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Cholesterol, Pleural Fluid/Serum Ratio

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

Compares cholesterol levels in pleural fluid and serum to help evaluate the cause of fluid around the lungs.

Quick summary

["This paired-sample ratio can help determine why fluid has accumulated around the lungs."]

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

Key facts at a glance

LOINC
70268-8
Short code
Chol Plr/Ser
Synonyms
Chol Plr/Ser
Category
lipid
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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

What is this test?

This test compares the amount of cholesterol in pleural fluid, the fluid surrounding the lungs, with the cholesterol level in blood serum. It is used as part of the evaluation of pleural effusions.

Why might I need this test?

A chest x-ray or ultrasound may show fluid around the lungs. This test can help clinicians distinguish between causes of pleural fluid, including fluid caused by heart, kidney, liver, or inflammatory conditions.

How is the test performed?

A blood sample is taken from a vein, and pleural fluid may be collected through a procedure called thoracentesis. The laboratory measures cholesterol in the samples and calculates the pleural fluid-to-serum ratio.

How do I prepare for the test?

Follow your clinician's instructions about eating, drinking, and medications. Pleural fluid collection requires a trained clinician and may involve temporary soreness or pressure at the procedure site.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Pleural Fluid Cholesterol Ratio

Frequently asked questions

What is pleural fluid?
Pleural fluid is the liquid that normally lubricates the space between the lung and chest wall. Excess fluid in this space is called a pleural effusion.
Why are blood and pleural fluid tested together?
Comparing the two cholesterol levels accounts for the cholesterol level in the blood. The resulting ratio is more useful than either measurement alone.
Does this result diagnose a specific condition?
No. The ratio can help narrow the cause of pleural fluid, but it must be interpreted with symptoms, imaging, and other laboratory findings.
  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