Kleihauer-Betke test - Revision history

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Ostermayer: Created page with "==Background== The Kleihauer-Betke (KB) test is the standard method for detecting and quantifying fetomaternal hemorrhage (FMH)Krywko DM, Yarrarapu SNS. Kleihauer Betke Test. In: ''StatPearls''. Treasure Island (FL): StatPearls Publishing; 2025. PMID 28613626. First described in 1957 by Enno Kleihauer and Klaus Betke Based on the principle that fetal hemoglobin (HbF) is resistant to acid elution, whereas adult hemoglobin (HbA) is not
2026-03-12T15:21:22Z

Created page with "==Background== The Kleihauer-Betke (KB) test is the standard method for detecting and quantifying fetomaternal hemorrhage (FMH)<ref name="statpearls">Krywko DM, Yarrarapu SNS. Kleihauer Betke Test. In: ''StatPearls''. Treasure Island (FL): StatPearls Publishing; 2025. PMID 28613626.</ref> First described in 1957 by Enno Kleihauer and Klaus Betke Based on the principle that fetal hemoglobin (HbF) is resistant to acid elution, whereas adult hemoglobin (HbA) is not<ref n..."

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==Background==
The Kleihauer-Betke (KB) test is the standard method for detecting and quantifying fetomaternal hemorrhage (FMH)<ref name="statpearls">Krywko DM, Yarrarapu SNS. Kleihauer Betke Test. In: ''StatPearls''. Treasure Island (FL): StatPearls Publishing; 2025. PMID 28613626.</ref>
First described in 1957 by Enno Kleihauer and Klaus Betke
Based on the principle that fetal hemoglobin (HbF) is resistant to acid elution, whereas adult hemoglobin (HbA) is not<ref name="statpearls"/>
'''Mechanism:''' A maternal blood smear is exposed to an acid bath (citric acid–phosphate buffer), which removes HbA from adult red blood cells while HbF-containing fetal cells remain intact; subsequent staining causes fetal cells to appear dark/rose-pink while adult "ghost" cells appear pale<ref name="statpearls"/>
'''Primary clinical purpose:''' Quantify the volume of FMH to guide dosing of Rho(D) immune globulin (RhoGAM) in Rh-negative mothers<ref name="emery">Emery CL, Morway LF, Chung-Park M, et al. The Kleihauer-Betke test: clinical utility, indication, and correlation in patients with placental abruption and cocaine use. ''Arch Pathol Lab Med''. 1995;119(11):1032-1037. PMID 7487403.</ref>
FMH occurs in up to 40% of trauma cases involving pregnant patients and can also occur during placental abruption, intrauterine fetal demise, and invasive obstetric procedures<ref name="statpearls"/>
As little as 0.01–0.03 mL of fetal blood is sufficient to trigger maternal Rh isoimmunization<ref name="statpearls"/>

==Clinical Features==
Fetomaternal hemorrhage is often clinically silent; the KB test is a laboratory screening/quantification tool rather than one prompted by specific symptoms
*Clinical scenarios in which FMH should be considered:
Decreased fetal movement
Abnormal or nonreassuring fetal heart rate tracing (sinusoidal pattern is classic for fetal anemia)
[[Hydrops Fetalis|fetal hydrops]] on ultrasound
Unexplained [[Intrauterine Fetal Demise|intrauterine fetal demise]]
Unexplained neonatal anemia at birth
Maternal trauma (blunt abdominal injury, motor vehicle collision)
**Antepartum hemorrhage of uncertain etiology
*Massive FMH (>30 mL of fetal blood) can cause:
Fetal tachycardia or bradycardia
Sinusoidal fetal heart rate pattern
**Fetal anemia, hydrops, and death

==Differential Diagnosis==
Causes of a positive KB test / elevated fetal cells in maternal circulation:
True fetomaternal hemorrhage (trauma, abruption, procedures, spontaneous)
Hereditary persistence of fetal hemoglobin (HPFH) — false positive<ref name="kush">Kush ML, Muench MV, Harman CR, Baschat AA. Persistent fetal hemoglobin in maternal circulation complicating the diagnosis of fetomaternal hemorrhage. ''Obstet Gynecol''. 2005;105(4):872-874. PMID 15802420.</ref>
Sickle cell disease — false positive<ref name="statpearls"/>
Thalassemia — false positive<ref name="statpearls"/>
Maternal malignancy (rare cause of elevated HbF)

