Lab Test

Acid Elution (Fetal Hemoglobin in Red Blood Cells)

Fetal Cells, Kleihauer and Betke, fetal hemoglobin, hemoglobin F, acid elution slide test, acid elution for fetal hemoglobin

Test Codes

Dearborn, Taylor, Trenton, Wayne use EPIC: LAB7190, KLBET
Farmington Hills, Grosse Pointe, Royal Oak, Troy use EPIC: LAB5135




At Royal Oak, except for Saturday afternoon, Sunday and holidays, all acid elution requests are performed as a Fetal RBC Assay by the Flow Cytometry Laboratory because of increased accuracy and precision.

Specimen Collection Criteria

Collect (preferred specimen): One 4.0 mL Lavender-top K2EDTA tube. (Minimum: 2.0 mL)
Also acceptable: One Lavender-top K2EDTA Microtainer®. (Minimum: 300 mcL)
One Pink-top K2EDTA Microtainer®. (Minimum: 200 mcL)

Physician Office/Draw Specimen Preparation

Maintain specimens refrigerated (2-8°C or 36-46°F) prior to transport. Room temperature (20-26°C or 68-78.8°F) is acceptable for a maximum of 2 hours.

Preparation for Courier Transport

Transport: Whole blood or capillary blood, refrigerated (2-8°C or 36-46°F). (Minimum: 2.0 mL whole blood or 300 mcL capillary blood)

Rejection Criteria

  • Specimens containing clots.
  • Insufficient volume.
  • Frozen specimens.
  • Centrifuged specimens. 


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 48 hours
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days


Dearborn Blood Bank Laboratory
Farmington Hills Hematology Laboratory
Grosse Pointe Hematology Laboratory
Royal Oak Hematology Laboratory
Taylor Blood Bank Laboratory
Trenton Blood Bank Laboratory
Troy Hematology Laboratory
Wayne Blood Bank Laboratory


Dearborn, Farmington Hills, Grosse Pointe, Troy & Wayne: 
Sunday – Saturday, 24 hours a day. Results available within 24 hours. 

Royal Oak:
Monday – Friday (before 3:00 pm), Saturday (before 1:30 pm) in Royal Oak Flow Cytometry. Results available within 4 hours. 

Saturday (after 1:30 pm), Sunday, and Holidays in Royal Oak Hematology Laboratory. Results available within 8 hours.

EC requests are trauma cases that define a possible fetal bleed. Afternoon, midnight and weekend requests from EC will be processed immediately.

Reference Range

Less than 0.3%.

Test Methodology

Flow Cytometry or Kleihauer-Betke.


Normal adult blood will contain less than 0.01% Hb F cells. Acceptable results for OB patients is less than 0.3%. In full term newborns, fetal cells are about 90%.

Clinical Utility

Fetal blood may enter into the maternal circulation during pregnancy, at delivery, during abortion, and as a result of trauma. When a Rh negative mother is carrying a Rh positive fetus the amount of fetal erythrocytes present in the maternal circulation determines the dose of Rh immune globulin that should be administered to the mother. This assay aids in determining the appropriate dose of Rh immune globulin that should be administered to the mother.

CPT Codes



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