CRP and COVID-19: The main findings are as follows: (i) on a patient group basis, high FLR values appear to be linked to impaired inpatient survival; (ii) on an individual-patient basis, FLR has relatively high sensitivity and negative predictive values (but poor specificity and positive predictive values) for predicting adverse clinical outcomes; (iii) FLR has a positively skewed distribution within the study population; (iv) FLR is weakly correlated with other established inflammatory markers; and (v) FLR performed similarly to CRP for predicting adverse clinical outcomes in acute COVID-19 patients.