Costs and benefits to the mother of antenatal HIV testing: estimates from simulation modelling

To assess the health service costs and benefits for the woman of an earlier HIV diagnosis as a result of antenatal HIV testing.

A model of maternal disease progression was developed based on the rate of decline in CD4 cell counts and applied to two matched simulated cohorts of women with identical initial CD4 cell levels and decline rates but whose HIV diagnosis occurred at different times as a result of antenatal HIV testing. UK data on CD4 cell count at HIV diagnosis and annual health service costs of care excluding antiretroviral therapy (ART) incurred at defined states of CD4 cell count were taken from published UK data. Costs of triple ART were added and effectiveness modelled by retarding the rate of CD4 cell count decline. Discounting costs at 6% and life-years at 2% per year, the additional costs per life-year gained by screening were calculated. Uncertainty was explored using sensitivity analysis.

Costs per life-year gained by antenatal diagnosis of women were pound sterling 51258 ($76887) assuming untested women were diagnosed a median of 20.4 months later than tested women, ART was initiated at a CD4 cell count of 350x10(6) cells/l and ART efficacy retarded decline in CD4 cell counts by 40% for life. Sensitivity analyses showed results were most sensitive to the assumed efficacy of lifetime ART and time assumed to HIV diagnosis for women not tested in pregnancy.

This model provides a way of estimating the additional costs and benefits of future care for the woman resulting from an earlier HIV diagnosis through antenatal testing. These should be included with the paediatric costs averted and life-years gained from interventions to reduce mother-to-child transmission in order to evaluate the cost-effectiveness of antenatal screening in different populations and settings.