Deirdre Corcoran1, Deirdre Murphy1, Jennifer C Donnelly2, Fionnuala Ni Ainle3. 1. Department of Laboratory Medicine, Rotunda Hospital, Dublin, Ireland. 2. Department of Obstetrics and Gynaecology, Rotunda Hospital, Dublin, Ireland. 3. Department of Haematology, Rotunda Hospital, Dublin, Ireland.
Abstract
BACKGROUND: Acid elution (AE) is used to estimate foeto-maternal haemorrhage (FMH). However AE cannot differentiate between cells containing foetal or adult haemoglobin F (F cells), potentially leading to false positive results or an overestimate of the amount of FMH. The prevalence of F cells in pregnant populations remains poorly characterised. The purpose of this study was to ascertain the incidence of HbF-containing red cells in our pregnant population using anti-HbF-fluorescein isothiocyanate flow cytometry (anti-HbF FC) and to assess whether its presence leads to a significant overestimate of FMH. MATERIAL AND METHODS: Eighty-eight pregnant patients were assessed for the presence of F cells and foetal red cells by AE and anti-HbF FC. The "FMH equivalent", estimated by AE and anti-HbF FC, was calculated. RESULTS: Thirty-six percent of the pregnant population had F-cell populations detectable by anti-HbF FC while AE detected F cells in 48% of the population. The mean estimated FMH equivalent determined by AE and anti-HbF FC was 0.59 mL (0-23.93 mL) and 0.41 (0 to 2.19 mL), respectively (p=0.012). In 3% of our population, AE overestimated the FMH by >3 mL due to the presence of an F-cell population of at least 16%. DISCUSSION: Thirty-six percent of a prospectively evaluated group of consecutive pregnant women were found to have F-cell populations. In some patients, these findings were clinically significant as AE overestimated the degree of FMH as a consequence.
BACKGROUND: Acid elution (AE) is used to estimate foeto-maternal haemorrhage (FMH). However AE cannot differentiate between cells containing foetal or adult haemoglobin F (F cells), potentially leading to false positive results or an overestimate of the amount of FMH. The prevalence of F cells in pregnant populations remains poorly characterised. The purpose of this study was to ascertain the incidence of HbF-containing red cells in our pregnant population using anti-HbF-fluorescein isothiocyanate flow cytometry (anti-HbF FC) and to assess whether its presence leads to a significant overestimate of FMH. MATERIAL AND METHODS: Eighty-eight pregnant patients were assessed for the presence of F cells and foetal red cells by AE and anti-HbF FC. The "FMH equivalent", estimated by AE and anti-HbF FC, was calculated. RESULTS: Thirty-six percent of the pregnant population had F-cell populations detectable by anti-HbF FC while AE detected F cells in 48% of the population. The mean estimated FMH equivalent determined by AE and anti-HbF FC was 0.59 mL (0-23.93 mL) and 0.41 (0 to 2.19 mL), respectively (p=0.012). In 3% of our population, AE overestimated the FMH by >3 mL due to the presence of an F-cell population of at least 16%. DISCUSSION: Thirty-six percent of a prospectively evaluated group of consecutive pregnant women were found to have F-cell populations. In some patients, these findings were clinically significant as AE overestimated the degree of FMH as a consequence.