Since the Freelite reagents use polyclonal antibodies, how is batch to batch variation minimised?
The FLC antisera are produced by immunisation with many different monoclonal FLC proteins. These are not representative of all monoclonal FLCs but the antibody target is the constant region of the molecule that has little structural variation. However, tumour produced monoclonal FLCs may be truncated, have amino acid substitutions or additions and may be abnormally polymerised. Therefore, occasional patient’s monoclonal FLCs may not be detected reliably by the immunoassays or may be detected differently with different antiserum batches. It is, therefore, ideal laboratory practice to assay current and previous samples alongside each other. This is no different from the situation when measuring IgG with different antiserum batches. To minimise batch-to-batch variation, antisera pools are large, are prepared from multiple immunisations and are carefully controlled to maintain consistency. Many monoclonal proteins are tested when new batches are prepared but there is a limit to the number
