Diagnostic yield of bone marrow aspiration in paediatric primary immune thrombocytopenia: impact of evolution and adherence to medical guidelines over the last 25 years.

The aim of this study is to analyse the diagnostic value of bone marrow aspiration (BMA) in a retrospective cohort of patients with suspected immune thrombocytopaenia (ITP). We further measure changes in the percentage of patients who underwent this study and whether testing or not was in accordance with current guidelines at the time of diagnosis. We conducted a chart review of 243 patients with ITP who underwent follow-up in our institution between 1995 and 2022. The patients were divided into historical cohorts based on the practice guidelines of the Spanish Society of Pediatric Hematology and Oncology (SEHOP) and the American Society of Hematology (ASH) in place at the time of follow-up. For each case, time of disease presentation or initial diagnosis was defined as that which occurred in the first 72 h following disease onset. Based on data from the historical cohorts studied, we observed a lower total number of BMAs at diagnosis over time (p < 0.005). A gradual reduction was seen in the number of BMAs with the introduction of guidelines, including a progressively lower number of BMAs performed without indication (p < 0.05). Subsequent to the initial diagnosis, the procedure played a decisive role in only 2 patients (0.58%), allowing for a diagnosis of acquired aplastic anaemia in both cases. In both of them on diagnosis, BMA did not appear to be indicated, although subsequent analysis after 72 h raised suspicion of bone marrow failure. CONCLUSION: BMA at presentation did not significantly alter the diagnosis in our cohort of patients with an initial suspicion of ITP, although the procedure was decisive in diagnosing 2 cases of acquired aplastic anaemia during the subsequent course of the disease. Regarding the number of aspirations performed, our findings show that increased physician compliance with current guidelines reduced the rate of unnecessary BMAs. WHAT IS KNOWN: • BMA is a supplementary test for the diagnosis of ITP. • The usefulness of this invasive diagnostic procedure is not clearly stated in current guidelines. WHAT IS NEW: • Adjustments to scientific guidelines have led to a reduction in the number of BMAs performed on our patients with suspected ITP in the last 27 years. • While the risks and benefits of BMA at the time of diagnosis are unclear in patients with suspected ITP, the procedure does not contribute significant information to support the diagnosis.

Mobilization with high-dose granulocyte colony-stimulating factor alone at 12 µg/kg twice a day in high-risk pediatric patients: A retrospective analysis of the experience in a single center.

INTRODUCTION: Mobilization regimes in pediatric patients at high risk for poor mobilization are not standardized across different institutions. We present a retrospective analysis of our experience with a high-dose granulocyte colony-stimulating factor (G-CSF) regime of 12 µg/Kg per body weight (BW) twice a day for 4 days used in high-risk patients. MATERIAL AND METHODS: We report the results of all pediatric patients mobilized with high-dose G-CSF between January 1999 and February 2021 in our center. A successful mobilization was defined as a peripheral blood (PB) CD34+ cell count of ≥10 CD34+ cells/µl on the fifth day of mobilization immediately before leukapheresis. A minimum cell yield of ≥2 × 106 CD34+ cells/Kg of BW was required for a successful collection. RESULTS: Of the 262 patients included in the analysis, mobilization failure was found in 27 (10.3%). In a univariate analysis, this was associated with age, weight, baseline diagnosis, and having undergone a previous mobilization cycle, the latter being the only factor that remained significantly associated in a multivariate analysis (P = 0.03). The 54 patients (20.6%) did not reach the minimum required CD34+ cell yield. 50.4% of the patients reported adverse events (AEs) during the mobilization period, and 23 (9.1%) reported 3 or more concomitant AEs. However, all of them were mild and did not affect the mobilization schedule. CONCLUSIONS: Although most high-risk pediatric patients are successfully mobilized with the high-dose G-CSF regime, this approach does not salvage all of them and significantly increases the presence of AEs in comparison to standard-dose regimes.

Role of the mesenchymal stromal cells in bone marrow failure of Fanconi Anemia patients.

