Cost Effectiveness of Diagnostic Strategies for Opportune Detection of Toxoplasma Gondii in Pregnant Women

Abstract

Objective: To estimate the cost effectiveness ratio of performing serologic screening for toxoplasma in the first prenatal control and to continue or not with monthly or quarterly monitoring, to increase the diagnosed cases of pregnant women with Toxoplasma gondii infection with timely treatment.Methods: We built a decision tree in TreeAge® which considered four diagnostic strategies: i) No screening ii) IgG and IgM for toxoplasma in the first prenatal visit, and the performance of an IgG avidity test and repetition in two weeks according with the results; iii) IgG and IgM for toxoplasma in the first prenatal control, performance of IgG avidity test and repetition in two weeks according with the results, and quarterly monitoring with IgM and iv) IgG and IgM for toxoplasma in the first prenatal control, performance of IgG avidity test and repetition in two weeks according with the results, and monthly monitoring with IgM. The costs were included from the perspective of the Colombian health system and expressed in Colombian pesos of 2010. Medicines cost information was obtained from the 2008 SISMED (1) and the value of the diagnostic tests was calculated by adjusting the values of the Tariff Manual ISS 2001 30% (2), these values were compared with information of the costs supplied by three EPS. The discount rate was 0%. We performed sensitivity univariate and probabilistic analyses for costs and effectiveness.Results: The most effective and expensive strategy was found to be monthly monitoring, followed by quarterly monitoring, and no screening. Screening only in the first prenatal visit is a dominated strategy. The incremental cost-effectiveness ratio (ICER) of quarterly monitoring versus screening only in the first prenatal visit is $ 163,895,455; while the ICER of monthly versus quarterly monitoring is $ 418.906.009. According to the one-way sensitivity analysis, the variables that best explain the ICER variability are the incidence of congenital toxoplasmosis and the specificity of the IgM test. The probabilistic sensitivity analysis shows that, for a willingness to pay (WTP) below $175 million pesos it is more likely than not screening is a cost effective strategy. Between 175 million pesos and 407 million pesos, quarterly monitoring is more likely to be cost effective. For a WTP above $407 million pesos, the cost effective strategy is monthly monitoring.Conclusions: The cost-effective strategy for Colombia depends on the WTP per additional case of Toxoplasma gondii infection in pregnant women opportunely detected and treated. The WTP should take into account the cost for society of neurological damage or blindness cases due to the infection.