Detection of the precursor protein is the finishing touch of amyloid characterisation. In AL amyloidosis free kappa or lambda light chains can be detected by immunofixation of blood or concentrated urine. A promising new technique is the so-called free light chain test. In AA amyloidosis the precursor protein SAA (serum amyloid A protein) reflects as acute phase reactant (similar to C-reactive protein) the severity of the underlying inflammatory disorder. In ATTR amyloidosis mutated TTR (transthyretin) can be detected in blood by iso-electric focusing.
Detection of these precursor proteins has more than only illustrative value. Therapy is aimed at the removal of the presence and further supply of the precursor protein in the deposition process. Monitoring of the presence and altitude of serum levels of the precursor protein during therapy can provide insight in the effectiveness of treatment.
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