FREE LIGHT CHAINS (SERUM) - (S)

Test Code: FLCH

Alternate Name(s): Free Light Chains, Kappa, Kappa FLC, Kappa-Free, Light Chain, Lambda, Lambda FLC, Lambda-Free Light Chain, Light Chains, Serum Free Light Chains, Kappa/Lambda Free Light Chain Ratio

The detection of immunoglobulin-free light chains in serum is important in the diagnosis, prognosis and management of patients with plasma dyscrasias.  In addition, the short physiological half life of sFLC in blood (kappa: 2-4 h and lambda: 3-6 h) allows this to be used as a serum marker for real-time monitoring of response to treatment as well as disease progresssion.
The specificity of this assay for detection of monoclonal light chains relies on the ratio of free kappa and lambda (K/L) light chains.  Elevated kappa and lambda (K/L) free light chain (FLC) may occur due to polyclonal hypergammaglobulinemia or impaired renal clearance.  A specific increase in FLC K/L ratio must be demonstrated for diagnostic purposes.
 
Values should be used in conjunction with other laboratory and clinical findings.
 

_SH Immunology Test Requisition (R250-10-21)

	Adult 19+
Kappa Free LC	3.30 – 19.40 mg/L
Lambda Free LC	5.71 – 26.30 mg/L
Free LC Ratio	0.26 – 1.65 ratio

Adult reference values adopted from:
Binding Site, Optilite Freelite Kappa Free Kit, INS016.OPT ver 26th November 2018
Binding Site, Optilite Freelite Lambda Free Kit, INS018.OPT ver 30th August 2018
 
Reference values have not been established for patients that are less than 19 years of age. 
 
A Free LC Ratio Reference Range of 0.37 to 3.10 is suggested for patients with chronic kidney disease (CKD). The ratio demonstrates a stepwise increase through the CKD stages and remains elevated in patients on hemodialysis. Hutchison CA et al, Clin J Am Soc Nephrol. 2008 Nov;3(6): 1684-90.
 
Increased serum FLC concentrations can occur not only when monoclonal light chains are present but also when immunoglobulin synthesis is elevated (e.g. autoimmune, liver and inflammatory diseases, Infection), or immunoglobulin excretion is reduced (e.g. renal impairment).

Method of Analysis: Turbidimetry – Binding Site Optilite

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MONOCLONAL PROTEIN INVESTIGATION - (S)

	Reportable Range
Kappa Free LC	0.60 – 127000.00 mg/L
Lambda Free LC	1.30 – 139000.00 mg/L

 
Undetected antigen excess is a rare event but cannot be excluded. If these free light chain results do not agree with other clinical or laboratory findings, or if the sample is from a patient that has previously demonstrated antigen excess, the result must be checked by retesting at a higher sample dilution. Results should always be interpreted in conjunction with other laboratory tests and clinical evidence; any anomalies should be discussed with the laboratory.