Introduction: Fanconi anemia (FA) is an inherited disorder characterized by bone marrow failure, congenital malformations, and predisposition to malignancies. Alterations in hematopoietic stem cells (HSC) have been reported, but little is known regarding the bone marrow (BM) stroma. Thus, the characterization of Mesenchymal Stromal Cells (MSC) would help to elucidate their involvement in the BM failure. Methods: We characterized MSCs of 28 FA patients (FA-MSC) before and after treatment (hematopoietic stem cell transplantation, HSCT; or gene therapy, GT). Phenotypic and functional properties were analyzed and compared with MSCs expanded from 26 healthy donors (HD-MSCs). FA-MSCs were genetically characterized through, mitomycin C-test and chimerism analysis. Furthermore, RNA-seq profiling was used to identify dysregulated metabolic pathways. Results: Overall, FA-MSC had the same phenotypic and functional characteristics as HD-MSC. Of note, MSC-GT had a lower clonogenic efficiency. These findings were not confirmed in the whole FA patients' cohort. Transcriptomic profiling identified dysregulation in HSC self-maintenance pathways in FA-MSC (HOX), and was confirmed by real-time quantitative polymerase chain reaction (RT-qPCR). Discussion: Our study provides a comprehensive characterization of FA-MSCs, including for the first time MSC-GT and constitutes the largest series published to date. Interestingly, transcript profiling revealed dysregulation of metabolic pathways related to HSC self-maintenance. Taken together, our results or findings provide new insights into the pathophysiology of the disease, although whether these niche defects are involved in the hematopoietic defects seen of FA deserves further investigation.

Optical Genome Mapping as a New Tool to Overcome Conventional Cytogenetics Limitations in Patients with Bone Marrow Failure.

Cytogenetic studies are essential in the diagnosis and follow up of patients with bone marrow failure syndromes (BMFSs), but obtaining good quality results is often challenging due to hypocellularity. Optical Genome Mapping (OGM), a novel technology capable of detecting most types chromosomal structural variants (SVs) at high resolution, is being increasingly used in many settings, including hematologic malignancies. Herein, we compared conventional cytogenetic techniques to OGM in 20 patients with diverse BMFSs. Twenty metaphases for the karyotype were only obtained in three subjects (15%), and no SVs were found in any of the samples. One patient with culture failure showed a gain in chromosome 1q by fluorescence in situ hybridization, which was confirmed by OGM. In contrast, OGM provided good quality results in all subjects, and SVs were detected in 14 of them (70%), mostly corresponding to cryptic submicroscopic alterations not observed by standard techniques. Therefore, OGM emerges as a powerful tool that provides complete and evaluable results in hypocellular BMFSs, reducing multiple tests into a single assay and overcoming some of the main limitations of conventional techniques. Furthermore, in addition to confirming the abnormalities detected by conventional techniques, OGM found new alterations beyond their detection limits.

Adverse events related to central venous catheters (CVC) and the influence of CVC characteristics on peripheral blood hematopoietic progenitor cell collection in children.

Introduction: The use of peripheral blood progenitor cells (PBPCs) as a source for hematopoietic stem cell transplantation (HSCT) in pediatric healthy donors is still under debate. The risk of a central venous catheter (CVC) placement and catheter-related complications continue to be the main arguments to discourage its use. Methods: we present a retrospective analysis of 140 PBPC collections in pediatric patients and donors, describing adverse events (AE) related to CVCs as well as the influence of catheterrelated variables on the efficiency of the leukapheresis. Results: 14 CVC-related AEs were recorded (10%). The most common was fever in 5 patients, 4 of which had a catheter-related bacteriemia. Thrombotic events were only observed in 3 patients with active malignancy. A healthy donor presented a moderate bleeding after catheter withdrawal that resolved with local measures, and none of the rest presented any AE. Regarding variables related to the development of AEs, the subject group (patient or donor) was the only one significantly associated (p < 0.0001). Of interest, efficiency was also related to catheter location, being worse in those located in the femoral vein than in into the jugular or the subclavian veins (p < 0.05). In a multivariate analysis, the only variable significantly associated was catheter size (beta 0.238, p < 0.01). Discussion: Placing a CVC for PBPC collection in pediatric subjects is overall safe; CVC-related complications in pediatric healthy donors are very rare. Furthermore, we should try to place catheters of the largest caliber possible, since the efficiency of the collection is related to this variable.

Initial study of anaemia profile for primary care centres with automated laboratory algorithms reduces the demand for ferritin, iron, transferrin, vitamin B12 and folate tests.

