From the Guidelines
Elevated kappa free light chains (FLC) with normal immunofixation and protein electrophoresis results is a significant finding that may indicate a condition that requires close monitoring, such as monoclonal gammopathy of undetermined significance (MGUS) or smoldering multiple myeloma 1.
Key Considerations
- It is recommended to repeat the FLC test in 3-6 months to assess for stability or progression 1.
- Additionally, consider ordering a serum protein electrophoresis (SPEP) with immunofixation, urine protein electrophoresis (UPEP) with immunofixation, and a complete blood count (CBC) with differential to rule out underlying plasma cell disorders or other conditions 1.
- If the elevated kappa FLC persists, referral to a hematologist for further evaluation and consideration of a bone marrow biopsy may be necessary 1.
- In the meantime, it is essential to monitor the patient's kidney function, blood cell counts, and overall clinical status 1.
Prognostic Value
The serum FLC assay has prognostic value in plasma cell disorders, including monoclonal gammopathy of undetermined significance, smoldering myeloma, active myeloma, immunoglobulin light chain amyloidosis, and solitary plasmacytoma 1.
Limitations
The serum FLC assay cannot replace the 24-hour urine protein electrophoresis for monitoring patients with measurable urinary M-protein and can also be affected by renal function 1.
From the Research
Significance of Elevated Kappa Free Light Chains
Elevated kappa free light chains (FLC) with normal immunofixation and protein electrophoresis results can be indicative of various conditions, including:
- Plasma cell dyscrasias, such as multiple myeloma 2
- B-cell non-Hodgkin lymphoma (NHL), where elevated FLC is associated with an inferior event-free survival (EFS) and overall survival (OS) 3, 4
- Systemic autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, and Sjögren's syndrome, where elevated polyclonal FLC levels reflect a strong interferon signature 5
- Multiple sclerosis, where elevated kappa FLC in cerebrospinal fluid (CSF) supports the diagnosis 6
Conditions Associated with Elevated FLC
The following conditions have been associated with elevated FLC:
- B-cell activation and chronic inflammation 2
- Autoimmune diseases, such as HCV infection 2
- Renal injury and cast nephropathy, where FLC in urine indicate kidney damage 2
- Central nervous system inflammatory diseases, such as multiple sclerosis, where FLC in CSF indicate intrathecal immunological processes 6
Prognostic Value of FLC
Elevated FLC has been shown to be a prognostic factor in various conditions, including:
- B-cell NHL, where elevated FLC is associated with an inferior EFS and OS 3, 4
- Diffuse large B-cell lymphoma, where elevated FLC is an independent adverse prognostic factor for EFS and OS 4
- Systemic autoimmune diseases, where elevated polyclonal FLC levels are associated with increased disease activity and autoreactivity 5