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HelpTest Code MISC Lecithin/Sphingomyelin (L/S) Ratio, Amniotic Fluid
Performing Laboratory
St. John's HospitalMethodology
Thin-Layer Chromatography (TLC)Specimen Requirements
Specimen Type: Amniotic fluidContainer/Tube: Sterile container
Specimen Volume: 10 mL
Collection Instructions:
1. Separate debris and cellular elements as soon as possible after collection by centrifugation.
2. Transfer supernatant to plastic vial.
Additional Information: If specimen is kept at 4° C or ambient temperature, phosphodiesterase activity in the amniotic fluid will destroy the lecithin, resulting in a falsely-depressed L/S ratio.
Reference Values
≤2.0 (immature)>2.0 (mature)
An L/S ratio of 2.0-2.5 together with the presence of phosphatidylglycerol (PG) is generally indicative of 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. For additional interpretive information, please call NetworkReferenceLab Customer Service at 314-653-4455.