The reliability and validity of the Turkish version of fibromyalgia survey diagnostic criteria and symptom severity scale

Background: The fibromyalgia survey diagnostic criteria and severity scale (FSDC) is a self-reported version of 2010 preliminary diagnostic criteria for fibromyalgia syndrome (FMS). FSDC not only facilitates to diagnose FMS, it measures pain (the Widespread Pain Index (WPI)/FSDC Section 3), the Symptom Severity (SS)/FSDC Sections 1 and 2, and provides a score, polysymptomatic distress (PSD)/FSDC Total score in patients with FMS. The purpose of our study is to evaluate the reliability and validity of Turkish version of FSDC in Turkish patients with FMS.

Methods: The Turkish version FSDC was obtained by two forward translations of the instrument into Turkish by two bilingual Turkish individuals, one of them was a physician. They were then back translated into English by two different bilingual individuals; another Turkish physician and a backtranslator whose mother tongue was English. The original version of FSDC, the two Turkish forward translations, and English back translations were then reviewed by the individuals involved in translations, and the last experimental Turkish version was created. This last version of Turkish FSDC studied on patients with newly diagnosed FMS by using American College of Rheumatology (ACR) 1990 classification criteria. Patients filled validated Turkish revised fibromyalgia impact questionnaire (rFIQ), our nonvalidated experimental Turkish FSDC; marked Visual Analog Scale (VAS) for pain and the disease severity. In 7 to 15 days, they have filled the nonvalidated Turkish FSDC for the second time.

Results: In 132 patients, by the test to retest reliability analysis of nonvalidated Turkish FSDC, for the 25 single items, correlation coefficients ranged 0.383 to 0.818 (all p< 0.01). There were significant correlations between nonvalidated Turkish FSDC assessment 1 and assessment 2 for Section 1+2 (SS) (r = 0.748), Section 3 (WPI) (r = 0.775), and the total scores (PSD) (r = 0.821) (all p< 0.01). Cronbach alpha was 0.766 for the nonvalidated Turkish FSDC assessment 1 total score, and 0.77 for the Turkish FSDC assessment 2 total score. There were significant correlations between nonvalidated Turkish FSDC assessment 1 total score and total rFIQ (r= 0.576), VAS pain (r= 0.443), VAS disease severity (r= 0.342) (all p< 0.01). Our results indicated that 94.7 % to 96 % of our patients satisfying 1990 FMS criteria also satisfied 2010 modified diagnostic criteria.

Conclusions: The Turkish experimental version of FSDC is a reliable and valid instrument in Turkish FMS patients. It is easily completed, simple to score providing valuable instrument to diagnose and follow FMS.