title: Diagnostic approach to and follow-up of difficult cases of AL amyloidosis.
abstract: BACKGROUND
  Routine electrophoretic analysis fails to detect a monoclonal component (MC) in a considerable portion of AL amyloidosis patients. We investigated whether the combination of immunofixation (IF) on agarose gel electrophoresis and bone marrow plasma cell (BMPC) light chain kappa/lambda ratio analysis could contribute to diagnosis in these cases. The possible use of the BMPC kappa/lambda ratio in monitoring the clone was also investigated.
  
  
  METHODS
  We performed BMPC kappa/lambda ratio analysis and IF of serum and urine in 16 selected patients with no detectable MC at routine analysis, despite clinical features suggestive of primary amyloidosis. An anti-idiotypic monoclonal antibody specific for the amyloidogenic immunoglobulin and the BMPC kappa/lambda ratio were used to monitor the clone in a patient who underwent autologous peripheral blood stem cell transplantation.
  
  
  RESULTS
  Abnormal kappa/lambda ratios were found in 14 (sensitivity 87.5%), and a MC in 12 (sensitivity 75%). Combination of the two analyses confirmed diagnosis in all cases. In one patient changes in the size of the clone, monitored on serial bone marrow aspirates by an anti-idiotypic antibody, paralleled variations of the kappa/lambda ratio.
  
  
  CONCLUSIONS
  This study demonstrates that the combined use of IF and the BMPC kappa/lambda ratio is extremely powerful in AL amyloidosis. In addition, the BMPC kappa/lambda ratio should be considered for monitoring the amyloidogenic clone when serum or urine MC is not quantifiable.
authors.affiliation: Research Laboratory of Biotechnology, University of Pavia, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Perfetti
authors.forename: P
authors.initials: P
authors.lastname: Garini
authors.forename: M C
authors.initials: MC
authors.lastname: Vignarelli
authors.forename: M G
authors.initials: MG
authors.lastname: Marinone
authors.forename: I
authors.initials: I
authors.lastname: Zorzoli
authors.forename: G
authors.initials: G
authors.lastname: Merlini
mesh_terms: D000328:Adult; D000368:Aged; D000682:Amyloid / Q000737:chemistry*; D000686:Amyloidosis / Q000097:blood / Q000175:diagnosis* / Q000473:pathology / Q000652:urine; D000911:Antibodies, Monoclonal / Q000032:analysis*; D001706:Biopsy; D001853:Bone Marrow / Q000473:pathology; D004587:Electrophoresis, Agar Gel; D005260:Female; D006801:Humans; D007122:Immunoelectrophoresis; D007145:Immunoglobulin kappa-Chains / Q000032:analysis*; D007146:Immunoglobulin lambda-Chains / Q000032:analysis*; D007668:Kidney / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000473:pathology; D010950:Plasma Cells / Q000276:immunology; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity
chemical_list: D000682:Amyloid; D000911:Antibodies, Monoclonal; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains