Do serum free light chain levels of kappa 32 mg/L, lambda 27.7 mg/L, with a kappa/lamda ratio of 1.16 suggest a monoclonal plasma‑cell disorder such as multiple myeloma, or are they within normal limits?

Interpretation of Serum Free Light Chain Results

Your Results Are Within Normal Limits

Your serum free light chain values (kappa 32 mg/L, lambda 27.7 mg/L, ratio 1.16) fall within the normal reference range and do not suggest a monoclonal plasma cell disorder such as multiple myeloma. 1, 2

Normal Reference Ranges

• Normal kappa/lambda ratio: 0.26-1.65 1, 2
• Your ratio of 1.16 sits comfortably in the middle of this normal range
• Normal kappa range: 3.3-19.4 mg/L (though your value of 32 mg/L is slightly elevated) 2
• Normal lambda range: 5.7-26.3 mg/L (your value of 27.7 mg/L is at the upper limit) 2

Key Diagnostic Thresholds You Do NOT Meet

For a monoclonal plasma cell disorder to be suspected, you would need:

• Abnormal ratio defined as >4:1 or <1:2 (0.5) for serum free light chains 1
• Myeloma-defining event requires a highly abnormal ratio ≥100 (for kappa predominance) or ≤0.01 (for lambda predominance) 1, 3
• Your ratio of 1.16 is nowhere near these thresholds

Why Both Values Are Slightly Elevated

The most likely explanation for both kappa and lambda being at the upper end of normal is:

• Polyclonal B-cell activation from infection, inflammation, or autoimmune conditions 4
• Renal impairment can decrease clearance of both light chains, causing proportional elevation while maintaining a normal ratio 1, 4
• Check your serum creatinine and estimated glomerular filtration rate (eGFR), as renal function significantly affects free light chain levels 5, 6

What These Results Rule Out

Your normal ratio effectively excludes:

• Multiple myeloma (would show ratio >4:1 or <1:2) 1
• Light chain myeloma (would show highly abnormal ratio ≥100 or ≤0.01) 1, 3
• AL amyloidosis (would show abnormal ratio with monoclonal predominance) 7
• Light chain MGUS (requires abnormal ratio by definition) 4

Important Caveats

Serial monitoring considerations:

• If repeat testing is needed, use the same assay method to ensure accurate comparison 5, 4
• A single normal result does not completely exclude early plasma cell disorders if clinical suspicion remains high based on other findings 5
• If you have unexplained anemia, renal dysfunction, hypercalcemia, or bone lesions (CRAB criteria), further workup with serum protein electrophoresis, immunofixation, and bone marrow biopsy would still be warranted regardless of this normal free light chain ratio 3

No Further Workup Needed Based on These Results Alone

Unless you have other concerning clinical features (unexplained bone pain, anemia, renal dysfunction, hypercalcemia), no additional testing for plasma cell disorders is indicated. 1, 3