Coombs test is performed to predict what complication in fetus?

JSSH Staff Nurse - 2019

Obstetrics & Gynaecology

Easy

Appeared in: JSSH Staff Nurse - 2019

Explanation

The Coombs test is a key diagnostic tool for detecting alloimmune hemolysis, where maternal antibodies attack fetal red blood cells.
The Indirect Coombs test, performed on the mother's serum, screens for circulating antibodies (e.g., anti-D in Rh incompatibility) that have the potential to cross the placenta.
A positive Indirect Coombs test indicates the mother is sensitized and the fetus is at risk for Hemolytic Disease of the Fetus and Newborn (HDFN).
HDFN is characterized by the destruction (hemolysis) of fetal red blood cells by these maternal antibodies, which can lead to severe anemia, jaundice, and hydrops fetalis.

Option A: Metabolic disorders are inborn errors of metabolism, such as galactosemia or phenylketonuria (PKU). They are not caused by an immune reaction and are not detected by the Coombs test.
Option B: Physiologic hyperbilirubinemia is a common, mild, and non-hemolytic form of jaundice in newborns due to the immaturity of the liver's bilirubin conjugation pathway. The Coombs test would be negative.
Option C: Thalassemia is a genetic blood disorder characterized by reduced or absent synthesis of hemoglobin chains. It is a production problem, not an immune destruction problem.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Use of Coombs test in prenatal screening for hemolytic disease as background academic context rather than a clinical decision trigger.
The Coombs test is a cornerstone of prenatal care for preventing the severe consequences of HDFN, including kernicterus (brain damage from high bilirubin) and hydrops fetalis.
Nurses play a vital role in patient education and ensuring Rh-negative mothers receive Rh immunoglobulin (RhoGAM) at the correct times (around 28 weeks gestation and postpartum) to prevent maternal sensitization.
For a newborn with a positive Direct Coombs test, nurses must closely monitor for jaundice, anemia, and signs of distress, and be prepared for interventions like phototherapy or exchange transfusion.

How to Approach the Question

First, identify the core subject of the question: the 'Coombs test'.
Recall or deduce the primary purpose of this test. The name 'Coombs' is strongly associated with immunohematology, blood banking, and transfusion reactions, which involve antigen-antibody interactions on red blood cells.
Analyze the options in this context. 'Acute hemolytic disease' directly relates to the destruction (lysis) of red blood cells (hemo-), which is what an antibody-mediated attack would cause.
Evaluate the other options to confirm your choice. 'Metabolic disorder', 'physiologic' (normal) jaundice, and 'genetic thalassemia' (a hemoglobin production issue) do not involve an immune attack on RBCs, making them incorrect diagnoses for a positive Coombs test.

Concept Tested & Keywords

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E6 Nelson Textbook of Pediatrics(2024) — Volume 1 pp. 1117-1119, 1133-1135, 1132-1134