Wednesday, April 19, 2017

Apt Test in Newborn: Maternal vs Neonatal Blood

We had few cases of suspected GI bleeding, admitted or referred to our NICU. One was case of Hematochezia and other was case of fresh blood in vomitus. Both babies were born to mother with Antepartum hemorrhage. The general condition of the babies were fine, and the vitals. There was no other reason for GI bleed at such early period in these neonates.

Generally, in absence of Apt test, we would get Sepsis workup, PT, aPTT, platelets done and baby would also be given IV antibiotics, Vitamin K and possibly FFP.
But a Simple test can prevent unnecessary interventions when history is clear and baby is well.

Vomiting of blood mixed content on first day or two in newborn is a commonly encountered problem. In Neonates, swallowed maternal blood is the most common cause in case of suspected GI bleeding. Blood can be either swallowed during delivery or swallowed from cracked maternal nipples during breast feeding. 1. As gastric transit is quick, newborn even present mimicking hematochezia or malena.

A simple bedside test can rule out lot of confusion and prevent unnecessary intervention, specially when amount is significant and requires evaluation. Apt test is useful for differentiating between newborn swallowing mother’s blood and fetal gastrointestinal bleeding. One is a benign condition and other is a worrisome one.

How is Apt Test done?
- non-quantitative method based on resistance of hemoglobin F to alkali denaturation. This test is useful ONLY on frankly bloody (red) stool or gastric specimens, not tarry (black) specimens.

Concept is- Fetal Hb is resistant to alkali denaturation.

Color change in Positive and Negative test. Alkali Denaturation Test

- false-positive result as oxyhemoglobin has been converted to hematin. 
- Visual judgement of color produced by test procedure may lead to error if only a small amount of blood is present. 
-Bilirubin containing meconium and possibly other substances may cause stool color interference. 2

Other Diagnsotic consideration should be
Midgut volvulus
Sepsis- DIC
Early onset hemorrhagic disease of Newborn
Stress gastic ulcer
Traumatic bleed- NG or CPAP induced nasal or gastric mucosal bleed.

In a sick newborn, just relying on Apt test does not seem logical and detail work up is needed.