[Laboratory investigations to rule out AL amyloidosis: practical guidance for the cardiologist].

Cardiac amyloidosis is an increasingly recognized cause of heart failure. Among systemic forms, immunoglobulin light chain (AL) amyloidosis is characterized by the most rapid progression and worst prognosis in the absence of prompt treatment, but also by the greatest potential for complete reversal of cardiac dysfunction. Therefore, rapid exclusion of AL amyloidosis is the first and most critical step in the diagnostic work-up of patients with suspected cardiac amyloidosis. The presence of a monoclonal protein in serum and/or urine, detectable in 98-100% of AL amyloidosis cases, must be investigated by combining serum and urine immunofixation electrophoresis with free light chain (FLC) assay. Five different FLC assays are currently available in Italy; they are not interchangeable and require the use of method-specific reference intervals for the κ/λ ratio. The cardiologist should select one method and apply it consistently to the same patient, using the validated reference intervals for that specific assay, preferably performed in the same laboratory to optimize data standardization. This review article provides practical guidance on ordering and interpreting these laboratory tests, which are essential for promptly directing patients to the appropriate diagnostic and therapeutic pathway.