Which test is commonly used to assess fetal lung maturity by evaluating surfactant composition?

Which test is commonly used to assess fetal lung maturity by evaluating surfactant composition?

• A. L/S ratio
• B. Acetylcholinesterase
• C. Lamellar body count
• D. Foam stability

Answer: (A)

Measuring the amount of lecithin relative to sphingomyelin in amniotic fluid is a direct reflection of fetal lung maturity because lecithin (phosphatidylcholine) levels rise as the lungs develop and begin producing surfactant, while sphingomyelin stays relatively constant. When the lecithin-to-sphingomyelin ratio reaches about 2:1, lungs are typically mature, and the risk of neonatal respiratory distress syndrome is lower. This test uses amniotic fluid obtained by amniocentesis and provides a chemical assessment of surfactant composition, not just its presence or function. Other tests either assess different aspects of amniotic fluid or surfactant function rather than composition. Acetylcholinesterase is used to detect rupture of membranes by identifying amniotic fluid in vaginal secretions, not to evaluate surfactant makeup. Lamellar body count reflects surfactant-containing vesicles released by fetal lung cells and can correlate with maturity, but it’s a surrogate marker rather than a direct measure of surfactant composition. Foam stability tests the functional ability of surfactant to stabilize air-liquid interfaces, not its chemical composition.

Measuring the amount of lecithin relative to sphingomyelin in amniotic fluid is a direct reflection of fetal lung maturity because lecithin (phosphatidylcholine) levels rise as the lungs develop and begin producing surfactant, while sphingomyelin stays relatively constant. When the lecithin-to-sphingomyelin ratio reaches about 2:1, lungs are typically mature, and the risk of neonatal respiratory distress syndrome is lower. This test uses amniotic fluid obtained by amniocentesis and provides a chemical assessment of surfactant composition, not just its presence or function.

Other tests either assess different aspects of amniotic fluid or surfactant function rather than composition. Acetylcholinesterase is used to detect rupture of membranes by identifying amniotic fluid in vaginal secretions, not to evaluate surfactant makeup. Lamellar body count reflects surfactant-containing vesicles released by fetal lung cells and can correlate with maturity, but it’s a surrogate marker rather than a direct measure of surfactant composition. Foam stability tests the functional ability of surfactant to stabilize air-liquid interfaces, not its chemical composition.