Days Set Up
Monday - Saturday
Analytic Time

2 - 3 days

Soft Order Code

Test Updated:


Phosphatidylglycerol (PG)
Lecithin/Sphingomyelin Ratio
Lecithin / Sphingomyelin Ratio
Fetal Lung Maturity
L/S Ratio

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Test Overview

Test Methodology

Thin-Layer Chromotography

Test Usage

Amniotic fluid test for fetal maturity, indicator to determine optimal time for obstetrical intervention in cases of possible fetal distress (maternal diabetes, toxemia, isoimmune hemolytic disease, postmaturity).

Reference Range

IMMATURE: L/S <2.5, Phosphatidylglycerol Absent; INDETERMINATE: L/S >=2.5, Phosphatidylglycerol Absent or L/S <2.5, Phosphatidylglycerol Trace; MATURE: L/S >=2.5, Phosphatidylglycerol Trace or L/S Any Ratio, Phosphatidylglycerol Present.

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Specimen Requirements

Collection Onsite

Amniotic fluid. Send sample to the laboratory IMMEDIATELY after collection. Fetal Lung Maturity screening test will be performed before L/S ratio is run; L/S ratio is not indicated if FLM is > or = 55mg/gm. Cause for Rejection: Specimen contaminated with blood.

Collection Offsite

Collect amniotic fluid. Centrifuge at 1000 rpm or 200 x G for 10 minutes, aliquot supernatent into a plastic tube and send both supernatent and sediment frozen. Label specimens appropriately, "supernatent" and "sediment". Include estimated duration of pregnancy (in weeks).

Normal Volume
10 mL amniotic fluid
Minimum Volume
3 mL amniotic fluid

Billing Information

CPT Code
83661 L/S Ratio, 84081 Phosphatidylglycerol
Pro Fee Code

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Our High Standard

Quality that sets us apart

As the reference laboratory division of Michigan Medicine's Department of Pathology, MLabs shares the institution's commitment to applying established quality principles to clinical laboratory testing. Like other large organizations in complex, consequential fields, we rely on an established approach to monitor quality throughout the testing process.