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Test Code LS Lecithin/Sphingomyelin (L/S) Ratio, Phosphatidylglcerol(PG), Amniotic Fluid

Important Note

  Do Not Order


Test no longer available at any Referral Laboratory-


Please order LBC as replacement.

Performing Laboratory

Quest Teterboro


Thin-Layer Chromatography (TLC), Latex Agglutinatin

Reference Values

Interpretation of the lecithin/sphingomyelin (L/S) Ratio is made as follows:

Interpretation     L/S Ratio         Phosphatidyl Glycerol          Weeks Gestation
Immature                <1.0                    Not detected                           26-30 
Premature            1.0-1.5                  Not detected                           30-34
Transitional          1.5-1.9                  Not detected                           35-36
Mature (Caution)  2.0-2.5                Not detected                            36-37
Mature                    >2.5                     Detected                                   37-40
A lecithin/sphingomyelin ratio of >2.0 together with the presence of phosphatidylglycerol may suggest mature fetal lung development.
The designation "Mature (Caution)" refers to patients other than those with diabetes. Phospholipid data in diabetic pregnancies do not necessarily follow the above classification.


Test Classification and CPT Coding



Physician Office Specimen Requirements

Obtain 10 mL of amniotic fluid. Freeze immediately, and send specimen frozen in a screw-capped, sterile container. Protect specimen from light.