Influence of Cell Size Changes after Irradiation on Reliability of an Impedance Measurement-based Hematology Analyzer

Radiological nuclear scenarios remain a persistent threat due to civil use and military possession of radiation sources. Therefore, it is crucial to be prepared for events involving a large number of patients exposed to radiation. In such cases, it is important to quickly and simply predict whether potential patients will develop severe, mild, or no Acute Radiation Syndrome (ARS). To address this challenge, the Bundeswehr Institute of Radiobiology developed the H-module, a prediction module that estimates the severity of ARS based on peripheral blood cell counts in the context of an exposure event. For accurate predictions, correct blood counts, especially lymphocyte and granulocyte counts, are essential. Mobile hematology analyzers (HA) are a possible portable and easy-to-learn solution for assessing patient blood counts. These analyzers use impedance measurements to identify cell populations, with cell volume primarily responsible for providing differential blood cell counts. We investigated the influence of alterations in leukocyte size after irradiation on the performance of this method. Whole blood samples from healthy donors were irradiated with different doses (0, 1, and 5 Gy). The samples were analyzed after 0, 1, 6, and 24 h post-irradiation. At each time point, a blood count was performed using impedance measurements via HA, and in parallel, a differential blood count of white blood cells (WBC) was performed using imaging-based flow cytometry. Lymphocytes and granulocytes were differentiated using CD15, CD3, and CD19 markers, by their different side scatter, and by their size in brightfield mode. In addition, peripheral blood mononuclear cells were monitored using a live-cell imaging system equipped with image acquisition and cell size measurement. The HA indicated a discrete increase in the lymphocyte fraction when blood counts were performed 24 h after irradiation, whereas at earlier time points, all WBC fractions remained comparable between both methods. These findings demonstrate that morphological changes in WBC do not impair the ability of the device to distinguish granulocytes from lymphocytes, provided that measurements are performed promptly. However, after 24 h, a reduction in cell size, due to delayed handling of the samples, resulted in an artificial increase in the lymphocyte fraction, potentially masking the lymphocyte depletion characteristic of H-ARS. Thus, timely sample processing when using a HA is essential to ensure diagnostic accuracy.