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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Kappa/Lambda Quantitative Free Light

Test Code(s): KLLTCH / XKAPLAM

CPT Code(s): 83883 x 2

Methodology: Nephelometry

Clinical Significance: Serum free light chain (FLC) assay is a new test to detect abnormal ratios of free light chains in the serum. The test is reported as a ratio that can be used to support a diagnosis of a plasma cell disorder. The serum FLC assay involves the binding of antibodies to light chains when they are free but not when they are bound to heavy chains in intact immunoglobulin molecules. Abnormalities of the free light chain ratio (kappa/lambda) provide a more sensitive indication of monoclonal disease than simple elevations of one light chain. This is because a plasma cell tumor will usually express a surplus of one light chain but also suppress the production of the alternate light chain. FLC testing is now recommended for the initial evaluation of suspected myeloma; for prognosis of plasma cell dyscrasias; and for monitoring oligosecretory myeloma and AL amyloidosis.

Days Performed: Mon-Fri, dayshift.

Turnaround Time: Stat: Not available stat.
Routine: 4 days.

Specimen Requirements

Specimen: Blood

Collection Instructions: If there is the possibility that the patient has a cryoprotein, specimen MUST BE KEPT WARM UNTIL AFTER TESTING IS COMPLETE.

BEFORE COLLECTING SPECIMEN, pre-warm a collection tube (e.g. in an infant heel warmer). Have another infant heel warmer on hand to deliver the blood to the laboratory after collection. Keep specimen at 37C by wrapping a hot pack (infant heel warmer) around the tube immediately after collection. Transport specimen to UWHC Core laboratory (B4/220) within 10 minutes of collection. Contact laboratory if unable to assure delivery within 10 mintues.

Collection Container: Preferred: Red top
Also Acceptable: Red cap with yellow ring (SST)

Collection Volume: Preferred: 3 mL
Pediatrics: 1 mL

Sample Analyzed: Serum

Volume Required: Preferred: 1 mL
Pediatrics: 0.3 mL

Specimen Processing: Transfer cell-free serum to plastic vial. Refrigerate.

For samples from patients suspected of having a cryoprotein, keep collection tube at 37C during entire processing procedure. Place collection tube in 37C incubator for two hours. Spin tube at 3000 rpm for 10 minutes at 37C. Remove spun serum to labeled tube. Place WARM sticker on tube and refrigerate.

Specimen Transport: Transport specimen to UWHC Core Laboratory (B4/220). Transport with coolant pack if coming from UWHC Satellite lab location.

For samples on patients suspected of having a cryoprotein, transport blood specimen to UWHC Core Laboratory (B4/220) within 10 minutes of collection. Keep specimen at 37C by wrapping tube in a hot pack (infant heel warmer). Specimen MUST be processed using the Specimen Processing procedure above prior to transport if coming from a UWHC Satellite lab location. Write WARM on the tube and transport  with coolant pack after processing is complete.

Outreach Specimen Transport: IF THE PATIENT HAS A CRYOPROTEIN, specimen MUST be collected and processed using the Collection and Specimen Processing procedures above prior to transport. Write WARM on the tube and transport with coolant pack after processing is complete.

Unacceptable Criteria: Grossly hemolyzed samples are not acceptable.

Stability: Ambient: Not acceptable
Refrigerated: 21 days
Frozen: No limit when stored at or below -20 C


Reference Interval:

Reference interval: 0 days to 9 years-- No reference interval available


10 years and up:


Kappa Free Light Chain: 0.33-1.94 mg/dL
Lambda Free Light Chain:

0.57-2.63 mg/dL

Kappa/Lambda FLC Ratio: 0.26-1.65


Reference intervals apply to individuals with normal renal function.  


Test Limitations:

The specificity of this assay for detection of monoconal light chains relies on the ratio of free kappa and lambda light chains. Once an abnormal FLC K/L ratio has been demonstrated and a diagnosis has been made, the quantitation of the monoclonal light chain is useful for monitoring disease activity.


Changes in FLC quantitation reflect changes in the size of the monoclonal plasma cell population. Experience to date is limited, but changes of >25% or trending of multiple specimens are needed to conclude biological significance.

Free Light Chains, Kappa FLC, Kappa Free Light Chains, Lambda FLC, Lambda Free Light Chains, Serum Free Light Chains, FLC Ratio, Kappa Lambda Free Light Ratio, Serum FLC, FLC

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