Abstract
The Immature Platelet Fraction (IPF) is a novel parameter available on the Sysmex XE-Series Hematology analyzers. It can be expressed as both IPF percent (IPF %) and absolute IPF count (AIPF#). It has been shown that IPF% is higher in Immune Thrombocytopenia (ITP) than in the normal population, and correlates with bone marrow platelet production or thrombopoiesis.
To evaluates the utility of the IPF parameters to predict treatment response or recovery in pediatric ITP patients.
This is a retrospective, single institution study performed at a 165 bed tertiary care pediatric hospital (Children's Hospital of Eastern Ontario, Ottawa, Canada). We reviewed the medical charts and electronic databases of all patients with ITP who had measured IPF parameters between June 2011 and June 2013. The standard definitions and terminology of the International Working Group were used.
Patient age, phase of ITP at the time of the study (acute, persistent, and chronic), initial platelet count, IPF%, AIPF#, and type of therapy given (including observation alone) were recorded. For patients who responded to treatment or had spontaneous recovery without treatment, we analyzed the platelet count, IPF% and AIPF# on subsequent CBCs, then looked at the course of IPF% during platelet count recovery.
Comparisons between groups were performed using Kruskal-Wallis tests or Mann-Whitney tests, as appropriate. Association between measured blood parameters was measured using the Spearman correlation coefficient. Within-patient Spearman correlations were also used to study the association between IPF% and platelet counts during recovery. The combined significance of these associations was determined using Stouffer’s method.
47 patients were included, median age was 9.3 years (Interquartile range (IQR) 4.9-13.3). 16 (34%) patients had newly diagnosed ITP (0-3 Months), 6 (12.8%) had persistent ITP (3-12 Months), and 25 (53.2%) had chronic ITP (>12 Months) at the time of the study.13 patients (27.6%) received treatment and responded (complete response (CR) in 10 patients or response (R) in 3 patients), 11 (23.4%) had recovery without treatment, and 23 (49%) had no recovery.
The initial platelet count was lower in patients who responded to treatment at 8x109/L (IQR 3-8.5) compared to patients who recovered without treatment (21x109/L, IQR 6-30) and those who had no recovery (24x109/L, IQR 9-59) (p=0.008).
AIPF# was lower in patients who responded to treatment at 1.3x109/L (IQR 0.7-1.5) compared to those who had spontaneous recovery of platelet counts without treatment (i.e recovery without treatment) (1.8x109/L, IQR 1.3-3.1)) and those who had no recovery (3.4x109/L, IQR 1.6-4.3) (p= 0.03) (figure 1). IPF% was higher in patients who responded to treatment at 19.4% (IQR 13.8-25) compared to patients who had no recovery (16.4%, IQR9.7 -23)) (p=0.052); there was no significant difference between patients who recovered without treatment and who had no recovery.
IPF% on initial CBC correlated positively to platelet counts on subsequent CBCs (p=0.034 at CBC # 2), indicating that patients with higher IPF% recovered faster.
For patients who responded to treatment and who recovered without treatment the IPF% dropped very significantly with platelet recovery (combined p = 0.04 and 0.001 respectively) (figure 2A&B).
Recovery with treatment
Recovery without treatment
IPF measurements are easily available parameters that are useful in the management of ITP in pediatric patients. This study suggests the use of AIPF# as a predictive factor for recovery in pediatric ITP patients with and without treatment, and IPF% as a predictive factor for early recovery.
No relevant conflicts of interest to declare.
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