Examinations
Examinations
The analysis of free kappa light chains is used for the diagnosis and monitoring of monoclonal gammopathy.
Immunoglobulins (antibodies) are produced by lymphocytes and plasma cells. Each immunoglobulin molecule consists of two identical heavy chains and two identical light chains. Light chains are of two types: kappa and lambda. A single B-lymphocyte produces either kappa or lambda light chains, but not both simultaneously.
During antibody synthesis, light chains are produced in excess and are present in serum not only as part of immunoglobulin molecules but also as free light chains. The concentration of free light chains in serum depends on the balance between production and clearance.
Free light chains are cleared from the blood by the kidneys, filtered through the glomeruli, and metabolized in the proximal tubules. Under normal conditions, this process prevents the accumulation of free light chains. However, in the case of hyperproduction or impaired renal function, free light chains accumulate in the blood.
In plasma cell dyscrasias, such as multiple myeloma, monoclonal plasma cells produce excessive amounts of either kappa or lambda light chains. This results in an abnormal kappa/lambda ratio in serum, which is a key diagnostic marker for plasma cell disorders. Approximately 60–70% of patients with multiple myeloma show an abnormal kappa/lambda ratio.
The half-life of free light chains in serum is short (2–4 hours for kappa chains and 3–6 hours for lambda chains), making them an early and sensitive marker for treatment response. In about 20% of patients with multiple myeloma, the monoclonal protein consists solely of free light chains.
Studying the concentration of free light chains in plasma is valuable not only for diagnosis but also for monitoring treatment, especially in patients with renal impairment. Monoclonal free light chains are a major cause of kidney damage associated with multiple myeloma and related monoclonal gammopathies.
- Avoid alcohol consumption for 24 hours before the test.
- Children under 1 year should not eat for 30–40 minutes before the test.
- Adults should fast for 4 hours before the test; drinking non-carbonated water is allowed.
- Avoid physical and emotional stress for 30 minutes before the test.
- Do not smoke for 30 minutes before the test.
- Initial assessment, in addition to serum protein electrophoresis and immunofixation, in cases of suspected monoclonal gammopathy (this test may replace urine electrophoresis for certain diagnostic purposes, except for AL amyloidosis).
- Prognosis, risk assessment, and monitoring of patients with:
- Multiple myeloma.
- Solitary plasmacytoma.
- Non-secretory myeloma.
- Monoclonal gammopathy of undetermined significance (MGUS).
- AL amyloidosis.
- Screening nephrotoxic levels of free kappa chains for early detection of myeloma kidney.
Normal Results:
- Normal concentrations of free kappa and lambda light chains with a normal kappa/lambda ratio indicate that monoclonal gammopathy is unlikely, especially in the absence of paraproteins on serum protein electrophoresis.
Abnormal Results:
- An abnormal kappa/lambda ratio along with elevated levels of free kappa or lambda light chains suggests monoclonal gammopathy. Small deviations should be interpreted cautiously but may warrant further investigation.
- Borderline abnormalities in the kappa/lambda ratio may occur in patients with polyclonal increases in free light chains (e.g., due to renal impairment or hypergammaglobulinemia caused by infection or inflammation).
Criteria for Active Multiple Myeloma:
- According to the International Myeloma Working Group, an abnormal kappa/lambda ratio less than 0.01 or greater than 100 (along with absolute serum concentrations of the involved free light chain type ≥100 mg/L) is a diagnostic criterion for active multiple myeloma.
Low Free Light Chain Levels:
- The uninvolved free light chain type is typically suppressed and falls below the normal range.