Utilization of disease activity scores and acute phase reactants in predicting colchicine response assessed by FMF50: a retrospective cohort study in children with Familial Mediterranean Fever.

Objectives: Monitoring disease activity in Familial Mediterranean Fever (FMF) patients might be challenging, mainly due to accompanying inflammatory conditions. This study assessed disease activity and colchicine response in children with FMF, using Auto-Inflammatory Diseases Activity Index (AIDAI), Pras, Mor, International Severity Score for FMF (ISSF), and FMF50 scores, and examined their acute phase reactant (APR) predictive value for FMF50 response.

Methods: FMF patients meeting Eurofever/PRINTO criteria and receiving colchicine for ≥ 6 months were included. Patients without exon 10 mutations and with poor adherence were excluded. Disease activity was assessed using AIDAI, Pras, Mor, and ISSF scores, while FMF50 evaluated treatment response. Concordance among activity scores was analyzed using Cohen's and Fleiss's Kappa. Patients were grouped as FMF50 responders or non-responders. Logistic regression identified FMF50 response predictors.

Results: A total of 117 pediatric FMF patients (44.4% female) were included. ISSF, AIDAI, and Pras scores were significantly higher in non-responders compared to responders (p < 0.001). Elevated CRP (OR 1.035, 95% CI 1.002-1.070, p < 0.05), ISSF (OR 1.703, 95% CI 1.135-2.557, p < 0.05), and AIDAI scores (OR 1.253, 95% CI 1.053-1.491, p < 0.05) at 3 months predicted FMF50 non-response at 6 months. Multivariate analysis identified high ISSF (OR 1.745, 95% CI 1.129-2.698, p < 0.05) and AIDAI scores (OR 1.265, 95% CI 1.056-1.514, p < 0.05) as independent predictors. APRs were correlated with ISSF, Pras, and AIDAI scores. Kappa analyses revealed poor agreement among activity scores (Kappa values 0.157 to - 0.048).

Conclusion: ISSF, AIDAI scores, and CRP can predict FMF50 response three months in advance and recommend earlier evaluation of further therapies in non-responders. Key Points • This study is the only investigation in the literature that evaluates all disease activity scores and examines the correlations between these scores and APRs. • As the second study to utilize the FMF50 score in assessing colchicine response, it contributes significantly to the literature with a larger patient cohort. • Elevated CRP values, along with high ISSF and AIDAI scores at the third month, play a critical role in predicting the FMF50 response at the sixth month, indicating the necessity for early evaluation of advanced treatment options.