NEW
KAPPA/LAMBDA FREE LIGHT CHAINS,
SERUM
EFFECTIVE 11/19/2013
KAPPA/LAMBDA FREE LIGHT CHAINS, SERUM
LABP000459
Beginning 11/19/2013 the Special Chemistry section of the Department of Pathology and
Laboratory Medicine will begin performing the Kappa/Lambda Free Light Chains, Serum panel
inhouse. This assay was previously sent to UCSF; and our methodology and instrumentation are
the same as that at UCSF. The method is turbidimetric, and the analyzer is The Binding Site’s
SPAPLUS.
Measurement of free light chains aids in the diagnosis and monitoring of multiple myeloma,
lymphocytic neoplasms, Waldenström’s macroglobulinemia, AL amyloidosis, and light chain
deposition disease, when used in conjunction with other laboratory and clinical findings. Kappa
and lambda free light chains are ordered as a panel. The individual values, as well as, the
kappa/lambda ratios are reported.
Immunoglobulin molecules consist of two identical heavy chains (α, δ, ε, γ or μ) which 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 chain 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
over-production and secretion of FLC by the plasma cells. While the molecular weight of both
light chains is ~22.5 kD, in serum, κ free light chain (κ-FLC) exists predominantly as a monomer
and λ free light chain (λ-FLC) exists as a covalently linked dimer with a molecular weight of ~45
kD. This leads 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.
Elevated serum levels of monoclonal FLC are associated with the diseases mentioned above.
Patients with renal impairment can have κ/λ FLC ratios above the reference range [when
compared to non-renal impaired patients] with no other evidence of monoclonal proteins. This
reflects a change in the dynamics of serum FLC clearance in renal failure.
Sample Requirements
Collect:
One 4-mL SST (gold top) or serum (red top) vacutainer tube.
(Minimum volume of serum: 0.5 mL). Avoid hemolysis.
Patient Preparation:
An 8 hour fast is recommended to avoid lipemia.
Specimen Preparation:
Storage/Transport:
Separate serum from cells as soon as possible.
Transport separated serum at 2-8°C. Serum is stable 21 days at
2-8°C; for longer term storage, freeze at -20°C.
Unacceptable Conditions:
Sample type other than serum. GROSSLY LIPEMIC or
GROSSLY HEMOLYZED samples.
LIS mnemonic: FKL
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Reference Interval:
For Normal renal function (EGFR ≥ 60 mLs/min/1.73m
Free Kappa Light Chains
3.3 - 19.4 mg/L
Free Lambda Light Chains
5.7 - 26.3 mg/L
K/L Ratio
0.26 - 1.65
3
3
For patients with EGFR < 60 mL/min/1.73m
K/L Ratio
0.37 – 3.1
Routine Testing:
Tuesday and Thursday day shift, STAT testing is not available.
Interpretation of Results
Kappa and lambda free light chain results should be considered under the following categories
and investigated appropriately:
Test Results
Normal samples: serum kappa, lambda,
and kappa/lambda ratio are all within the
normal ranges.
Abnormal kappa/lambda ratio
Low concentrations of kappa, lambda, or
both
Elevated concentrations of both kappa
and lambda with normal kappa/lambda
ratio
Elevated concentrations of both kappa
and lambda with an abnormal
kappa/lambda ratio
Interpretation
If accompanying serum electrophoretic tests are
normal, monoclonal gammopathy is unlikely.
Supports the diagnosis of a monoclonal
gammopathy and requires further investigation.
Borderline elevated kappa/lambda ratios occur
with renal impairment, and may require
appropriate renal function tests.
Indicate bone marrow suppression.
May be due to (1) renal impairment (common);
(2) Over-production of polyclonal FLC from
inflammatory conditions (common); (3) Biclonal
gammopathies of different FLC types (rare).
Suggest a combination of monoclonal
gammopathy and renal impairment.
If you have questions or need additional information please contact Laboratory Client Services at
734-7373 or email pathologyclientservices@ucdmc.ucdavis.edu.
LIS mnemonic: FKL
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