A flow-cytometric equivalent of the Kleihauer test

Background and Objectives: The Kleihauer slide test is in general use to sc reen obstetric patients for possible fetomaternal haemorrhage. Since 1993, Rh(D)-negative patients have been tested in our laboratory by a flow-cytome tric method detecting Rh(D)-positive fetal cells, a method, which offers im proved sensitivity and accuracy. We report another flow-cytometric method o f broader application which quantitates cells according to haemoglobin F (H bF) content, Materials and Methods: The red cells are fixed with glutaralde hyde and permeabilized by exposure to Triton X-100, A polyclonal sheep anti body to HbF is incubated with the cells followed by a fluorescein-labelled anti-sheep antibody. Results: Quantitation of the percentage of fetal cells following a FMH. can be achieved irrespective of the blood groups of eithe r mother or infant, and the presence of maternal F cells need not interfere since the intensity of staining is usually less than that of fetal cells. Two of 19 transfusion-dependent patients with beta-thalassaemia have been f ound to have red cells indistinguishable from fetal cells on the basis of H bF content, but these patients also have been found to give positive result s by the Kleihauer test. Conclusions: The flow-cytometric method may serve to replace the traditional Kleihauer test since it appears to offer improve d accuracy and objectivity.