Serum Free Light Chains
Department of Immunology
Notes
- Quantifies serum free light chains kappa and lambda, and their kappa: lambda ratio. When tumours produce a monoclonal excess of only one of the light chains the ratio becomes abnormal. When there is renal impairment or an increase in polyclonal production the ratio remains normal.
- Of value in the diagnosis and monitoring of patients with light chain myeloma, non-secretory myeloma and primary light chain amyloidosis (AL amyloidosis). Also automatically added to patients with a new diagnosis of multiple myeloma, particularly in those with poor renal function.
- After initial diagnosis it is only necessary to re-test every 6 months, unless under the care of Haematology.
- Test performed by Immunology, North Bristol NHS Trust.
Sample Requirements
Clotted blood. (No special patient preparation needed)
Adult
5ml Gold-top SST tube or 3.5ml Rust-top gel tube (Trust users only)
Paediatric
1ml Serum Sample
Time Limit for Add-ons
3 days
Turnaround Times
7 days
Reference Range
| Patient Group | Kappa FLC (mg/L) | Lambda FLC (mg/L) | K:L Ratio |
|---|---|---|---|
| Age <70, eGFR 60+ | 6.3 - 39.0 | 5.9 - 36.7 | 0.44 - 2.16 |
| Age ≥70, eGFR60+ | 7.0 - 55.8 | 6.4 - 48.0 | 0.46 - 2.59 |
| All ages, eGFR 45-59 (CKD 3a) | 7.8 - 83.6 | 7.3 - 65.1 | 0.46 - 2.62 |
| All ages, eGFR 30-44 (CKD 3b) | 8.8 - 103.3 | 8.2 - 73.2 | 0.48 - 3.38 |
| All ages, eGFR <30 (CKD 4&5) | 11.7 - 265.1 | 12.6 - 150.9 | 0.54 - 3.30 |
Information:
Updated: January 2026