Conditions that may prompt KB testing:
[[Placental Abruption]]
[[Trauma in Pregnancy]]
[[Intrauterine Fetal Demise]]
Antepartum hemorrhage of unknown origin
Post-procedure (amniocentesis, external cephalic version, cordocentesis)

==Evaluation==
===Indications for KB Testing===
'''Rh-negative mothers:'''
All Rh-negative mothers after a potentially sensitizing event to determine if additional RhoGAM doses (beyond the standard 300 mcg) are needed<ref name="emery"/>
ACOG recommends KB testing in all Rh-negative pregnant trauma patients<ref name="statpearls"/>
'''Additional indications (regardless of Rh status):'''<ref name="emery"/>
Maternal trauma (the KB test predicts preterm labor risk after trauma more accurately than clinical assessment alone)<ref name="muench">Muench MV, Baschat AA, Reddy UM, et al. Kleihauer-Betke testing is important in all cases of maternal trauma. ''J Trauma''. 2004;57(5):1094-1098. PMID 15580038.</ref>
Unexplained elevated maternal serum alpha-fetoprotein
Unexplained fetal distress or abnormal heart rate tracings
Intrauterine fetal death
**Unexplained neonatal anemia
*'''Not recommended for:'''
**Diagnosis or exclusion of [[Placental Abruption|placental abruption]] — the KB test has no diagnostic utility for abruption<ref name="emery"/>

===Test Procedure===
Specimen: maternal peripheral venous blood (EDTA tube)
Timing: should be obtained as soon as possible after the suspected event; fetal cells are cleared from maternal circulation over hours to days
A blood smear is made, exposed to acid buffer, then stained
2000 cells are counted; fetal cells (dark/pink) are distinguished from maternal ghost cells (pale)
Result is reported as a percentage of fetal cells

===RhoGAM Dosing Calculation===
One standard vial of RhoGAM = 300 mcg, which covers 30 mL of fetal whole blood (15 mL of fetal RBCs)<ref name="statpearls"/>
'''Formulas:'''
Volume of fetal blood (mL) = % fetal cells × 50
Number of vials needed = volume of fetal blood ÷ 30
'''Rounding rule:'''<ref name="statpearls"/>
If the decimal is < 0.5 → round down and add 1 vial
If the decimal is ≥ 0.5 → round up and add 1 vial
'''Example:''' KB test reports 1.5% fetal cells
Volume = 1.5% × 50 = 75 mL fetal blood
Vials = 75 ÷ 30 = 2.5 → round up to 3, add 1 = '''4 vials'''

===Screening Algorithm===
Many institutions use a two-step approach<ref name="statpearls"/>:
Step 1: '''Rosette test''' (qualitative screen) — if negative, standard 300 mcg RhoGAM dose is sufficient
Step 2: If rosette test is positive → '''KB test''' (quantitative) to determine additional RhoGAM dosing
In major trauma, many centers proceed directly to KB testing

