Models to assess the quality of stored erythrocyte suspensions by diffuse reflectance measurements

Legislation in transfusion medicine define hemolysis level as the quality measure for erythrocyte suspensions (ES). Since the golden standard test for hemolysis is destructive and causing wastage of units, the hemolysis levels of ES are currently assessed with deceptive visual inspection method and the national blood banks periodically perform statistical quality analysis by measuring the hemolysis levels of only few units on their expiration dates. There are numerous studies revealing negative consequences of storage lesions on recipients. Therefore, a non-invasive biomedical diagnostic technique should be developed for the quality of each stored ES, before administering them to especially critically ill patients. Transparent thin plastic blood bags allow optical measurements. Diffuse reflectance spectroscopy (DRS) can be utilized for rapid and non-invasive evaluation of stored blood quality. The purpose of this study is to create models for predicting the hemolysis level or free hemoglobin (FHB) concentration of ES, with spectral parameters acquired from non-invasive diffuse reflectance measurements. After attempts with mixed model, a physically based exponential theory was used and a model was created with fresh ES having negligible FHB to observe the effect of hematological variables on the diffuse reflectance spectra. High levels of goodness of fits were observed (R2~0.93). A semi-empirical equation, expressing the reflectance as a linear function of the reduced scattering coefficient of ES, was utilized. Its validity was confirmed with Monte Carlo simulations. Finally, FHB concentrations in ES were modelled as the linear function of the reflectance and other hematological variables. The highest correlation coefficient between predicted and actual FHB concentrations was 0.89. The error rate of the model in diagnosis was about 10%.