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HelpTest Code LAB10147 IMMUNOGLOBULIN FREE LIGHT CHAIN, SERUM
Performing Laboratory
Mohawk Valley Health System Laboratory
Day(s) Performed
Performed: M,W,F
Routine TAT: 1-3 Days
Intended Use
N Latex FLC kappa and N Latex FLC lambda are in-vitro diagnostic reagents for the quantitative
determination of free light chains (FLC), type kappa or type lambda in human serum and EDTA-plasma.
N Latex FLC kappa and N Latex FLC lambda assays are used on the BN Systems and Atellica® CH
Analyzer:
• as an aid in the diagnosis and monitoring of multiple myeloma (MM).
• as an aid in the diagnosis and monitoring of immunoglobulin light-chain amyloidosis (AL).
• as an aid in the evaluation of Monoclonal Gammopathy of Undetermined Significance (MGUS).
Results of FLC measurements should always be interpreted in conjunction with other laboratory and
clinical findings.
Specimen Collection and Handling
Collect gold top serum separator tube (SST), or red top (serum).
Serum samples must have completely coagulated and, after centrifugation, must not contain
any particles or traces of fibrin. Lipemic samples, or frozen samples which became turbid after
thawing, must be clarified by centrifugation (10 minutes at approximately 15 000 x g) prior to testing.
Clinical Summary
In a normal immune response complete immunoglobulin molecules are built, composed of two
identical heavy chains and two identical light chains. The type of immunoglobulin
(IgA, IgG, IgM, IgD, IgE) is defined by the heavy chain, which is combined with either kappa or lambda light chains. A single plasma cell produces one type of heavy chain, and one type of light chain, whichare assembled and secreted into the plasma. Compared to the amount of heavy chains produced byeach plasma cell clone, a slight excess of light chains is always produced and released into the blood stream as unbound or free light chains (FLC). Thus, in healthy individuals, the majority of light chainsexists in bound form as complete immunoglobulins, and only few FLC circulate. While FLC kappa circulate as monomers of about 22.5 kD the FLC lambda form dimers of about 45 kD. Both FLCs are eliminated by the kidney, and, due to the different molecular size, the glomerular filtration rate is higher for FLC kappa compared to FLC lambda, resulting in a mean FLC kappa/lambda ratio of 0.6 in plasma, compared to a plasma ratio for a total light chains of about 22.
Monoclonal gammopathy typically goes along with a grossly increased production of one specific
immunoglobulin, and an excess production of the specific FLC involved. As a result, either the plasma
level of FLC kappa or that of FLC lambda is elevated, and the ratio FLC kappa/lambda is either increased or decreased compared to the reference range. The determination of FLC in serum is part of recent international recommendations for diagnosis and monitoring multiple myeloma3–7 and
immunoglobulin light-chain amyloidosis (AL)8–12.
Limitations
• The performance of N FLC KAPPA and N FLC LAMBDA has not been thoroughly studied in IgM and LightChain MGUS patients due to the low prevalence of these subtypes.
• Patients with decreased renal function (e.g. chronic kidney disease) may have elevated FLC kappa
and FLC lambda1.
• Sample populations excluded MGUS populations that were further diagnosed with a disease/
disorder in subsequent testing with another medical device such as human immunodeficiency virus, hepatitis, and chronic lymphocytic leukemia. Thus, because the samples were enriched the
specificity of the test may be inflated.
Storage
Can be stored for 4 days at 2-8 C or frozen at -20 C for 6 months.