Which test is used to assess fetal lung maturity using a ratio involving surfactant and albumin?

Which test is used to assess fetal lung maturity using a ratio involving surfactant and albumin?

• A. Hematocrit
• B. Surfactant/albumin ratio by fluorescence polarization
• C. Blood gas analysis
• D. Amniotic fluid bilirubin

Answer: (B)

Surfactant production increases as fetal lungs mature, so a ratio that compares surfactant to a stable protein in amniotic fluid tracks how prepared the lungs are to breathe after birth. Measuring the surfactant/albumin ratio in amniotic fluid with fluorescence polarization provides a rapid, quantitative assessment: surfactant levels are quantified and then normalized to albumin to control for sample variability, and a higher ratio points to more mature lungs and a lower risk of neonatal respiratory distress syndrome. The other options don’t measure lung maturity—hematocrit looks at red cell mass, blood gas analysis gauges oxygenation and acid-base status, and amniotic fluid bilirubin reflects bilirubin handling—not surfactant-based maturity.

Surfactant production increases as fetal lungs mature, so a ratio that compares surfactant to a stable protein in amniotic fluid tracks how prepared the lungs are to breathe after birth. Measuring the surfactant/albumin ratio in amniotic fluid with fluorescence polarization provides a rapid, quantitative assessment: surfactant levels are quantified and then normalized to albumin to control for sample variability, and a higher ratio points to more mature lungs and a lower risk of neonatal respiratory distress syndrome. The other options don’t measure lung maturity—hematocrit looks at red cell mass, blood gas analysis gauges oxygenation and acid-base status, and amniotic fluid bilirubin reflects bilirubin handling—not surfactant-based maturity.