Alkali denaturation test

Source: Wikipedia, the free encyclopedia.
(Redirected from
Apt–Downey test
)
Alkali denaturation test
Purposedifferentiate neonatal from maternal blood

The alkali denaturation test, also known as A or Apt test, is a medical test used to differentiate fetal or

neonatal blood from maternal blood found in a newborn's stool or vomit, or from maternal vaginal blood.[1][2]

History

The test was developed by Leonard Apt (1922–2013),[3] an American pediatric ophthalmologist. The test was originally used to identify the source of bloody stools in newborn infants. It has been modified to distinguish fetal from maternal hemoglobin in blood samples from any source.[4]

Uses

The Apt test is most commonly used in cases of vaginal bleeding late during pregnancy (

antepartum haemorrhage) to determine if the bleeding is from the mother or the fetus. [citation needed
]

  • A positive test would indicate that blood is of fetal origin, and could be due to
    vasa previa
    .
  • A negative test indicates that the blood is of maternal origin.

In practice, the Apt test may not be done when there is suspicion of vasa previa, because the time to fetal collapse with bleeding from vasa previa is often very short.

The Apt test can also be used to detect the presence of fetal blood in the maternal circulation in cases of suspected

Kleihauer-Betke test
is more commonly used.

Finally, the Apt test can be used after birth (

postpartum hemorrhage
) if the newborn has bloody vomiting, bloody stool, or active bleeding from the nasogastric tube. A positive apt test would mean that the blood is either due to gastrointestinal or pulmonary bleeding from the neonate. A negative Apt test would indicate that the blood is of maternal origin, suggesting that the neonate swallowed or aspirated maternal blood, either during delivery or during breastfeeding (e.g., from breast fissures).

Theory

The test is based on differences between maternal and fetal

NaOH
) will denature the adult but not the fetal hemoglobin. The fetal hemoglobin will appear as a pinkish color under the microscope while the adult hemoglobin will appear as a yellow-brownish color.

Method

The blood is mixed with a small amount of sterile water to cause

hematin which has a hydroxide ligand.[5]

See also

  • Kleihauer-Betke test

References

  1. PMID 16079432
    .
  2. PMID 14392548
    .
  3. ^ Elaine Schmidt, Obituary: Leonard Apt, 90, doctor-scientist who gave gift of vision to millions of children, UCLA Newsroom, February 7, 2013
  4. ^ Venes, D. Taber's Cyclopedic Medical Dictionary - 20th Ed. F. A. Davis Company, Philadelphia, PA. 2005.
  5. ^ Pediatrics, Gastrointestinal Bleeding

Further reading

Retrieved from "https://en.wikipedia.org/w/index.php?title=Alkali_denaturation_test&oldid=1212409117"