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.

Expression of CD25 is a specific and relatively sensitive marker for the Philadelphia chromosome (BCR-ABL1) translocation in pediatric B acute lymphoblastic leukemia.

BACKGROUND: Precursor B acute lymphoblastic leukemia (B-ALL) is the most common cancer in children and overall, has an excellent prognosis. However, the Philadelphia chromosome translocation (Ph+), t(9;22)(q34;q11), is present in a small subset of patients and confers poor outcomes. CD25 (IL-2 receptor alpha chain) expression has been associated with Ph+ B-ALL in adults, but no similar study has been performed in pediatric B-ALL. METHODS: A retrospective analysis of 221 consecutive pediatric patients with a diagnosis of B-ALL (blood and/or bone marrow) from 2009 to 2012 was performed to determine an association between Ph+ B-ALL and CD25 expression. A threshold of 25% was used to define positive cases for CD25 expression by flow cytometry. RESULTS: There were 221 patients with a diagnosis of B-ALL ranging from 2 to 22 years (median, 6 years). Eight (3.6%) B-ALL patients were positive for the Philadelphia chromosome translocation (Ph+ B-ALL) and 213 were negative (Ph-negative B-ALL). CD25 expression was observed in 6 of 8 (75%) Ph+ B-ALL patients and 6 of 213 (2.8%) Ph-negative B-ALL patients. CD25 expression was significantly higher in Ph+ B-ALL compared to Ph-negative B-ALL, with median CD25 expression of 64% (range 0-93%) and 0.1% (range 0-91%), respectively (P ≤ 0.0002). Therefore, CD25 expression as a predictor of Ph+ B-ALL had 75% sensitivity, 97% specificity, 50% positive predictive value and 99% negative predictive value. CONCLUSIONS: CD25 expression is a specific and relatively sensitive marker for the identification of Ph+ B-ALL in the pediatric population.

Detection of malignancy in body fluids: a comparison of the hematology and cytology laboratories.

CONTEXT: Body fluids submitted to the hematology laboratory for cell counts may also be examined for the presence of malignancy. Previous studies evaluating the hematology laboratory's performance at detecting malignancy in body fluids have reached conflicting conclusions. OBJECTIVE: To investigate the hematology laboratory's ability to detect malignancy in body fluids by comparison with cytology. DESIGN: Retrospective analysis of 414 body fluid samples during an 18-month period, with introduction of new quality assurance measures after the first 210 cases. If no concurrent cytology was ordered, results were compared with recent previous and/or subsequent cytologic, histologic, or flow cytometric diagnoses. RESULTS: Of the initial 210 cases, the hematology laboratory detected 3 of 13 malignancies diagnosed by concurrent cytology (23% sensitivity), with no false-positives (100% specificity). Malignancy was not identified on retrospective review of the hematology slides in the 10 discrepant cases. After the initial study, educational sessions on morphology for the medical technologists and a more thorough hematology-cytology correlation policy were implemented. The subsequent 204 hematology laboratory cases had increased sensitivity for the detection of malignancy (60%; 6 of 10). Definitive features of malignancy were seen in only one discrepant hematology laboratory slide on retrospective review. This case had not been flagged for hematopathologist review. None of the discrepancies before or after implementation of the additional quality assurance measures impacted patient care. CONCLUSIONS: Body fluid processing by the hematology laboratory is not optimized for the detection of malignancy. Concurrent cytologic examination is critical for the detection of malignancy, and needs to be considered as cost-saving measures are increasingly implemented.