physician who knows how to diagnose both illnesses.
Note that it is very common for a patient to be diagnosed with both FM and ME/CFS.
Diagnosis of Fibromyalgia (FM)
In May 2010, the American College of Rheumatology (ACR) released new criteria for the clinical diagnosis of Fibromyalgia (FM). These replace older criteria published in 1990. Using the older criteria, besides having widespread pain on both sides of the body for at least 3 months, a patient needed to have pain (not just ‘tenderness’) present in 11 out of 18 specific tender point sites in order to be diagnosed with FM.
Computing the Widespread Pain Index and Severity Scale Symptoms Scores
The new criteria recommend that the tender point examination be replaced with a combination of a widespread pain index (WPI) and severity scale of symptoms (SS) as the revised standards for the diagnosis of FM.
The Widespread Pain Index is scored by asking the patient about whether pain was experienced in the last week in 19 different areas of the body. Score one point for each area (total WPI score is from 0 – 19).
The Symptom Severity Scale rates the severity in the last week of the following symptoms from 0 (no problems) to 3 (severe, life-disturbing):
- waking unrefreshed
- cognitive symptoms.
In addition to these three, the severity of any/all other symptoms is rated from 0 to 3. This results in a total SS score of from 0 – 12.
For more detail, see this chart [2010_diagnostic_criteria_graphic.pdf]
Making the diagnosis based on the scores
Using these new criteria, a diagnosis of Fibromyalgia will be made on the following basis:
- The values and ranges allowed for the WPI and the SS scales should meet one of the combinations: WPI >7 AND SS >5 or WPI 3–6 AND SS >9.
- Symptoms have persisted at this level for the past 3 months.
- The patient does not have any other disorder or cause to explain the pain.
Note: There is a new blood test for Fibromyalgia that is being developed by a private clinic. Independent validation of this test has shown mixed results so far.