What is a positive KB test?
The KB test is highly specific, with low sensitivity, having a threshold of 5 mL of FMH to be positive. Keep in mind that the amount of FMH to cause isoimmunization is only 0.01 mL to 0.03 mL. As such, it is not a test to determine if there is FMH, but rather to better estimate the amount of FMH.
What is a positive Kleihauer-betke?
This is a qualitative test that reveals the presence of Rh positive fetal cells in maternal circulation. The Kleihauer-Betke test, or flow cytometry if available, is then needed to quantify the number of fetal cells in circulation, which leads to the appropriate dose of RhIg to administer.
What is a normal Kleihauer-Betke test?
The normal range is 0 to 0.1% as reported by the lab. Calculations for Estimating the Number of Vials of Rhogam Needed: One 300 ml vial of RhIG will protect against 30 ml of D-positive fetal blood.
What is a KB screen?
A somewhat crude laboratory test used to screen maternal blood samples for the presence of fetal red blood cells. The “K-B” test, as it is known, takes advantage of the fact that baby RBCs are generally rich in hemoglobin F, and hemoglobin F is resistant to acid.
When should a Kleihauer test be done?
This test should be performed and any subsequent Anti-D required administered within 72 hours of delivery, sensitising event or invasive procedure.
How is maternal blood different from fetal blood?
Maternal blood contains adult hemoglobin composed of two alpha and two beta subunits (aka hemoglobin A or HbA; i.e., normal adult hemoglobin). Fetal blood contains fetal hemoglobin composed of two alpha and two gamma subunits (aka hemoglobin F or HbF; i.e., normal fetal hemoglobin).
What is the Kleihauer-Betke test used for?
Background: In maternal trauma, the Kleihauer-Betke (KB) test has traditionally been used to detect transplacental hemorrhage (TPH), so that Rh-negative women could receive appropriate Rh immune prophylaxis.
When do you give Anti-D?
Routinely, the Anti D injection is given to pregnant Rh Negative women at around 28 weeks and 36 weeks gestation. A sample of the mother’s blood is collected at delivery, for a test called either Quantative Feto-Maternal Haemorrhage (QFMH) or Kleihauer.
What does maternal blood mean?
Maternal blood is an ideal system for studying methylation changes and development of disease biomarkers, whereas fetal origin tissues like cord blood, cord tissue and placenta are good sources to study the deeper biological and molecular aspects of disease development.
What do you need to know about the KB test?
The KB test is an acid-elution assay performed on maternal blood to determine the amount of HbF that has passed into the maternal circulation. The process exposes maternal blood smear to an acid solution.
Can a positive KB test cause fetal distress?
None of these positive results were associated with a clinical abruption or fetal distress. One low-risk patient with sickle cell trait had a 40 mL KB result. Conclusion: The incidence of a positive KB test in low-risk pregnancies does not differ from maternal trauma patients.
Are there positive KB tests in trauma patients?
Results: Of the low-risk women 5 of 98 (5.1%) had a positive KB test, whereas 4 of 151 (2.6%) trauma patients had a positive test (P=.31). None of these positive results were associated with a clinical abruption or fetal distress.
How does the KB test for HBF work?
The KB test is an acid-elution assay performed on maternal blood to determine the amount of HbF that has passed into the maternal circulation. The process exposes maternal blood smear to an acid solution. HbF, being resistant to the acid, remains intact, whereas HbA is removed. Following this, the smear is stained via Shepard’s method*.