Fibromyalgia (FM) is a chronic pain disorder characterized by widespread musculoskeletal pain, profound fatigue, and cognitive difficulties, primarily based on the patient’s subjective report. Since there are no definitive laboratory tests or imaging scans to confirm the diagnosis, medical professionals rely on a detailed clinical assessment. This evaluation uses established diagnostic criteria and specific interview techniques and physical maneuvers to assess the consistency of the patient’s complaints and differentiate genuine FM symptoms from exaggerated reporting.
Characteristics of a Clinical Fibromyalgia Diagnosis
A fibromyalgia diagnosis is established using standardized criteria, most commonly the 2016 revised criteria from the American College of Rheumatology (ACR). These criteria require a combination of a widespread pain index (WPI) score and a symptom severity (SS) scale score. The WPI quantifies the number of body areas where the patient has experienced pain in the past week, while the SS scale rates the severity of fatigue, unrefreshed sleep, and cognitive symptoms.
To meet the criteria, a patient must report pain in at least four out of five body regions, establishing a generalized pain pattern. Symptoms must have persisted at a similar level for at least three months to rule out acute conditions. Clinicians look for a WPI score of 7 or higher paired with an SS score of 5 or higher, or a WPI score between 4 and 6 paired with an SS score of 9 or more.
Discrepancies in Subjective Symptom Reporting
During the initial interview, clinicians look for consistency in reported symptoms, noting that genuine FM pain is diffuse, bilateral, and involves the axial skeleton. Symptom magnification may be indicated by a description of pain that is overly dramatic, excessively detailed, yet vague in its precise location or quality. Patients with non-organic presentations may claim an incapacitating level of pain, sometimes rating it as “10 out of 10,” even while discussing activities inconsistent with such severe disability.
A specific inconsistency is the mapping of pain outside of known anatomical distributions, such as claiming pain across the entire body, including areas like the palms or soles of the feet. Another finding is “give-way weakness,” observed when testing muscle strength. The patient may appear to exert maximal effort, but the muscle suddenly collapses without a physiological reason, suggesting a lack of sustained effort. This non-physiological presentation contrasts sharply with the consistent, though reduced, strength found in patients with actual neurological weakness.
Non-Organic Findings During Physical Examination
The physical examination uses specific maneuvers designed to assess the patient’s pain response consistency and rule out non-physiological complaints. These non-organic signs are tools for evaluating the reliability of the patient’s reported pain and functional limitations, not tests for a specific disease. Superficial tenderness, where light touch or pinch over a wide area of skin elicits an exaggerated pain response, is one finding. Non-anatomic tenderness occurs when deep pain is reported over an area that does not correspond to a specific anatomical structure, nerve, or musculoskeletal distribution.
Simulation tests are useful because they appear to test a painful movement without actually stressing the affected body part. During an axial loading test, a physician applies gentle downward pressure to the top of a standing patient’s head, which should not cause low back pain. A report of significant pain in the lumbar spine during this light maneuver is considered a non-physiological response.
Another simulation is the simulated rotation test, where the physician passively rotates the patient’s shoulders and pelvis simultaneously while they stand. Since this rotation happens at the hips and does not move the lumbar spine, a report of back pain indicates symptom inconsistency. The concept of “inconsistent tenderness” is noted when a patient’s pain response shifts or changes intensity when the same tender area is re-tested or when the patient is distracted.
For example, a patient may exhibit limited range of motion during a formal test, but then demonstrate a much greater range of motion when attention is diverted. When several of these non-organic signs are present, they suggest a behavioral component, indicating symptom magnification or an illness behavior disproportionate to the underlying physical findings.