==Limitations==
'''Sensitivity:''' Poor sensitivity for small hemorrhages; interobserver variability is significant<ref name="pelikan">Pelikan DM, Mesker WE, Scherjon SA, Kanhai HH, Tanke HJ. Improvement of the Kleihauer-Betke test by automated detection of fetal erythrocytes in maternal blood. ''Cytometry B Clin Cytom''. 2003;54(1):1-9. PMID 12827463.</ref>
'''False positives:''' Maternal conditions with elevated HbF (HPFH, sickle cell disease, thalassemias) cause false elevations — one study found 32% of maternal samples had high HbF-containing cells, and 69% of those yielded clinically significant false positives<ref name="statpearls"/>
'''Poor prognostic value:''' Larger retrospective studies have demonstrated limited correlation between KB test positivity and adverse pregnancy outcomes; its primary value is in quantifying FMH for Rh immune prophylaxis rather than predicting outcomes<ref name="engel">Dhanraj D, Lambers D. The incidences of positive Kleihauer-Betke test in low-risk pregnancies and maternal trauma patients. ''Am J Obstet Gynecol''. 2004;190(5):1461-1463.</ref><ref name="cahill">Cahill AG, Bastek JA, Engel SM, et al. Minor trauma in pregnancy — is the evaluation warranted? ''Am J Obstet Gynecol''. 2008;198(2):208.e1-5.</ref>
'''Not useful for diagnosing abruption:''' A retrospective cohort study found no positive KB tests among placentas later confirmed to have abruption on pathologic review<ref name="emery"/>
'''Operator-dependent:''' Manual counting introduces subjectivity; results can vary between technicians
'''Flow cytometry''' is a more precise alternative that uses anti-HbF antibodies to quantify fetal cells, with improved sensitivity and reproducibility, but is limited by higher cost and availability<ref name="chen">Chen JC, Davis BH. Detection of fetal red cells in fetomaternal hemorrhage using a fetal hemoglobin monoclonal antibody by flow cytometry. ''Transfusion''. 1998;38(8):749-756.</ref><ref name="pelikan"/>

==Management==
'''Rh-negative mothers:'''
Administer standard 300 mcg RhoGAM for all potentially sensitizing events
If KB test indicates FMH > 30 mL fetal whole blood, administer additional vials per calculation above
RhoGAM should ideally be given within 72 hours of the sensitizing event
Before 12 weeks GA: mini-dose (150 mcg) is appropriate<ref name="statpearls"/>
*'''Trauma:'''
All pregnant trauma patients > 20 weeks GA should have continuous fetal monitoring (minimum 4–6 hours; extended to 24 hours if KB-positive or other concerning features)<ref name="muench"/>
A positive KB test after trauma predicts increased risk of preterm labor and warrants extended monitoring<ref name="muench"/>
**Rh-negative trauma patients should receive RhoGAM regardless of KB result; KB test guides additional dosing
'''Massive FMH (fetal compromise):'''
Immediate OB consultation
Continuous fetal monitoring
Consider emergent delivery if fetal heart rate tracing is nonreassuring
Intrauterine transfusion may be considered in select preterm cases in consultation with maternal-fetal medicine

==Disposition==
All Rh-negative patients with a potentially sensitizing event should receive RhoGAM prior to discharge from the ED
Patients with a positive KB test should be admitted for continuous fetal monitoring and serial labs
Patients with a negative KB test after minor trauma and reassuring fetal heart rate monitoring for ≥ 4–6 hours may be considered for discharge with close OB follow-up<ref name="muench"/>
OB consultation should be obtained for all cases of suspected significant FMH, abnormal fetal monitoring, or intrauterine fetal demise
Transfer to a facility with obstetric and neonatal intensive care capabilities if not available on site

==See Also==
[[Trauma in Pregnancy]]
[[Placental Abruption]]
[[Intrauterine fetal demise]]
[[Third trimester bleeding]]
[[Rh Incompatibility]]
[[Vaginal Bleeding (Pregnant)]]

==External Links==
[https://www.ncbi.nlm.nih.gov/books/NBK430876/ Kleihauer Betke Test - StatPearls]
[https://pubmed.ncbi.nlm.nih.gov/15580038/ Kleihauer-Betke testing is important in all cases of maternal trauma - J Trauma 2004]
[https://pubmed.ncbi.nlm.nih.gov/7487403/ The Kleihauer-Betke test: clinical utility, indication, and correlation - Arch Pathol Lab Med 1995]
[https://www.nature.com/articles/s41372-021-01185-5 Diagnostic accuracy of KB testing to predict fetal outcomes - J Perinatology 2021]

==References==
<references/>

[[Category:OBGYN]]
[[Category:Labs]]

