Serum Free Light Chains (Kappa & Lambda)

What is Serum Free Light Chain (Kappa & Lambda) test?

The serum free light chains (sFLC) assay measures the amounts of unbound immunoglobulin light chains—kappa (κ) and lambda (λ)—circulating in blood and calculates the κ/λ ratio to assess for monoclonal overproduction by clonal plasma cells, aiding diagnosis and monitoring of plasma cell disorders such as multiple myeloma, AL amyloidosis, and related conditions.

Why consider Serum Free Light Chain (Kappa & Lambda) test?

• It improves detection and monitoring of plasma cell disorders.
• The kappa/lambda ratio helps distinguish monoclonal excess from polyclonal elevations due to inflammation or renal impairment, guiding further workup and reducing false positives when interpreted with appropriate reference intervals.
• International Myeloma Working Group (IMWG) criteria incorporate sFLC as a myeloma-defining event that can establish a diagnosis of active multiple myeloma even before classic CRAB features develop.

Who should get this Serum Free Light Chain (Kappa & Lambda) test?

• Individuals being evaluated for suspected monoclonal gammopathy (unexplained anemia, bone pain/lesions, hypercalcemia, renal dysfunction, neuropathy, cardiomyopathy suggestive of amyloidosis), typically alongside serum protein electrophoresis and immunofixation per guideline-based screening strategies.
• Patients with known plasma cell disorders (MGUS, smoldering myeloma, multiple myeloma, AL amyloidosis, light chain deposition disease) for disease monitoring and treatment response assessment, particularly when disease is light chain–predominant or oligosecretory/nonsecretory.
• Patients with CKD and suspected monoclonal disease, where interpretation should use kidney- and eGFR-adjusted reference intervals to avoid misclassification.

More Information - Serum Light Chains (Kappa & Lambda)

Multiple myeloma is a malignant clonal proliferation of plasma cells in the bone marrow that produce a monoclonal immunoglobulin (M‑protein) or free light chains, leading to organ damage. Diagnosis hinges on demonstrating clonal plasma cells plus specific biomarkers or end‑organ effects and then staging/risk‑stratifying the disease to guide therapy.

Other Names – Multiple Myeloma, Free light Chain test, Kappa chain test, Lambda chain test, multiple myeloma panel, Serum Free Light Chain test, Kappa Lambda Light chain test, Kappa Lambda Ratio