Coombs test is performed to predict which complication in a fetus?

JODHPUR AIIMS SNO-2018

Obstetrics & Gynaecology

Easy

Appeared in: JODHPUR AIIMS SNO-2018

Explanation

The Coombs test is designed to detect antibodies that target and bind to red blood cells (RBCs).
In a fetal context, it specifically identifies maternal antibodies that have crossed the placenta and are causing the destruction of fetal RBCs.
This immune-mediated destruction of red blood cells is known as hemolysis, which is the defining characteristic of acute hemolytic disease of the fetus and newborn (HDFN).
The direct Coombs test confirms antibodies are attached to fetal RBCs, while the indirect Coombs test assesses the mother's blood for the presence of these potentially harmful antibodies.

Option A: Physiologic hyperbilirubinemia is a common, non-pathological condition in newborns due to the immaturity of the liver's bilirubin conjugation system and a shorter RBC lifespan. It is not caused by an immune reaction.
Option B: Metabolic disorders are a broad category of genetic diseases affecting metabolism (e.g., galactosemia, hypothyroidism). They are diagnosed through specific biochemical assays or newborn screening panels, not the Coombs test.
Option D: Thalassemia is a genetic disorder affecting the production of hemoglobin. It is an inherited condition, not an immune-mediated one. Diagnosis is made through hemoglobin electrophoresis and genetic testing.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The clinical application of the Coombs test in prenatal and neonatal care as background academic context rather than a clinical decision trigger.
The indirect Coombs test is a standard part of antenatal screening for all Rh-negative pregnant women to identify sensitization and the risk of HDFN.
A positive direct Coombs test in a jaundiced newborn is a critical finding that alerts the clinical team to ongoing hemolysis, prompting close monitoring of bilirubin levels and potential interventions like phototherapy or exchange transfusion to prevent kernicterus.
What if the mother is Rh-positive and the baby is also Rh-positive? In this case, Rh-induced hemolytic disease is not a concern. However, HDFN can still occur due to ABO incompatibility (e.g., O-type mother and A or B-type baby), which is usually less severe but can still cause significant jaundice and a positive direct Coombs test.

How to Approach the Question

First, analyze the question, which asks for the specific complication a Coombs test predicts in a fetus.
Examine the provided image. It clearly shows the mechanism of the Coombs test, involving antibodies and red blood cells (RBCs) clumping together (agglutination). This visual cue points towards an immune reaction involving blood cells.
Recall the purpose of the Coombs test: to detect antibodies that attack RBCs.
Evaluate the options based on this mechanism. 'Hemolytic disease' literally means disease involving the destruction ('lysis') of blood ('hemo'). This directly matches the function of the antibodies detected by the Coombs test.
Eliminate the other options: Physiologic hyperbilirubinemia is non-immune, metabolic disorders are diagnosed differently, and thalassemia is a genetic hemoglobin defect, not an immune issue.

Concept Tested & Keywords

Concept Tested: The clinical application of the Coombs test in prenatal and neonatal care.
Stem keywords: Coombs test, fetus, complication
Lead-in keywords: predict
Negative lead-in flag: false

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