. 2016 Jul 29;3(3):ofw161. doi: 10.1093/ofid/ofw161

Table 2.

Maximum Cost of Viral Load Test for Net Health Benefit in the Context of Changes in Values of Each Attribute of the Viral Load Testing Approach, Changing the Value of Only One Attribute at a Time

Attribute of Viral Load Testing Approach	Values for Factor Considered		Maximum Fully Loaded Cost of Viral Load Test for Reduced Net DALYs Compared With Base Scenario
(1) Delay in result	No delay		$23
(1) Delay in result	3 mo delay^a		$22
(2) Sensitivity/specificity relative to plasma for 1000 copies/mL cutoff	Sensitivity/Specificity
	58/96	84/89^a	$21	$22
	60/99	89/93	$20	$21
	69/97	90/85	$20	$22
	70/79	95/90	$19	$21
	74/75	96/65	$17	$15
	78/93	96/77	$20	$17
	79/71	99/69	$15	$20
	80/84	100/100	$19	$23
	82/96		$21
(3) VL threshold used to define first-line ART failure (copies/mL) (cutoff for qualitative assay)	200		$20
	500		$23
	1000^a		$22
	3000		$19
	5000		$19
(4) Proportion of tests failed or result lost^b	0.80		$5
	0.50		$16
	0.30		$19
	0.15^a		$22
	0.00		$24
(5) Probability of differentiated care if VL < 1000 being implemented	0.5		$14
	0.6		$16
	0.7		$19
	0.8^a		$22
	0.9		$24
(6) Difference in coverage of population with VL testing	70%		$20
	75%^a		$22
	80%		$23
	85%		$25
	90%		$26
	95%		$26
	100%		$28
(7) Probability of switch to second-line ART per 3 mo once failure definition met	0.05		$17
	0.10		$20
	0.15		$20
	0.20^a		$22
	0.25		$22
	0.30		$23
	0.40		$23
	0.60		$23
	1.00		$25
(8) Probability of ART interruption/loss to follow up (per 3 mo)	0.030		$3
	0.025		$14
	0.020^a		$22
	0.015		$29
	0.010		$41
	0.005		$48

Abbreviations: ART, antiretroviral therapy; DALYs, disability adjusted life years; VL, viral load.

^a Base scenario (VL cost $22).

^b Assumed that there is a 90% chance that the cost of the test is nevertheless incurred.