Objective assessment of stored blood quality by deep learning.

Stored red blood cells (RBCs) are needed for life-saving blood transfusions, but they undergo continuous degradation. RBC storage lesions are often assessed by microscopic examination or biochemical and biophysical assays, which are complex, time-consuming, and destructive to fragile cells. Here we demonstrate the use of label-free imaging flow cytometry and deep learning to characterize RBC lesions. Using brightfield images, a trained neural network achieved 76.7% agreement with experts in classifying seven clinically relevant RBC morphologies associated with storage lesions, comparable to 82.5% agreement between different experts. Given that human observation and classification may not optimally discern RBC quality, we went further and eliminated subjective human annotation in the training step by training a weakly supervised neural network using only storage duration times. The feature space extracted by this network revealed a chronological progression of morphological changes that better predicted blood quality, as measured by physiological hemolytic assay readouts, than the conventional expert-assessed morphology classification system. With further training and clinical testing across multiple sites, protocols, and instruments, deep learning and label-free imaging flow cytometry might be used to routinely and objectively assess RBC storage lesions. This would automate a complex protocol, minimize laboratory sample handling and preparation, and reduce the impact of procedural errors and discrepancies between facilities and blood donors. The chronology-based machine-learning approach may also improve upon humans' assessment of morphological changes in other biomedically important progressions, such as differentiation and metastasis.

Feasibility of photoacoustic imaging for the non-invasive quality management of stored blood bags.

BACKGROUND AND OBJECTIVES: During the in vitro storage of red blood cells (RBCs), unfavourable changes (storage lesions) cause a rapid consumption of intracellular diphosphoglycerate. The latter deregulates the oxygen-haemoglobin binding potential, subsequently increasing oxygen saturation (SO2 ) and membrane degradation, transforming RBCs from biconcave discs to rigid spherical bodies (spheroechinocytes). Current laboratory techniques invasively extract RBC samples to assess the quality of red cell concentrate (RCC) units. Optical technologies could provide a means of assessing quality non-invasively. MATERIALS AND METHODS: A photoacoustic (PA) imaging technique was developed for acquiring the SO2 of blood bags non-invasively. Seven RCC units were monitored every 3-5 days until expiry (6 weeks). Measurements were validated against a conventional blood gas analyzer (BGA). Using an image flow cytometry assay, morphological profile trends were compared against the SO2 trends during blood bag storage. RESULTS: A strong correlation (r2  ≥ 0·95) was found when comparing temporal data between PA and BGA SO2 measurements. Inter-sample PA variability was found to be similar to that produced by BGA (±0·8%). A strong correlation was found to exist between the temporal changes in SO2 and relative spheroechinocyte population (0·79 ≤ r2  ≤ 0·97). CONCLUSION: This study suggests that PA imaging can non-invasively track the SO2 of stored RBCs non-invasively. By longitudinally monitoring the change in SO2 , it is possible to infer the effects of the storage lesion on RBC morphology. This non-invasive monitoring technique allows for the assessment of blood bags, without compromising sterility pre-transfusion.

Label-Free Analysis of Red Blood Cell Storage Lesions Using Imaging Flow Cytometry.

Deleterious changes, collectively termed as storage lesions, alter the characteristics of red blood cell (RBC) morphology during in vitro storage. Due to gradual loss of cellular membrane, RBCs lose their original biconcave disk shape and begin a process of spherical deformation that is characterized by well-defined morphological criteria. At the spheroechinocyte stage, the structure of RBC is irreversibly damaged and lacks the elasticity necessary to efficiently deliver oxygen. Quantifying the prevalence of spheroechinocytes could provide an important morphological measure of the quality of stored blood products. Unlike the conventional RBC morphology characterization assay involving light microscopy, we introduce a label-free assay using imaging flow cytometry (IFC). The technique captures 100,000 images of a sample and calculates a relative measure of spheroechinocyte population in a fraction of the time required by the conventional method. A comparative method study, measuring a morphological index for 11 RCC units through storage, found that the two techniques measured similar trends with IFC reporting the metric at an average of 3.9% higher. We monitored 18 RCC units between Weeks 1 and 6 of storage and found that the spheroechinocyte population increased by an average of 26.2%. The large (3.5-64.1%) variation between the units' spheroechinocyte population percentage at Week 1 suggests a possible dependence of blood product quality on donor characteristics. Given our method's ability to rapidly monitor large samples and refine morphological characterization beyond conventional methods, we believe our technique offers good potential for studying the underlying relationships between RBC morphology and blood storage lesions. © 2019 International Society for Advancement of Cytometry.