← Revisión anterior		Revisión del 16:15 19 mar 2026
Línea 3:		Línea 3:
	*First described in 1957 by Enno Kleihauer and Klaus Betke		*First described in 1957 by Enno Kleihauer and Klaus Betke
	*Based on the principle that fetal hemoglobin (HbF) is resistant to acid elution, whereas adult hemoglobin (HbA) is not<ref name="statpearls"/>		*Based on the principle that fetal hemoglobin (HbF) is resistant to acid elution, whereas adult hemoglobin (HbA) is not<ref name="statpearls"/>
	*~~'''~~Mechanism:~~'''~~ A maternal blood smear is exposed to an acid bath (citric acid–phosphate buffer), which removes HbA from adult red blood cells while HbF-containing fetal cells remain intact; subsequent staining causes fetal cells to appear dark/rose-pink while adult "ghost" cells appear pale<ref name="statpearls"/>		*Mechanism: A maternal blood smear is exposed to an acid bath (citric acid–phosphate buffer), which removes HbA from adult red blood cells while HbF-containing fetal cells remain intact; subsequent staining causes fetal cells to appear dark/rose-pink while adult "ghost" cells appear pale<ref name="statpearls"/>
	*~~'''~~Primary clinical purpose:~~'''~~ Quantify the volume of FMH to guide dosing of Rho(D) immune globulin (RhoGAM) in Rh-negative mothers<ref name="emery">Emery CL, Morway LF, Chung-Park M, et al. The Kleihauer-Betke test: clinical utility, indication, and correlation in patients with placental abruption and cocaine use. ''Arch Pathol Lab Med''. 1995;119(11):1032-1037. PMID 7487403.</ref>		*Primary clinical purpose: Quantify the volume of FMH to guide dosing of Rho(D) immune globulin (RhoGAM) in Rh-negative mothers<ref name="emery">Emery CL, Morway LF, Chung-Park M, et al. The Kleihauer-Betke test: clinical utility, indication, and correlation in patients with placental abruption and cocaine use. ''Arch Pathol Lab Med''. 1995;119(11):1032-1037. PMID 7487403.</ref>
	*FMH occurs in up to 40% of trauma cases involving pregnant patients and can also occur during placental abruption, intrauterine fetal demise, and invasive obstetric procedures<ref name="statpearls"/>		*FMH occurs in up to 40% of trauma cases involving pregnant patients and can also occur during placental abruption, intrauterine fetal demise, and invasive obstetric procedures<ref name="statpearls"/>
	*As little as 0.01–0.03 mL of fetal blood is sufficient to trigger maternal Rh isoimmunization<ref name="statpearls"/>		*As little as 0.01–0.03 mL of fetal blood is sufficient to trigger maternal Rh isoimmunization<ref name="statpearls"/>
Línea 40:		Línea 40:
	==Evaluation==		==Evaluation==
	===Indications for KB Testing===		===Indications for KB Testing===
	*~~'''~~Rh-negative mothers:~~'''~~		*Rh-negative mothers:
	**All Rh-negative mothers after a potentially sensitizing event to determine if additional RhoGAM doses (beyond the standard 300 mcg) are needed<ref name="emery"/>		**All Rh-negative mothers after a potentially sensitizing event to determine if additional RhoGAM doses (beyond the standard 300 mcg) are needed<ref name="emery"/>
	**ACOG recommends KB testing in all Rh-negative pregnant trauma patients<ref name="statpearls"/>		**ACOG recommends KB testing in all Rh-negative pregnant trauma patients<ref name="statpearls"/>
	*~~'''~~Additional indications (regardless of Rh status):~~'''~~<ref name="emery"/>		*Additional indications (regardless of Rh status):<ref name="emery"/>
	**Maternal trauma (the KB test predicts preterm labor risk after trauma more accurately than clinical assessment alone)<ref name="muench">Muench MV, Baschat AA, Reddy UM, et al. Kleihauer-Betke testing is important in all cases of maternal trauma. ''J Trauma''. 2004;57(5):1094-1098. PMID 15580038.</ref>		**Maternal trauma (the KB test predicts preterm labor risk after trauma more accurately than clinical assessment alone)<ref name="muench">Muench MV, Baschat AA, Reddy UM, et al. Kleihauer-Betke testing is important in all cases of maternal trauma. ''J Trauma''. 2004;57(5):1094-1098. PMID 15580038.</ref>
	**Unexplained elevated maternal serum alpha-fetoprotein		**Unexplained elevated maternal serum alpha-fetoprotein
Línea 49:		Línea 49:
	**Intrauterine fetal death		**Intrauterine fetal death
	**Unexplained neonatal anemia		**Unexplained neonatal anemia
	*~~'''~~Not recommended for:~~'''~~		*Not recommended for:
	**Diagnosis or exclusion of [[Placental Abruption\|placental abruption]] — the KB test has no diagnostic utility for abruption<ref name="emery"/>		**Diagnosis or exclusion of [[Placental Abruption\|placental abruption]] — the KB test has no diagnostic utility for abruption<ref name="emery"/>

