Kappa/Lambda, Free, with Ratio (FRKLR)

Test Code

Quest Code

CPT Codes
83520 (x2)

Preferred Specimen
2 mL serum in gold top tube

Minimum Volume
1 mL

Other Acceptable Specimens
Plain red top tube

Transport Container
Transport tube

Transport Temperature

Room temperature

Specimen Stability
Room temperature: 72 hours
Refrigerated: 21 days
Frozen: 30 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis • Grossly lipemic • Microbially contaminated • Heavy visible particulate


Setup Schedule
Day shift Monday thru friday

Report Available

Reference Range
Kappa Light Chain, Free, Serum 3.3-19.4 mg/L
Lambda Light Chain, Free, Serum 5.7-26.3 mg/L
Kappa/Lambda Light Chains Free with Ratio, Serum 0.26-1.65

Clinical Significance
The Kappa/Lambda Light Chains, Free with Ratio, Serum test measures the amount of kappa and lambda free light chains (FLCs) in the blood and calculates the kappa to lambda ratio. It is used to assist in the diagnosis of plasma cell disorders, including multiple myeloma, primary amyloidosis, monoclonal gammopathy of unknown significance (MGUS), Waldenström’s macroglobulinemia, and related disorders. It is also used to monitor disease activity and treatment [1].

Kappa and lambda light chains link with heavy chains to form immunoglobulins. In healthy individuals, most serum light chains are bound to heavy chains. However, excess plasma-cell proliferation associated with plasma-cell disorders can cause an excess of circulating FLCs and increase or decrease the K/L ratio [1].

This test is intended for patients clinically suspected of having hematologic disease, based on certain symptoms and medical conditions. These include bone pain, bone fractures, normocytic anemia, kidney disease, and recurrent infections suggestive of an underlying plasma-cell disorder [1].

Note that blood samples that are grossly hemolyzed or lipemic or contain high levels of circulating immune complexes (CICs) should not be tested, because of the unpredictable degree of nonspecific scatter these sample types may generate.

1. AACC. Serum free light chains. https://labtestsonline.org/tests/serum-free-light-chains. Accessed September 3, 2019.

Performing Laboratory
Quest Diagnostics - South Region

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.