An oximeter sensor system for use in a whole-blood COOx analyzer to measure oxygen saturation of a whole-blood sample, the oximeter sensor system comprising: a light-emitting module comprising: a light source group having a plurality of LEDs including at least a first visible light LED (34, 36) having a low wavelength visible light range, a second visible light LED (34, 36) having a high wavelength visible light range and an infrared LED having a wavelength range in the near infrared wavelength range; a light source housing having a base, one or more sidewalls and a light-emitting end opposite the base, wherein the light source housing has a frustum shape with the light-emitting end being smaller than the base, and wherein the light source group is disposed adjacent the base and facing the light-emitting end, and wherein the one or more sidewalls has a reflective coating thereon; a light detector disposed opposite to, spaced from and facing the light-emitting end of the light source housing; and a cuvette assembly disposed between the light-emitting end of the light source housing and the light detector whereby the cuvette assembly is configured to receive the whole-blood sample; and a processor module; wherein the oximeter sensor system is configured to calculate an optical absorbance of the whole-blood sample based on a transmitted light intensity received at the light detector, and wherein the processor module is configured to subject the calculated absorbance to a mapping kernel-based orthogonal projections to latent structures function that maps absorbance values to percent oxygen saturation. a light-emitting module comprising: a light source group having a plurality of LEDs including at least a first visible light LED (34, 36) having a low wavelength visible light range, a second visible light LED (34, 36) having a high wavelength visible light range and an infrared LED having a wavelength range in the near infrared wavelength range; a light source housing having a base, one or more sidewalls and a light-emitting end opposite the base, wherein the light source housing has a frustum shape with the light-emitting end being smaller than the base, and wherein the light source group is disposed adjacent the base and facing the light-emitting end, and wherein the one or more sidewalls has a reflective coating thereon; a light source group having a plurality of LEDs including at least a first visible light LED (34, 36) having a low wavelength visible light range, a second visible light LED (34, 36) having a high wavelength visible light range and an infrared LED having a wavelength range in the near infrared wavelength range; a light source housing having a base, one or more sidewalls and a light-emitting end opposite the base, wherein the light source housing has a frustum shape with the light-emitting end being smaller than the base, and wherein the light source group is disposed adjacent the base and facing the light-emitting end, and wherein the one or more sidewalls has a reflective coating thereon; a light detector disposed opposite to, spaced from and facing the light-emitting end of the light source housing; and a cuvette assembly disposed between the light-emitting end of the light source housing and the light detector whereby the cuvette assembly is configured to receive the whole-blood sample; and a processor module; wherein the oximeter sensor system is configured to calculate an optical absorbance of the whole-blood sample based on a transmitted light intensity received at the light detector, and wherein the processor module is configured to subject the calculated absorbance to a mapping kernel-based orthogonal projections to latent structures function that maps absorbance values to percent oxygen saturation.