The present invention comprises medical diagnostic methods and devices that quantify neutrophil populations in blood by using optical spectroscopy, either ex vivo with collected blood or non-invasively in vivo. In certain embodiments, fluorescent and Raman spectroscopy may be used to distinguish and/or quantify the neutrophils from the other blood components. The methods and devices of the invention advance the detection of sepsis by developing a point of care diagnostic device capable of rapid and/or real-time quantification of neutrophils. Other embodiments of the technology are also envisaged, particularly for analysing blood constituents both endogenous and administered.
