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Test for Fetal Hemoglobin - Provincial

Discipline

Transfusion Medicine

Overview

Description

  • A test used to detect and quantitate the presence of fetal red cells in maternal circulation.

Alias

Screening tests

  • FMH Screen
  • Rosette Test

Quantitative tests

  • Kleihauer Betke
  • Fetal Hemoglobin

Specimen Information

Specimen types accepted

  • Whole blood

Specimen collection container

Required volume

  • ​Optimal volume: 4 mL
  • Minimum volume: 1 mL

(Submitting the minimum volume makes it impossible to repeat the test or perform confirmatory/reflex testing. In some situations, a minimum volume may require a second collection.)

    Transport and stability

    • ​Store at 2-8ºC

    • Must be tested within 48 hours of collection

    Rejection criteria

    Testing Information

    Relevant clinical history

    • Diagnosis

    • Gestational age of pregnancy, if not postpartum.

    Clinical interpretation

    • Rh negative expectant or post-partum patients: A negative test result (FMH screen or Kleihauer Betke test) indicates that one standard dose of 300 micrograms RhIg shall be given in any potentially sensitizing situation in an Rh negative patient, which is sufficient to prevent immunization by 15 mL of fetal red cells or 30 mL of whole blood. 
    • Rh negative expectant or post-partum patients: A positive result indicates the need for a quantitative test (e.g. Kleihauer-Betke) to determine the volume of FMH.
    • Rh positive expectant or post-partum patients: a Kleihauer-Betke may be requested at the discretion of the Most Responsible Physician (MRP), in consultation with on-call Transfusion Medicine Physician. The FMH screen cannot be utilized in Rh positive patients.

    Performance

    Methodology

    • FMH RapidScreen (may utilized as an initial screen, if available).
    • Fetal Cell Stain Kit.

    Days/times performed

    • Complex sites (RUH and RGH): testing available 24 hours/7 days a week. 

    • Advanced sites: testing available; hours variable. 

    • Basic sites: testing not available; sample referred to complex or advanced sites.

    • Current State Blood Drop Map

    Maximum laboratory time

    • Routine: 
      • Within 24 hours of receipt in Transfusion Medicine.
    • Urgent: 
      • Within 4 hours of receipt in Transfusion Medicine.
    • STAT: 
      • Testing not available. 

    Specimen retention time

    • 5 weeks

    Other information

    Reflex Testing
    • If the Fetal Maternal Hemorrhage (FMH) RapidScreen is found to be positive, a Kleihauer-Betke Test will be performed to determine the volume of the fetal-maternal hemorrhage.
    • Regina Only:  Kleihauer Betke testing is performed by Hematology at RGH
    Forms Required

    Last Updated: August 9, 2024