The prevalence of an elevated F cell population in a maternal and gynaecology cohort.

OBJECTIVES: This study aimed to determine F cell prevalence in a cohort of maternal and gynaecology specimens using QuikQuant anti-HbF flow cytometry (FC) kit and to investigate if the presence of maternal F cells can lead to fetomaternal haemorrhage (FMH) overestimation. BACKGROUND: The gold standard to estimate FMH is the Kleihauer-Betke test (KBT). The KBT has proved to be insufficiently sensitive to detect low numbers of circulating fetal cells due to the presence of maternal F cells. At present, the prevalence of false positive KBT results due to raised maternal F cell population, defined as >5%, is poorly characterised. METHODS: A total of 120 specimens were tested for the presence of F cells and fetal cells by KBT and anti-HbF FC. The results calculated were compared to determine FMH overestimation. RESULTS: Of our cohort, 32% showed an elevated F cell population, of which 69% (27 of 39) were clinically significant according to KBT (>2 mL FMH). The mean FMH volumes by KBT and anti-HbF FC were 3·90 mL (0·20-35·40 mL) and 4·09 mL (0·20-9·70 mL), respectively. CONCLUSION: The study highlighted that an elevated F cell level could be found in the cohort tested, with an F cell level of >10% causing significant FMH overestimation by KBT.

Screening and confirmation of hereditary spherocytosis in children using a CELL-DYN Sapphire haematology analyser.

INTRODUCTION: Multidimensional optical scatter of sphered erythrocytes can identify and enumerate hyperchromic erythrocytes, which might be used for hereditary spherocytosis (HS) screening. The flow cytometric eosin-5'-maleimide test (EMA) is highly sensitive and specific for HS as a confirmatory method. The aims of this study were to assess the utility of hyperchromic erythrocytes in HS screening and to evaluate the EMA test performed on CELL-DYN Sapphire analyser compared with the reference method. METHODS: Blood from 740 paediatric patients presenting at our institution was analysed in reticulocyte mode of the CELL-DYN Sapphire haematology analyser (Abbott Diagnostics) to obtain hyperchromic erythrocyte counts. The EMA test was performed using a flow cytometer as a reference, as well as CELL-DYN Sapphire as an investigational method. RESULTS: Hyperchromic erythrocytes were the highest in patients with HS (median 11.5%; range 5.1-29.2%). Patients with autoimmune haemolytic disease had significantly less hyperchromic erythrocytes (median 4.9%; range 0.0-18.3%). Hyperchromic erythrocytes showed a high area under the ROC curve: 0.972. At 4.9% cut-off, hyperchromic erythrocytes detected HS with 96.4% sensitivity and 99.1% specificity. The EMA test on CELL-DYN Sapphire correlated strongly with the reference test and had identical diagnostic power. Stability studies with blood from HS patients showed a significant decrease in hyperchromic erythrocytes after 6 h storage. CONCLUSIONS: Measurement of hyperchromic erythrocytes is highly sensitive and specific for detecting HS and can be used for rapid and inexpensive screening. If required, the EMA test can be performed on CELL-DYN Sapphire or a standard flow cytometer for confirmation of HS.