The Prevalence of Fibromyalgia in Rheumatoid Arthritis Patients Using the Fibromyalgia Assessment Screening Tool (FAST 4) Based on the Multidimensional Health Assessment Questionnaire (MDHAQ).

Introduction Fibromyalgia (FM) is characterized by widespread pain and fatigue, accompanied by symptoms such as decreased concentration, autonomic dysfunction, and abdominal pain. It can be either primary or secondary, notably to rheumatoid arthritis (RA). The Fibromyalgia Assessment Screening Tools (FAST 4), derived from the Multidimensional Health Assessment Questionnaire (MDHAQ), is a composite tool allowing for the rapid screening of FM. Our primary objective is to determine the prevalence of FM among RA patients using the FAST 4 index. Secondary objectives include comparing the FAST 4 index with the FiRST score and describing the correlation between FM and RA activity and different factors associated with FM in RA patients. Methods This was an observational cross-sectional study including patients diagnosed with RA according to the ACR/EULAR criteria. The FAST questionnaire comprises four sections assessing pain and fatigue on a visual analog scale, painful joints reported by the patient, and a list of 60 symptoms. A FAST 4 score of ≥ 3/4 indicates a positive screening for FM. Demographics and disease features were compared using descriptive statistics. Univariate and multivariate analyses using logistic regression models were performed to calculate odds ratios (ORs) with 95% CI. The sensitivity and specificity of the FAST 4 index were evaluated, and Fagan's nomograms were used to illustrate post-test probability. Statistically significant results were considered for p-values less than 0.05. Results The study enrolled 97 patients diagnosed with RA. The mean age of the patients was 56 ± 12.7 years, with a predominance of females (90.7%, N=88). The mean duration of RA was 13.5 ± 8.69 years. RA activity measured by DAS 28-ESR showed that 40.2% (N=39) had high disease activity, 38.1% (N=37) had moderate disease activity, 11.3% (N=11) had low disease activity, and 10.3% (N=10) were in remission. The prevalence of comorbid FM, according to the FAST 4 index, was 30.9% (N=30). Based on the Multidimensional Health Assessment Questionnaire (MDHAQ), depression was observed in 66.7% (N=20) patients with FM, while anxiety was reported in 60% (N=18). Moreover, 30.4% of patients screened positive for FM using the FiRST score. The FAST 4 index detected FM patients defined by FiRST with a sensitivity of 78.6% and a specificity of 87.1%. The positive predictive value (PPV) was 73.3%, and the negative predictive value (NPV) was 90%. Univariate analysis revealed that a positive FAST 4 index was associated with the number of painful and swollen joints (p<0.001 and 0.03, respectively). Additionally, patients with a positive FAST 4 index showed higher DAS 28 scores (p=0.002). No significant association was found with CRP levels (p=0.328), ESR (p=0.499), or the use of biological treatments (p=0.146) or corticosteroids (p=0.940). In multivariate analysis, only depression remained a risk factor, increasing the risk sixfold with an OR of 5.917, 95% CI (1.91-18.3), p=0.002. Conclusion Our study suggests a high prevalence of concomitant FM in our population, highlighting the importance of screening for FM, particularly using the FAST 4 index based solely on the MDHAQ questionnaire.