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Free Light Chains
(a.k.a Serum Free Light Chains, SFLC, sFLC)
minimum sample volume required ~ 5ml
Test Code: FLC
Tube type: SST
Other acceptable tube types
None
Special instructions
Not routinely available for initial myeloma screen. Request serum electrophoresis and urine Bence Jones Protein (Myeloma Screen profile on ICE).
Minimum retesting interval: Test should not be repeated within 21 days.
Reference range
Kappa: 3.3 - 19.4, Lambda: 5.71 - 26.3, K/L Ratio: 0.26 - 1.65. In renal impairment, K:L ratio 0.37-3.10.
Units
mg/L
Turnaround Time
4
days
Department: Biochemistry
Clinical Application
sFLC analysis is used for monitoring the disease state in patients with Myeloma and precursor condition, Monoclonal Gammopathy of Undetermined Significance (MGUS).
Following a myeloma screen, if a serum paraprotein is detected, the laboratory will add sFLC. This aids risk stratification of MGUS; sFLC replaces the need for urine BJP analysis. Patients should be referred or monitored on the basis of serum electrophoresis and sFLC results, results of other routine haematology and biochemistry tests and clinical findings (please see local MGUS guideline).
Where all other clinical and laboratory findings point to MGUS, patients with K:L ratio falling within the extended range of 0.1 – 7.0 may be monitored in the community, initially 6 months after diagnosis, then annually if all clinical and laboratory findings remain stable. Otherwise obtain a Haematology opinion.
Use of the K/L ratio increases the sensitivity of detecting monoclonal sFLC. Raised sFLC with normal K/L suggests a polyclonal increase, rather than monoclonal gammopathy. This is a non-specific finding, sFLC are not typically monitored in this case.
Webpage updated: October 2024.
