Optimization of cytogenetic procedures for population triage in case of radiological emergency
Introduction
Following exposure of cells to ionizing radiation, chromosomal aberrations are produced. The yield of unstable chromosomal aberrations as dicentrics and centric rings are used as dose indicators in biological dosimetry (IAEA, 2001). To have a statistically usable result 500 cells have to be scored to estimate the dose received. Scoring so many cells requires at least 2 days for one operator. This is not conceivable for a population triage where hundreds of persons may be exposed.
The aim of a population triage is to identify the victims who require early medical assistance from those less exposed. The population triage can be based on clinical signs such as the lymphocyte counts, nausea and diarrhoea, and local skin burns. However, those symptoms varies from one person to other and may result in false positive and false negative identifications. Biological indicator of dose could avoid such erroneous identifications. Such indicators should allow for a rapid assessment of a dose on a large number of victims.
Once the population has undergone early triage, it is required, in a second step, to better characterise the dose received. In this case, the time factor is less critical and a sensitive technique is necessary. Therefore, the ideal biological indicator of dose should be able to provide a rapid and sensitive response.
In a recent publication, the possibility to score the number of translocations detected using the fluorescent in situ hybridization technique has been evaluated for a population triage (Szeles et al., 2006). The reported result is a reduction of the sensitivity compared to the conventional dicentric approach.
Several other possibilities are proposed to deal with a large number of cases: (a) scoring only 50 cells using the dicentric assay; (b) the use of automation; (c) setting up national or international networks to be able to handle more samples; and (d) setting up new techniques that are faster and easier to carry out such as the micronuclei assay and the -H2AX assays. This paper discussed the advantages and disadvantages of these different approaches.
Section snippets
The dicentric assay: triage strategy
The standard technique (IAEA, 2001) has been adapted to improve the response time when triage is required to identify potentially irradiated individuals. The technique to prepare and analyse chromosomal aberrations is simplified and the number of metaphases observed is reduced. The observation of 50 cells requires 1 h scoring without the help of any image analysing system and allows a dose estimation with an uncertainty of (Voisin et al., 2001a, Voisin et al., 2001b). This margin of
Automatic dicentric detection
In order to reduce the time required for estimating the dose, image analysis systems were developed. Such systems, specific for biological dosimetry, are rare and not always commercialized. One of them is the METAFER developed by METASYSTEMS (Germany). It allows the automatic finding of metaphases, the acquisition of images at high magnification and the automatic detection of dicentrics stained uniformly with Giemsa (Schunck et al., 2004). The METAFER is the only system that allows the
Use of micronuclei in population triage
The interest of this technique is the simplicity in the scoring. Indeed, it is much easier to score micronuclei in binucleated cells than dicentrics among 46 chromosomes. This technique has already been described in Voisin et al. (2001a). A comparison of the main characteristics between the dicentric approach and the micronuclei one is presented in Table 1. The two techniques were compared during a triage exercise where 35 samples were exposed to doses from 0 to 3 Gy of 137cesium gamma
The use of -H2AX foci for a population triage
Another easy approach is the possibility to use immunostaining to detect double-strand breaks (DSBs). These lesions have been known as one of the most significant lesion producing lethal and mutagenic effects after exposure to ionising radiation. Recently, some inmunofluorescence studies have demonstrated that the number of radio-induced DNA DSBs correlates to the number of -H2AX nuclear foci that appear as the result of phosphorylation of H2AX histone (Brenner et al., 2003).
The advantage of
Conclusion
The biological triage is complementary to the clinical triage as some false positive and false negative can be identified. After comparison of several techniques, it appears that the automatic detection of dicentrics has the advantage to be fast and allows, in a second step, the manual scoring to better estimate the dose if necessary, however, it is not possible with this assay to discriminate heterogeneous exposures from whole body exposures. In the first step of triage situation the
References (8)
- et al.
Cancer risks attributable to low doses of ionizing radiation: assessing what we really know
Proc. Nat. Acad. Sci. USA
(2003) - IAEA, 2001. Cytogenetic analysis for radiation dose assessment: a manual, Vienna, 127...
- et al.
Evidence for a lack of DNA double-strand break repair in human cells exposed to very low X-ray doses
Proc. Nat. Acad. Sci. USA
(2003) - Schunck, C., Johannes, T., Varga, D., Lörch, T., Plesch, A., 2004. New developments in automated cytogenetic imaging:...
Cited by (22)
The cytokinesis-blocked micronucleus assay: Dose estimation and inter-individual differences in the response to γ-radiation
2014, Mutation Research - Genetic Toxicology and Environmental MutagenesisCitation Excerpt :Moreover, several studies have been conducted to validate the use of the CBMN assay for triage in cases of mass casualty events, where a large number of individuals are involved. For this purpose, the approaches identified are based in the automation of the assay and in the reduction of the number of cells scored [2,24,25]. According to McNamee et al. [5], scoring of only 200 bi-nucleated cells per subject is sufficient to detect radiation doses above 1 Gy.
Dose-response relationship of γ-H2AX foci induction in human lymphocytes after X-rays exposure
2011, Radiation MeasurementsCitation Excerpt :Biological dosimetry for assessment of individuals accidentally overexposed to ionising radiation is based on the use of several biological methods (IAEA, 2001). Recently, it has been recommended to add the γ-H2AX assay as another endpoint for population triage (Roy et al., 2007; Andrievsky and Wilkins, 2009; Riecke and Meineke, 2010; Roch-Lefèvre et al., 2010). The methodology allows the detection of the phosphorylated form of H2AX histone variant, known as γ-H2AX foci as a response to DNA double-strand break (DSB) formation few minutes after exposure of cells to ionising radiation (Rogakou et al., 1999).
Metaphase Cells Enrichment for Efficient Use in the Dicentric Chromosome Assay
2022, Cell Biochemistry and BiophysicsMetaphase Cells Enrichment for Efficient Use in the Dicentric Chromosome Assay
2022, Research SquareNATO Science for Peace and Security (SPS) project “BioPhyMeTRE”: “Novel biological and physical methods for triage in radiological and nuclear (R/N) emergencies”
2020, Nuovo Cimento della Societa Italiana di Fisica CA NOVEL BIOLOGICAL DOSIMETRY ASSAY AS A POTENTIAL TOOL FOR TRIAGE DOSE ASSESSMENT IN CASE OF LARGE-SCALE RADIOLOGICAL EMERGENCY
2019, Radiation Protection Dosimetry