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Test Code FLCS Immunoglobulin Free Light Chains, Serum

Specimen Required


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 1 mL

Secondary ID


Useful For

Monitoring serum from patients with monoclonal light chain diseases without a M-spike on protein electrophoresis


May be useful as a diagnostic test in patients in whom there is a suspicion of primary systemic amyloidosis, light chain deposition disease, or non-secretory myeloma

Profile Information

Test ID Reporting Name Available Separately Always Performed
KFLCS Kappa Free Light Chain, S No Yes
LFLCS Lambda Free Light Chain, S No Yes
KLRS Kappa/Lambda FLC Ratio No Yes

Testing Algorithm

The following algorithms are available in Special Instructions:

-Laboratory Approach to the Diagnosis of Amyloidosis

-Laboratory Screening Tests for Suspected Multiple Myeloma

Method Name


Reporting Name

Immunoglobulin Free Light Chains, S

Specimen Type


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  72 hours

Reject Due To

Gross hemolysis OK
Gross lipemia Reject
Gross icterus OK

Reference Values


0.33-1.94 mg/dL



0.57-2.63 mg/dL




Clinical Reference

1. Kaleta E, Kyle R, Clark R, Katzmann J: Analysis of patients with gamma-heavy chain disease by the heavy/light chain and free light chain assays. Clin Chem Lab Med. 2014;52(5): 665-669. doi: 10.1515/cclm-2013-0714

2. Palladini G, Russo P, Bosoni T, et al: Identification of amyloidogenic light chains requires the combination of serum-free light chain assay with immunofixation of serum and urine. Clin Chem. 2009;55(3): 499-504. doi: 10.1373/clinchem.2008.117143

3. Dispenzieri A, Kyle R, Merlini G, et al: International Myeloma Working Group guidelines for serum-free light chain analysis in multiple myeloma and related disorders. Leukemia. 2009;23(2): 215-224. doi: 10.1038/leu.2008.307

4. Drayson M, Tang LX, Drew R, et al: Serum free light chain measurements for identifying and monitoring patients with nonsecretory multiple myeloma. Blood. 2001;97(9):2900-2902

Method Description

The determination of the soluble antigen concentration by turbidimetric methods involves the reaction with specific antiserum to form insoluble complexes. When light is passed through the suspension formed a portion of the light is transmitted and focused onto a photodiode by an optical lens system. The amount of transmitted light is indirectly proportional to the specific protein concentration in the test sample. Concentrations are automatically calculated by reference to a calibrations curve stored within the instrument.(Package inserts: Optilite Freelite Kappa Free Kit. The Binding Site Group, Ltd; 06/2015; Optilite Freelite Lambda Free Kit. The Binding Site Group, Ltd; 06/2015)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been cleared, approved or is exempt by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

83520 x2

LOINC Code Information

Test ID Test Order Name Order LOINC Value
FLCS Immunoglobulin Free Light Chains, S In Process


Result ID Test Result Name Result LOINC Value
LFLCS Lambda Free Light Chain, S 33944-0
KLRS Kappa/Lambda FLC Ratio 48378-4
KFLCS Kappa Free Light Chain, S 36916-5