Serum or Plasma Free Light Chain Ratio (kappa to lambda)
This test measures the balance of two types of light chains (kappa and lambda) found in your blood, which can help detect conditions affecting plasma cells, such as multiple myeloma or other monoclonal gammopathies.
["Assessing light chain imbalance may help diagnose or monitor blood disorders."]
Key facts at a glance
- LOINC
- 18046-3
- Short code
- LV EF US.2D.mod
- Synonyms
- LV EF US.2D.mod
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- us-d-mod
- 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, or unexplained bone pain. It may also be used to monitor conditions like multiple myeloma, lymphoma, or other plasma cell disorders. Sometimes, it’s part of a broader evaluation for kidney disease or other blood-related issues.
What Does the Test Measure?
The test measures the ratio of free kappa light chains to free lambda light chains in your serum or plasma. These light chains are fragments of heavy chains found in antibodies. An imbalance can indicate abnormal production of monoclonal proteins, which can affect blood cells and organs.
How Is the Test Performed?
A blood sample is drawn from a vein in your arm. The sample is then sent to a lab where it is analyzed using a specialized immunoassay method to separate and measure the kappa and lambda light chains.
What Are Common Results?
Results are typically reported as a ratio (e.g., kappa/lambda). A normal ratio is usually balanced (close to 1:1), but abnormal ratios can indicate conditions like multiple myeloma, where one type of light chain may dominate.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Free Light Chain Ratio
Frequently asked questions
An abnormal free light chain ratio may signal an underlying condition such as multiple myeloma, where plasma cells produce an excess of one type of light chain. It can also be used to monitor treatment response or detect early signs of kidney involvement in blood disorders.
An elevated ratio of one type of light chain (e.g., kappa or lambda) may suggest an overproduction of monoclonal proteins, which can lead to symptoms like kidney problems, infections, or bone pain. Your doctor will interpret results in the context of your symptoms and other tests.
If you have a diagnosed condition like multiple myeloma, your doctor may recommend regular monitoring of free light chain ratios to track disease progression or response to treatment. Follow their specific guidelines for follow-up testing.
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 16, 2026. · Read our editorial policy