title: Immunocytometric quantitation of foeto-maternal haemorrhage with the Abbott Cell-Dyn CD4000 haematology analyser.
abstract: This study evaluated the extended use of a haematology analyser (Abbott Cell-Dyn CD4000) for the immunofluorescent enumeration of foeto-maternal haemorrhage (FMH) with fluorescein isothiocyanate-labelled monoclonal anti-RhD. Method performance was assessed with artificial FMH standards, and a series of 44 clinical samples. Within run precision was <15% (coefficient of variation, CV) for FMH volumes of 3 ml and above, 18.8% at an FMH volume of 2 ml and 31.7% at an FMH volume of 1 ml. Linearity analysis showed excellent agreement (observed FMH% = 0.98x expected FMH% + 0.02), and a close relationship (R(2) = 0.99) between observed and expected FMH percentages. The lower limit of quantification of the CD4000 (SRP-Ret) method with a maximum CV of 15% was 1.6 ml, and the limit of detection was <1 ml. Parallel Kleihauer-Betke test (KBT) assessments of FMH standards showed an overall trend for higher KBT values (observed = 1.25x expected - 0.38). At an FMH level of 4 ml, KBT observer estimates ranged from 0.57 to 11.94 ml with a mean inter-observer CV of 63%. For 44 clinical samples, there was decision point agreement between KBT and SRP-Ret results for 42 samples with an FMH of <2 ml. Analysis in the low FMH range (<1 ml) showed that small volume foetal leaks could be detected with the SRP-Ret method in most of 23 samples with negative KBT results. CD4000 SRP-Ret method performance for FMH determination was similar to that reported for flow cytometry.
authors.affiliation: Queen Margaret Hospital, Branch Laboratory, Whitefield Road, Dunfermline, Fife, UK.
authors.forename: B H
authors.initials: BH
authors.lastname: Little
authors.forename: R
authors.initials: R
authors.lastname: Robson
authors.forename: B
authors.initials: B
authors.lastname: Roemer
authors.forename: C S
authors.initials: CS
authors.lastname: Scott
mesh_terms: D000328:Adult; D001322:Autoanalysis / Q000295:instrumentation / Q000379:methods*; D002452:Cell Count; D004912:Erythrocytes / Q000166:cytology / Q000276:immunology; D005260:Female; D005331:Fetomaternal Transfusion / Q000175:diagnosis*; D006403:Hematologic Tests / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D019044:Image Cytometry / Q000295:instrumentation / Q000379:methods*; D007150:Immunohistochemistry / Q000379:methods; D016014:Linear Models; D008297:Male; D015588:Observer Variation; D011247:Pregnancy; D012204:Rh-Hr Blood-Group System / Q000032:analysis; D012680:Sensitivity and Specificity
chemical_list: D012204:Rh-Hr Blood-Group System; C026410:Rho(D) antigen