Validation of fibromyalgia survey questionnaire and polysymptomatic distress scale in a Persian population

The aim of this study was to assess validity of the fibromyalgia survey questionnaire (FSQ) and polysymptomatic distress scale (PSD) in an Iranian population. We also sought to classify the severity levels of fibromyalgia (FM) symptoms according to the PSD scale. Participants were divided into FM and non-FM chronic pain disorder groups according to expert physician diagnosis. Patients in both groups answered to Persian-translated version of FSQ, fibromyalgia impact questionnaire (FIQ) and Short-Form-12 (SF-12). Both 1990 ACR criteria and FSDC were assessed in participates of two groups. Internal consistency and construct validity were evaluated. There was good internal consistency measured by Cronbach's alpha (0.814 for FSQ). FSQ and its subscales correlated significantly with FIQ scores and SF-12 subscales, indicating acceptable construct validity. The concordance rates of FSQ with 1990 ACR criteria and expert diagnosis were 61.2 and 75.7, respectively (convergence validity). The mean score of PSD and its components in FM group were significantly more than in control groups (discriminative validity). Using lower PSD score cutoff (≥8.5) for the diagnosis of fibromyalgia appeared to be the most effective approach in our population. ROC analysis of the PSD scores revealed 8.5-11.5, 11.5-15 and more than 15, respectively, as a mild, moderate and severe FM. Persian version of FSQ was a valid instrument for application in survey research among Iranian patients with chronic pain disorders. The current study revealed that PSD could be used as a valid tool for assessment of symptoms intensity regardless of fibromyalgia diagnosis.