Línea 61:		Línea 61:
	===RhoGAM Dosing Calculation===		===RhoGAM Dosing Calculation===
	*One standard vial of RhoGAM = 300 mcg, which covers 30 mL of fetal whole blood (15 mL of fetal RBCs)<ref name="statpearls"/>		*One standard vial of RhoGAM = 300 mcg, which covers 30 mL of fetal whole blood (15 mL of fetal RBCs)<ref name="statpearls"/>
	*~~'''~~Formulas:~~'''~~		*Formulas:
	**Volume of fetal blood (mL) = % fetal cells × 50		**Volume of fetal blood (mL) = % fetal cells × 50
	**Number of vials needed = volume of fetal blood ÷ 30		**Number of vials needed = volume of fetal blood ÷ 30
	*~~'''~~Rounding rule:~~'''~~<ref name="statpearls"/>		*Rounding rule:<ref name="statpearls"/>
	**If the decimal is < 0.5 → round down and add 1 vial		**If the decimal is < 0.5 → round down and add 1 vial
	**If the decimal is ≥ 0.5 → round up and add 1 vial		**If the decimal is ≥ 0.5 → round up and add 1 vial
	*~~'''~~Example:~~'''~~ KB test reports 1.5% fetal cells		*Example: KB test reports 1.5% fetal cells
	**Volume = 1.5% × 50 = 75 mL fetal blood		**Volume = 1.5% × 50 = 75 mL fetal blood
	**Vials = 75 ÷ 30 = 2.5 → round up to 3, add 1 = '''4 vials'''		**Vials = 75 ÷ 30 = 2.5 → round up to 3, add 1 = '''4 vials'''
Línea 78:		Línea 78:

