L/S Ratio

Test Code

CPT Codes
83661

Preferred Specimen

Amniotic Fluid

Minimum Volume

3 ml

Other Acceptable Specimens

Vaginal pool

Instructions

PROTECT FROM LIGHT

Transport Container

SPECIAL/1

Transport Temperature

Amniotic fluid must be on ice.

Specimen Stability

3 Hrs on ice

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

specimen at room temp too long

Methodology
TLC

Setup Schedule

Monday - Friday, 8:00 - 14:00, Report available: Upon Completion of Analysis

Report Available

Upon Completion to Analysis

Limitations

**Precence of blood will elevate result**

Reference Range

Ratio of 1.5 or less indicates immaturity
Ratio of 1.5 - 1.9 is borderline
Ratio of 2.0 or greater indicates maturity(PI is present after 30 weeks and peaks at 36-37 weeks. PG appears after 35 weeks and increases beyond term.

Clinical Significance

The determination of lectithin levels in amniotic fluid is the most sensitive method for estimating fetal lung maturity. A deficiency of surfactant in the lungs is considered the primary etiological defect in RDS. In the mature lung 90-95% of the lipids are phosphlipids, the major surface active component is dipalmitoyl lecithin. The second major component is phosphatidyglycerol(PG), and other minor components including sphingomyelin. As the pregnancy progresses, the sphingomyelin level remains fairly constant while the lecithin level continues to increase, showing a very sharp increase after the 35th week.

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.