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Serum Free Light Chain Immunoassay (Quantitative)

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

This test measures the levels of free light chains (kappa and lambda) in your serum, which are protein fragments produced by plasma cells. It helps diagnose conditions like multiple myeloma, lymphoma, or other monoclonal gammopathies.

Quick summary

["This test helps identify abnormal protein production that may signal serious blood disorders."]

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

Key facts at a glance

LOINC
59239-4
Short code
PSA Free Fld-mCnc
Synonyms
PSA Free Fld-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
4
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84153
SNOMED
39392002
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 Is This Test Done?

Your healthcare provider may order this test if you have symptoms like unexplained fatigue, frequent infections, bone pain, or if blood tests show unusual protein patterns. It’s also used to monitor treatment progress in certain cancers.

What Does the Test Measure?

The test detects free light chains (kappa and lambda) in your blood, which are small protein fragments. These chains are normally balanced, but in conditions like multiple myeloma, one type may become overproduced.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The serum is then analyzed using an immunoassay method to measure the concentration of free light chains.

What Are Common Results?

Results are reported as separate measurements for kappa and lambda light chains. Elevated levels of one type (or an imbalance) may indicate a disorder affecting plasma cells.

Reference range

Normal: <4.0 ng/mLN/A

Specimen: serum

No special preparation required. For PSA, avoid sexual activity for 24-48 hours before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test plays a key role in diagnosing and managing conditions like multiple myeloma, where abnormal plasma cells produce excessive light chains. It helps track disease progression and response to treatment by monitoring light chain levels.

Short name

Free Light Chain Test

Frequently asked questions

What does a high or low level of free light chains mean?
High levels of one type (kappa or lambda) alone or an imbalance between them can signal conditions like multiple myeloma or other monoclonal gammopathies. Your doctor will interpret results in the context of your symptoms and other tests.
How often should I get this test?
Your doctor will determine the frequency based on your diagnosis, symptoms, and treatment plan. Regular monitoring may be needed if you have a known disorder affecting plasma cells.
Does this test require fasting?
No fasting is required for this test. You can eat and drink normally before the blood draw.
  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