Diagnosing Fibromyalgia
Fibromyalgia is diagnosed clinically when a patient has widespread pain for at least 3 months, affecting multiple body regions, without requiring the traditional 11 of 18 tender point examination that was previously mandated. 1
Diagnostic Criteria
The American College of Rheumatology has evolved its diagnostic approach, moving away from tender point counts to symptom-based criteria that are more practical for clinical use 1:
- Widespread pain duration: Pain must be present for at least 3 months in multiple body regions 1
- Symptom assessment: Evaluate pain intensity, functional limitations, sleep quality, fatigue severity, cognitive symptoms (often described as "fibro fog"), and mood disturbances including depression and anxiety 1
- The Fibromyalgia Rapid Screening Tool can be used as an initial screening method for patients presenting with diffuse chronic pain 2
Key Clinical Features to Identify
- Central pain processing abnormality: Fibromyalgia represents abnormal central pain processing (central sensitization) rather than peripheral tissue damage or inflammation 1, 3
- Associated symptoms beyond pain: Fatigue, non-restorative sleep, cognitive dysfunction, stiffness, anxiety, and depressed mood are characteristic 4, 5
- Functional somatic symptoms: Raynaud's phenomenon, irritable bowel syndrome, heat and cold intolerance, temporomandibular disorder, chronic fatigue syndrome, and migraine frequently overlap 4, 3
Diagnostic Work-Up Algorithm
Step 1: Clinical Assessment
- Obtain complete medical history including current medications 6
- Perform complete physical examination focusing on pain distribution and functional limitations 6
- Screen for psychiatric comorbidities, particularly primary mood disturbances, as these have higher prevalence in fibromyalgia patients 5, 1
Step 2: Laboratory Testing
- Order basic laboratory tests to screen for inflammatory or endocrine diseases that could mimic fibromyalgia 6
- Important caveat: There are no specific laboratory abnormalities diagnostic of fibromyalgia; testing is performed to exclude other conditions 4, 5
Step 3: Differential Diagnosis
- Fibromyalgia is NOT a diagnosis of exclusion - it has positive diagnostic criteria 1
- Rule out systemic and rheumatic diseases through history, physical examination, and laboratory investigations 5
- Distinguish from other central pain disorders (irritable bowel syndrome, chronic fatigue syndrome, migraine) using screening questions based on published criteria 5
- Consider rheumatology referral only when inflammatory rheumatic diseases are suspected or difficult to exclude 6
Step 4: Functional Assessment
- Assess limitations in daily functioning 6
- Screen for other functional somatic symptoms 6
- Refer to mental health specialists if mental disorder is identified 6
Common Diagnostic Pitfalls to Avoid
- Do not rely solely on tender point examination: The newer criteria no longer require the 11 of 18 tender point threshold, as this approach has inherent limitations 1, 5
- Do not delay diagnosis waiting to exclude every possible condition: Establishing the diagnosis early and providing education can reassure patients and decrease unnecessary testing 2
- Do not miss concomitant conditions: Fibromyalgia is highly prevalent in patients with rheumatic diseases and other chronic conditions; unrecognized fibromyalgia results in high morbidity 3
- Do not assume fibromyalgia is a psychiatric disorder: While psychiatric comorbidities are common, fibromyalgia is a distinct clinical entity with central nervous system pain processing abnormalities 1, 3
When Specialist Referral is Needed
- Rheumatology consultation: Only when concomitant inflammatory rheumatic diseases are difficult to diagnose or exclude 6
- Mental health specialist: When primary psychiatric disorders are present and require specific treatment 6
- Most patients with chronic widespread pain and fibromyalgia can be diagnosed and managed in primary care without requiring rheumatology expertise 6