The Prognostic Value of Platelet Kinetics Assessment in Pediatric Chronic Idiopathic Thrombocytopenic Purpura

<b>Background/Objectives</b>: The assessment of platelet kinetics (APK) is recommended for patients with chronic idiopathic thrombocytopenic purpura (chITP). The aim of this study was to examine the importance of APK as a prognostic instrument in the selection of therapy in children with chITP. <b>Methods:</b> Retrospective, observational research, which included chITP children who were treated and subjected to APK in Serbia for 25 years (total number was 152). <b>Results:</b> In the acute phase of the disease, 15% of patients had life-threatening bleeding, 15% were asymptomatic, and there were no cases of fatal bleeding. Mean platelet life was 0.89 ± 0.47 days. A total of 45% of patients had normal platelet production, and 35% had very low production. Among the patients, 55% exhibited splenic platelet sequestration, 35% had mixed sequestration, and 10% showed hepatic platelet sequestration. Platelet lifespan and production indices were less reliable parameters, due to numerous contradictory results, especially when compared with the location of platelet sequestration. Distribution of bleeding and therapy-resistant patients was dominant with mixed sequestration. Good therapy responders had dominant splenic sequestration. In the chronic phase of the disease, initial therapy was sufficient for 40-45% of patients, while another 25% required second-line therapy, regardless of platelet sequestration location. A total of 25% percent of patients had undergone splenectomy, and all of them were in stable remission. The remaining 10%, which represented the most severe cases, required all available therapies, had equally mixed and liver sequestration, and splenectomy showed no effect. <b>Conclusions:</b> APK may be a determining factor for the selection of splenectomy as a therapeutic option in case of predominantly splenic sequestration. Although the platelet production index has been explored in several studies, its clinical relevance remains controversial. In our findings, it did not contribute to therapeutic decision-making and may even lead to misinterpretation. The factors distinguishing the minority of bleeding and therapy-resistant patients with similar laboratory profiles remain unclear.