title: The Cutoff Level for Urine Protein in Urine Immunofixation Electrophoresis.
abstract: BACKGROUND
  Immunofixation electrophoresis (IFE) maintains its importance in diagnosing monoclonal gammopathies. In particular, urine IFE detects free light chains (FLC) in urine samples even at low concentrations and offers higher sensitivity compared to serum electrophoresis and serum IFE. The aim of the present study was to determine the place and significance of quantitative urinary protein measurement before IFE in interpreting the results of subsequent IFE and to determine the most appropriate protein concentrations for the appearance of bands.
  
  
  METHODS
  The records of a total of 600 patients, who underwent screening for Bence Jones proteinuria using IFE on 24-hour urine, were retrospectively reviewed. Urine IFE was performed using Helena SAS-I and SAS-I devices. The total protein concentration in the urine was quantitatively determined by the Pyrogallol red method, and the urine albumin level was determined using the immunoturbidimetric method. These analyses were measured on an Olympus/Beckmann AU5800.
  
  
  RESULTS
  The evaluation of IFE results revealed that 311 patients had normal results, 108 patients had monoclonal bands, five patients had biclonal bands, 28 had polyclonal bands, and 148 patients had various degrees of proteinuria. ROC curves were created in order to determine the most appropriate urinary protein and albumin levels to observe bands in IFE. Accordingly, urine baseline protein level (mg/dL) showed the highest AUC value (cutoff value: 19.4 mg/dL, sensitivity: 92%, specificity: 98.2%, AUC: 0.972).
  
  
  CONCLUSIONS
  The present study showed that quantitative protein measurement before IFE eliminated the disadvantages associated with the IFE method and its interpretation.
authors.forename: Hamit Yasar
authors.initials: HY
authors.lastname: Ellidag
authors.forename: Gulten
authors.initials: G
authors.lastname: Curek
authors.forename: Esin
authors.initials: E
authors.lastname: Eren
authors.forename: Ozgur
authors.initials: O
authors.lastname: Aydin
authors.forename: Necat
authors.initials: N
authors.lastname: Yilmaz
mesh_terms: D000368:Aged; D000418:Albumins / Q000032:analysis; D000911:Antibodies, Monoclonal / Q000737:chemistry; D019540:Area Under Curve; D001536:Bence Jones Protein / Q000652:urine; D002624:Chemistry, Clinical / Q000592:standards; D005260:Female; D006801:Humans; D007122:Immunoelectrophoresis / Q000592:standards*; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry; D010265:Paraproteinemias / Q000652:urine*; D011748:Pyrogallol / Q000031:analogs & derivatives / Q000032:analysis; D012372:ROC Curve; D012189:Retrospective Studies
chemical_list: D000418:Albumins; D000911:Antibodies, Monoclonal; D011748:Pyrogallol; C058731:pyrogallol sulfonphthalein; D001536:Bence Jones Protein