A system for detecting an infection in a fluid sample drawn from a patient at the patient's point-of-care, the system comprising: a white blood cell ("WBC") concentration function configured to determine a WBC concentration from the fluid sample, the WBC concentration function comprising: a vial receptacle for receiving a vial containing the fluid sample; one or more light sources configured to illuminate the fluid sample in the vial; a vial optical sensor configured to detect scattered and/or absorbed light intensity by white blood cells in the fluid sample and to convert that light intensity to a vial electrical signal; and at least one immunoassay strip function configured to determine a marker concentration of a selected marker in the fluid sample, the IA strip function comprising: at least one IA strip receptacle (106; 108) configured to receive an IA strip (114; 116) having a marker reagent and a portion of the fluid sample, wherein the marker reagent is configured to generate a marker light intensity from a reaction between the marker reagent and a marker in the fluid sample; and an IA strip optical sensor (150a; 152) configured to detect the marker light intensity and to convert the marker light intensity to an IA marker electrical signal; an optical sensor reader configured to receive the vial electrical signals and the IA marker electrical signals, and to store the vial electrical signals as vial sensor data and the IA marker electrical signals as IA marker sensor data; and a communications interface configured to communicate the vial sensor data and the IA marker sensor data to a sensor data processor configured to determine a WBC concentration and a leukocyte concentration from the vial sensor data and from the IA marker sensor data. a white blood cell ("WBC") concentration function configured to determine a WBC concentration from the fluid sample, the WBC concentration function comprising: a vial receptacle for receiving a vial containing the fluid sample; one or more light sources configured to illuminate the fluid sample in the vial; a vial optical sensor configured to detect scattered and/or absorbed light intensity by white blood cells in the fluid sample and to convert that light intensity to a vial electrical signal; and at least one immunoassay strip function configured to determine a marker concentration of a selected marker in the fluid sample, the IA strip function comprising: a vial receptacle for receiving a vial containing the fluid sample; one or more light sources configured to illuminate the fluid sample in the vial; a vial optical sensor configured to detect scattered and/or absorbed light intensity by white blood cells in the fluid sample and to convert that light intensity to a vial electrical signal; and at least one immunoassay strip function configured to determine a marker concentration of a selected marker in the fluid sample, the IA strip function comprising: at least one IA strip receptacle (106; 108) configured to receive an IA strip (114; 116) having a marker reagent and a portion of the fluid sample, wherein the marker reagent is configured to generate a marker light intensity from a reaction between the marker reagent and a marker in the fluid sample; and an IA strip optical sensor (150a; 152) configured to detect the marker light intensity and to convert the marker light intensity to an IA marker electrical signal; an optical sensor reader configured to receive the vial electrical signals and the IA marker electrical signals, and to store the vial electrical signals as vial sensor data and the IA marker electrical signals as IA marker sensor data; and a communications interface configured to communicate the vial sensor data and the IA marker sensor data to a sensor data processor configured to determine a WBC concentration and a leukocyte concentration from the vial sensor data and from the IA marker sensor data.