Lecithin-sphingomyelin ratio

Keywords: L/S ratio

Specimen:

Amniotic fluid.

Method:

Thin layer chromatography. Some laboratories also measure phosphatidyl glycerol or count lamellar bodies.

Reference Interval:

L/S ratio > 2.0 indicates fetal lung maturity.

Application:

Assessment of foetal lung maturity.

See also Phosphatidyl glycerol and Lamellar bodies.

Interpretation:

L/S ratio < 2.0 indicates an increased risk of RDS at delivery.

L/S ratio < 1.5 indicates a very high risk of developing RDS.

Babies of diabetic mothers can develop RDS with L/S ratios > 2.0.

Reference:

Spillman T et al. Crit Rev Clin Lab Sci. 1989; 27: 341-389.