Frequency of Paroxysmal Nocturnal Hemoglobinuria Clones by Multiparametric Flow Cytometry in Pediatric Aplastic Anemia Patients of Indian Ethnic Origin

FLAER as a standalone reagent for paroxysmal nocturnal hemoglobinuria: Do we need to reconsider the guidelines for testing?

INTRODUCTION

Flow cytometry-based paroxysmal nocturnal hemoglobinuria (PNH) testing involves utilization of monoclonal antibodies against GPI-linked proteins and FLAER. The ability of FLAER to bind to a wide variety of GPI-linked structures and to be utilized across different leukocyte subsets is remarkable. We hypothesize that FLAER as a standalone reagent may be equally effective for detecting PNH clones. The present study intends to compare the results of a FLAER alone-based strategy to the recommended FLAER+GPI-linked protein-based approach for applicability in clinical settings.

METHODS

EDTA-anticoagulated blood samples from patients for PNH workup were tested for PNH by multiparametric flow cytometry. A conventional panel comprising gating markers (CD45 for WBC, CD15 for granulocytes, and CD64 for monocytes) and a combination of FLAER and GPI-linked markers, such as CD24 and CD14, henceforth referred to as the "routine panel," was employed. Second, a "FLAER-only panel" comprising the gating markers and FLAER alone (excluding the GPI-linked markers CD24 and CD14) was set up. The samples were processed using the lyse-wash-stain-wash technique, and events were acquired on BC Navios Ex flow cytometer (Beckman Coulter, Inc., USA) and analyzed on Kaluza Software 2.1. The presence of a PNH clone was reported at a value of ≥0.01%.

RESULTS

A total of 209 patients were tested. Both panels found a PNH clone in 20.1% of patients (n = 42/209) with a 100% concordance rate. The PNH clone range for granulocytes was 0.01%-89.68%, and for monocyte was 0.04%-96.09% in the routine panel. The range in the FLAER-only panel for granulocytes was 0.01%-89.61%, and for monocytes, it was 0.01%-96.05%. Pearson correlation statistics revealed a significant correlation between the size of the PNH clone of granulocytes and monocytes among the two panels tested (granulocytes r = 0.9999, p < 0.0001, 95% CI = 0.9999 to 1.000; monocytes r = 0.9974, p < 0.0001, 95% CI = 0.9966-0.9980).

CONCLUSION

Based on our results, FLAER as a standalone marker is specific and sensitive for identifying PNH clones in granulocytes and monocytes, even for high-sensitivity PNH assay. The proposed "FLAER-only panel" panel is efficient and cost-effective for highly sensitive PNH testing in two different cell lineages, especially in resource-limited clinical settings.

Childhood aplastic anaemia with paroxysmal nocturnal haemoglobinuria clones: A retrospective single-centre study in South Africa

Background: Paroxysmal nocturnal haemoglobinuria (PNH) clones in children are rare but commonly associated with aplastic anaemia (AA) and myelodysplasia.Objective: This study aimed to determine the prevalence of PNH clones in paediatric patients with idiopathic AA, identify differences in clinical and laboratory features and outcomes, and determine the impact of clone size on clinical presentation.Methods: Patients with confirmed idiopathic AA who were tested for PNH between September 2013 and January 2018 at the Inkosi Albert Luthuli Central Hospital, Durban, KwaZulu-Natal, South Africa, were included. PNH clones were detected in neutrophils and monocytes by flow cytometry using fluorescent aerolysin, CD24, CD66b and CD14.Results: Twenty-nine children with AA were identified and 11 were excluded. Ten patients (10/18, 55.6%) had PNH clones ranging from 0.11% to 24%. Compared to the PNH-negative group, these children were older (median: 10 years vs 4 years, p = 0.02) and had significantly lower total white cell counts (median 1.7 × 109/L vs 3.2 × 109/L; p = 0.04). There was no difference in median absolute neutrophil count or haemoglobin concentration. Four patients in each group received immunosuppressive therapy (IST). At six months, all four patients with PNH clones had responded, compared to one in the PNH-negative group.Conclusion: More than half of children with AA had a PNH clone. The size of the clone did not impact clinical severity; however, IST use may positively impact prognosis. We recommend early initiation of IST in patients with AA to avoid delays associated with human leukocyte antigen typing. 

