Preventing Transmission of Chagas Disease in the U.S. Blood Supply: A Cost Effectiveness Analysis of Testing the Blood Bank Donations Danielle Doughman Health Policy and Management, Gillings School of Global Public Health, University of North Carolina at Chapel Hill Chagas disease is a parasitic infection common in rural areas of the Americas with substandard housing Precise prevalence figures difficult to ascertain due to lack of detection as nearly half of all cases remain asymptomatic. Chagas not endemic in the U.S., but between 3,000 and 1 Million cases estimated in the US, especially along US- Mexico border, Appalachia, and Mississippi Delta regions Only 7 known cases of Chagas disease transmission via blood transfusion in the US and Canada. FDA does not require blood banks to test blood for Chagas disease, and the disease prevalence is not tracked by the CDC, though 65% of blood banks voluntarily test With heightened attention to immigration from Latin America to the U.S., there have been concerns about Chagas in the U.S. blood supply. Those with symptoms develop life-long gastrointestinal or cardiac complications, sometimes leading to death. In December 2006, the FDA approved a Chagas screening assay for blood called the Ortho T. cruzi ELISA Test System (enzyme-linked immune sorbent assay) Background Results Limitations Conclusions Background: Chagas Disease is a parasitic infection that affects people living in poor, rural areas of the Americas. Though Chagas is not endemic to the U.S., increased attention on immigration from Latin America to the U.S. coupled with the availability of a highly effective assay highlight the need for testing of blood donations for Chagas, which may be transmitted through transfusion. Currently, blood banks are not required to test for Chagas, although 65% voluntarily do so. Objective: To estimate incremental cost-effectiveness of blood bank testing and screening strategies for Chagas. Design: Cost-effectiveness analysis with a decision tree model. Data Sources: Peer-reviewed literature. Target Population: U.S. adult blood donors and transfusion recipients ages Time Horizon: 20 years. Perspective: Societal. Interventions: 1) the ELISA test for all blood donations, 2) verbal screen with ELISA testing for those with a positive screen, and 3) testing new donors only. Outcome Measures: Costs (in 2008 U.S. dollars), cases averted, and incremental cost per case averted. Results of Base-Case Analysis: Testing All averts 20 additional cases over Screen and Test, but at a cost of $3.6 million per additional case averted. Test New Donors resulted in worse outcomes (increase of 14 cases) but lower costs than the standard (Screen and Test). Results of Sensitivity Analysis: The analysis is most sensitive to whether or not a negative verbal screen was obtained. The model results were relatively insensitive to all other variables. Conclusions: Testing All averts the most cases, however, it is cost-prohibitive at a threshold of $100,000 per case averted. ABSTRACT Assumptions Data Methods Acknowledgements Assume same transmission risk for both red blood cell and platelet transfusion For a person with Chagas becomes symptomatic, the disease outcomes have been collapsed into two categories: 1) Cardiac abnormalities, and 2) gastrointestinal disease. Cases of Chagas disease due to reactivation have been excluded The model assumes testing requires only one ELISA test, and does not include costs associated with notification and appropriate follow-up with infected individuals and their families. Blood donation losses due to other screening and expiration not included and assumed to be consistent across the three alternatives All donors positive for Chagas will present in the chronic stage and not require the treatment appropriate for those with newly acquired. Assuming 100% cure of those with acute disease when rate is only about 85% No costs assumed for tracking of established donors’ Chagas status. This study used a cost-effectiveness analysis with a decision tree model to estimate the costs and outcomes for three tsting alternatives over a 20 year period for a cohort of 15 million U.S. adults ages 18 to 65 (the average number of blood donations in the U.S. each year, rounded to the nearest million). Blood Banks decide to either 1) Verbally Screen each donor, and test the blood donations of those at high risk, 2) Test all blood donations, or 3) Test only new donors. Blood found to be infected is discarded, donors with Chagas are deferred, and blood believed to be uninfected is given to transfusion recipients. If a person is given infected blood, they may be treated successfully in the first two months, or will progress to chronic disease. Of those, about half will develop gastrointestinal or cardiac symptoms, some requiring surgery or leading to death. Thanks to Andrea Biddle, Stephanie Wheeler, Rebecca Garr, Cheri Poss, and Elizabeth Walker for their valuable suggestions. This study does not consider deaths averted so the high costs of Chagas care in the last year of life may make testing seem less cost-effective. Prevalence rates of Chagas are very difficult ot ascertain with any certainty since many cases go undiagnosed and the disease is not tracked in the U.S. Base-Case Analysis: DeterministicIncremental CostsTotal Cases Costs Cases Averted CE Ratio Screen &Test $55,579, Test All$129,178,677-25$73,599,63920 $3,621,824 Test New Donors$27,247, $28,331, $1,963,019 With the given probabilities, assumptions and costs, testing more frequently for Chagas disease in the blood supply is not cost effective. These results contradict the analysis conducted by Wilson in 2008, which found both Testing All and Test and Screen cost- effective alternatives to No Testing. Sensitivity analysis demonstrates that the decision is most sensitive to whether or not a person has a negative verbal screen, so a more precise screen that limits the need for tests may help bring costs down, but probably not nearly enough for any alternative to be cost-effective any where near $100,000 per case. If costs in the last year of life due to Chagas were taken into account, the intervention would become most cost effective, but, again, not at the $100,000 threshold. Only the variable Negative Verbal Screen for Chagas Risk demonstrated caused significant variability in model results. At typical rates of $100,000 per case averted, no alternative is cost-effective. At $2,000,000 per case averted, Screen and Test and Testing New Donors cross, indicating equalibrium in cost-effectiveness Testing New Donors is cheapest, but results in the most cases of disease. Testing only new donors is the cheapest option but still costs nearly $2 million per case averted, and increases the total number of disease cases over Screen and Test Testing All is most effective in reducing the total number of cases, but costs an additional $73.6 million for only 20 additional cases averted over the standard.