RESUMO
Despite many approaches, diagnosis of fibromyalgia (FM) remains a difficult clinical task, especially in the case of comorbidity of FM with other rheumatic diseases, such as ankylosing spondylitis (AS). The prevalence of FM among the population is 2.9-4.7%; whereas in patients with AS, it increases to 12.6-28.5%. The aim of the study was to evaluate the prevalence of FM in AS patients according to different criteria and to characterize them. 143 patients with AS, according to the modified New York Criteria, were examined. The FiRST used for screening of a possible FM. The FM was detected using the ACR 1990 criteria, mARC 2010, ACR 2016 and AAPT 2019 diagnostic criteria. All data were analyzed using IBM Statistics SPSS 22 software. The study was carried out in compliance with bioethical standards. According to ACR 1990, mACR 2010, ACR 2016, and AAPT 2019, the prevalence of FM in patients with AS ranged from 21.0% to 35.7%. The strongest correlation was observed in the mACR 2010 and ACR 2016 criteria (Cohen's κ = 0.871, p < 0.001); ACR 1990 and mACR 2010 as well as ACR 2016 criteria also demonstrated quite a strong level of agreement (Cohen's κ = 0.675 and 0.684, p < 0.001). Our results showed a high prevalence of FM in AS patients. mACR 2010 and ACR 2016 criteria are optimal for clinical practice to diagnose FM in AS patients.