Apt-Test for Neonatal Hematemesis

We all are well aware that there are many perils and pitfalls awaiting those who choose to trust a neonate. It is not that the neonate is innately malicious or malingering. She or he is clearly not determined to be deceptive. Through no fault of their own, neonates are just tricky. We know that relatively innocuous appearing or sounding complaints may, in fact, be the subtle sign of chaos on the horizon (ex, Neonatal Seizures, Neonatal Bloody Stool, Neonatal Leukemia, Vitamin K Deficiency, Vitamin B6 Deficiency). It then stands to reason that an objectively abnormal finding, like a neonate vomiting BRIGHT RED BLOOD is most certainly a harbinger of destruction and the end of times; HOWEVER, it may not be. It may, instead be benign. WHAAAT??? A simple test may help you sort out the benign from the malevolent. Let’s consider using the Apt-Test for Neonatal Hematemesis:

Neonatal Hematemesis: Basics

Think Worst First

Ok… clearly, in the Emergency Department, we must always think about the Lions, Tigers and Bears… while being aware that horses can trample us just as ferociously as zebras… so

  • The differential for hematemesis in a neonate is vast and has many concerning entities within it (similar to other aged patients).
  • Some concerning items to consider would include (but not limited to):
    • Esophagitis, Gastritis, GI Ulcers [Kataria-Hale- 2020]
    • Vascular anomaly, Congenital malformations, Intestinal duplication
    • Prolapse Gastropathy (forceful vomiting causing the stomach to prolapse into the esophagus)
    • Mallory-Weiss tears
    • Heterotopic pancreatic tissue
  • Some more common and benign issues are:
    • Swallowed Maternal Blood [Moustafa, 2005]
      • Swallowed during birth
      • Swallowed during breastfeeding (related to cracked nipples)
    • Cow’s Milk Allergy
  • Important to realize that typical Gastroesophageal Reflux in an infant is not associated with GIB.
Make a plan…
  • In toxic/ill appearing infant, proceed with “worst-first” mentality and act quickly to stabilize.
    • Vascular Access is needed!
    • Volume resuscitate
      • But remember, they are not hemorrhaging saline… be judicious with IV fluids
      • Consider PRBCs transfusion based on clinical response to IV fluids, Hematocrit, and anticipated ongoing losses.
  • For well appearing (which most will be), keep the “worst-first” in mind, but proceed with reason.
    • Is this mother’s blood or baby’s blood??
    • How long has this been going on?
    • When is it occurring?
    • Does it occur only when the child consumes mother’s breastmilk?
  • If you happened to order a bunch of “bleeding tests,” realize that: [Davenport, 2021]
    • Platelet Counts are normally relatively lower in infants compared to adults.
      • Lower values more often seen in pre-term infants.
      • Counts < 100×10^9/L are still ABNORMAL!
    • PT and PTT values can be normally HIGHER in healthy infants.
      • Highest amongst extremely pre-term and pre-term infants.
      • Consult a reference before making a rash judgement.

Apt-Test for Neonatal Hematemesis

The Apt-Downey test can help answer an important question… is this maternal or neonatal blood?
  • Apt-Downey Test (AKA Apt-Test… poor Downey is often left off): [Moustafa, 2005]
    • Is based on the fact that fetal hemoglobin is resistant to alkali denaturation.
    • Specimen of fresh, red blood is mixed in equal amount of water to lyse the RBCs.
    • After centrifugation, the supernatant should have a pink color (from a ton of free hemoglobin floating around).
    • 1% NaOH is added to the supernatant and then set aside for 2 minutes.
      • Persistently Pink = Fetal Hemoglobin (it did not denature)
      • Turns Yellow = Adult Hemoglobin (it did denature)
    • Fetal hemoglobin is replaced relatively quickly by adult hemoglobin, so the test becomes less useful with age and really should not be used in infants > 6 months of age (really, most helpful in the neonatal period).
  • Apt-Downey Test: important specifics to know about the test include:
    • Can be used to test stool or emesis.
    • Requires a GROSSLY bloody specimen (bright red blood is best… not melena… not coffee grounds).
    • Best performed with a “fresh” specimen (within 30 min of collection).
    • Send the freshest and bloodiest specimen to the lab… and you may want to call ahead so it doesn’t just sit out.
If Maternal source of the blood is confirmed, then…
  • Get more details about the birth (If the child is NEWLY born, it may be from the birth process).
  • Ask to inspect the mother’s nipples.
    • The mother may also prefer to pump the breast milk and have that inspected.
    • Some pumps will need to have the suction power increased in order to generate force similar to that which the infant does (seriously, Mother’s are the bravest and strongest!).
    • Sometimes, only one breast is the source of bleeding.
    • Resolution of hematemesis after avoidance of maternal blood further confirms the suspicions.

Moral of the Morsel

  • Bright Red Blood is noticeable! Likely that a parent will become concerned about this and come in at odd hours when they cannot seek information form their PCPs. Have a plan.
  • The Apt-Downey Test is an apt test for that! The source (maternal or infant) of bright red blood in the emesis (or stool) can be differentiated through use of this test that we learned about in 1st year of medical school. Use it!
  • Normal values may be different. Particularly for pre-mature children, it is important to consult a reliable reference to compare your laboratory studies (if you obtained them) as PT/PTT and Plts may be different than the normal adult values.

References

Default image
Sean M. Fox
I enjoy taking care of patients and I finding it endlessly rewarding to help train others to do the same. I trained at the Combined Emergency Medicine and Pediatrics residency program at University of Maryland, where I had the tremendous fortune of learning from world renowned educators and clinicians. Now I have the unbelievable honor of working with an unbelievably gifted group of practitioners at Carolinas Medical Center. I strive every day to inspire my residents as much as they inspire me.
Articles: 550