What causes a false positive Kleihauer-Betke test?

The Kleihauer-Betke test is used to detect fetal red blood cells in maternal circulation, typically to assess the extent of fetal-maternal hemorrhage. A false positive result may occur due to the presence of maternal hemoglobin F (HbF), which can be found in women with certain hematologic conditions or during pregnancy.

Hemoglobin F has a similar resistance to acid elution as fetal hemoglobin, and in the context of the test, it may be misidentified as fetal hemoglobin, leading to an overestimation of fetal red blood cells in the maternal sample. This misunderstanding can skew results and give a false indication of fetal-maternal hemorrhage when, in reality, the maternal blood is simply exhibiting HbF.

In contrast, while the presence of maternal HbA, iron deficiency, and sickle cell disease are all important considerations in maternal and fetal health, they do not significantly influence the specific outcome of the Kleihauer-Betke test in the context of false positives. HbA is the predominant adult hemoglobin and is expected to show a different response in the test. Maternal iron deficiency and conditions like sickle cell disease affect maternal health but do not have the same acid resistance properties that lead to confusion of