One of the political goals of the European Union is to achieve a more unified approach to public health regulation and practice. This is particularly true of blood transfusion safety. Dr. Arturo Pereira’s research at the Hospital Clinic in Barcelona, Spain has been directed at the question of how to predict with some assurance the health and economic consequences of blood transfusion procedures.
In many parts of the world, increased sophistication in blood donor screening has virtually eliminated the risk of post-transfusion HIV and other serious viral infections. The only significant disease for which transfusions continue to pose a risk is from the hepatitis B virus (HBV). The current risk of acquiring this infection through blood transfusion is below 1:75,000 blood units (risks for HIV and hepatitis C stand around 1 in 1 million and 1:300,000 transfused blood units, respectively).
In the late 1990s a new technology for detecting HBV, based on nucleic acid testing (NAT), was introduced. It is more sensitive than the current detection method, known as HBsAg assays, though considerably more expensive. Because the risk of transfusion-transmitted HBV infection is already very low, and the infection is usually mild and self-limited when acquired in adult life, concern arose about the fairness of allocating resources to NAT at the expense of diverting them from other health care priorities. At present, only Japan and Germany have introduced HBV NAT in the routine testing of blood donors. Complicating the decision-making is the fact that improved versions of the HBsAg assay, which are nearly as sensitive as NAT but substantially cheaper, are under development and will soon be licensed.
In 2001, Dr. Pereira began research into the question: how will improved donor screening for hepatitis B affect health outcomes and medical costs across the EU? The study, funded in part by a grant from the Ministry of Health of the Government of Spain, was intended to inform public health policy makers.
In the course of three studies, Dr. Pereira was able to increase the sophistication of his modeling procedure to better mimic real-world health and economic outcomes. According to Dr. Pereira, “Monte Carlo simulation is a procedure that has remarkable capacity to adapt to variation and uncertainty, and to the augmentation of detail. In addition, software allowing Monte Carlo simulation of complex spreadsheet models, in this case @RISK, has simplified the modeling and calculation phases of the study, leaving more time and energy for result analysis and interpretation.”
@RISK’s mathematical and reporting capabilities enabled Dr. Pereira to take full account of uncertainties in his analysis of cost-effectiveness. Any uncertain variables were represented with probability distributions and these distributions allowed him to extend results to a wider population: the European Union. For most of the variables used in the cost-effectiveness analysis, not enough information was available on the shape of their probability distributions. Therefore triangular distributions were specified for these; that is, the functions accounted for three parameters: minimum, most likely, and maximum values. But in those cases where Dr. Pereira had enough data on a given variable, @RISK allowed him to select the best-fitting probability distribution by using the product’s built-in distribution fitting feature.
It is important to note that the results of a Monte Carlo simulation are themselves probability distributions. Therefore Dr. Pereira examined his @RISK results before drawing conclusions from them.
The model predicts that 0.97 percent of EU patients with post-transfusion hepatitis B die of liver disease. The mean loss of life expectancy was 0.178 years per patient, and the present value of lifetime costs of treating HBV-related complications was about $4,700 per patient. For the European Union population, the projected cost for each life-year gained using single donation HBV NAT was $6,519,000. Using the enhanced sensitivity HBsAg method, the cost for each life expectancy year gained was $888,000. If single donation HBV NAT were implemented after the current residual risk of HBV transmission had already been reduced by the new, more sensitive HBsAg assays, the cost per life year gained would increase to $47 million.
It is not difficult to see that single-donation HBV NAT would provide a small health benefit at a very high cost. Under some circumstances, however, the cost effectiveness of enhanced-sensitivity HBsAg assays would be acceptable for new public health interventions.
» Read full case study article from the journal Tranfusion