A modified Kleihauer technique for the quantification of foetomaternal haemorrhage

The Kleihauer technique, based on acid elution of maternal red cells, is the mostly widely used technique in the UK to screen for, and estimate the volume of, foetomaternal haemorrhage (FMH) and for determining the need for additional doses of anti-D immunoglobulin to prevent maternal alloimmunization. However, technicians often report difficulties in identifying and accurately counting maternal red cells in the blood film, leading to imprecision in the calculated FMH. In this report, we describe a simple modification of the standard Kleihauer technique, based on performing acid elution of only half of the film. Compared to the standard method, the modified technique showed improved accuracy and reduced interobserver variability across a range of simulated FMH volumes. There was a high degree of correlation between the new technique and FMH estimated by flow cytometry (r2 = 0.916, P < 0.001). Technicians found the new technique easy to incorporate into routine practice in a busy teaching hospital laboratory and were impressed by the relative ease of counting maternal ghost cells. The modified technique has been used routinely in our laboratory for 3 years, during which time our performance in the UK National External Quality Assurance Scheme for FMH has been uniformly satisfactory.