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RENEB Inter-Laboratory comparison 2017: limits and pitfalls of ILCs

Purpose:In case of a mass-casualty radiological event, there would be a need for networking toovercome surge limitations and to quickly obtain homogeneous results (reported aberration fre-quencies or estimated doses) among biodosimetry laboratories. These results must be consistentwithin such network. Inter-laboratory comparisons (ILCs) are widely accepted to achieve thishomogeneity. At the European level, a great effort has been made to harmonize biological dosim-etry laboratories, notably during the MULTIBIODOSE and RENEB projects. In order to continue theharmonization efforts, the RENEB consortium launched this intercomparison which is larger thanthe RENEB network, as it involves 38 laboratories from 21 countries. In this ILC all steps of the pro-cess were monitored, from blood shipment to dose estimation. This exercise also aimed to evalu-ate the statistical tools used to compare laboratory performance.Materials and methods:Blood samples were irradiated at three different doses, 1.8, 0.4 and 0 Gy(samples A, C and B) with 4-MV X-rays at 0.5 Gy min-1, and sent to the participant laboratories.Each laboratory was requested to blindly analyze 500 cells per sample and to report the observedfrequency of dicentric chromosomes per metaphase and the corresponding estimated dose.Results:This ILC demonstrates that blood samples can be successfully distributed among labora-tories worldwide to perform biological dosimetry in case of a mass casualty event. Havingachieved a substantial harmonization in multiple areas among the RENEB laboratories issues wereidentified with the available statistical tools, which are not capable to advantageously exploit therichness of results of a large ILCs. Even thoughZ- andU-tests are accepted methods for biodosim-etry ILCs, setting the number of analyzed metaphases to 500 and establishing a tests’commonthreshold for all studied doses is inappropriate for evaluating laboratory performance. Anotherproblem highlighted by this ILC is the issue of the dose-effect curve diversity. It clearly appearsthat, despite the initial advantage of including the scoring specificities of each laboratory, the lackof defined criteria for assessing the robustness of each laboratory’s curve is a disadvantage for the‘one curve per laboratory’model.

Inter laboratory comparison ; biodosimetry ; chromosomal aberrations ; statistical tests

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