At this time, there is no specific test that can be used to diagnose fibromyalgia. The syndrome is usually diagnosed by documenting the patient’s medical history, ruling out disorders and diseases that may be mimicking or exacerbating fibromyalgia, and by utilising the criteria developed by the American College of Rheumatology (ACR) in 1990. These criteria include:
- A history of widespread chronic pain for at least three months in all four body quadrants – right and left upper body and right and left lower body; pain in the axial skeleton (cervical, down the spine, and/or in the chest)
- Pain in 11 of 18 tender points, as measured by palpation using a 4 kg force [Illustration of tender point locations; test must be performed by a trained professional].
The ACR criteria were originally developed to guide fibromyalgia research, and there is some controversy in using them clinically. Because a patient’s symptoms may vary and may come and go, a person may not meet the criteria at the time they are initially tested. Doctors generally consider the results of this evaluation in conjunction with other findings.
Laboratory tests can be useful to help diagnose conditions with symptoms similar to fibromyalgia and to identify disorders that may be coexisting with fibromyalgia, such as rheumatoid arthritis, Sjögren’s syndrome, thyroid disease, and lupus. It is not usually cost effective or necessary to do extensive screening. General tests that may be ordered include:
- E/LFT's – to examine electrolytes, proteins, liver and kidney function, calcium, and glucose
- FBC (full blood count) – to look for anaemia, white and red blood cell abnormalities
- TSH (thyroid stimulating hormone) and/or other thyroid testing as hypothyroidism can cause symptoms similar to fibromyalgia
- ANA (anti-nuclear antibody) - to help rule out autoimmune disorders if features are present.
- CK (creatine kinase) - to rule out other conditions that can cause muscle weakness or pain.
Other specific tests may be ordered to rule out diseases that mimic fibromyalgia based on the patient's symptoms and on the findings of these general screening tests. It should be noted that any abnormal laboratory test results are usually due to something other than fibromyalgia.
Some very specialised laboratory tests, such as the measurement of Substance P (a neurochemical that signals the brain to register pain), may be used in a research setting to attempt to better understand the cause and course of fibromyalgia, but they are not considered clinically useful at this time.
Occasionally, an imaging scan may be ordered to help rule out a disorder that is causing symptoms similar to fibromyalgia, such as an MRI (magnetic resonance imaging) to help identify multiple sclerosis.