Towards a standardization of biological dosimetry by cytogenetics.

When individuals are accidentally overexposed to ionising radiations, follow-up investigations may include dose assessment by cytogenetics. Scoring of unstable chromosome aberrations (dicentrics, centric rings and acentrics) in peripheral blood lymphocytes is regarded as the most specific method to estimate the exposure dose. It has acquired, in some countries, a medico-legal recognition. Paradoxically, there is no universally adopted technique and so important variations occur in methods and these may influence the quality of results. The only published documents supplying some standardization background are International Atomic Energy Agency (IAEA) Technical Reports No 260 (1986) and 405 (2001). Even they do not address crucial areas such as the organization of service laboratories and the need for quality assurance programmes. The significant role of biological dosimetry in many countries has proved the need for a standardized technique that is compatible with national radiological protection programmes. Thus, an International Standards Organization working group for the standardization of biological dosimetry by cytogenetics was created. This group comprises 13 scientists from 11 countries plus an IAEA representative. On the basis of a group consensus, a text defining minimal constraints on all the steps of the process was proposed. A working draft was submitted to ISO in 2001 and its structure is presented here.