Treatment of Acute Childhood Idiopathic Thrombocytopenic Purpura (ITP): A Cost-Utility Analysis.

Background & Aim: Controversy exists regarding treatment of children with typical acute ITP, a generally benign self-limited disease. Among physicians who actively treat ITP, the primary objective is to rapidly increase the platelet count to greater than 20x10⁹/L. This practice is due to the belief that the greatest risk factor for intracranial hemorrhage (ICH) is the number of days of severe thrombocytopenia following the start of treatment. We built a decision analytic model to evaluate the cost-utility of four commonly used treatment strategies for acute ITP: 1) single dose 0.8 gm/kg IVIG 2) single dose 75 mcg/kg anti-D 3) methylprednisolone (IV) 30 mg/kg/dose given daily for 3 days or 4) oral prednisone 4 mg/kg/day given for 4 days with no tapering.

Methods: In our model, we assumed that all children were hospitalized upon presentation, and were discharged once the platelet count reached ≥ 20x10⁹/L. We also assumed that the incidence of ICH was 0.1%, regardless of treatment strategy. We performed a literature search to estimate the time to platelet count ≥ 20x10⁹/L for each of the strategies, as well as the probability of side effects. We obtained quality of life measures (utilities) and cost data from institutional and published data sources. Costs included wholesale drug costs, infusion costs, hospitalization, and lost parental wages. Using a societal perspective, we compared strategies based on costs and quality-adjusted life-days (QALDs). Based on published data, and using declining exponential distributions, we estimated the average time to platelet count ≥ 20x10⁹/L as follows: 1.4 days for IVIG, 0.7 days for anti-D, 2.4 days for methylprednisolone, and 1.6 days for prednisone.

Results: The total cost of one-time treatment for a 20 kg child with acute ITP was $786 with prednisone, $1346 with methylprednisolone, $2035 with anti-D, and $2912 with IVIG. In the final analysis, the strategies of IVIG and methylprednisolone were dominated by prednisone. In cost-effectiveness analyses, a strategy is “dominated” when it is both less effective and more costly than an alternative strategy. Although anti-D caused the most rapid rise in platelet counts, the incremental cost-utility ratio (net increase in cost divided by net increase in health effect) of anti-D compared to prednisone was $7616 per QALD (day of severe thrombocytopenia avoided). Cost-utility results were sensitive to variation in hospitalization costs, anti-D costs, disutility of hospitalization, and estimated time to reach a platelet count ≥ 20x10⁹/L.

Conclusion: While the use of anti-D instead of prednisone leads to earlier hospital discharges in our model, this clinical benefit was offset by a substantial cost increase of $7616 per day of hospitalization and severe thrombocytopenia avoided. The higher total cost in the anti-D strategy was primarily due to the much higher medication cost of anti-D as compared to prednisone. Although often overlooked in favor of newer agents, a brief course of high-dose prednisone is an inexpensive and effective treatment for acute ITP.