Table 1.

Volunteer details, radiolabeling, and sensitization combinations and individual platelet recovery and survival data using the COST program

UPN	Platelet count	HPA-1a expression levels, MFI	Radiolabel and antibody combination		Five-minute recovery, %		COST data
			Unsensitized	B2G1Δnab	Unsensitized	B2G1Δnab	Unsensitized		B2G1Δnab
							Recovery, %	Survival, h	Recovery, %	Survival, h
1	172	16.3	Cr51	111In	66	94	48	83	73	98
2	270	15.8	111In	Cr51	72	94	59	191	71	177
3	412	15.6	Cr51	111In	47	36	36	151	30	283
4	260	18.2	Cr51	111In	54	68	54	214	65	238
5	270	No data	111In	Cr51	51	42	51	254	33	215
6	299	17.1	Cr51	111In	38	61	32	212	57	216
7	324	16.9	111In	Cr51	69	77	61	212	65	243
							Unsensitized		B2G1
			Unsensitized	B2G1	Unsensitized	B2G1	Recovery, %	Survival, h	Recovery, %	Survival, min
8	249	19.2	111In	Cr51	93	53	62	198	38	14
9	311	14.3	Cr51	111In	57	63	42	223	39	18
							Unsensitized		B2G1Δnab75*
			Unsensitized	B2G1Δnab75	Unsensitized	B2G1Δnab75	Recovery, %	Survival, h	Recovery, %	Survival, min
10	190	No data	Cr51	111In	70	82	58	152	56	48
11	257	17.7	111In	Cr51	70	75	60	219	43	40
12	230	18.2	111In	Cr51	60	50	54	162	59	45
							B2G1		B2G1Δnab90*
			B2G1	B2G1Δnab90	B2G1	B2G1Δnab90	Recovery, %	Survival, min	Recovery, %	Survival, min
13	234	14.7	111In	Cr51	95	83	70	28	50	45
14	238	15.2	Cr51	111In	51	77	27	14	30	50
15	175	14.0	111In	Cr51	65	60	63	15	44	77
16	239	18.0	111In	Cr51	60	79	65	18	86	62
17	198	16.6	111In	Cr51	78	79	36	17	61	56
18	276	26.3†	Cr51	111In	57	69	81	19	96	25

The COST program is a mathematical tool that fits a theoretical survival curve to the measurements of platelet recovery at the various time points³² and infers platelet survival and recovery at time 0 from the fitted curve using the multiple hit calculation model. The first time point used for the curve fitting should be taken after equilibrium.^33,34 For unsensitized and B2G1Δnab-sensitized platelets which showed a plateau phase during the first 24 hours (see Figure 1), the 24-hour time point was used as the first point for the curve fit. For B2G1-sensitized platelets and platelets sensitized with a combination of 75% B2G1Δnab/25% B2G1 and 90% B2G1Δnab/10% B2G1B2G1Δnab 90%/ B2G1 10% (*B2G1Δnab75 and -90, respectively) where rapid destruction was observed without a plateau phase (see Figure 1), the 5-minute time point was used (see “Results”).

^†UPN 18 had a much higher HPA-1a expression level (MFI 26.3 vs mean ± SD MFI of 16.5 ± 1.6 for the rest of the volunteers), and platelet survival data were very different from other volunteers (see supplemental Figure 1). Data from this volunteer were therefore excluded from subsequent analysis.