Table 2. The BCR-ABL1 secondary reference panel was highly concordant with the WHO panel.

Reference gene	RT-ddPCR IS CF	WHO panel			Secondary panel
		Panel member	Mean empirical %BCR-ABL1	Nominal %BCR-ABL1IS	Panel member	Mean empirical %BCR-ABL1	Assigned %BCR-ABL1IS
(a) Empirical and %BCR-ABLIS values
ABL1	0.93	4 (08/198)	11.2250	10.7469	A	13.7178	12.7575
		3 (08/196)	1.2540	1.1672	B	1.2841	1.1942
		2 (08/194)	0.1260	0.1112	C	0.1095	0.1019
		1 (08/192)	0.0130	0.0118	D	0.0116	0.0108
					E	0.0041	0.0038
BCR	1.85	4 (08/198)	9.8135	16.3129	A	11.5502	21.3678
		3 (08/196)	0.8441	1.6627	B	0.7300	1.3505
		2 (08/194)	0.0988	0.1753	C	0.0759	0.1404
		1 (08/192)	0.0098	0.0195	D	0.0081	0.0150
					E	0.0027	0.0050
GUSB	1.28	4 (08/198)	6.5834	10.1235	A	9.1800	11.7504
		3 (08/196)	0.5924	0.8295	B	0.6219	0.7960
		2 (08/194)	0.0677	0.0749	C	0.0628	0.0804
		1 (08/192)	0.0065	0.0071	D	0.0068	0.0087
					E	0.0023	0.0029

Reference gene	WHO panel		Secondary panel
	Panel member	Mean copy number per ng RNA	Panel member	Mean copy number per ng RNA
(b) Copy numbers of BCR-ABL1, ABL1, BCR and GUSB per ng of RNA
BCR-ABL1	4 (08/198)	92.98	A	103.27
	3 (08/196)	9.75	B	8.56
	2 (08/194)	0.99	C	0.72
	1 (08/192)	0.10	D	0.08
			E	0.03
ABL1	4 (08/198)	831.74	A	754.55
	3 (08/196)	778.56	B	665.80
	2 (08/194)	784.95	C	651.95
	1 (08/192)	785.90	D	653.85
			E	642.71
BCR	4 (08/198)	948.59	A	973.44
	3 (08/196)	1036.91	B	1058.25
	2 (08/194)	1004.05	C	1012.51
	1 (08/192)	1033.21	D	1079.15
			E	1017.74
GUSB	4 (08/198)	1380.43	A	1198.94
	3 (08/196)	1454.12	B	1238.22
	2 (08/194)	1390.83	C	1261.53
	1 (08/192)	1388.23	D	1283.79
			E	1244.11

Abbreviations: CF, conversion factor; IS, International Scale; RT-ddPCR, reverse-transcription droplet digital PCR; WHO, World Health Organization.