IDO1 and infection: Consequently, we computed some composite scores: (a) the acute phase of infection: z PBT + z duration of acute infection – z SpO2, (b) insulin resistance: z FBG + z insulin (z IR), (c) IDO activity: z KYN – z TRY (labeled KYN/TRY ratio) and the sum of all z transformed TRYCATs, (d) a composite based on z CRP + z KYN/TRY + z IR; and (e) a composite based on acute and Long COVID biomarkers: z CRP + z KYN/TRY + z IR + z PBT – z SpO2.