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This study investigated the immature platelet fraction (IPF) in assessing treatment effects in immune thrombocytopenia (ITP). IPF was measured on the Sysmex XE2100 autoanalyzer. The mean absolute-IPF (A-IPF) was lower for ITP patients than for healthy controls (3.2 vs 7.8 × 10⁹/L, P < .01), whereas IPF percentage was greater (29.2% vs 3.2%, P < .01). All 5 patients with a platelet response to Eltrombopag, a thrombopoietic agent, but none responding to an anti-FcγRIII antibody, had corresponding A-IPF responses. Seven of 7 patients responding to RhoD immuneglobulin (anti-D) and 6 of 8 responding to intravenous immunoglobulin (IVIG) did not have corresponding increases in A-IPF, but 2 with IVIG and 1 with IVIG anti-D did. This supports inhibition of platelet destruction as the primary mechanism of intravenous anti-D and IVIG, although IVIG may also enhance thrombopoiesis. Plasma glycocalicin, released during platelet destruction, normalized as glycocalicin index, was higher in ITP patients than controls (31.36 vs 1.75, P = .001). There was an inverse correlation between glycocalicin index and A-IPF in ITP patients (r² = -0.578, P = .015), demonstrating the relationship between platelet production and destruction. Nonresponders to thrombopoietic agents had increased megakaryocytes but not increased A-IPF, suggesting that antibodies blocked platelet release. In conclusion, A-IPF measures real-time thrombopoiesis, providing insight into mechanisms of treatment effect.

Original publication




Journal article



Publication Date





5723 - 5732


Adolescent, Adult, Aged, Aged, 80 and over, Benzoates, Blood Platelets, Case-Control Studies, Child, Child, Preschool, Female, Humans, Hydrazines, Immunoglobulins, Intravenous, Infant, Isoantibodies, Male, Middle Aged, Platelet Count, Prognosis, Purpura, Thrombocytopenic, Idiopathic, Pyrazoles, Receptors, IgG, Retrospective Studies, Rh-Hr Blood-Group System, Rho(D) Immune Globulin, Thrombocytosis, Thrombopoiesis, Young Adult