Serum Free Light Chain Immunoassay (Quantitative)
This test measures the free light chains (κ or λ) produced by plasma cells, often used to monitor conditions like multiple myeloma or other B-cell disorders.
["This test helps track protein abnormalities linked to certain cancers or immune system disorders."]
Key facts at a glance
- LOINC
- 109305-3
- Short code
- SFLC
- Synonyms
- BJ Protein Free Msmt Ser
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or red-top vacutainer tube
- Units
- N/A
- Ref low
- 3.3
- Ref high
- 19.4
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–99 years
- Method
- Nephelometry or Turbidimetry (latex-enhanced immunoassay)
- CPT
- 83521
- SNOMED
- 395122002
- Specimen volume
- 1.0 mL serum (minimum 0.5 mL)
- Stability
- Room temperature: 8 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 3 months. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 50
- TAT
- 24–72 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order this test if you have symptoms like unexplained fatigue, frequent infections, or kidney problems, or if you’ve been diagnosed with a blood-related condition like multiple myeloma or lymphoma. It helps assess whether abnormal light chains are present in your bloodstream.
What Does the Test Involve?
A blood sample is drawn from a vein in your arm. The serum (liquid part of blood after clotting) is then tested for free light chains using an immunoassay method to detect and measure their concentration.
What Are Free Light Chains?
Light chains are small protein fragments produced by healthy plasma cells. When plasma cells become cancerous (e.g., in multiple myeloma), they may overproduce abnormal light chains, which can accumulate in the blood or kidneys and cause health issues.
How Might Results Affect My Care?
Elevated levels of free light chains can indicate conditions like multiple myeloma, amyloidosis, or other B-cell disorders. Your doctor will use these results alongside other tests and symptoms to guide treatment decisions, such as monitoring disease progression or adjusting therapy.
Reference range
Kappa free light chains: 3.3-19.4 mg/L; Lambda free light chains: 5.7-26.3 mg/L; Kappa/Lambda ratio: 0.26-1.65. Reference ranges vary by assay manufacturer (e.g., Freelite, N Latex)N/A
No special preparation required. Fasting is not necessary. Patients should maintain normal hydration prior to specimen collection.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: Free Light Chains in Health and Disease
Short name
Free Light Chain Test
Frequently asked questions
What does a high or low result mean?
How often will I need this test?
Can I prepare for this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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 15, 2026. · Read our editorial policy