Introduction
Detectionandquantificationoffetalredbloodcells(fRBCs)inmaternalbloodsamplesisessentialforobstetricalmanagement.MeasurementoffRBCsiscriticalastheextentofFetomaternalHemorrhage(FMH),thetransplacentalpassageoffRBCsintothematernalcirculation,hasconsequencesforfurthertreatmentofmotherandchild.FrequencyandsizeofFMHisdirectlyinfluencedbycomplicationsinaBDominaltrauma,sUSPectedplacentalinjuryorafteracaesareansection.SevereFMHmayleadtointra-uterinedeath.IncaseofantigenincompatibilitybetweenmotherandchildFMHmayresultinrespiratoryproblemsoranaemia,likeHaemolyticDiseaseoftheNewborn.
AdultRBC’scontainsapopulationofHbF(F-cells),whichcanbedifferbetween0and14%.TheF-cellscangiveapositiveresultintheKleihauer-Betkeacid-elutiontestorsingleHbFflowcytometrytest.TheseF-cellsmaybetheresultofphysiologicalvariationsduringpregnancyortraitssuchasthalassemia,sicklecellanaemiaorhereditarypersistenceoffetalhaemoglobin.
Thedetection(andthusenumeration)offRBCsisusedtocalculatetheextentofFMH,eitherincaseoftraumawithsuspectedplacentalinjuryorinthesituationofaRhDincompatibilitybetweenthefetusandthemother.TheamountoffRBCsisameasureforthepreventionofhemolyticdiseaseofthenewbornusing(prophylactic)anti-Dtherapy.
PrincipleoftheFetalCellCount™Kit
TheFetalCellCount™Kitassayisaflowcytometryproduct.Theassayisbasedona patentedcombinationoftwoantibodies.OneisdirectedagainstHbFwhilethesecondisspecificforcarbonicanhydrase(CA),anenzymepresentinadultRBCsand,atverylowdetectablelevel,inlatepregnancystage.• Resultswithin90minutes• PreciseandaccuratedetectionoffRBCs• IntracellulardetectionofHbFandCA• DistinguishesbetweenfRBCsandmaternalF-cellsandRBCs,iteliminatessubjectiveinterpretationsanempiricsignalcutoffsCytogramsillustratingtypicaldataobtainedwiththeFetalCellCountKitA1;fetalRBCs/A2;F-cells/A4;maternalRBCs.
ConclusionThedatademonstratetheusefulnessofCAasaredbloodcellMarker.Itallows,incombinationwithHbF,anaccuratediscriminationbetweenthedifferentRBCpopulationsinmaternalblood.Withouttheuseofthissecondmarker,discriminationbetweenthefetalRBCsandthevariableconcentrationsofHbFcontainingmaternalF-cellsbecomeslessprecise.