Composite Inflammatory Indices in Idiopathic Restless Legs Syndrome: Associations with Disease Presence and Symptom Severity

AIM: Peripheral inflammation in idiopathic restless legs syndrome (RLS) remains incompletely characterized. This study evaluated the associations of blood cell-derived inflammatory indices with RLS presence and symptom severity.
MATRERIAL and METHOD: This single-center retrospective case-control study included 94 patients with idiopathic RLS and 94 age- and sex-matched healthy controls. Symptom severity was assessed using the International Restless Legs Syndrome Study Group Rating Scale (IRLS). The neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic inflammation response index (SIRI), systemic immune-inflammation index (SII), and pan-immune-inflammation value (PIV) were evaluated using group comparisons, Spearman correlations, separate age- and sex-adjusted logistic regression models, and receiver operating characteristic analysis.
RESULTS: All five indices were higher in RLS than in controls (all p < 0.001) and were associated with RLS after adjustment for age and sex. The severity groups comprised 49 mild, 20 moderate, and 25 severe cases. PIV showed a stepwise increase across these groups and the strongest correlation with IRLS score (rho = 0.586, p < 0.001), followed by SIRI (rho = 0.527), SII (rho = 0.418), and NLR (rho = 0.348; all p < 0.001). PLR was not correlated with severity (p = 0.274). SII had the highest AUC for RLS presence (0.810; 95% CI 0.747–0.874). PIV had the highest AUCs for mild versus moderate (0.778) and moderate versus severe disease (0.731).
CONCLUSION: Composite inflammatory indices were associated with idiopathic RLS. SII showed the highest observed discrimination for disease presence, whereas PIV was most closely related to symptom severity. External validation is required before these measures can inform clinical assessment.