From the Guidelines
A kappa free light chain level of 1.80 mg/L is generally within the normal reference range, which typically falls between 0.33-1.94 mg/L, though exact ranges may vary slightly between laboratories. This result suggests normal production of kappa light chains by plasma cells. No specific treatment or intervention is needed for this value. Free light chains are proteins produced by plasma cells, and they normally circulate in small amounts in the bloodstream. Elevated levels can indicate conditions like multiple myeloma, amyloidosis, or other plasma cell disorders, while normal levels, as in this case, generally suggest absence of these conditions. However, interpretation should always consider the lambda free light chain level and the kappa/lambda ratio, as these provide more diagnostic information than the kappa value alone. If there are clinical symptoms suggesting a plasma cell disorder despite normal kappa levels, further testing may be warranted, as recommended by the International Myeloma Working Group 1.
Some key points to consider in the interpretation of kappa free light chain levels include:
- The kappa/lambda ratio is crucial for diagnosis, with a ratio > 1.65 or < 0.26 indicating an abnormality 1
- The presence of clinical symptoms such as hypercalcemia, renal insufficiency, anemia, or bone lesions (CRAB) can indicate a plasma cell disorder despite normal kappa levels 1
- The serum free light chain assay is a useful tool for diagnosing and monitoring plasma cell disorders, including multiple myeloma and light chain amyloidosis 1
- A full diagnostic workup, including bone marrow aspiration and biopsy, skeletal survey, and serum and urine protein electrophoresis, is necessary to confirm a diagnosis of multiple myeloma 1
In the context of real-life clinical medicine, it is essential to prioritize the patient's clinical symptoms and overall health status when interpreting kappa free light chain levels, rather than relying solely on laboratory results. If clinical symptoms suggest a plasma cell disorder, further testing and evaluation should be pursued, even if the kappa free light chain level is within the normal range.
From the Research
Kappa Free Light Chains
- Kappa free light chains are a type of protein found in the blood and urine, and elevated levels can be an indicator of certain diseases, such as multiple myeloma 2, 3, 4, 5, 6.
- A value of 1.80 for kappa free light chains is relatively low compared to the extremely high levels reported in some studies, such as >33,000 mg/dL in a patient with light chain myeloma and acute renal injury 2.
- However, the prognostic value of serum free light chain ratio at diagnosis in multiple myeloma has been investigated, and a high ratio (> or = the observed median value) has been correlated with poorer outcomes, including elevated serum creatinine and lactate dehydrogenase, extensive marrow infiltration, and light chain type MM 6.
Monitoring and Treatment
- Serum free light chain concentrations can be used to monitor the disease course in multiple myeloma patients, and changes in these concentrations can provide a rapid indication of the response to treatment 3.
- Therapeutic plasma exchange (TPE) has been used to reduce extremely high kappa free light chain levels in patients with myeloma cast nephropathy, and can be effective in rapidly reducing these levels, although multiple procedures may be required to reduce the risk of hemodialysis dependency 2.
- The use of serum free light chain assays has been adopted by many laboratories as a first-line screen in patients with suspected monoclonal gammopathies, due to the limited sensitivity and practical constraints of urine analysis 5.
Prognosis and Survival
- High serum free light chain concentrations have been associated with poorer outcomes, including renal damage and shorter survival, in patients with light chain multiple myelomas 4.
- The survival rate and estimated glomerular filtration rate (eGFR) have been shown to be significantly worse in patients with high serum free light chain concentrations compared to those with low concentrations 4.