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Free Light Chains
minimum sample volume required ~ 5ml
Test Code: FLC
Tube type: SST
Other acceptable tube types
None
Special instructions
Do not request as part of an initial myeloma screen, serum electrophoresis plus urine Bence Jones Protein should be requested (use Myeloma Screen profile on ICE).
Reference Ranges
Kappa: 3.3 - 19.4
Lambda: 5.71 - 26.3
Kappa/Lambda Ratio: 0.26 - 1.65
In renal impairment, absolute serum FLC concentrations increase, the K:L ratio reference range increases to: 0.37-3.10.
Units
mg/L
Turnaround Time
4
days
Department: Biochemistry
Clinical Application
Serum FLC analysis is used for monitoring the disease state in patients with Myeloma and the precursor condition, Monoclonal Gammopathy of Undetermined Significance (MGUS).
Following a myeloma screen, if a serum paraprotein is detected, the laboratory will add analysis of serum FLC, this aids risk stratification of MGUS. In this case, sFLC replaces the need for urine BJP analysis. Patients should be referred or monitored on the basis of serum electrophoresis and FLC results, along with results of other routine haematology and biochemistry tests plus 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 of MGUS, 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
