ECONOMIC EVALUATION OF INTRAVENOUS IMMUNOGLOBULIN (IVIG) IN ADULTS WITH CHRONIC IMMUNE THROMBOCYTOPENIA PURPURA (ITP)

Objective: To compare the costs and effectiveness of IVIg and prednisone as a first line treatment for adults with persistent chronic ITP in Canada.

Methods: The lifetime costs and effectiveness of IVIg and prednisone were estimated from the perspective of a publicly funded health care system in Canada using a Markov model. Model parameters were estimated using a systematic literature review with a random-effect meta-analysis. The target patient population was a hypothetical cohort of adults with persistent chronic ITP presenting with platelet counts <20,000/µL and without active bleeding. Probabilistic sensitivity analysis was performed using Monte Carlo simulations. The total expected value of perfect information (EVPI) and the expected value of partial perfect information (EVPPI) were estimated using the one-level Monte Carlo sampling algorithm with the assumption of independency of the parameters.

Results: The total costs of IVIg were $8050 more than the costs of prednisone. The incremental QALYs of IVIg compared to prednisone were 0.0048, resulting an ICER of $1,700,000/QALY. The probability that IVIg is more cost effective than prednisone is only 0.2 even if the willingness to pay value increases to $100,000. The individual EVPI and EVPPIs are zero if the societal willingness to pay value is less than $30,000. If the value increases to $100,000, the EVPI is $760 and the EVPPI is $30 and $14 for the initial response rate to IVIg and prednisone, respectively. The utility weight for refractory ITP has the highest EVPPIs for both IVIg ($124) and prednisone ($101).

Conclusions: IVIg is not a cost-effective initial treatment for adults with chronic ITP based on current available evidence. Given the certain willingness to pay threshold values, it might be worthwhile obtaining some empirical evidence of the impact of treatments on patients’ utilities.