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Reticulated platelets are a fraction of newly released circulating elements characterized by a residual amount of RNA. It has been suggested that the reticulated platelet count, providing an estimate of thrombopoiesis in the same way as erythrocyte reticulocyte count is a measure of erythropoiesis, may be useful in the study of thrombocytopenic disorders. Reticulated red cells and platelets can be analyzed by flow cytometry using specific stains for nucleic acids such as Thiazole Orange and Auramine-O. The aim of our work was to perform the simultaneous evaluation of reticulated elements in whole blood using a standard flow cytometer and to correlate the results obtained with a dedicated cytometer. A group of 14 patients with abnormal absolute reticulocyte counts (range 1.1-11%) and a group of 41 patients showing a platelet discrimination error when analyzed with a dedicated flow cytometer (Sysmex R1000) were enrolled. Linear amplification of both scatter and fluorescence was used to perform reticulocyte count. A gate was set on platelet dimensions, and logarithmic amplification of scatter and fluorescence was used to count reticulated platelets. A good correlation was obtained both for results of reticulocyte count (r2 = 0.9825) and for reticulated platelets (r2 = 0.8717) between our method and those using dedicated instruments. These data show that reticulated platelet count may be easily introduced in clinical laboratories that routinely perform reticulocyte count by flow cytometry.

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Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): The MIOT project receives “no-profit support” from industrial sponsorships (Chiesi Farmaceutici S.p.A., ApoPharma Inc.). Background. Sickle β-thalassemia (Sβ-thal) is a hereditary hemoglobinopathy resulting from the combined heterozygosity for sickle cell and β-thalassemia genes. Cardiac involvement in Sβ-thal patients has been poorly investigated. Aim. We aimed to evaluate myocardial iron overload and cardiac function by cardiovascular magnetic resonance (CMR) in patients with Sβ-thal. Methods. One hundred and eleven Sβ-thal patients consecutively enrolled in the Myocardial Iron Overload in Thalassemia (MIOT) network were studied and compared with 46 sickle cell disease (SCD) patients. Biatrial and biventricular function CMR parameters of Sβ-thal patients were compared with those of 111 healthy volunteers, matched by gender and age. Myocardial iron overload (MIO) was assessed by T2* technique. Cine images were acquired to quantify biventricular function. Macroscopic myocardial fibrosis was evaluated by late gadolinium enhancement (LGE) technique. Results. In Sβ-thal and SCD patients morphological and functional MR parameters were not significantly different, except for left atrial area and SVI (p = 0.023 and p = 0.048, respectively) that were significantly higher in SCD patients. No significant differences between the two groups were found in terms of myocardial iron overload and macroscopic myocardial fibrosis. When compared to healthy subjects, Sβ-thal patients showed significantly higher bi-atrial and biventricular parameters except for LVEF that was significantly lower (Fig.1). Conclusions. The CMR analysis confirmed that Sβ-thal and SCD patients are phenotypically similar. Since Sβ-thal patients showed markedly different morphological and functional indices from healthy subjects, it would be useful to identify Sβ-thal/SCD-specific bi-atrial and biventricular reference values.

Background. Cardiac function indices in patients with hemoglobinopathies are different from those in healthy population, mainly due to chronic anemia. Normal reference values specific for SCD patients are not available by CMR. Aim. We aimed to define the normal cut-off value in SCD patients for bi-atrial and biventricular cardiac magnetic resonance (CMR) parameters. Methods. We considered forty-eight adult SCD patients with no known risk factors or cardiac disease, normal electrocardiogram, no macroscopic myocardial fibrosis, and all cardiac segments with T2*≥20 ms, consecutively enrolled in the MIOT network (Myocardial iron overload in thalassemia). SCD patients were compared with ninety-six healthy controls and 96 thalassemia major (TM) patients without cardiac damage, both matched for age and gender. Nine pediatric SCD patients were also analysed in comparison with 9 TM patients and 9 healthy subjects matched for age and gender. Cine images were acquired to quantify biventricular function parameters: LV and RV end-diastolic volume (EDV), end-systolic volume (ESV) and stroke volume (SV) were normalized for body surface area (EDVI, ESVI, SVI), as well as biventricular mass and atrial areas. Myocardial iron overload was assessed by segmental T2* technique. Late gadolinium enhancement (LGE) images were acquired for evaluation of macroscopic myocardial fibrosis. Results. In all three groups males showed higher biventricular volumes and mass indexes than females. SCD male patients had significantly higher LVEDVI (p<0.0001), LVESVI (p=0.010), LVSVI (p=0.003), cardiac index (p=0.002), LV and RV mass index (p=0.008 and p=0.001, respectively) and left and right atrial areas (p<0.001 and p=0.011) than healthy subjects. No significant differences were found in RVEDVI, EVESVI and biventricular EF. Compared to healthy volunteers, females with SCD showed a larger LVEDVI (p=0.020), LVSVI (p=0.039), RV mass index (p=0.002) and left atrial area (p=0.008). SCD and TM patients showed comparable values of bi-atrial and biventricular volumes and function. When compared to TM, SCD patients showed a larger LV (p<0.001) and RV mass index (p=0.001) in male group and a larger RV mass index (p=0.001) in female group. Table 1 shows the cut-offs for bi-atrial and biventricular MR parameters for adult SCD patients by gender. No significant differences in MR parameters were found among the pediatric groups. Conclusions. Normal reference ranges of bi-atrial and biventricular MR parameters for adult males and females SCD patients were established. The use of these reference values will prevent possible misdiagnosis of cardiomyopathy in patients with SCD. Figure 1 Figure 1. Disclosures Pepe: Chiesi Farmaceutici S.p.A: Other: no profit support; Bayer S.p.A.: Other: no profit support. Quarta: Sanofi - Genzyme: Membership on an entity's Board of Directors or advisory committees, Other: collaboration relationships for Advisory boards, Webinar events, editorial projects; Speaker at conferences; Blue Bird Bio: Other: collaboration relationships for Advisory boards, Webinar events, editorial projects; Celgene: Other: collaboration relationships for Advisory boards, Webinar events, editorial projects; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: collaboration relationships for Advisory boards, Webinar events, editorial projects; Speaker at conferences; Takeda: Other: collaboration relationships for Advisory boards, Webinar events, editorial projects; speaker at conferences; Bristol Meyer Squibb: Membership on an entity's Board of Directors or advisory committees, Other: Speaker at conferences. Maggio: Bluebird Bio: Membership on an entity's Board of Directors or advisory committees; Celgene Corp: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees.