Uncertainty analysis of base case incremental costs and effectiveness of gene therapy compared with prophylaxis and on-demand replacement treatments. (A) Gene therapy compared with standard half-life FIX prophylaxis and on-demand treatments. (B) Gene therapy compared with extended half-life FIX prophylaxis and on-demand treatments. The y-axis represents the incremental costs of gene therapy compared with on-demand treatment or prophylaxis. The x-axis represents the incremental effects on a scale of –20 QALYs to 20 QALYs. Each dot represents the mean of the 500 000 simulants, and the ellipse surrounds 95% of the results. All results in the dominant quadrant are favorable for gene therapy and represent data points for which gene therapy is less costly and more effective than the alternative strategy. All results in the dominated quadrant are unfavorable for gene therapy and represent data points for which gene therapy is more costly and less effective compared with the alternative strategy. Results that lie within the right upper quadrant are considered cost-effective if the cost per QALY is equal to or below the threshold of $150 000/QALY. Above the threshold of $150 000/QALY, gene therapy is not considered cost-effective.