Cost Effectiveness of Diagnostic Strategies for Detecting Congenital Toxoplasmosis in Newborns

Objective: To estimate the incremental cost-effectiveness ratio of different diagnostic schemes in newborns of mothers with a clinical history of infection with Toxoplasma gondii during the pregnancy, in order to increase the detected cases of congenital toxoplasmosis.Methods: We built a decision tree in TreeAge®, with identified infection cases as an outcome, in which three diagnostic strategies were considered: i) IgG, IgM and IgA together, in the face of negative results in IgA and IgM, Western Blot confirmation, and in the face of negative results in the all three tests but IgG positive, monthly monitoring of the newborn for six months and then every three months until the first year with with IgG; ii) IgM and IgA together, with Western -Blot confirmation for negatives; and iii) Western Blot. The costs were included from the perspective of the Colombian health system, expressed in Colombian pesos of 2010. The information of medicines costs was obtained from 2008 SISMED, and the value of the procedures was calculated by adjusting the values of the Manual of Rates ISS 2001 30% (1), these values were compared with information of the costs supplied by three EPS. The discount rate was 0%. Sensitivity analyzes were performed univariate and probabilistic cost-effectiveness. Univariate and probabilistic sensitivity analyzes were performed for costs and effectiveness.Results: The most effective and expensive strategy is i) (based on IgG, IgM and IgA), followed by ii) (based on IgM and IgA and iii) (Western Blot). The incremental cost effectiveness ratio (ICER) of strategy ii) against iii) is $ 6,189,871. This ICER is sensitive to the cost and the sensitivity of Western Blot, and the prevalence of congenital toxoplasmosis. The ICER of strategy i) against ii) is $ 65,529,979, a result that is sensitive to the prevalence of congenital toxoplasmosis, the sensitivity of the joint test of IgM and IgA and the sensitivity of Western Blot. The probabilistic sensitivity analysis shows that, for a willingness to pay (WTP) per correctly identified case below $6,5 million pesos, the strategy with higher probability of being cost effective is iii); between $6,5 million and $74 million pesos, is strategy ii); for a WTP above $74 million pesos, is strategy i).Conclusions: The cost-effective alternative for Colombia depends on the WTP for additional case of congenital toxoplasmosis detected. Below $6,5 million pesos, strategy iii) is more likely to be cost effective; between $6,5 million and $74 million pesos, strategy ii); and above $74 million pesos, strategy i). The WTP should take into account the cost for the society of neurological lesions and blindness caused by the infection. As the results are sensitive to the prevalence of the infection, it is important to advance in the knowledge of this value for different regions in the country.