Free ? and ? Light Chains Plus Ratio, Quantitative

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

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

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

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