TABLE 2.

Overall specificity analysis for the Elecsys HTLV-I/II assay and comparator assays in blood donor samples

Parameterb	Elecsys HTLV-I/II			Abbott Architect rHTLV-I/II serum	Abbott Prism HTLV-I/HTLV-II serum	Ortho Avioq HTLV-I/II serum
	Total	Serum	Plasma
No. of samples
Total	11,574a	9,550a	2,024	5,737a	3,813	2,024
Negative	11,568	9,546	2,022	5,734	3,812	2,022
With ≥1 s/co
IRpos	9	8	1	6	5	3
IRfpos	6	6	0	5	5	2
RRpos	9	8	1	6	0	2
RRfpos	6	6	0	5	0	1
No. of samples with HTLV-1/2 immunoblot assay result/total no. tested
Positive	0/9	0/8	0/1	0/6	0/0	0/3
Indeterminate	3/9	2/8	1/1	1/6	0/0	1/3
Negative	6/9	6/8	0/1	5/6	0/0	2/3
% specificity IR ≥ 1 s/co	99.95	99.94	100	99.91	99.87	99.90
95% confidence limit (two-sided, IR ≥ 1)	99.89–99.98	99.86–99.98	99.82–100	99.80–99.97	99.69–99.96	99.64–99.99
% specificity RR ≥ 1 s/co	99.95	99.94	100	99.91	100	99.95
95% confidence limit (two-sided, RR ≥ 1)	99.89–99.98	99.86–99.98	99.82–100	99.80–99.97	99.90–100	99.72–100

^aOne sample excluded from specificity calculations: Elecsys HTLV-I/II reactive; Abbott Architect rHTLV-I/II nonreactive; Fujirebio INNO-LIA HTLV I/II Score reactive, “env gp21 1/2” (“1+”), “env gp46 1/2,” “env gp46-I” (“+/−”). No clarification by nucleic acid technology (NAT) testing or by a sequential bleed was possible due to anonymization of samples.

^bTotal, number of analyzed samples; negative, number of true-negative samples (excluding indeterminate, positive, and false-negative samples); IR, initially reactive; IRpos, initially reactive sample, including true-positive samples; IRfpos, initially reactive sample, not including true-positive samples; RR, repeatedly reactive; RRpos, repeatedly reactive sample, including true-positive samples; RRfpos, repeatedly reactive sample, not including true-positive samples; s/co, signal/cutoff ratio.