title: Immunofixation electrophoresis was highly specific for the diagnosis of renal light-chain amyloidosis.
abstract: BACKGROUND
  Renal light-chain amyloidosis (AL) is one of the common causes of massive proteinuria and nephrotic syndrome, especially in elderly patients. This study aimed to evaluate the sensitivity and specificity of serum and urine using immunofixation electrophoresis (IFE) in the diagnosis of renal AL amyloidosis in patients older than 40 years.
  
  
  METHODS
  Patients receiving native renal biopsy in the hospital who meet the following criteria were recruited in this retrospective study: (1) proteinuria excretion ≥3.5 g/24 hr; (2) age ≥ 40 years when receiving renal biopsy and (3) biopsy-proven glomerulopathy. Serum and urine monoclonal free immunoglobulin light chains were detected using IFE.
  
  
  RESULTS
  A total of 625 patients were recruited. Of them, 32 patients (5.12%) were diagnosed as renal AL amyloidosis. The specificities of serum, urine and serum combined urine IFE in the total 625 patients (ie, monoclonal free immunoglobulin light chain in serum or urine) for diagnosis of renal AL amyloidosis were 98.6%, 98.0% and 97.6%, respectively. For patients older than 60 years, the specificities of serum, urine and serum combined urine IFE for diagnosis of renal AL amyloidosis were 98.5%, 98.0% and 97.6%, respectively and the sensitivity of serum, urine and serum combined urine IFE for diagnosis of renal AL amyloidosis were 68.6%, 81.3% and 81.3%, respectively.
  
  
  CONCLUSIONS
  Serum or urine IFE was highly specific for renal AL amyloidosis for patients older than 40 years with nephrotic-range proteinuria. In older patients (>60 years), both the sensitivity and specificity of IFE for renal AL amyloidosis were high. Combination of serum and urine IFE could improve the sensitivity with comparable specificity.
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Institute of Nephrology, Peking University, and Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China.
authors.forename: Fu-de
authors.initials: FD
authors.lastname: Zhou
authors.forename: Lu-xia
authors.initials: LX
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Yao
authors.forename: Su-xia
authors.initials: SX
authors.lastname: Wang
authors.forename: Wan-zhong
authors.initials: WZ
authors.lastname: Zou
authors.forename: Gang
authors.initials: G
authors.lastname: Liu
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Ming-hui
authors.initials: MH
authors.lastname: Zhao
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000686:Amyloidosis / Q000097:blood / Q000175:diagnosis* / Q000652:urine; D015415:Biomarkers / Q000097:blood / Q000652:urine; D004586:Electrophoresis; D005260:Female; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000097:blood* / Q000652:urine*; D007159:Immunologic Tests; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis* / Q000652:urine; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; D007147:Immunoglobulin Light Chains