Systematic review of defibrotide studies in the treatment of veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS)

Veno-occlusive disease (VOD), also called sinusoidal obstruction syndrome (SOS), is a potentially life-threatening complication of hematopoietic stem cell transplantation (HSCT) conditioning or high-dose nontransplant chemotherapy. VOD/SOS with multi-organ dysfunction (MOD) is associated with a mortality rate of > 80%. Defibrotide (25 mg/kg/day) is approved to treat hepatic VOD/SOS with renal or pulmonary dysfunction post HSCT in the United States and to treat severe hepatic VOD/SOS in patients > 1 month of age in the European Union. A random effects model was used for pooling data from 17 systematically chosen defibrotide studies. For patients in these reports (n = 2598), and those in the subset of 10 reports of patients treated with ~ 25 mg/kg/day (n = 1691), estimated Day + 100 survival rates were 54% and 56%, respectively. Among those patients treated with ~ 25 mg/kg/day, estimated Day + 100 survival was 44% among patients with MOD and 71% in patients without MOD; survival was 41% and 70%, respectively, for the population of patients receiving any dose of defibrotide. Safety results were not pooled owing to differences in reporting methodology but were generally consistent with the known tolerability profile of defibrotide. This analysis provides the largest assessment of survival in patients treated with defibrotide for VOD/SOS with or without MOD.

Aplastic anemia in children: How good is immunosuppressive therapy?

Aplastic anemia (AA) is an uncommon disorder in children, with hematopoietic stem cell transplant being the 1st line therapy; immunosuppressive therapy (IST) is the alternative therapy and is the most commonly used modality of treatment. There is paucity of data from the developing countries regarding treatment outcome with IST. We aimed to assess the outcome of IST in children with AA. Data for 43 children treated with IST from January 2012 to January 2017 (5 years) were retrieved from clinic records. IST included equine antithymocyte globulin (ATG) along with cyclosporine A. Complete response, partial response and nonresponse was seen in 9 (21%), 14 (32.5%) and 20(46.5%) patients, respectively. The median time to best response in the whole cohort was 19.1 months. However, complete response occurred nearly 2-year post-IST. There was no difference in outcome related to severity of AA, the presence of PNH clone, higher ALC or different available brands of ATG. There was a significantly better rate of response (p value: .03) at 6 months in patients who went on to achieve a CR vs patients who achieved a final PR only. An overall response rate, including partial and complete response, of 53.5% was seen in our cohort with a 3-year OS of 63%. This is not at par to the outcome reported from developed nations. The available brands of ATG were similar in terms of response kinetics as well as survival. A delayed time to complete response with prolonged requirement of cyclosporine therapy was seen in the cohort.

Clinicopathological profile of paroxysmal nocturnal haemoglobinuria clone-positive aplastic anaemia paediatric patients-A single centre study from North India

INTRODUCTION

There is a paucity of literature related to the prevalence of Paroxysmal Nocturnal haemoglobinuria (PNH) clones in paediatric aplastic anaemia (AA) patients.

METHODS

We performed a retrospective analysis over a period of 42 months to study the prevalence of PNH clones in paediatric (age less than 18 years) AA cases, using Fluorescein-labelled proaerolysin-based flow cytometric screening and analysed their clinico-pathological features.

RESULTS

PNH clone was identified in 100 (33.2%) of the 301 patients screened. These were comprised of 51 cases of non-severe AA, 33 cases of severe AA and 16 cases of very severe AA. The median age was 13 years with an M:F ratio of 2.5:1. The median clone size (taken as the proportion of PNH-positive neutrophils) was 2.15% (range: 0.05%-93.1%). Although a majority of patients (n = 77) had a clone size of less than 10%, a significant proportion (n = 23) did harbour a clone size of more than 10%. Evidence of haemolysis was observed in 3 patients, all of them having a clone size of more than 10%. Interestingly, 1 patient with dural sinus thrombosis harboured a clone size of 1.25% only. Chromosomal breakage analysis was performed in 61 patients, none of which was positive. Complete and partial response to immunosuppressive therapy was found in 55.1% patients (16/29).

CONCLUSION

There is a high prevalence of PNH clones in paediatric AA patients, which in a majority of cases are of small clone sizes. The use of immunosuppressive therapy does not show a better outcome as compared to PNH-negative cases.

Diagnosis of Paroxysmal Nocturnal Hemoglobinuria: Recent Advances

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematopoietic stem cell disorder with its protean clinical manifestations. This is due to partial or complete absence of 'glycophosphatidyl-inositol-anchor proteins' (GPI-AP). The main aim of this review is to highlight various diagnostic modalities available, basic principle of each test and recent advances in the diagnosis of PNH. Recently among various tests available, the flow cytometry has become 'the gold standard' for PNH testing. In order to overcome the difficulties encountered by the testing and research laboratories throughout the world, International Clinical Cytometry Society has come up with guidelines regarding the indications for testing, protocol for sample collection, processing, panel of antibodies as well as gating strategies to be used, how to interpret the test and reporting format to be used. It is essential to test at least two GPI-linked markers on at least two different lineages particularly on red cells and granulocytes/monocytes. The fluorescent aerolysin combined with other monoclonal antibodies in multicolour flow cytometry offered an improved assay not only for diagnosis but also for monitoring of PNH clones. It is equally important to diagnose this rare entity with high index of suspicion.

