Selective determination of free light chains in the serum

Improvement in diagnostics, monitoring and therapy supervision of monoclonal gammopathies

Monoclonal gammopathies are characterised by the malignant proliferation of a single plasma cell clone with excessive formation of a single monoclonal immunoglobulin (M protein).

In addition to the synthesis of intact immunoglobulins, the synthesis and secretion of isolated free light chains of the kappa or lambda type may also occur in some 60 % of patients, which were previously detectable only in 24-hour urine collection by means of immunofixation (Bence Jones proteins).

These isolated free light chains are not detected in serum protein electrophoresis used as a screening method because of the low sensitivity of this method, and they are only detected to an incomplete extent by the immunofixation method, which is generally not used unless electrophoresis findings are regarded as unreliable. There is the risk that discrete, yet clinically relevant changes will be overlooked.
Both methods also provide only qualitative results, which are only conditionally suitable for progress monitoring and therapy control.

Using the immunonephelometric method for the highly specific and very sensitive determination of free kappa and lambda light chains, it is possible to quantitatively measure free light chains in the serum and calculate the kappa/lambda ratio, which is important for detecting and monitoring light chain paraproteinaemia.
The assessment of both the absolute concentrations of the two free light chains in the serum as well as their relationship to each other (kappa/lambda ratio) makes it possible to distinguish between a monoclonal increase and polyclonal surplus production in inflammatory processes and renal dysfunction.

Determining the free light chains in the serum is preferred to detecting them in the urine, due to the influence on light chain excretion from the kidney function and preanalytical problems when recovering and treating urine as a test material and because it is less of a burden for the patients in general.

Indications for determining the free light chains

The immunonephelometric quantification of free light chains in the serum is suitable for diagnostics, monitoring and therapy control along with relapse assessment in:

  • Multiple myeloma
  • Light chain myeloma, light chain amyloidosis and light chain deposition disease of asecretory myeloma in which only two-thirds of cases
  • exhibit detectable free light chains in low concentrations

Furthermore, the concentration of free light chains and especially the kappa/lambda ratio, among other factors, represent important independent risk indicators for the progression of monoclonal gammopathy of undetermined significance (MGUS).

The combination of serum protein electrophoresis, potential immunofixation and the analysis of the free light chains in the serum makes it possible to identify all significant monoclonal gammopathies.

Reference ranges

Normal adult
serum
Average
mg/l
Median
mg/l

Reference Range
mg/l

Kappa

8,36

7,30

3,30 - 19,40

Lambda

13,43

12,40

5,71 - 26,30

Kappa/lambda ratio

0,63

0,60

0,26 - 1,65

Preanalytics
No special requirements

Test material

1 ml of serum

Further diagnostics
Immunofixation in the serum and urine

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