AIM: To evaluate the influence of an algorithm designed to incorporate reflex testing according to haemogram results for analytical tests ordered to investigate anaemia. METHODS: In 2020, a new request for 'initial study of anaemia' was created in three primary care pilot centres for suspected anaemia or new anaemias. A haemogram was ordered and the remainder of the tests were created in a reflex manner according to an algorithm integrated in the laboratory information system that also generates a comment that is completed and validated by a haematologist. The demand for tests was evaluated over three time periods. RESULTS: Of 396 requests, anaemia was detected in 80 (20.2%), with 26 microcytic anaemias (6.57%), 20 iron deficiency anaemias, 41 (10.3%) normocytic anaemias and 13 macrocytic anaemias (3.28%); 4 with folate deficiency; and 1 haemolytic anaemia. No haematological diseases were detected. Twenty-four (6.06%) cases exhibited microcytosis/hypochromia without anaemia, 12 of which exhibited iron deficiency. Four young women exhibiting within-limit haemoglobin levels had iron deficiency. There were 56 (14.1%) cases of macrocytosis without anaemia.With the new profile of 'initial study of anaemia', the demand for tests was reduced and was significantly lower than in the remainder of primary centres for iron, transferrin, ferritin, vitamin B12 and folate. CONCLUSIONS: A new profile of 'initial study of anaemia' in the request form with algorithms integrated in the laboratory information system enabled submission of orders and decreased the demand for unnecessary iron, transferrin, ferritin, vitamin B12 and folate tests.

T-Cell Depleted Haploidentical Transplantation in Children With Hematological Malignancies: A Comparison Between CD3+/CD19+ and TCRαß+/CD19+ Depletion Platforms.

Background: T-cell depleted (TCD) haploidentical transplantation using CD3+/CD19+ and TCRαß+/CD19+ depletion techniques has been increasingly used in children with hematological malignancies. We present a retrospective study aimed to compare transplant outcomes in children with leukemia receiving a TCD haploidentical transplant using either CD3+/CD19+ or TCRαß+/CD19+ platforms. Methods: A total of 159 children with leukemia (ALL=80) (AML=79) that received a TCD haploidentical transplantation using either CD3+/CD19+ (n=79) or TCRαß+/CD19+ (n=80) platforms between 2005 and 2020 were included. Median age was 9 years in both groups. There were no differences in patient, donor, and transplant characteristics between groups except for donor KIR B genotype more frequent in the TCRαß+/CD19+ group (91%) than in the CD3+/CD19+ group (76%) (p=0.009) and a high number of NK+ cells and lower CD19+ cells infused in the TCRαß+/CD19+ group (35.32x106/kg and 0.06 x106/Kg) than in the CD3+/CD19 group (24.6x106/Kg and 0.25 x106/Kg) (p=0.04 and p=0.0001), respectively. Conditioning was based on TBF. Median follow-up for survivors was 11 years (range; 8-16 y) in CD3+/CD19+ group and 5 years (range; 2-9 y) in the TCRαß+/CD19+ group. Results: Engraftment kinetics were similar in both groups (13 days for neutrophils and 10 days for platelets). There was no difference in the incidence of acute GvHD II-IV (29 ± 5% in the CD3+/CD19+ group vs 38 ± 5% in the TCRαß+/CD19+ group) and chronic GvHD (32 ± 5% vs 23 ± 4%, respectively). NRM was 23 ± 5% in the CD3+/CD19+group vs 21 ± 4% in the TCRαß+/CD19+group. Relapse incidence was also similar, 32 ± 5% vs 34 ± 6%, respectively. DFS and OS were not different (45 ± 5% vs 45 ± 6% and 53 ± 6% vs 58 ± 6% respectively). As there were no differences on transplant outcomes between groups, we further analyzed all patients together for risk factors associated with transplant outcomes. On multivariate analysis, we identified that early disease status at transplant (HR: 0.16; 95%CI (0.07-0.35) (p=0.0001), presence of cGvHD (HR: 0.38; 95%CI (0.20-0.70) (p= 0.002), and donor KIR-B genotype (HR: 0.50; 95%CI (0.32-0.90) (p=0.04) were associated with better DFS. Conclusions: Our data suggest that there are no advantages in transplant outcomes between TCD platforms. Risk factors for survival are dependent on disease characteristic, donor KIR genotype, and chronic GvHD rather than the TCD platform used.