Aim: Valproic acid is a commonly used therapeutic agent in childhood epilepsies. Monitoring toxic doses of valproic acid is important due to serious adverse effects such as hepatotoxicity and encephalopathy. In this study, we aimed to investigate the relationship between valproic acid levels and inflammatory markers, including the pan-immune inflammation value (PIV) and the systemic immune-inflammation index (SII).

Materials and Methods: This retrospective study evaluated data obtained from the hospital information system between January 2023 and December 2024. Valproic acid results were classified into three groups: subtherapeutic (<50 mg/L), therapeutic (50–100 mg/L), and toxic (>100 mg/L). Hemogram parameters and derived inflammatory indices—SII, PIV, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), neutrophil × lymphocyte / platelet ratio (NLPR), and systemic inflammatory response index (SIRI)—were compared among groups. Statistical analyses were performed using SPSS version 25.0.

Results: A total of 4,596 data points from 154 patients were evaluated. When groups were compared, platelet count was significantly different between Groups 1 and 2 (p=0.0001). In comparisons between Groups 1 and 3, basophil count (p=0.037), platelet count (p=0.0001), PLR (p=0.001), PIV (p=0.027), and SII (p=0.003) were statistically significant. Between Groups 2 and 3, platelet count (p=0.0001), PLR (p=0.001), PIV (p=0.027), and SII (p=0.003) showed statistically significant differences.

Conclusion: Our study demonstrated that SII and PIV ratios are effective in predicting valproic acid toxic levels. This study aimed to contribute to the literature by presenting easily accessible primary care tests for epileptic children who have difficulty accessing tertiary care, thus monitoring toxic doses.