Genomic Maintenance & Repair

Monday, October 17, 2005 3:00 PM-5:00 PM Exhibit Hall

(PP302) Canadian Cytogenetic Emergency Network (CEN) for biological dosimetry following radiological/nuclear accidents.

Miller, Susan1, Ferrarotto, Catherine*,1, Vlahovich, Slavica2, Wilkins, Ruth1, Boreham, Douglas3, Dolling, Jo-Anna3, 4, 1 Consumer and Clinical Radiation Protection Bureau, Ottawa, ON, Canada2 Radiation Protection Bureau, Ottawa, ON, Canada3 McMaster Institute of Applied Radiation Sciences, Hamilton, ON, Canada4 Genetics Department, Mississauga, ON, Canada

ABSTRACT- The frequency of radiation-induced dicentric and ring chromosomes, found in lymphocytes blocked in metaphase, can be converted to dose estimates using the dicentric assay. Traditionally up to 1000 metaphases per sample are analysed, allowing detection of exposures as low as 0.15 Gy. However, when turnaround time is critical, such as with a large number of samples following a radiation accident or terrorist attack, the detection threshold can be raised to 1 Gy for initial triage, thus reducing the number of metaphases to be analysed to 50. More metaphases can be analysed later to refine these dose estimates. Currently, Canada has four core laboratories that can perform the dicentric assay for biological dosimetry. We are developing a network of clinical cytogenetic laboratories across Canada to increase this capacity for emergency situations. A workshop on biological dosimetry was held in May 2004 for interested clinical cytogenetic laboratories. Blinded slides, prepared for dicentric assay analysis following in vitro irradiation of blood from a healthy volunteer to a range of gamma-ray doses, were distributed to the participants and to the four core laboratories. A total of 41 people at 22 different laboratories analysed a minimum of 50 metaphases per slide to mimic triage scoring. Dose estimates were calculated based on a dose response curve generated at Health Canada. Of the 104 blocks of 50 metaphases analysed, 92 (88.5%) of the resulting dose estimates fell within the expected range using triage scoring criteria established by Lloyd et al. (2000). In Spring 2005, blood samples will be shipped to interested clinical cytogenetic laboratories that participated in the 2004 scoring exercise for assessment of culturing and slide making techniques and chromosome analysis. Preliminary data from this exercise will be presented. When this network is fully operational, it will be ready to respond to radiological/nuclear emergencies and provide triage quality biological dosimetry. Funded by Chemical, Biological, Radiological/Nuclear Research & Technology Initiative

Key words: biological dosimetry, dicentric assay, triage

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2005 RRS