The British Committee for Standards in Haematology guidelines on the diagnosis and investigation of AL amyloidosis state that immunofixation of blood and urine and sFLCs should be measured in all patients with suspected AL amyloidosis . They also recognise that Freelite sFLC assays are well established, whilst FLC assays from other manufacturers have not been validated (Chapter 8).
Clinical case history
AL amyloidosis identified by FLC analysis when electrophoretic tests were doubtful .
IFE showed a weak λ band without a corresponding intact immunoglobulin Figure 28.7. Quantitative immunoglobulin measurements were: IgG 4.9 g/L; IgA 1.02 g/L and IgM 0.32 g/L indicating hypogammaglobulinaemia. sFLC analysis showed: κ 7.8 mg/L; λ 210 mg/L and κ/λ ratio of 0.04. This supported a diagnosis of AL amyloidosis.
Nephelometric sFLC quantification was clearly abnormal and provided a measurable parameter for subsequent disease monitoring. In contrast, FLCs were barely detectable by conventional electrophoretic assays.