title: Urinary albumin excretion patterns of patients with cast nephropathy and other monoclonal gammopathy-related kidney diseases.
abstract: OBJECTIVE
  Multiple myeloma is responsible for a wide variety of renal pathologies. Urinary protein and monoclonal spike cannot be used to diagnose cast nephropathy (CN). Because albuminuria is a hallmark of glomerular disease, this study evaluated the percentage of urinary albumin excretion (%UAE) as a tool to differentiate CN from Ig light chain amyloidosis (AL), light chain deposition disease (LCDD), and acute tubular necrosis (ATN).
  
  
  METHODS
  Patients were selected from the Renal Biopsy Database and the Dysproteinemia Database. Participants were excluded if laboratory data were missing within 1 week of the renal biopsy. The %UAE was obtained from urine protein electrophoresis.
  
  
  RESULTS
  From 1992 to 2011, 260 patients were biopsied (177 with AL, 28 with LCDD, 43 with CN, and 12 with ATN). The %UAE for CN patients was significantly lower (7%) than for ATN (25%), LCDD (55%), and AL (70%) patients (P<0.001). Significant differences were also found in serum creatinine, serum albumin, free light chain ratio, total urine protein, and urine monoclonal spike; only the %UAE remained independently associated with CN in a logistic regression model (P<0.001). The area under the curve for the receiver operator characteristic curve for %UAE was 0.99. At <25%, the %UAE had a sensitivity of 0.98, specificity of 0.94, positive predictive value of 0.75, and negative predictive value of 0.99.
  
  
  CONCLUSIONS
  This study showed that %UAE was significantly less in CN than the other three renal lesions and %UAE may thus be helpful in diagnosis of CN.
authors.affiliation: Division of Hematology, Mayo Clinic, Rochester, Minnesota 55901, USA. leung.nelson@mayo.edu
authors.forename: Nelson
authors.initials: N
authors.lastname: Leung
authors.forename: Morie
authors.initials: M
authors.lastname: Gertz
authors.forename: Robert A
authors.initials: RA
authors.lastname: Kyle
authors.forename: Fernando C
authors.initials: FC
authors.lastname: Fervenza
authors.forename: Maria V
authors.initials: MV
authors.lastname: Irazabal
authors.forename: Alfonso
authors.initials: A
authors.lastname: Eirin
authors.forename: Shaji
authors.initials: S
authors.lastname: Kumar
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Cha
authors.forename: S Vincent
authors.initials: SV
authors.lastname: Rajkumar
authors.forename: Martha Q
authors.initials: MQ
authors.lastname: Lacy
authors.forename: Steve R
authors.initials: SR
authors.lastname: Zeldenrust
authors.forename: Francis K
authors.initials: FK
authors.lastname: Buadi
authors.forename: Suzanne R
authors.initials: SR
authors.lastname: Hayman
authors.forename: Samih H
authors.initials: SH
authors.lastname: Nasr
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Sethi
authors.forename: Marina
authors.initials: M
authors.lastname: Ramirez-Alvarado
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Witzig
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Herrmann
authors.forename: Angela
authors.initials: A
authors.lastname: Dispenzieri
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000419:Albuminuria / Q000097:blood / Q000652:urine*; D000686:Amyloidosis / Q000097:blood / Q000175:diagnosis / Q000652:urine*; D000704:Analysis of Variance; D019540:Area Under Curve; D016009:Chi-Square Distribution; D003404:Creatinine / Q000097:blood; D005260:Female; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000097:blood / Q000652:urine; D007683:Kidney Tubular Necrosis, Acute / Q000097:blood / Q000175:diagnosis / Q000652:urine*; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000097:blood / Q000175:diagnosis* / Q000652:urine*; D011237:Predictive Value of Tests; D012372:ROC Curve; D012709:Serum Albumin / Q000378:metabolism; D018709:Statistics, Nonparametric
chemical_list: D007147:Immunoglobulin Light Chains; D012709:Serum Albumin; D003404:Creatinine