A faster and easier biodosimetry method based on calyculin A-induced premature chromosome condensation (PCC) by scoring excess objects

Abstract

Dicentric analysis and the ring PCC assay as established biodosimetry methods both have limitations in the estimation of absorbed doses in suspected overexposure cases between 5 and 10 Gy. The proposed method based on calyculin A-induced PCC overcomes these limitations by scoring excess objects as the endpoint. This new scoring method can potentially serve as a faster and up-scalable approach that complements the existing methods with higher accuracy at different dose ranges. It can also potentially be performed by less skilled workers when no automated system is available in mass casualty emergency cases to assist with the triage of patients. Additionally, it offers the possibility to further reduce the sample size and PCC induction time. In this pilot study, a calibration curve for excess objects was constructed using the new scoring method for the first time and a blind validation test composed of three unknown doses was carried out. Almost all the dose estimates were within the 95% confidence limits of the actual test doses by scoring only 50–100 PCC spreads. This method was found to be more accurate than ring PCC for doses below 10 Gy.

Applicability of Scoring Calyculin A-Induced Premature Chromosome Condensation Objects for Dose Assessment Including for Radiotherapy Patients

“…Further evidence has been referenced in a previously published study [Sun et al, 2019]. After appropriate statistical testing, the data for the above indicated irradiation doses were combined with the previously published data [Sun et al, 2020b] to generate a combined new curve covering 0-10 Gy.…”

“…Data from the previously published blind test [Sun et al, 2020b] were used to evaluate the combined calibration curve. 50 or 100 cells were scored for these three samples irradiated at higher doses (2-10 Gy).…”

“…This highly efficient and up-scalable method is particularly advantageous when there is very limited availability of blood for analysis or when metaphase spreads cannot be obtained due to very high dose exposure. Recently, scoring the number of chromosomal objects in excess of 46 in calyculin A-induced PCC has been proposed as an easy and suitable biodosimetry method in the estimation of absorbed doses between 2 and 10 Gy [Sun et al, 2020b]. PCC objects can easily be confused with chromosomal fragments that are generated during the formation of chromosomes with multiple centromeres (e.g., dicentrics and tricentrics, etc.)…”

“…1). In addition, when an exposure scenario is unknown, scoring objects and rings in parallel allows both high and low doses to be analyzed using the same sets of slides or digital images [Sun et al, 2020b].…”

“…In the present study, a calibration curve for doses between 0 and 2 Gy was constructed, and the suitability for this curve to be combined with a previously published curve for doses between 2 and 10 Gy [Sun et al, 2020b] was assessed. This combined curve was validated using blind tests before it was used to evaluate the PCC method in comparison to DCA in clinical sample dose estimation.…”