Standardized high-sensitivity flow cytometry testing for paroxysmal nocturnal hemoglobinuria in children with acquired bone marrow failure disorders: A single center US study

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired hematopoietic stem cell disorder that has not been well-documented in children, particularly those with acquired bone marrow failure disorders (ABMFD)-acquired aplastic anemia (AAA) and myelodysplastic syndrome (MDS). Therefore, we sought to determine the prevalence of PNH populations in children with ABMFD.

METHODS

PNH testing was performed in children with an ABMFD diagnosis using high sensitivity (≥0.01%) fluorescent aerolysin (FLAER)-based assay according to 2010 International Clinical Cytometry Society (ICCS) PNH Consensus Guidelines and 2012 Practical PNH Guidelines. FLAER/CD64/CD15/CD24/CD14/CD45 and CD235a/CD59 panels were used for white blood cell and red blood cell testing, respectively.

RESULTS

Thirty-seven patients with ABMFD (34 AAA, 3 MDS) were included (17M/20F, age 2-18 years, median 9 years). PNH populations were identified in 17 of 37 (46%) patients. Of the 17 patients with PNH populations identified, 7 were PNH clones (>1% PNH population), and 10 had minor PNH population or rare cells with PNH phenotype (≤1% PNH population).

CONCLUSIONS

This is the first study to use a standardized high-sensitivity FLAER-based flow cytometry assay and the recommended cutoff of 0.01% to identify cells with PNH phenotype in pediatric patients with ABMFD in the United States. The identification of a PNH population in 46% of ABMFD supports the recommendation for high sensitivity PNH testing in children with these disorders. As a less sensitive assay using a cutoff of ≥ 1% PNH population would have missed 10 (27%) patients with minor PNH population or rare cells with PNH phenotype. © 2017 International Clinical Cytometry Society.

Multicenter validation of a simplified method for paroxysmal nocturnal hemoglobinuria screening

BACKGROUND

Paroxysmal nocturnal hemoglobinuria (PNH) diagnostic guidelines recommend single-tube five- to six-color or two-tube four-color assays. PNH clones are detectable in only a fraction of patients at risk, and screening for new PNH cases can be complex and expensive. In this multicenter study, we have validated a simplified, one-tube two-color FLAER-based assay suitable for PNH screening.

METHODS

Six laboratories received samples containing spiked PNH leukocyte clones to be analyzed in parallel with a common six-color cocktail (FLAER/CD24/CD45/CD64/CD15/CD14) and a simplified two-color mixture (FLAER/CD15), a shared calibration procedure, and a common analysis protocol. Replicate precision and sensitivity tests were performed on PNH patients, from undiluted to 1:10 000. Specificity tests were performed on normal donors to identify the possible sources of artifacts.

RESULTS

The performance comparison between six-color and two-color assays showed an excellent agreement for granulocyte PNH clones. Dilution experiments showed an accurate detectability down to 0.01% sensitivity level for granulocyte PNH clones and to 1% for monocytes. Specificity experiments disclosed that basophils and platelets can contaminate the monocyte gate and generate false PNH events.

CONCLUSIONS

A simplified two-color (FLAER/CD15) PNH screening test has been validated in a highly standardized multicenter study and proved feasible and effective in ongoing regional programs. Precision, sensitivity, and specificity of the simplified test for granulocytes were comparable to the more complex and expensive six-color assay and applicable for screening also in peripheral laboratories. The diagnostic confirmation of PNH should be always performed by a reference center using the established technique on all cell lineages.

A retrospective study of paroxysmal nocturnal hemoglobinuria in pediatric and adolescent patients

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disease, especially in children, characterized by intravascular hemolysis, thrombotic events, serious infections and bone marrow failure. We describe 16 patients who were diagnosed with PNH in childhood or adolescence. The time interval between the onset of symptoms and the PNH diagnosis and its treatment were compared in patients with classic PNH versus PNH associated with bone marrow disorder (PNH/BMD). A greater delay in diagnosis was observed in classic PNH compared to PNH/BMD patients. The first group of patients had higher levels of LDH, total bilirubin and absolute reticulocyte count and a bigger PNH clone size compared to PNH/BMD patients; also thrombotic events were observed only in the classic form of PNH. Conversely, PNH/BMD patients showed lower median levels of platelets. Apart from standard supportive measures, four patients with classic PNH received eculizumab whereas four patients with PNH/BMD underwent hematopoietic stem cell transplantation. Our series confirm that the most frequent presentation of PNH in the pediatric-adolescent age is PNH/BMD. The delay between the onset of symptoms and PNH diagnosis is relevant principally in the classic form. Moreover, our study showed that any case of unexpected thrombosis represents a criterium to perform a PNH screening.