For a particular Hevylite isotype, both κ and λ assays (e.g. IgAκ and IgAλ) should always be measured, and the HLC ratio calculated (e.g. IgAκ/IgAλ). Definitions of commonly used terms are given in Table 11.5. For serial measurements, either the iHLC, dHLC or the HLC ratio may be used . When an abnormal HLC ratio is present, and the concentration of the uninvolved HLC-pair is below the normal reference interval, this is termed “HLC pair suppression”.
|Term||Definition||Comment||For an IgGκ MM tumour...|
|iHLC||Involved HLC||The HLC isotype that is produced by the tumour.||IgGκ|
|uHLC||Uninvolved HLC||The same heavy chain isotype but alternate light chain type to the iHLC.||IgGλ|
|HLC ratio||e.g. IgGκ/IgGλ||For a particular immunoglobulin isotype, a ratio of the concentration of Hevylite κ to λ. Indicates monoclonality.||IgGκ/IgGλ|
|dHLC||iHLC - uHLC||For a particular immunoglobulin isotype, the difference in concentration between iHLC and uHLC.||IgGκ - IgGλ|
|HLC pair suppression||When the concentration of the uHLC is below the normal reference interval||The HLC ratio must be abnormal.||Suppression of IgGλ|
Table 11.5. Summary of HLC terminology.