Fig. 1From: Serum neopterin levels in relation to mild and severe COVID-19Concentrations of first measurements of serum neopterin, tryptophan, and kynurenine, as well as kynurenine to tryptophan ratio (K/T) in patients with mild (green) and severe (red) form of COVID-19 (n = 34). The dashed line represents the upper normal reference limit of neopterin at 9.1 nmol/L.Back to article page