The second gamma-H2AX assay inter-comparison exercise carried out in the framework of the European biodosimetry network (RENEB)

Figures & data

Table 1. Reported foci yields ± Poisson standard errors (SE) obtained by the laboratories using manual and automated scoring. Also shown are the constant (C) and linear calibration coefficients (α) and associated standard errors used to convert foci counts into dose estimates.

	Dose (Gy)
	0.5		2.5
	Blood	Lymphocytes	Blood	Lymphocytes	Calibration coefficients ± standard errors
	foci/cell ± SE	foci/cell ± SE	foci/cell ± SE	foci/cell ± SE	C ± SE	α ± SE
Cells scored manually
1-4h	1.90 ± 0.19	3.44 ± 0.26	5.20 ± 0.32	3.10 ± 0.25	0.04 ± 0.02	2.15 ± 0.09
3-4h	1.98 ± 0.20	2.20 ± 0.21	4.54 ± 0.30	4.84 ± 0.31	0.44 ± 0.16	1.90 ± 0.21
4-4h	*	1.78 ± 0.19	*	6.36 ± 0.36	0.07 ± 0.02	2.24 ± 0.09
5-4h	1.82 ± 0.19	1.82 ± 0.19	3.14 ± 0.25	3.12 ± 0.25	0.10 ± 0.09	1.47 ± 0.22
6-4h	2.52 ± 0.22	3.78 ± 0.27	9.68 ± 0.44	9.64 ± 0.44	0.12 ± 0.08	3.57 ± 0.23
7-4h	*	0.72 ± 0.12	*	1.86 ± 0.19	0.88 ± 0.25	1.21 ± 0.37
8-4h	1.70 ± 0.18	2.26 ± 0.21	5.70 ± 0.34	5.16 ± 0.32	0.58 ± 0.08	2.18 ± 0.17
1-24h	0.26 ± 0.07	1.46 ± 0.17	0.50 ± 0.10	2.34 ± 0.22	0.03 ± 0.04	0.79 ± 0.14
3-24h	0.40 ± 0.09	1.38 ± 0.17	0.68 ± 0.12	1.80 ± 0.19	0.28 ± 0.12	0.92 ± 0.14
4-24h	*	1.12 ± 0.15	*	4.94 ± 0.31	0.06 ± 0.02	1.41 ± 0.07
6-24h	*	2.12 ± 0.21	*	5.06 ± 0.33	0.09 ± 0.03	1.35 ± 0.06
Cells scored automatically
6-4h	1.84 ± 0.10	2.54 ± 0.11	3.54 ± 0.13	3.42 ± 0.13	0.45 ± 0.28	3.52 ± 0.46
7-4h	*	0.67 ± 0.06	*	1.36 ± 0.08	0.88 ± 0.25	1.21 ± 0.37
8-4h	1.42 ± 0.08	1.08 ± 0.07	3.01 ± 0.12	3.66 ± 0.14	0.26 ± 0.03	1.19 ± 0.60

Samples were fixed, immunostained and scored manually and/or automatically with Metacyte®. The yields of foci per cell ± SE (Poisson standard error) are shown based on manual scoring of 50 cells or automated scoring of 200 cells and the calibration coefficients (± SE) used to convert foci counts into dose estimates.

* No result

Figure 1. Average gamma-H2AX-based dose estimates versus the true doses for blood and lymphocyte ex vivo incubated samples; excluding 24-h blood samples. Error bars show the standard deviation between 5 and 7 (blood) and 11–14 (lymphocyte) measurements for each sample taken from Table 2. The line is not a fit but indicates the ideal 1:1 relationship.

Table 2. Reported foci-based dose estimates ± standard error obtained by the laboratories for the coded blood and lymphocyte samples shipped from lab1 to the participants following ⁶⁰Co gamma irradiation and 4-/24-h ex vivo incubation at 37 °C. Triage categories of <1 Gy, 1–2 Gy and >2 Gy are highlighted in the table in white, light grey and dark grey, respectively.

	Dose (Gy)
	0.5		2.5
	Blood	Lymphocytes	Blood	Lymphocytes
Cells scored manually	50	50	50	50
1-4h	0.86 ± 0.21	1.58 ± 0.22	2.39 ± 0.24	1.42 ± 0.22
3-4h	0.81 ± 0.33	0.93 ± 0.33	2.16 ± 0.35	2.32 ± 0.36
4-4h	*	0.76 ± 0.16	*	2.77 ± 0.21
5-4h	1.17 ± 0.30	1.17 ± 0.30	2.07 ± 0.31	2.05 ± 0.31
6-4h	0.45 ± 0.07	0.69 ± 0.07	2.58 ± 0.17	2.14 ± 0.12
7-4h	*	0.00 ± 0.12	*	1.16 ± 0.29
8-4h	0.64 ± 0.28	0.77 ± 0.34	2.69 ± 0.32	2.10 ± 0.36
1-24h	0.30 ± 0.11	1.82 ± 0.23	0.60 ± 0.11	2.94 ± 0.28
3-24h	0.13 ± 0.09	1.20 ± 0.19	0.44 ± 0.07	1.65 ± 0.21
4-24h	*	0.75 ± 0.13	*	3.46 ± 0.24
6-24h	*	1.00 ± 0.19	*	3.51 ± 0.44
Cells scored automatically	200	200	200	200
6-4h	0.63 ± 0.09	1.35 ± 0.19	1.92 ± 0.18	2.13 ± 0.26
7-4h	*	0.00 ± 0.24	*	0.39 ± 0.25
8-4h	1.00 ± 0.86	0.69 ± 0.09	2.37 ± 0.12	2.86 ± 0.12

Samples were fixed, immunostained and scored manually and/or automatically with Metacyte®. Dose estimates ± standard error are shown based on manual scoring of 50 cells or automated scoring of 200 cells. Shading reflects triage categories of <1 Gy (white), 1–2 Gy (light grey) and >2 Gy (dark grey) based on the dose estimate alone.

* No result