The tryptophan catabolite or kynurenine pathway in COVID-19 and critical COVID-19: a systematic review and meta-analysis

Table 2 Results of meta-analysis performed on several outcome variables of the tryptophan catabolite (TRYCAT) pathway

Outcome feature sets	n	Groups	SMD	95% CI	z	p	Q	df	p	I² (%)	τ²	Τ
Cohort 1: COVID-19 patients versus non-COVID-19 control
KYN/TRP	10	Overall	1.099	0.714; 1.484	5.594	< 0.0001	85.310	9	< 0.0001	89.450	0.616	0.785
	4	Serum	1.359	0.889;1.829	5.666	< 0.0001	9.104	3	0.028	67.049	0.145	0.390
	6	Plasma	0.569	− 0.103; 1.241	1.661	0.097	38.093	5	< 0.0001	86.874	0.591	0.769
	Q = 3.568, df = 1, p = 0.059
KYN	7	Overall	1.123	0.730; 1.516	5.595	< 0.0001	29.745	7	< 0.0001	76.467	0.221	0.470
TRP	7	Overall	− 1.002	− 1.738; − 0.266	− 2.668	0.008	88.926	6	< 0.0001	93.253	0.892	0.944
KA	4	Overall	0.164	− 0.120; 0.449	1.133	0.257	6.947	3	0.074	56.816	0.128	0.358
	2	Serum	0.649	0.170; 1.129	2.653	0.008	0.617	1	0.432	0.000	0.000	0.000
	2	Plasma	-0.098	− 0.451;0.255	− 0.546	0.585	0.275	1	0.600	0.000	0.000	0.000
	Q = 6.055, df = 1, p = 0.014
KA/(KYN + TRP)	10	Overall	0.297	0.089;0.506	2.794	0.005	40.957	9	< 0.0001	78.026	0.255	0.505
(KYN + KA)/TRP	10	Overall	0.789	0.261;1.318	2.926	0.003	87.188	9	< 0.0001	89.678	0.624	0.790
KA/KYN	8	Overall	− 0.398	− 0.967; 0.170	-1.373	0.170	66.867	7	< 0.0001	89.531	0.569	0.754
Cohort 2: severe/critical COVID-19 patients versus mild/moderate COVID-19 patients
KYN/TRP	8	Overall	0.945	0.629; 1.262	5.848	< 0.0001	25.776	8	0.001	68.964	0.151	0.389
KYN	6	Overall	0.806	0.462; 1.149	4.593	< 0.0001	13.343	5	0.020	62.528	0.108	0.328
TRP	5	Overall	− 0.909	− 1.569; − 0.249	− 2.699	0.007	28.165	4	< 0.0001	85.798	0.462	0.680

ISSN: 1471-2334