Extensive investigations are not needed for diagnosing FM. Diagnosis can be suspected after obtaining a thorough history and clinical examination. When the pretest probability for FM is high, the minimum screening tests recommended are complete blood counts, ESR, CRP, and TSH. (Clauw & Goldenberg 2009; Fitzcharles et al., 2013). Normal inflammatory markers are supportive of FM diagnosis.

In some patients, assessment of serum transaminases, CPK, creatinine, calcium, phosphorus, and alkaline phosphatase may be needed, especially if the symptom combinations are not typical of FM. Moreover, the laboratory and clinical workup would be different depending upon the duration of CWP. More extensive workup is required in acute or sub-acute presentation to rule out more serious disorders like osteomalacia, secondaries (metastatic bone
disease), SLE, and polymyalgia rheumatica. In individuals with chronic waxing and waning symptoms and normal physical examination, a serious autoimmune, endocrine or neoplastic condition is extremely unlikely (Fitzcharles et al., 2013). Hence extensive investigations are not needed.

It is better to avoid testing of rheumatoid factor, anti-CCP or ANA, unless there is a strong suspicion of connective tissue diseases. ANA titer of 1:40 is common and may occur in 30% of the global population (Clauw et al., 2005; Tan et al., 1997). Only less than 1 in 100 with positive ANA will have
SLE. Similarly, extensive neurological and radiological investigations are not warranted in FM suspected cases.

REFERENCES
1. Clauw D, Goldenberg DL. Fibromyalgia. In Stone JH (ed.) A Clinician’s Pearls and Myths in Rheumatology. Springer. 2009; 341-349.
2. Fitzcharles MA, Ste-Marie PA, Goldenberg DL, Pereira JX, Abbey S, Choinière M, Ko G, Moulin DE, Panopalis P, Proulx J, Shir Y; National Fibromyalgia Guideline Advisory Panel. 2012 Canadian Guidelines for the diagnosis and management of fibromyalgia syndrome: executive summary. Pain Res Manag. 2013; 18(3):119-26.
3. Clauw DJ. The Evaluation of Individuals with Chronic Widespread Pain. In Wallace DJ & Clauw DJ (eds). Fibromyalgia and other Central Pain Syndromes. LWW. 2005; 293-298.
4. Tan EM, Feltkamp TE, Smolen JS et al. Range of antinuclear antibodies in “healthy” individuals. Arthritis Rheum 1997; 40(9):1601-1611.