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Pleural Fluid Albumin Test

Published: July 31, 2026Updated: August 17, 2026

This test measures the amount of albumin, a protein made by the liver, in fluid that has collected in the space around your lungs inside the chest.

Quick summary

{"Albumin is a protein made by the liver that helps maintain fluid balance in the body","This test helps doctors determine if fluid in the chest is a transudate or exudate","Results help identify the cause of fluid buildup around the lungs"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
1748-3
Short code
ALB PF
Synonyms
Albumin Plr-mCnc
Category
chemistry
Sample
fluid
Container
Sterile collection container (plain red-top tube or sterile falcon tube)
Units
not specified
Ref low
1
Ref high
3
Critical range
1.5 not specified – —
Fasting
false
Population
adult
Sex
all
Age range
≥ 18 years
Method
Colorimetric assay (bromocresol green or bromocresol purple method)
CPT
82085
SNOMED
444164008
Specimen volume
1-3 mL of pleural fluid minimum; 5-10 mL preferred for comprehensive analysis
Stability
Room temperature: 24 hours; Refrigerated (2-8°C): 72 hours. Avoid freezing. Centrifuge if analysis delayed >24 hours.
Hemolysis max
50
Lipemia max
100
Icterus max
20
TAT
4–24 hours
Order
routine

What is this test?

The Pleural Fluid Albumin test measures the concentration of albumin in fluid that has accumulated in the pleural space (the area between your lungs and chest wall). This fluid is called pleural fluid. The test is part of a group of tests called pleural fluid analysis, which helps doctors understand why fluid is building up in your chest.

Albumin is a protein produced by your liver that plays a crucial role in keeping fluid inside your blood vessels. When the balance of albumin or pressure in your blood vessels changes, fluid can leak into spaces like the pleural cavity, causing what doctors call pleural effusion.

During the test, a doctor will use a thin needle to withdraw a small sample of pleural fluid from your chest. This procedure is called thoracentesis. The sample is then sent to a laboratory where technicians measure the albumin concentration.

Why might I need this test?

Your doctor may order this test if you have symptoms of pleural effusion, such as shortness of breath, chest pain, or a persistent cough. The test helps determine the cause of the fluid buildup, which can include heart failure, liver disease, kidney disease, infection, cancer, or tuberculosis.

How to prepare

Before the test, tell your doctor about all medications you are taking, especially blood thinners. You may need to stop taking certain medications temporarily. The procedure is usually done while you are awake but may use local anesthesia to numb the area. You may have a chest X-ray before or after the procedure to check your lungs.

Reference range

Not established (interpret relative to concurrent serum albumin)not specified

Specimen: fluid

No special preparation; specimen obtained by thoracentesis

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

The pleural fluid albumin level helps distinguish between two types of pleural fluid: transudates and exudates. Transudates are caused by systemic factors like heart failure or liver cirrhosis, while exudates are caused by local inflammation or infection. This distinction is critical for determining the underlying cause and appropriate treatment.

When compared with blood albumin levels, doctors can calculate the pleural fluid to serum albumin ratio. A ratio greater than 0.5 suggests an exudate, while a ratio less than 0.5 suggests a transudate. This information guides further testing and treatment decisions.

Abnormal albumin levels in pleural fluid may indicate conditions such as congestive heart failure (transudate), pneumonia, tuberculosis, lung cancer, or rheumatoid arthritis (exudates). The test is often performed together with other pleural fluid tests including protein, glucose, LDH, and cell count for a complete picture.

Frequently asked questions

Is the thoracentesis procedure painful?
You may feel some discomfort or pressure during the procedure, but the area is numbed with local anesthesia. You may feel some soreness in your chest for a day or two afterward. Serious complications are rare but can include infection, bleeding, or pneumothorax (air in the chest cavity).
How long does it take to get results?
Results are typically available within 1-2 days, depending on the laboratory. Your doctor will discuss the results with you and explain what they mean for your specific condition.
What do high albumin levels mean?
High albumin levels in pleural fluid (exudate) usually indicate local inflammation, infection, or disease such as pneumonia, tuberculosis, cancer, or autoimmune conditions. This is different from conditions that cause fluid buildup due to systemic imbalances.
What do low albumin levels mean?
Low albumin levels in pleural fluid (transudate) typically indicate that the fluid buildup is due to systemic problems rather than local disease. Common causes include heart failure, liver cirrhosis, nephrotic syndrome, or malnutrition.
Will I need other tests?
Yes, pleural fluid albumin is usually interpreted along with other tests including pleural fluid protein, lactate dehydrogenase (LDH), glucose, pH, and cell count. Your doctor may also order blood tests to compare albumin levels between your blood and the pleural fluid.
  1. 1
    Mayo Clinic - Pleural effusionSource
  2. 2
    MedlinePlus - Pleural fluid analysisSource
  3. 3
    American Thoracic Society - Pleural DiseaseSource

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 17, 2026. · Read our editorial policy