Linkage of kynurenine pathway metabolites to neuroinflammation in drug-naive children with attention-deficit/hyperactivity disorder: A cross-sectional, case–control study

Table 4 Correlation between biochemical parameters and time since symptoms onset, Conner Parent Rating Scale-48 subscale scores, Conner Parent Rating Scale-48 total score in the attention-deficit/hyperactivity disorder group

n = 51	Time since symptoms onset		CPRS-48, CP1		CPRS-48, LP1		CPRS-48, P1		CPRS-48, I-H1		CPRS-48, A1		CPRS-48, total score1
	r	P value	r	P value	r	P value	r	P value	r	P value	r	P value	r	P value
TRP (μmol/L)	0.032	0.825	-0.237	0.093	-0.061	0.672	0.127	0.376	-0.001	0.994	-0.070	0.628	-0.083	0.564
KYN (nmol/L)	0.082	0.565	-0.152	0.286	0.006	0.964	0.096	0.501	-0.100	0.485	-0.158	0.270	-0.151	0.289
KYNA (nmol/L)	0.050	0.728	0.016	0.911	0.046	0.747	0.184	0.196	0.146	0.307	0.001	0.993	0.062	0.668
QUIN (μmol/L)	0.162	0.256	0.007	0.963	-0.075	0.602	0.076	0.594	0.063	0.663	-0.024	0.869	-0.005	0.970
KYN/TRP × 1000 (IDO/TDO)	-0.040	0.783	0.165	0.248	0.054	0.708	-0.090	0.529	-0.059	0.680	0.039	0.788	0.032	0.824
KYNA/KYN × 100 (KAT activity)	0.107	0.455	-0.165	0.248	0.099	0.490	0.165	0.247	0.210	0.138	0.096	0.501	0.183	0.199
KYNA/QUIN (neuroprotective)	-0.105	0.463	0.055	0.703	0.237	0.094	0.265	0.060	0.173	0.224	0.126	0.379	0.166	0.243
OUIN/KYNA (neurotoxic)	0.117	0.413	-0.058	0.685	-0.237	0.095	-0.264	0.061	-0.176	0.216	-0.127	0.373	-0.167	0.240
OUIN/KYN (KMO activity)	0.195	0.170	0.090	0.530	-0.032	0.824	0.050	0.728	0.151	0.291	0.050	0.726	0.101	0.479

¹Spearman correlational analysis was performed.

r: Correlation coefficient; CPRS-48: Conner Parent Rating Scale-48; CP: Conduct problems; LP: Learning problems; P: Psychosomatic; I-H: Impulsive-Hyperactive; A: Anxiety; KYN: Kynurenine; TRP: Tryptophan; IDO/TDO: Indoleamine 2,3-dioxygenase/tryptophan 2,3-dioxygenase; KYNA: Kynurenic acid; KAT: Kynurenine aminotransferases; QUIN: Quinolinic acid; KMO: Kynurenine monooxygenase.