Remote infrared infrared spectroscopy, using a chalcogenide glass optical fiber, allows the study of the functional groups of the molecules present in a biological sample. It showed its ability, through the demonstration of changes in spectroscopic profiles, to discriminate samples representing physiological and pathological situations. This method has shown an interest in the early diagnosis of septic arthritis from joint puncture fluid, for the diagnosis of RA from serum and for staging of hepatic steatosis from serum.