A Revisit of the Criteria To Define Remission in Patients with Idiopathic Thrombocytopenia Undergoing Splenectomy.

Introduction

In patient with immune thrombocytopenic purpura (ITP), the responses to splenectomy are traditionally categorized based on the platelet count. A platelet count of 150 x10⁹/L is generally considered as complete remission. However, asplenic patients may have higher baseline platelet counts. To investigate whether the definition of the remission affects the interpretation of follow up data, we have studied patients with ITP undergoing splenectomy. The results were also compared with a meta-analysis of all the trials published in the past 30 years.

Methods and Materials

Phase I: A retrospective chart review was performed of all patients referred to a tertiary medical center before the splenectomy. The peak post-splenectomy count (PPSC) was defined as the platelet count within 100 days after splenectomy. The patients were followed for various durations. Long-term outcomes after splenectomy were categorized as remission or failure. A failure was defined as a platelet count of less than 30 x10⁹/L after the first 100^th post-operative day or the need for further long-term therapy to maintain the platelet count at a safe level. The clinical outcomes were independently assessed by two investigators. The relationship between PPSC and clinical outcome was assessed via logistic regression.

Phase II: The published case series of patients with ITP were identified through MEDLINE® search. Study inclusion criteria were defined as cohort of adult patients with ITP or adult patients undergoing splenectomy. 2550 articles were found through MEDLINE® search. The results of the 51 publications involving 4198 patients were summarized.

As the focus of this review is on the failure rates of splenectomy for patients with ITP, the published results were recalculated according to a set of pre-defined criteria with dichotomized variables (remission or failure). A failure was defined as a platelet count of less than 50 x10⁹/L, 100 x10⁹/L or 150 x10⁹/L whatever the lowest platelet count used in the study or the need for further long term post-splenectomy therapy. Two reviewers extracted the information from the publications independently to ensure consistent reporting of the results.

Results

Phase I: There was a significant correlation between the PPSC and clinical outcome only when the PPSC was higher than 150 x10⁹/L. Logistic regression indicated that for each increase in the PPSC of 10 x10⁹/L there was a 5% risk reduction in the failure rate after splenectomy.

Phase II: The long-term failure rates were extracted from published series. There has been no significant difference in the long-term failure rate of splenectomy when the initial remission criteria were defined as a post-splenectomized platelet count above 50 x10⁹/L, 100 x10⁹/L or 150 x10⁹/L.

Discussion

The post-splenectomy platelet counts are determined by remaining platelet clearance mechanism(s); the perioperative medical treatments; and other concomitant medical conditions. The normal range of platelet count in asplenic population is poorly defined. As the consensus is not to treat asymptomatic ITP patients with a platelet count higher 30 x10⁹/L, the parameter used to measure the long-term outcome of patients with ITP should derive from these clinical criteria. Simplified dichotomized variables (remission or failure) may provide a better description of the outcome of the treatments after splenectomy in patients with ITP.