How Fibromyalgia Is Diagnosed

Diagnosis begins by excluding other causes

fibromyalgia diagnosis
© Verywell, 2018

Fibromyalgia is a difficult disorder to diagnose. Because it is so poorly understood, there is no clear consensus as to what measures could or should be used to confirm it. Moreover, even if you have signs of the disorder—including chronic widespread pain and fatigue—available lab and imaging tests will often appear perfectly normal. Because of this, the only way to get a fibromyalgia diagnosis is to embark on a "diagnosis of exclusion." This can be a painstaking process in which your doctor reviews and weeds out many other possible causes of your symptoms. Only when these causes are excluded can a diagnosis of fibromyalgia be made.

Diagnostic Criteria

Because there is no test available to confirm fibromyalgia, your doctor must rely solely on your panel of symptoms to make a diagnosis. The diagnosis is typically overseen by a medical specialist known as a rheumatologist who specializes in musculoskeletal diseases and autoimmune disorders. Some neurologists and general practitioners may also have the experience to oversee the evaluation.

The criteria for diagnosis was established by the American College of Rheumatology (ACR) in 1990 and then provisionally updated in 2010 to allow for a more practical approach to diagnosis. Instead of diagnosing the disorder based on the history and location of the pain, the current guidelines instruct physicians to evaluate three key criteria:

  1. How widespread the pain is and how you experience symptoms
  2. Whether the symptoms have persisted at this level for at least three months
  3. Whether there are no other explanations for the symptoms

The score-based ACR Fibromyalgia Diagnostic Criteria system includes an evaluation called the widespread pain index (WPI) and another called the symptom severity (SS) scale.

While the ACR system is commonly used, it does have its detractors who believe that fibromyalgia should not be evaluated as a purely somatic (physical) disorder but one in which psychological factors and psychosocial stresses are also assessed.

Exclusionary Diagnosis

Before closely evaluating your current symptoms, your doctor needs to exclude other diseases or disorders with similar symptoms and characteristics. Depending on the range of symptoms you have (digestive, urinary, psychological, etc.), the list can become quite extensive.

Among the possibilities:

The challenge in diagnosing fibromyalgia is that other conditions can often co-exist with fibromyalgia and have similar or overlapping symptoms. For instance, if arthritis or sleep apnea is diagnosed, the diagnosis might explain some of the key symptoms you are experiencing, but not others.

As such, you need an experienced clinician who is able to make the subtle distinctions.

Widespread Pain Index

The widespread pain index (WPI) breaks the body down into 19 sections, each of which is considered a characteristic area of involvement. Your doctor will ask if you experienced pain in each area in the past week. A score of 1 is registered for every "yes" you give.

You may also be asked to characterize the type of pain you had (such as severe or diffuse) or consider tender points (pain trigger points) that used to be central to the diagnosis.

The 19 pain sites included in the evaluation are (from top to bottom):

  • Right jaw
  • Left jaw
  • Neck
  • Right shoulder girdle
  • Left shoulder girdle
  • Right upper arm
  • Left upper arm
  • Right lower arm
  • Left lower arm
  • Upper back
  • Lower back
  • Chest
  • Abdomen
  • Right hip/buttock/upper thigh
  • Left hip/buttock/upper thigh
  • Right upper leg
  • Left upper leg
  • Right lower leg
  • Left lower leg

The maximum score for the WPI is 19.

Symptom Severity Scale

The symptom severity (SS) scale evaluates four symptoms considered defining in a fibromyalgia diagnosis. Each symptom is scored on a scale of 0 to 3, with 0 meaning no symptoms; 1 meaning mild symptoms; 2 meaning moderate symptoms; and 3 meaning serious symptoms. The score is based purely on the severity of symptoms that have occurred within the past week.

The four symptoms evaluated in the criteria are:

The maximum score on the SS scale is 12.

Confirming the Diagnosis

If no other explanation for your symptoms can be found, your doctor will look to see if your combined WPI and SS scores meet either one of two ACR criteria for possible fibromyalgia diagnosis:

  • A WPI score of 7 or more AND an SS score of 5 or more
  • A WPI score of 3 to 6 AND an SS score of 9 or more

Thereafter, if the doctor can establish that your symptoms have been present at the same or similar level for at least three months, you would be officially diagnosed as having fibromyalgia.

Once the diagnosis is confirmed, you and your doctor can then begin exploring treatment options. This can another be a long and protracted process, but one that can put you on the road to better health and sustained remission.

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