Free ? and ? Light Chains Plus Ratio, Quantitative

Overview:

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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