Apt Test

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The Apt Test, developed by Leonard Apt, allows differentiation between foetal and maternal blood, for example in vomit, stool or per vaginal blood.

Once collected and prepared (see below), the sample is mixed with an alkali solution. Adult (maternal) haemoglobin consists of two alpha and two beta subunits: this is denatured by the alkali and the sample turns yellow-brown. However, foetal haemoglobin contains two alpha and two gamma subunits: this combination is not susceptible to being denatured by alkali, and the solution remains pink under a microscope.

For example, if a newborn baby has blood-stained vomit, this test may allow you to differentiate between maternal swallowed blood and foetal gastric bleeding.

Laboratory Method

  1. Collect bloody fluid
  2. Add a small amount of water to haemolyse the blood
  3. Centrifuge sample
  4. Add pink supernatant to Sodium Hydroxide 1% (5:1 volume ratio)
  5. Assess after 2 minutes
    1. Pink sample --> fetal Hemoglobin (positive result)
    2. Yellow-Brown sample --> adult Hemoglobin (negative result)
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