Free κ and λ Light Chains Plus Ratio, Quantitative

CPT: 83883(x2)
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Test Details

Synonyms

  • Freelite®
  • Kappa Free Light Chains, Quantitative, Serum
  • Kappa:Lambda Free Light Chains Ratio, Quantitative, Serum
  • Kappa:Lambda Free Light Chains, Quantitative, Serum
  • Lambda Free Light Chains, Quantitative, Serum
  • Light Chains, Free κ and Free λ, Quantitative, Serum

Test Includes

κ free light chain quantitation in serum; λ free light chain quantitation in serum; calculated κ:λ light chains ratio in serum

Use

Free light chain (FLC) results should be considered under the following categories and investigated appropriately (κ = kappa free light chain; λ = lambda free light chain).

1. Normal samples: Serum κ, λ, and κ:λ are all within the normal ranges. If accompanying serum electrophoretic tests are normal, it is most unlikely that the patient has a monoclonal gammopathy.

2. Abnormal κ:λ ratios: Support the diagnosis of a monoclonal gammopathy and require an appropriate tissue biopsy. Borderline elevated κ:λ ratios occur with renal impairment and may require appropriate renal function tests.

3. Low concentrations of κ, λ, or both: Indicate bone marrow function impairment.

4. Elevated concentrations of both κ and λ with a normal κ:λ ratio: May be due to the following:

• Renal impairment (common)

• Overproduction of polyclonal FLCs from inflammatory conditions (common)

• Biclonal gammopathies of different FLC types (rare)

5. Elevated concentrations of both κ and λ with an abnormal κ:λ ratio: Suggest a combination of monoclonal gammopathy and renal impairment.

Interpretation of Serum-free Light Chain Results

Kappa (κ)

Lambda (λ)

κ:λ Ratio

Interpretation

Key: BM = bone marrow; MG = monoclonal gammopathy; pIg = polyclonal immunoglobulin.

Normal

Normal

Normal

Normal serum

Low

Low

Normal

BM suppression without MG

High

MG with BM suppression

Low

Normal

Normal

Normal serum or BM suppression

Low

MG with BM suppression

High

Low

Normal

Low

High

MG with BM suppression

Normal

Normal serum or BM suppression

Normal

High

MG with BM suppression

Low

High

Normal

pIg increase or renal impairment

Low

MG without BM suppression

High

Low

High

MG with BM suppression

Normal

High

MG without BM suppression

Normal

pIg increase or renal impairment

High

Normal

High

MG with renal impairment

Low

Methodology

Immunologic

Reference Interval

• Free κ light chains: 3.3−19.4 mg/L

• Free λ light chains: 5.7−26.3 mg/L

• κ:λ free light chain ratio: 0.26−1.65

Additional Information

Immunoglobulin molecules consist of two identical heavy chains (α, δ, ε, γ, or μ) that define the immunoglobulin class and two identical light chains (κ or λ). Each light chain is covalently linked to a heavy chain and the two heavy chains are linked covalently at the hinge region. In healthy individuals, the majority of light chains in serum exists in this form, bound to heavy chain; however, low levels of free light chain (FLC) are found in serum of normal individuals due to the overproduction and secretion of FLC by the plasma cells. While the molecular weight of both light chains is approximately 22.5 kilodaltons, in serum, κ free light chain (κ-FLC) exists primarily as a monomer and λ free light chain (λ-FLC) as a covalently-linked dimer with a molecular weight of approximately 45 kilodaltons. This will lead to a differential glomerular filtration rate for κ-FLC and λ-FLC and may explain the observed ratio of κ-FLC to λ-FLC of 0.625 in serum compared to the ratio of bound κ to λ of 2.0.

FLC levels in urine are low. In a healthy kidney, the tubular cells selectively reabsorb all FLC so their presence in urine is probably due to secretion into the urinary tract.

Elevated serum levels of monoclonal FLC are associated with malignant plasma cell proliferation (eg, multiple myeloma), primary amyloidosis, and light chain deposition disease. Raised serum levels of polyclonal FLC may be associated with autoimmune diseases such as systemic lupus erythematosus. The appearance of higher levels of FLC in urine may be indicative of kidney disease or malignant lymphoproliferative disease such as multiple myeloma. The monoclonal urinary FLC associated with lymphoid malignancy is called a Bence Jones protein.

Specimen Requirements

Specimen

Serum

Volume

0.5 mL

Minimum Volume

0.2 mL

Container

Red-top tube or gel-barrier tube

Patient Preparation

Patient should be fasting for eight hours to avoid lipemic sample interference.

Collection

Separate serum immediately after coagulation (30 minutes) to prevent hemolysis. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions

Refrigerate; samples are stable for 21 days at 2°C to 8°C. For longer storage, freeze at -20°C.

Causes for Rejection

Microbially-contaminated specimen; specimen containing particulate matter; lipemic or hemolyzed specimen

Clinical Information

Special Instructions

Values obtained with different assay methods should not be used interchangeably in serial testing. It is recommended that only one assay method be used consistently to monitor each patient's course of therapy. This procedure does not provide serial monitoring; it is intended for one-time use only. If serial monitoring is required, please use the serial monitoring number 121155 to order.

References

Bradwell AR, Carr-Smith HD, Mead GP, et al. Highly sensitive, automated immunoassay for immunoglobulin free light chains in serum and urine. Clin Chem. 2001; 47(4):673-680. 11274017
Carr-Smith HD, Smith L, Mead GP, et al. Development of serum free light chain immunoassays for the detection and monitoring of patients with Bence Jones myeloma. Proceedings of the VIIIth International Myeloma Workshop, Banff, Canada, May 2001, p176.
Cole PW, Durie BGM, Salmon SE. Immunoquantitation of free light chain immunoglobulins: applications in multiple myeloma. J Immunol Methods. 1978; 19(4):341-349. 416145
Drayson M, Tang LX, Drew R, Mead GP, Carr-Smith H, Bradwell AR. Serum free light-chain measurements for identifying and monitoring patients with nonsecretory multiple myeloma. Blood. 2001 May 1; 97(9):2900-2902. 11313287
Katzmann JA, Clark RJ, Abraham RS, et al. Serum reference intervals and diagnostic ranges for free kappa and free lambda immunoglobulin light chains: Relative sensitivity for detection of monoclonal light chains. Clin Chem. 2002 Sep; 48(9):1437-1444. 12194920
Pascali E, Pezzoli A. The clinical spectrum of pure Bence Jones proteinuria. A study of 66 patients. Cancer. 1988 Dec 1; 62(11):2408-2415. 3179959
Sølling K, Sølling J, Rømer FK. Free light chains of immunoglobulins in serum from patients with rheumatoid arthritis, sarcoidosis, chronic infections and pulmonary cancer. Acta Med Scand. 1981; 209(6):473-477. 6266206
Tang LX, Showell P, Carr-Smith HD, et al. Evaluation of F (ab′)(2)-based latex-enhanced nephelometric reagents for free immunoglobulin light-chains on the Behring Nephelometer II. Clin Chem. 2000 Jun; 46:(6 Suppl):705, A181.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
121137 Free K+L Lt Chains,Qn,S 121138 Free Kappa Lt Chains,S mg/L 36916-5
121137 Free K+L Lt Chains,Qn,S 121139 Free Lambda Lt Chains,S mg/L 33944-0
121137 Free K+L Lt Chains,Qn,S 121140 Kappa/Lambda Ratio,S 48378-4

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