Serum Free Light Chains

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Also known as: Free Light Chains; SFLC; FLC; Kappa and Lambda Free Light Chains; Quantitative Serum Free Light Chains with Ratio
Formal name: Light Chains, Free; Free Kappa/Lambda Ratio

At a Glance

Why Get Tested?

To help detect, diagnose, and monitor light chain plasma cell disorders (dyscrasias) such as light chain multiple myeloma and primary amyloidosis, and to monitor the effectiveness of treatment.

When to Get Tested?

When you have bone pain, fractures, anaemiakidney disease, and recurrent infections that your doctor suspects are due to a plasma cell disorder; when you are being treated for a light chain plasma cell disorder.

Sample Required?

A blood sample drawn from a vein in your arm.

Test Preparation Needed?


The Test Sample

What is being tested?

The test measures the amount of free kappa and lambda light chains in the blood and calculates a kappa/lambda ratio. It does this to help detect, diagnose, and monitor conditions associated with an increased production of free light chains (FLC).

Kappa and lambda light chains and several types of heavy chains are proteins produced by plasma cells. The protein chains are used as component parts by the immune system to assemble immunoglobulins (Ig), antibodies that target and neutralize specific threats to the body, such as bacteria and virus.

Each type of immunoglobulin is composed of four protein chains - two identical heavy chains and two identical light chains. A particular plasma cell will produce only one type of immunoglobulin. Normally, there is a slight excess of free light chains produced, so low levels of free kappa and lambda chains can be detected in the blood.

With a group of conditions called plasma cell disorders (dyscrasias) or monoclonal gammopathies, a plasma cell becomes malignant, dividing uncontrollably and producing a large number of copies (clones) of itself that crowd out other cells in the bone marrow. Since the clones come from a single plasma cell, they produce large amounts of the same type of abnormal monoclonal immunoglobulin (M-protein). This may take the form of an intact immunoglobulin, a light chain, or rarely a heavy chain. Excess light chain production may be seen with any plasma cell disorder, such as multiple myelomaMGUS (monoclonal gammopathy of unknown significance – a condition that may progress to multiple myeloma), and monoclonal light chain (primary) amyloidosis. In the beginning, these conditions may cause few symptoms, but as time progresses, they can cause bone pain and fractures, anaemia, fatigue, weight loss, and kidney dysfunction.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.