Phosphatidylcholine, a type of phospholipid in<unk> . The<unk>  (a.k.a. L-S or L/S ratio) is a test of fetal amniotic fluid to assess for fetal lung immaturity. Lungs require surfactant, a soap-like substance, to lower the surface pressure of the alveoli in the lungs. This is especially important for premature babies trying to expand their lungs after birth. Surfactant is a mixture of lipids, proteins, and glycoproteins,<unk>  and<unk>  being two of them.<unk>  makes the surfactant mixture more effective.
Lecithin–sphingomyelin ratio
Lamellar body count
Sucrose gap
Anton blood group antigen
Alkali denaturation test
Osmol gap
Euglobulin lysis time
Gluten immunochemistry