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.


CONCLUSIONS
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.
Xie
Feng
F
Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada. fengxie@mcmaster.ca
Blackhouse
Gord
G
Assasi
Nazila
N
Campbell
Kaitryn
K
Levin
Mitchell
M
Bowen
Jim
J
Tarride
Jean-Eric
JE
Pi
David
D
Goeree
Ron
R
D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage / Q000191:economics / Q000627:therapeutic use; D002170:Canada; D002908:Chronic Disease; D003362:Cost-Benefit Analysis / Q000379:methods / Q000706:statistics & numerical data; D003661:Decision Support Techniques; D006801:Humans; D016756:Immunoglobulins, Intravenous / Q000008:administration & dosage / Q000191:economics* / Q000627:therapeutic use*; D008875:Middle Aged; D018803:Models, Economic; D011241:Prednisone / Q000008:administration & dosage / Q000191:economics / Q000627:therapeutic use; D011696:Purpura, Thrombocytopenic / Q000188:drug therapy* / Q000191:economics*; D019057:Quality-Adjusted Life Years; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
D000893:Anti-Inflammatory Agents; D016756:Immunoglobulins, Intravenous; D011241:Prednisone