Assessment of an immature platelet fraction (IPF) in peripheral thrombocytopenia

Abstract

SummaryA new automated method to reliably quantify reticulated platelets, expressed as the immature platelet fraction (IPF), has been developed utilizing the XE-2100 blood cell counter with upgraded software (Sysmex, Kobe, Japan). The IPF is identified by flow cytometry techniques and the use of a nucleic acid specific dye in the reticulocyte/optical platelet channel. The clinical utility of this parameter was established in the laboratory diagnosis of thrombocytopenia due to increased peripheral platelet destruction, particularly autoimmune thrombocytopenic purpura (AITP) and thrombotic thrombocytopenic purpura (TTP). Reproducibility and stability results over 48 h were good. An IPF reference range in healthy individuals was established as 1AE1-6AE1%, with a mean of 3AE4%. Patients in whom platelet destruction might be abnormal, were studied and two of these patients followed serially during the course of treatment. The IPF was raised in several disease states. The most significant increases in IPF values were found in patients with AITP (mean 22AE3%, range 9AE2-33AE1%) and acute TTP (mean 17AE2%, range 11AE2-30AE9%). Following patients during treatment demonstrated that as the platelet count recovered the IPF% fell. These results show that a rapid, inexpensive automated method for measuring the IPF% is feasible and should become a standard parameter in evaluating the thrombocytopenic patient.

Reticulated platelets: analytical aspects and clinical utility

“…These reference values were later confirmed by others [50][51][52][53][54]. In all studies, patients with idiopathic thrombocytopenia (ITP) had increased IPF; in some patients IPF was even strongly increased, up to 50%-60% [49,54,55]. Such extreme values were later recognized to be artifacts due to interference by white blood cell fragments [56].…”

“…As before, a forward scatter versus fluorescence scatterplot defined platelets with the highest fluorescence intensity as immature platelets (Figure 2A). The reference values in a healthy population were clearly higher than with the previous R-3000 method: mean 3.4% (range 1.1%-6.1%) [49]. These reference values were later confirmed by others [50][51][52][53][54].…”

“…Regarding storage temperature before analysis, most authors agree that XE-2100 IPF is stable for 24-48 h after blood collection, provided the samples are kept at ambient temperature [49,70,71]. Others, however, reported stability for 3-8 h only [50,51].…”

“…This enabled automated quantification of what from then on was called immature platelet fraction (IPF) [49]. As these instruments employ a 633 nm diode laser as the light source, other dyes were needed and a mixture of polymethine and oxazine was selected.…”

Platelet analysis in laboratory hematology

“…This is why the devices currently available, despite claims to the contrary, have a poor specificity for "reticulated" platelets even if the addition of RNAse is used as evidence and somewhat reduces the signal. Therefore, the expectations in the follow-up studies to the original publications with manual measurement on the flow cytometer [6][7][8][9][10][11][12] have not been met, or only partially, on routine equipment with a reticulocyte channel [13][14][15][16][17][18], since the Spearman correlation coefficients are only at about 0.6. This clinically valuable parameter of the increased premature platelet release has therefore rarely been incorporated into clinical decisions in the differential diagnosis of thrombocytopenia.…”