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 plasma cell disorders (dyscrasias) such as multiple myeloma and primary amyloidosis, and to monitor the effectiveness of treatment

When to Get Tested?

When you have bone pain, fractures, anemia, kidney disease, and recurrent infections that your health practitioner suspects are due to a plasma cell disorder; when you are being treated for a plasma cell disorder

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Light chains are proteins produced by immune cells called plasma cells. Also called kappa and lambda light chains, they link together with other proteins (heavy chains) to form immunoglobulins, or antibodies that target and neutralize specific threats to the body such as bacteria and viruses. Free light chains (FLC) or serum free light chains (SFLC) refer to those that are not part of whole (intact) immunoglobulins and are present in the blood. This test measures the amount of free kappa and lambda light chains in the blood and calculates a kappa/lambda ratio to help detect, diagnose, and monitor conditions associated with an increased production of free light chains.

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 of the plasma cell disorders, such as multiple myeloma, MGUS (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, anemia, 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.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

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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Article Sources

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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.

Sources Used in Current Review

Tosi, P. et. al. (2013). Serum Free Light-chain Assay for the Detection and Monitoring of Multiple Myeloma and Related Conditions. Medscape Multispecialty from Ther Adv Hem. 2013;4(1):37-41. [On-line information]. Available online at http://www.medscape.com/viewarticle/779242 through http://www.medscape.com. Accessed December 2013.

Charafeddine, K. et. al. (2012). Extended Use of Serum Free Light Chain as a Biomarker in Lymphoproliferative Disorders. Medscape Multispecialty from Am J Clin Pathol. 2012;137(6):890-897. [On-line information]. Available online at http://www.medscape.com/viewarticle/765905 through http://www.medscape.com. Accessed December 2013.

Parmar, M. (Updated 2013 April 18). Light Chain-Associated Renal Disorders. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/244082-overview through http://emedicine.medscape.com. Accessed December 2013.

Bahler, D. et. al. (Updated 2013 June). Plasma Cell Dyscrasias. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/PlasmaCellDyscrasias.html?client_ID=LTD#tabs=0 through http://www.arupconsult.com. Accessed December 2013.

(© 1995–2013). Immunoglobulin Free Light Chains, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/84190 through http://www.mayomedicallaboratories.com. Accessed December 2013.

Boppana, S. and Sacher, R. (Updated 2013 April 29). Light-Chain Deposition Disease. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/202585-overview through http://emedicine.medscape.com. Accessed December 2013

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 150-151.

Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 243-244.

Sources Used in Previous Reviews

Rogoski, R. (2009 July). Serum free light chain assays: Detecting plasma cell disorders. Medical Laboratory Observer [On-line information]. Available online at http://www.mlo-online.com/features/2009_july/0709_coverstory.aspx through http://www.mlo-online.com. Accessed August 2010.

(© 1995–2010). Unit Code 84190: Immunoglobulin Free Light Chains, Serum. Mayo Clinic, Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/84190 through http://www.mayomedicallaboratories.com. Accessed August 2010.

Delgado, J. et. al. (Updated 2010 August). Plasma Cell Dyscrasias. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/PlasmaCellDyscrasias.html?client_ID=LTD#tabs=0 through http://www.arupconsult.com. Accessed August 2010.

Grethlein, S. and Thomas, L. (Updated 2010 June 28). Multiple Myeloma. eMedicine. [On-line information]. Available online at http://emedicine.medscape.com/article/204369-overview through http://emedicine.medscape.com. Accessed August 2010.

Hutchison, C. et. al. (2008 November 5). Serum Free Light Chain Measurement Aids the Diagnosis of Myeloma in Patients With Severe Renal Failure. Medscape from BMC Nephrology [On-line information]. Available online at http://www.medscape.com/viewarticle/582826 through http://www.medscape.com. Accessed August 2010.

Faix, J. (2009 March/April). Serum Free Light Chain for Monoclonal Immunoglobulin Detection and Management. Stanford Hospital and Clinics, LABletter [On-line information]. PDF available for download at http://www.stanfordlab.com/images/PDF/2009MarApr.pdf through http://www.stanfordlab.com. Accessed August 2010.

Nau, K. and Lewis, W. (2008 October 1). Multiple Myeloma. Am Fam Physician. 2008 Oct 1;78(7): 853-859 [On-line information]. Available online at http://www.aafp.org/afp/2008/1001/p853.html through http://www.aafp.org. Accessed August 2010.

Hutchison, C. et. al. (2009 November). Serum free light chain assessment in monoclonal gammopathy and kidney disease. Nature Reviews Nephrology 5, 621-628 [On-line information]. Available online at http://www.nature.com/nrneph/journal/v5/n11/full/nrneph.2009.151.html through http://www.nature.com. Accessed August 2010.

Killingsworth, L. (2009 January). Free Light Chain Assays, Enhanced Tools for the Diagnosis and Monitoring of Monoclonal Gammopathies. PAML Test Update [On-line information]. PDF available for download at http://www.paml.com/Files/TestUpdates/38270747_TestUpdateFreeLightChainAssays.pdf through http://www.paml.com. Accessed August 2010.

Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 203.

Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 674-675.

Dispenzieri A, et al. International Myeloma Working Group guidelines for serum-free light chain analysis in multiple myeloma and related disorders. Leukemia (2009) 23, 215–224. Available onlien at http://www.nature.com/leu/journal/v23/n2/full/leu2008307a.html through http://www.nature.com. Accessed September 2010.

MayoClinic.com. Amyloidosis. Available online at http://www.mayoclinic.com/health/amyloidosis/DS00431 through http://www.mayoclinic.com. Accessed September 2010.

(October 5, 2005) Amyloidosis Foundation. What is amyloidosis? Available online at http://amyloidosis.org/whatisit.asp. Accessed September 2010.

(January 2010) Cancer.net. Amyloidosis. Availble online at http://www.cancer.net/patient/Cancer+Types/Amyloidosis?sectionTitle=Symptoms through http://www.cancer.net. Accessed September 2010.