BACKGROUND: We aimed to explore the American College of Rheumatology (ACR) 1990 and 2011 fibromyalgia (FM) classification criteria’s items and the components of Fibromyalgia Impact Questionnaire (FIQ) to identify features best discriminating FM features. Finally, we developed a combined FM diagnostic (C-FM) model using the FM’s key features. METHODS: The means and frequency on tender points (TPs), ACR 2011 components and FIQ items were calculated in the FM and non-FM (osteoarthritis [OA] and non-OA) patients. Then, two-step multiple logistic regression analysis was performed to order these variables according to their maximal statistical contribution in predicting group membership. Partial correlations assessed their unique contribution, and two-group discriminant analysis provided a classification table. Using receiver operator characteristic analyses, we determined the sensitivity and specificity of the final model. RESULTS: A total of 172 patients with FM, 75 with OA and 21 with periarthritis or regional pain syndromes were enrolled. Two steps multiple logistic regression analysis identified 8 key features of FM which accounted for 64.8% of variance associated with FM group membership: lateral epicondyle TP with variance percentages (36.9%), neck pain (14.5%), fatigue (4.7%), insomnia (3%), upper back pain (2.2%), shoulder pain (1.5%), gluteal TP (1.2%), and FIQ fatigue (0.9%). The C-FM model demonstrated a 91.4% correct classification rate, 91.9% for sensitivity and 91.7% for specificity. CONCLUSIONS: The C-FM model can accurately detect FM patients among other pain disorders. Re-inclusion of TPs along with saving of FM main symptoms in the C-FM model is a unique feature of this model.
Back Pain ; Chronic Pain ; Classification ; Discriminant Analysis ; Fatigue ; Fibromyalgia ; Humans ; Logistic Models ; Neck Pain ; Osteoarthritis ; Periarthritis ; Rheumatology ; Sensitivity and Specificity ; Shoulder Pain ; Sleep Initiation and Maintenance Disorders

BACKGROUND: This study was designed to assess serum vitamin D status (25-OHD) in the fibromyalgia (FM) patients and to compare it with a healthy control group. It also aimed to investigate the correlation of serum vitamin D level with FM symptom severity and invalidation experiences. METHODS: A total of 74 consecutive patients with FM and 68 healthy control participants were enrolled. The eligible FM patients completed the Illness Invalidation Inventory (3*I), the Revised Fibromyalgia Impact Questionnaire (FIQR) and a short-form health survey (SF-12). Venous blood samples were drawn from all participants to evaluate serum 25-OHD levels. Mann-Whitney tests and multiple logistic regression analyses were performed and Spearman's correlations were calculated. RESULTS: 88.4% of FM patients had low levels of serum 25-OHD. FM patients had significantly higher level of serum 25-OHD than the control group (17.24 ± 13.50 and 9.91 ± 6.47 respectively, P = 0.0001). There were no significant correlations between serum 25-OHD levels and the clinical measures of disease impact, invalidation dimensions, and health status. Multiple logistic regression analyses revealed that an increased discounting of the disease by the patient's spouse was associated with a 4-fold increased risk for vitamin D deficiency (OR = 4.36; 95% CI, 0.95-19.87, P = 0.05). CONCLUSIONS: This study showed that although high rates of vitamin D insufficiency or deficiency were seen among FM patients and healthy non-FM participants, but it seems there was no intrinsic association between FM and vitamin D deficiency. Addressing of invalidation experience especially by the patient's spouse is important in management of FM.
Fibromyalgia* ; Health Surveys ; Humans ; Iran ; Logistic Models ; Spouses ; Surveys and Questionnaires ; Vitamin D Deficiency ; Vitamin D* ; Vitamins*