Investigation of Paraproteinaemia
Paraproteins are abnormal monoclonal immunoglobulins produced in plasma cell disorders (eg multiple myeloma), lymphoproliferative disorders (eg CLL, Waldenstrom’s macroglobulinaemia) and in some infections (hepatitis C).
The introduction of the assay, serum free light chains (FLC) has meant the initial investigation of paraproteinaemia has become much simpler.
Previously, serum tests had great difficulty in detecting immunoglobulin light chains for two reasons:
1. Light chains are rapidly cleared by the kidneys, up until a certain point where they ‘spilled’ over into the blood.
2. Assays had poor sensitivity in detecting ‘free’ light chains ie light chains not bound to heavy chains as in normal immunoglobulin.
The FLC assay (a propriety product) when combined with serum protein electrophoresis (EPP) and immunofixation allows detection of the vast majority (>99%) of paraproteins, virtually eliminating the need for urine collection and analysis, thus giving a greater degree of patient satisfaction.
With nearly all very sensitive assays, there are some costs to specificity.
In renal failure and in polyclonal gammopathy ...