Serum concentrations of complement C3 and C4 in dogs with idiopathic epilepsy

Background High concentrations of complement factors are presented in serum of animal epilepsy models and human patients with epilepsy. Objectives To determine whether complement dysregulation occurs in dogs with idiopathic epilepsy (IE). Animals The study included 49 dogs with IE subgrouped into treatment (n = 19), and nontreatment (n = 30), and 29 healthy dogs. Methods In this case‐control study, the serum concentrations of the third (C3) and fourth (C4) components of the complement system were measured using a canine‐specific ELISA kit. Results Serum C3 and C4 concentrations were significantly higher in dogs with IE (C3, median; 4.901 [IQR; 3.915‐6.673] mg/mL, P < .001; C4, 0.327 [0.134‐0.557] mg/mL, P = .03) than in healthy control dogs (C3, 3.550 [3.075‐4.191] mg/mL; C4, 0.267 [0.131‐0.427] mg/mL). No significant differences were observed in serum C3 and C4 concentrations between dogs in the treatment (C3, median; 4.894 [IQR; 4.192‐5.715] mg/mL; C4, 0.427 [0.143‐0.586] mg/mL) and nontreatment groups (C3, 5.051 [3.702‐7.132] mg/mL; C4, 0.258 [0.130‐0.489] mg/mL). Dogs with a seizure frequency >3 times/month had significantly higher serum C3 (6.461 [4.695‐8.735] mg/mL; P < .01) and C4 (0.451 [0.163‐0.675] mg/mL; P = .01) concentrations than those with a seizure frequency ≤3 times/month (C3, 3.859 [3.464‐5.142] mg/mL; C4, 0.161 [0.100‐0.325] mg/mL). Conclusions and Clinical Importance Dysregulation of classical complement pathway was identified in IE dogs. Serum C3 and C4 concentrations could be diagnostic biomarkers for IE in dogs with higher seizure frequency.