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Phospholipid Profile (Lecithin/Sphingomyelin Ratio) in Serum

Published: August 9, 2026Updated: August 16, 2026

This test measures the ratio of lecithin to sphingomyelin in your blood, often used to assess lung function, particularly in newborns or individuals with suspected lung disease.

Quick summary

["Helps evaluate lung maturity or potential respiratory conditions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
98027-6
Short code
Lecithin Smn Ql Micro
Synonyms
Lecithin Smn Ql Micro
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
microscopy-light
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Matters for Your Health

This test is primarily used in prenatal care to check lung development in a fetus or newborn. A higher lecithin-to-sphingomyelin ratio suggests mature lungs, reducing the risk of respiratory distress syndrome. It may also be used in adults with suspected lung disorders.

How the Test Works

Blood is drawn and analyzed to measure the natural phospholipids lecithin and sphingomyelin. The ratio of these substances is calculated to determine lung maturity or potential health risks.

Preparation Before the Test

No special preparation is needed. You may eat and drink normally before the test. If you are pregnant, inform your healthcare provider about any medications you are taking.

What to Expect During the Test

A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but it usually takes only a few minutes. You can resume normal activities immediately afterward.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Lecithin/Sphingomyelin Ratio

Frequently asked questions

When might I need this test?
This test is most commonly performed during pregnancy to assess fetal lung development or in newborns to diagnose respiratory issues. It may also be used in adults with suspected lung disorders.
What are the possible results and what do they mean?
Results are expressed as a ratio. A higher ratio typically indicates mature lungs. Your healthcare provider will interpret the results in the context of your medical history and symptoms.
Are there any risks or side effects?
The most common side effect is a slight bruise or minor discomfort at the injection site. Rarely, there may be a slight swelling or pain. Serious complications are very rare.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy