BS EN ISO 19238:2017 pdf download

BS EN ISO 19238:2017 pdf download.Radiological protection — Performance criteria for service laboratories performing biological dosimetry by cytogenetics
1 Scope
This International Standard provides criteria for quality assurance and quality control, evaluation of the performance, and the accreditation of biological dosimetry by cytogenetic service laboratories.
This International Standard addresses
a) the confidentiality of personal information, for the customer and the service laboratory,
b) the laboratory safety requirements,
c) the calibration sources and calibration dose ranges useful for establishing the reference dose-effect curves that contribute to the dose estimation from chromosome aberration frequency and the minimum resolvable doses,
d) the scoring procedure for unstable chromosome aberrations used for biological dosimetry,
e) the criteria for converting a measured aberration frequency into an estimate of absorbed dose,
f) the reporting of results,
g) the quality assurance and quality control,
h) informative annexes containing sample instructions for customer, sample questionnaire, sample of report, fitting of the low dose-response curve by the method of maximum likelihood and calculating the error of dose estimate, odds ratio method for cases of suspected exposure to a low dose, and sample data sheet for recording aberrations.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1 acentric
terminal or interstitial chromosome fragment of varying size, referred to as an excess acentric fragment when it is formed independently of a dicentric or centric ring chromosome aberration
2.2 background level
spontaneous frequency (or number) of chromosome aberrations recorded in control samples or individuals
2.3 bias
statistical sampling or testing error caused by systematically favouring some outcomes over others
2.4 centric ring
aberrant circular chromosome resulting from the joining of two breaks on separate arms of the same chromosome
Note 1 to entry: It is generally accompanied by an acentric fragment.
3 Dicentric assay
The frequency of unstable chromosomal aberrations seen at metaphase in cultured human peripheral blood lymphocytes is the recommended method for biological dosimetry. The chromosome aberrations to be used are dicentrics or dicentrics and centric rings. For the application of this International Standard, the service laboratory shall choose which type of aberrations to score for the purpose of assessing dose estimates and shall be consistent throughout. Hereafter, chromosome aberrations are referred to as dicentrics but may include centric rings if determined by the service laboratory. Lymphocytes are cultured by a method that permits first-division metaphases to be recognized for analysis (see 9.1). This requires whole blood, or lymphocytes separated from the other blood components, to be incubated in a culture medium that would enable scoring of first-generation metaphase cells. A mitotic blocking agent, colcemid or colchicine, is added to arrest dividing lymphocytes in metaphase. The duration of the cell culture and the timing of addition of the arresting agent are optimised to ensure an adequate mitotic index and predominance of first-division metaphases.