	==Limitations==		==Limitations==
	*~~'''~~Sensitivity:~~'''~~ Poor sensitivity for small hemorrhages; interobserver variability is significant<ref name="pelikan">Pelikan DM, Mesker WE, Scherjon SA, Kanhai HH, Tanke HJ. Improvement of the Kleihauer-Betke test by automated detection of fetal erythrocytes in maternal blood. ''Cytometry B Clin Cytom''. 2003;54(1):1-9. PMID 12827463.</ref>		*Sensitivity: Poor sensitivity for small hemorrhages; interobserver variability is significant<ref name="pelikan">Pelikan DM, Mesker WE, Scherjon SA, Kanhai HH, Tanke HJ. Improvement of the Kleihauer-Betke test by automated detection of fetal erythrocytes in maternal blood. ''Cytometry B Clin Cytom''. 2003;54(1):1-9. PMID 12827463.</ref>
	*~~'''~~False positives:~~'''~~ Maternal conditions with elevated HbF (HPFH, sickle cell disease, thalassemias) cause false elevations — one study found 32% of maternal samples had high HbF-containing cells, and 69% of those yielded clinically significant false positives<ref name="statpearls"/>		*False positives: Maternal conditions with elevated HbF (HPFH, sickle cell disease, thalassemias) cause false elevations — one study found 32% of maternal samples had high HbF-containing cells, and 69% of those yielded clinically significant false positives<ref name="statpearls"/>
	*~~'''~~Poor prognostic value:~~'''~~ Larger retrospective studies have demonstrated limited correlation between KB test positivity and adverse pregnancy outcomes; its primary value is in quantifying FMH for Rh immune prophylaxis rather than predicting outcomes<ref name="engel">Dhanraj D, Lambers D. The incidences of positive Kleihauer-Betke test in low-risk pregnancies and maternal trauma patients. ''Am J Obstet Gynecol''. 2004;190(5):1461-1463.</ref><ref name="cahill">Cahill AG, Bastek JA, Engel SM, et al. Minor trauma in pregnancy — is the evaluation warranted? ''Am J Obstet Gynecol''. 2008;198(2):208.e1-5.</ref>		*Poor prognostic value: Larger retrospective studies have demonstrated limited correlation between KB test positivity and adverse pregnancy outcomes; its primary value is in quantifying FMH for Rh immune prophylaxis rather than predicting outcomes<ref name="engel">Dhanraj D, Lambers D. The incidences of positive Kleihauer-Betke test in low-risk pregnancies and maternal trauma patients. ''Am J Obstet Gynecol''. 2004;190(5):1461-1463.</ref><ref name="cahill">Cahill AG, Bastek JA, Engel SM, et al. Minor trauma in pregnancy — is the evaluation warranted? ''Am J Obstet Gynecol''. 2008;198(2):208.e1-5.</ref>
	*~~'''~~Not useful for diagnosing abruption:~~'''~~ A retrospective cohort study found no positive KB tests among placentas later confirmed to have abruption on pathologic review<ref name="emery"/>		*Not useful for diagnosing abruption: A retrospective cohort study found no positive KB tests among placentas later confirmed to have abruption on pathologic review<ref name="emery"/>
	*~~'''~~Operator-dependent:~~'''~~ Manual counting introduces subjectivity; results can vary between technicians		*Operator-dependent: Manual counting introduces subjectivity; results can vary between technicians
	*~~'''~~Flow cytometry~~'''~~ is a more precise alternative that uses anti-HbF antibodies to quantify fetal cells, with improved sensitivity and reproducibility, but is limited by higher cost and availability<ref name="chen">Chen JC, Davis BH. Detection of fetal red cells in fetomaternal hemorrhage using a fetal hemoglobin monoclonal antibody by flow cytometry. ''Transfusion''. 1998;38(8):749-756.</ref><ref name="pelikan"/>		*Flow cytometry is a more precise alternative that uses anti-HbF antibodies to quantify fetal cells, with improved sensitivity and reproducibility, but is limited by higher cost and availability<ref name="chen">Chen JC, Davis BH. Detection of fetal red cells in fetomaternal hemorrhage using a fetal hemoglobin monoclonal antibody by flow cytometry. ''Transfusion''. 1998;38(8):749-756.</ref><ref name="pelikan"/>

	==Management==		==Management==
	*~~'''~~Rh-negative mothers:~~'''~~		*Rh-negative mothers:
	**Administer standard 300 mcg RhoGAM for all potentially sensitizing events		**Administer standard 300 mcg RhoGAM for all potentially sensitizing events
	**If KB test indicates FMH > 30 mL fetal whole blood, administer additional vials per calculation above		**If KB test indicates FMH > 30 mL fetal whole blood, administer additional vials per calculation above
	**RhoGAM should ideally be given within 72 hours of the sensitizing event		**RhoGAM should ideally be given within 72 hours of the sensitizing event
	**Before 12 weeks GA: mini-dose (150 mcg) is appropriate<ref name="statpearls"/>		**Before 12 weeks GA: mini-dose (150 mcg) is appropriate<ref name="statpearls"/>
	*~~'''~~Trauma:~~'''~~		*Trauma:
	**All pregnant trauma patients > 20 weeks GA should have continuous fetal monitoring (minimum 4–6 hours; extended to 24 hours if KB-positive or other concerning features)<ref name="muench"/>		**All pregnant trauma patients > 20 weeks GA should have continuous fetal monitoring (minimum 4–6 hours; extended to 24 hours if KB-positive or other concerning features)<ref name="muench"/>
	**A positive KB test after trauma predicts increased risk of preterm labor and warrants extended monitoring<ref name="muench"/>		**A positive KB test after trauma predicts increased risk of preterm labor and warrants extended monitoring<ref name="muench"/>
	**Rh-negative trauma patients should receive RhoGAM regardless of KB result; KB test guides additional dosing		**Rh-negative trauma patients should receive RhoGAM regardless of KB result; KB test guides additional dosing
	*~~'''~~Massive FMH (fetal compromise):~~'''~~		*Massive FMH (fetal compromise):
	**Immediate OB consultation		**Immediate OB consultation
	**Continuous fetal monitoring		**Continuous fetal monitoring