Three-Wavelength Method for the Optical Differentiation of Methemoglobin and Sulfhemoglobin in Oxygenated Blood

Methemoglobinemia and sulfhemoglobinemia are rare, but potentially life threatening, diseases that refer to an abnormal amount of methemoglobin or sulfhemoglobin in the blood, respectively. Unfortunately, blood samples containing abnormal quantities of methemoglobin or sulfhemoglobin have similar spectral characteristics. This makes it difficult to optically differentiate them and, hence, difficult to diagnose a patient with either disease. However, performing treatments for one of the diseases without a correct diagnosis can introduce increased risk to the patient. In this paper, we propose a method for differentiating the presence of methemoglobin and sulfhemoglobin in blood, under several conditions, using reflectance values measured at three wavelengths. In order to validate our method, we perform in silico experiments considering various levels of methemoglobin and sulfhemoglobin. These experiments employ a cell-based light interaction model, known as CLBlood, which accounts for the orientation and distribution of red blood cells. We then discuss the reflectance curves produced by the experiments and evaluate the efficacy of our method. In particular, we consider various experimental conditions by modifying the flow rate, hemolysis level and incident light direction.