text: Assessment of tryptophan and kynurenine as prognostic markers in patients with SARS CoV 2 Immune dysregulation and inflammation in patients with SARS CoV 2 is associated with a poor clinical outcome We investigated the value of the inflammatory markers tryptophan and kynurenine in predicting the survival outcome of patients with SARS CoV 2 The study included 252 inpatients with a SARS CoV 2 infection hospitalized between August 2020 and April 2021 Two groups were generated based on disease survival survival group n 199 deceased group n 53 Plasma concentrations of tryptophan kynurenine and interleukin 6 IL 6 were measured on admission In a subset of patients n 105 81 survivors and 24 deceased concentrations of tryptophan and kynurenine were checked 7 days after admission The kynurenine tryptophan ratio TRP KYN ratio was calculated On admission the deceased group showed significantly higher concentrations of kynurenine and a significantly higher KYN TRP ratio compared to the survival group p values 0 001 Kynurenine and the KYN TRP ratio significantly correlated with IL 6 ρ 0 441 and 0 448 p values 0 001 In the survival group kynurenine and the KYN TRP ratio were significantly lower after seven days p values 0 001 In the deceased group no significant differences were found between the measurements Kynurenine and the KYN TRP ratio are potentially useful parameters in predicting the survival outcome in SARS CoV 2 positive patients 