Results of a model analysis to estimate cost utility and value of information for intravenous immunoglobulin in Canadian adults with chronic immune thrombocytopenic purpura.

OBJECTIVE: The aim of this work was to estimate the cost-effectiveness of intravenous immunoglobulin (IVIg) compared with oral prednisone as a treatment for Canadian adults with persistent chronic immune thrombocytopenic purpura (ITP).

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 that was developed based on a systematic clinical and economic review and recommendations of clinical experts in Canada. Transition probabilities (ie, point estimates and 95% CIs) were estimated from the studies identified in a systematic literature review using a random-effect meta-analysis; point estimates were weighted-mean values from the meta-analysis. No published studies directly estimate the utility weight for patients with relapsed or refractory ITP; therefore, a value of 0.76 was used, based on the mean of the utilities for thrombocytopenia without major bleeding or hemorrhagic stroke. Costs and incremental cost-effectiveness ratios were reported as year-2007 Can $.

RESULTS: The incremental costs and quality-adjusted life-years (QALYs) of IVIg versus prednisone were Can $8080 and 0.0071, respectively, resulting in an incremental cost-effectiveness ratio of Can $1.13 million/ QALY in the base-case analysis. The probability of IVIg being cost-effective was 0 if the maximum willingness-to-pay (WTP) value for an additional QALY was below Can $40,000. The probability that IVIg would be cost-effective was only 20%, even if the WTP increased to Can $100,000. The expected value of perfect information (EVPI) and expected value of partial perfect information (EVPPI) were 0 if the WTP was less than Can $30,000. If WTP increased to Can $100,000, the EVPI was Can $1700, and the EVPPI was Can $1010 for utility weights of relapse/refractory states, Can $136 for initial response rates of the treatments, and Can $6 for first-year relapse rates for the treatments.

CONCLUSION: Based on the current available clinical evidence, this model analysis of hypothetical patients suggests that IVIg may not be a cost-effective option for adults with persistent chronic ITP in Canada.