Role of neopterin as a biochemical marker for peripheral neuropathy in pediatric patients with type 1 diabetes: Relation to nerve conduction studies

Background: Neopterin, a marker of inflammation and cellular immune response, is elevated in conditions of T-cell or macrophages activation. Diabetic peripheral neuropathy (DPN) is associated with inflammatory/immune processes and therefore, we hypothesized that neopterin could be used as a marker of neuropathy in type 1 diabetes mellitus (T1DM). Aim: To measure neopterin levels in children and adolescents with T1DM and assess its possible relation to DPN and nerve conduction studies (NCS). Methods: Sixty patients aged <= 18 years and > 5 years disease duration were subjected to neurological assessment by neuropathy disability score (NDS) and NCS for median, ulnar, posterior tibial and common peroneal nerves. Mean fasting blood glucose, lipid profile, HbAlc, high sensitivity Creactive protein (hs-CRP) and serum neopterin levels were assessed. Patients were compared with 30 age- and sexmatched healthy controls. Results: The frequency of DPN according to NDS was 40 (66.7%) patients out of 60 while NCS confirmed that only 30 of those 40 patients had this complication (i.e. 50% out of the total studied patients). Neopterin levels were significantly higher in patients with DPN than those without (median [IQR], 53.5 [35-60] nmol/L versus 17 [13 32] nmol/L) and healthy controls (5.0 [3.2-7.0] nmol/L) (p < 0.001). Significant positive correlations were found between neopterin levels and HbAlc (r = 0.560, p = 0.005), serum creatinine (r = 0.376, p = 0.003), total cholesterol (r = 0.405, p = 0.026) and hs-CRP (r = 0.425, p = 0.012) among patients with DPN. Neopterin levels were positively correlated to motor latency of tibial and common peroneal nerves as well as motor and sensory latencies of median and ulnar nerves. Logistic regression analysis revealed that neopterin was a significant independent variable related to DPN (Odds ratio, 2.976). Neopterin cutoff value 32 nmol/L could differentiate patients with and without DPN with 100% sensitivity and 96.7% specificity. Conclusions: Neopterin could be used as an early reliable serum biomarker for DPN in pediatric patients with T1DM.