- J K M Duguid,
- I Bromilow
- Correspondence to: Dr Duguid
- Accepted 7 February 1994
The standard dose of 500 IU of anti-D immunoglobulin given in Britain to Rh D negative mothers postnatally is lower than that used in Europe, the United States, and Canada, where 1000-1500 IU is the routine dose. In Britain a Kleihauer test is performed after the 500 IU dose is given.1 The results of this test should indicate the volume of fetomaternal haemorrhage that has occurred and whether a further dose of anti-D immunoglobulin is required. Kleihauer testing is not performed routinely in Europe, the United States, or Canada as the higher dose of anti-D immunoglobulin used prevents Rh sensitisation in all but 0.3% of cases.
Use of the Kleihauer test in Rh D negative mothers who have been given anti-D immunoglobulin is intrinsically incorrect as the test measures fetal haemoglobin and not Rh D positive cells. Up to a quarter of women have an increased proportion of fetal haemoglobin during pregnancy, and increased proportions of fetal haemoglobin can also occur in women with haemoglobinopathies. The Kleihauer test can be performed and reported in several ways but has poor reproducibility.2 In Britain no quality assurance scheme exists for assessing Kleihauer testing.
These factors detract from the test's reliability in assessing accurately the size of a fetomaternal haemorrhage. We undertook a survey of the laboratories responsible for Kleihauer testing for a single transfusion centre in Britain to assess how effective Kleihauer testing is in monitoring the outcome of doses of anti-D immunoglobulin.
Subjects, methods, and results
We surveyed all hospital transfusion laboratories served by the Mersey and North Wales Blood Transfusion Service. Using a questionnaire, we requested information on the techniques used for Kleihauer testing, the methods of reporting, and situations in which increased doses of anti-D immunoglobulin and further Kleihauer testing were recommended. We also asked about antenatal Kleihauer testing after potentially sensitising episodes to see whether the British recommendations for antenatal use of anti-D immunoglobulin and Kleihauer testing were being followed.3
We contacted 23 hospital transfusion laboratories, all of which returned a completed questionnaire. Eleven hospitals did not perform Kleihauer testing since they were not responsible for an obstetric unit. The remaining 12 hospitals performed Kleihauer testing for all Rh D negative mothers delivered of an Rh D positive baby. No uniformity existed, however, with regard to the technique or counting procedure used or the reporting of the test (table).
Most of the hospitals reported the number of fetal cells per low power field. None indicated whether the result represented a large fetomaternal haemorrhage, requiring a further dose of anti-D immunoglobulin. Ten hospitals indicated that they would give advice on further doses of anti-D immunoglobulin if asked. One hospital would not recommend repeat Kleihauer testing after a large transplacental haemorrhage for which an increased dose of anti-D immunoglobulin had been given.
Antenatal Kleihauer testing also showed wide variations in practice (table). Only one hospital complied with all the current recommendations.3
If the hospitals we contacted are representative the results of our survey are worrying. European recommendations state that the postpartum dose of anti-D immunoglobulin should be 1000-1500 IU4; routine Kleihauer testing is not recommended. The failure rate of anti-D prophylaxis in Britain, though low at 1.5%, is considerably higher than that in some other European countries - for example, in the Netherlands it is 0.65%.
Because of this failure rate, the known variability and poor reproducibility of Kleihauer testing, and the results of our survey we believe that the adequacy of the dose of anti-D immunoglobulin given to Rh D negative mothers should be assessed with a more reliable and accurate technique. The technique should measure Rh D positive cells rather than fetal haemoglobin. Furthermore, because of the reported failure rate in Britain the recommended dose of 500 IU anti-D immunoglobulin should be reviewed.
We thank the staff of all the transfusion laboratories in north Wales and Merseyside for cooperating with this survey, and Mrs M Laffoley for her typing.