|Cost-Effectiveness Tool for Evaluating Interventions to Prevent Mother-to-Child Transmission - Manual and Model (UNAIDS, 2000, 94 p.)|
External cost of VCT refers to the portion of the cost that could be attributed to non-MTCT health benefits. VCT for vertical transmission prevention may also reduce horizontal (adult-adult) transmission. This reduction in horizontal transmission is not captured by the model in its calculation of health benefits to children and is referred to as external. One way to capture or internalize the potential horizontal transmission reduction benefits is to reduce the cost of VCT attributable to MTCT. If, for example, we believed that 30% of the total health benefits of VCT take the form of horizontal transmission reduction, we could reduce the cost of VCT by 30%. However, because this external benefit of VCT has not been documented, we have set the default value of this parameter to zero.3 This is likely to introduce a conservative bias to the cost-effectiveness results (tending to make results appear less favorable than they really are). The consequences of non-zero values for this external benefit can be assessed by entering other values in cell VCT C5.
3 Interested readers can refer to (Wolitski, et al., 1997), and (Zoysa, et al., 1995) for a review of recent studies regarding sexual risk behavioral change following VCT. Studies vary in their findings from significant increase in condom use (Kamenga, et al., 1991) to no benefit from one session (Temmerman, et al., 1990).
Influence on cost-effectiveness: High. The portion of the cost of VCT that is billed to horizontal transmission benefits has a major influence on the effective cost of VCT attributed to MTCT and therefore on overall program costs. This is especially true for the less drug intensive regimens such as HIVNET-012 and PETRA-B. VCTs importance is also greater if substitute feeding interventions are not implemented.
Expected effort of data collection: Low. Estimating VCTs benefits for horizontal transmission would be a major research undertaking in its own right. We suggest that for the base case analysis you use the default value of 0%.
C14. Specifying external cost of VCT. Enter numbers from 0% to 100% to evaluate changes in the value of this parameter. Note that the table in cells VCT I18 - VCT P29 show the current values of the various cost components of VCT. The left-hand side shows these values assuming no external benefits of VCT and the right-hand side shows these same values assuming the external benefit entered in C5 (and displayed also in P29).