Purpose: Micro-costing is often conducted to determine incremental costs of an intervention for cost-effectiveness analysis, but may not be consistent with budgetary costs used for implementation. We describe these differences using a case study of implementation of rapid HIV testing and counseling in a substance abuse treatment program following a clinical trial.
Method: During the clinical trial, we used micro-costing methods to determine the cost of HIV testing in substance abuse treatment programs to conduct a cost-effectiveness analysis. Time and materials were from study records (including start and stop times for time conducting on-site testing and counseling) and site interviews; labor costs assume full capacity and were valued at local labor rates; and overhead was calculated from site financial records and applied as a percentage of labor costs. Costs include counselor and other labor, rapid HIV test and materials, supervision, quality control, and overhead. After the trial, one site implemented on-site rapid HIV testing with risk-reduction counseling in its detoxification program for 30 weeks. We compared projected costs in 2009 US dollars of implementation at this site based on micro-costing to budgetary costs reported by the site.
Result: The site administered 184 rapid HIV tests during the implementation period. Projected total costs for this period using micro-costing were $13,900 versus $20,300 budgetary costs. Labor costs based on micro-costing were $5,500 (245 hours) versus $16,700 (784 hours) budgeted for staff assigned to implementation. Overhead based on micro-costing was $5,500 versus $3,500 budgeted. Costs of tests and counseling supplies were estimated at $2,200 using micro-costing, whereas in the implementation the tests and supplies were provided from public health sources without cost to the site. Quality assurance costs using micro-costing were $700 but these costs were not separately budgeted in the implementation.
Conclusion: Cost estimates developed for cost-effectiveness analysis using micro-costing should not be indiscriminately applied when planning for implementation. Micro-costing may underestimate some costs (e.g. by assuming full capacity labor utilization) and overestimate others (e.g. by not considering donated materials and services). Micro-costing, however, may also identify cost categories not fully covered by implementation budgets (e.g. overhead and quality assurance).