Modified Apt Test

Aka: Modified Apt Test, Apt Test

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II. Indications

  1. Vasa Previa
    1. Late Pregnancy Bleeding evaluation
  2. Infant with black stools thought due to swallowed maternal blood
    1. See Neonatal Black Stool

III. Mechanism

  1. Differentiates Fetal from Maternal Blood
  2. Fetal Hemoglobin contains 2 alpha subunits and 2 gamma subunits (contrast with beta subunits in adults)
    1. Fetal blood is resistant to denaturation when alkali is applied (fetal blood remains pink)
    2. Adult blood denatures in contact with alkali and turns brown

IV. Technique

  1. Collect bloody fluid
  2. Add a small amount of tap water (Hemolyzes blood)
  3. Centrifuge sampleppp
  4. Add 5 cc pink supernatant to 1 cc Sodium Hydroxide 1%
  5. Read in 2 minutes (may be difficult)
    1. Pink sample indicates fetal Hemoglobin
    2. Yellow-Brown sample indicates adult Hemoglobin

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