Immunoglobulin G (IgG) Heavy and Light Chain (HLC) Pairs, κ and λ With Ratio

Serum

0.75 mL

0.5 mL

Red-top tube or gel-barrier tube

Patient should be fasting for eight hours to avoid lipemic sample interference.

For the quantitative measurement of human IgG heavy chain and light chain intact immunoglobulin in serum. The IgG HLC ratio can be used when monitoring previously diagnosed IgG multiple myeloma in conjunction with other laboratory tests and clinical evaluations.

Heavy and light chain pair quantitation may be useful for:

1. Distinguishing between broadly migrating monoclonal proteins and restricted polyclonal immunoglobulin patterns on serum protein electrophoresis.

2. Quantitating monoclonal IgG proteins that are difficult to quantitate using serum protein electrophoresis alone.

3. Providing a more specific quantitation of the monoclonal protein than total IgG measurements alone.

Decisions on patient evaluation and management must not be given on the basis of IgG κ, IgG λ, or IgG κ:IgG λ ratio measurements alone. Clinical history and other laboratory findings must be taken into account.

Heavy and light chain (HLC) quantitation should be used as a complementary method to serum protein electrophoresis.

The effect of therapeutic drugs on the measurement of IgG κ and IgG λ by this assay has not been evaluated.

Small increases in the concentrations of monoclonal IgG proteins may not result in an altered HLC pair ratio.

For initial detection of monoclonal proteins, see:

• Immunofixation (IFE), Serum and Protein Electrophoresis, Serum [001495]

• Immunofixation (IFE), Serum, Protein Electrophoresis (PE), Serum, and Quantitative Free κ and λ Light Chains (FLC) Plus Ratio, Serum [120256]

• Immunofixation (IFE) and Protein Electrophoresis, 24-Hour Urine [003467]

Nephelometry

• IgG κ (g/L): 4.03−9.78

• IgG λ (g/L): 1.97−5.71

• IgG κ:IgG λ ratio: 0.98−2.75

An elevated IgG heavy and light chain (HLC) pair ratio suggests a clonal proliferation of an IgG κ clone of plasma cells.

A low IgG HLC pair ratio suggests a clonal proliferation of an IgG λ clone of plasma cells.

Elevated serum concentrations of monoclonal protein are indicative of an underlying abnormality, such as monoclonal gammopathy of undetermined significance (MGUS), multiple myeloma, and other lymphoproliferative disorders. International guidelines recommend serum protein electrophoresis or nephelometric immunoglobulin quantification as tools to monitor patients' disease¹ (alongside other tests including flow cytometry and serum free light chain analysis).² Total IgG nephelometric assays will include nontumor immunoglobulin, and measurement of either IgG κ or IgG λ may give a more accurate representation of tumor production.

Furthermore, measurement of both IgG κ and IgG λ, calculation of the IgG κ:IgG λ ratio, and comparison with values found in normal subjects can give a more sensitive indication of clonality.^3-5 Additionally, changes in the IgG κ:IgG λ ratio and its normalization when compared to a normal ratio range should assist in monitoring patients' disease. Use of the IgG κ:IgG λ ratio will also compensate for any changes in plasma volume and correct for half life variations due to receptor saturation.