Materials and methods

A retrospective study including 168 outpatients with chronic non-specific musculoskeletal pain presenting between April 2015 and June 2015 was conducted at the department of Neurology, Guntur Medical College. Patients with at least two months of non-specific pain, no abnormal findings on physical examination and normal results in laboratory tests or imaging studies were included. Patients with fibromyalgia (as defined by American College of Rheumatology criteria) or complex regional pain syndrome were not included. The laboratory tests included complete blood count; erythrocyte sedimentation rate; C-reactive protein level; thyroid, liver and kidney function tests; levels of creatinine phosphokinase, rheumatoid factor and 25-hydroxyvitamin D; and a peripheral blood smear. The patients had no documented previous medical condition that would alter vitamin D metabolism. None of the participants were using vitamin D supplementation, and none had been diagnosed previously with hypovitaminosis D.