7.4. Intervention costs

In the implementation of generalised cost-effectiveness analysis (GCEA) (Section 9) via the WHO-CHOICE project, costs are divided into those incurred at the patient or programme level. Patient-level costs involve face-to-face delivery by a health provider (broadly defined) to a recipient - e.g. medicines, outpatient visits, in-patient stays, individual health education messages. Programme-level costs include all resources required to establish and maintain an intervention - administration, publicity, training, delivery of supplies. Interventions like radio delivery of health education messages largely involve the former, while treatment at health centres largely involves the latter. A standardised ingredients approach is used, requiring information on the quantities of physical inputs needed and their unit cost (i.e. total costs are quantities of inputs multiplied by their unit costs) [Johns, Baltussen and Hutubessy, 2003 [34]][Johns, Adam and Evans, 2006 [33]].

For patient-level costs, quantities are taken from a variety of sources. Where effectiveness estimates were available from published studies, the resources necessary to ensure the observed level of effectiveness are identified. In other cases, the resources implied by the activities outlined in WHO treatment practice guidelines were estimated. Since it is not always possible to identify the exact quantities of primary inputs (human resources, consumables) necessary for patient-level costs, certain quantities and prices are estimated at an intermediate level for several inputs - inpatient days at different hospital levels, outpatient visits and health centre visits [Tan-Torres et al., 2003 [57]].

Unit costs for each input were derived from an extensive search of published and unpublished literature and databases along with consultation with costing experts. For goods that are traded internationally, the most competitive price available internationally was used. For example, estimates of drug prices were based on the median supply price published in the International Drug Price Indicator Guide subsequently marked-up to account for transportation and distribution costs. For goods available only locally (e.g. human resources, inpatient bed days) unit costs have been shown to vary substantially across countries, although international comparisons found similar cost-of-illness patterns in several OECD countries [Heijink et al., 2008 [30]]. As a result, cross country regressions, mainly accounting for country GDP and local characteristics of the supply of health care, have been run using the collected data to estimate the average cost (with adjustments for capacity utilisation) for each setting [Adam, Evans and Murray, 2003 [1]].

Costs are reported in international dollars, or dollar purchasing power parities ($PPPs) rather than US dollars, with 2010 as the base year. An international dollar has the same purchasing power as the US dollar has in the United States, and therefore provides a more appropriate basis for comparison of cost results across countries or world regions. Future costs are discounted using a 3% discount rate.