Introduction: The relationship between ionizing radiation (IR) exposure levels and the elevation of frequencies of different types of structural chromosomal aberrations (CA) is not yet completely clarified specifically at presumably chronic low-dose cumulative exposures. Aim of work: measurement of frequency of chromosomal aberrations (CA) and hematologic alterations in different radiation exposed occupational groups, verification of the presence of relevant health effects and measurement of accuracy of White Blood Cells (WBCs) count compared to chromosomal gene culture as biomarkers
of exposure to IR. Materials and methods: A comparative cross-sectional study was carried out over a period of one calendar year in 2016 upon 97 Health Care Workers (HCWs) occupationally exposed to radiation in Diagnostic Radiology, Intervention Cardiology and Radiotherapy departments of Mansoura University Hospitals (MUHs) and a reference age- matched group of 50 HCWs unexposed to IR. They were subjected to interview-based semi-structured questionnaire including enquiries on sociodemographic data, full occupational history and clinical history and to blood sampling
for both chromosomal culture and complete blood count analysis. Results: Significant reduction in the count of WBCs and lymphocytes among the exposed groups was found compared to reference group (p<0.001). This reduction was not revealed in MRI operators. Frequency of chromosomal aberrations increased significantly among radiologists, radiotherapists, interventional cardiologists (P<0.001, <0.001, 0.04; respectively). Significant positive correlation between frequency of aberrations and  lifetime exposure score was found. The accuracy of WBCs count Area Under Curve (AUC=0.69) was estimated to be less than Chromosomal Culture (AUC=0.71). Conclusion: HCWs in Radiology Departments of MUHs may be considered to be exposed to higher-than-guidelines doses of IR. Chromosomal aberrations analysis can be used as a sensitive biomarker for IR exposure added to regular CBC done periodically in classified high-risk groups.