Determining the PASS cut-off points for the FIQR, FASmod and PSD in patients with fibromyalgia: a registry-based study

Objectives: To determine the cut-off values of Patient Acceptable Symptom State (PASS) for the revised Fibromyalgia Impact Questionnaire (FIQR), the modified Fibromyalgia Assessment Scale (FASmod), and the Polysymptomatic Distress scale (PSD) and to determine the predictors of PASS in patients with fibromyalgia (FM). Methods: FM patients belonging to the Italian Fibromyalgia Registry (IFR) completed the FIQR, the FASmod and the PSD. The PASS was assessed using a dichotomous answer. The cut-off values were obtained through the receiver operating characteristic curve (ROC) analyses. A multivariate logistic regression analysis was performed to determine predictors of achieving the PASS. Results: 5545 women (93.7%) and 369 males (6.3%) were included in the study. The 27.8% of patients reported an acceptable symptom state. Patients in PASS differed in all patient-reported outcome measures (p <0.001). The FIQR PASS threshold was ≤58 (area under the ROC curve [AUC] = 0.819). The FASmod PASS threshold was ≤23 (AUC = 0.805) and the PSD PASS threshold was ≤16 (AUC = 0.773). In the pairwise AUC comparison, the discriminatory power of the FIQR PASS outperforms both FASmod PASS (p = 0.0124) and PSD PASS (p <0.0001). Multivariate logistic analysis showed that FIQR items related to memory and pain were the only predictors of PASS. Conclusions: The FIQR, FASmod, and PSD PASS cut-off points for FM patients have never been determined before. This study provides additional information to facilitate interpretation of the severity assessment scales in daily practice and clinical research related to FM patients.