An algorithmic approach using kappa/lambda ratios to improve the diagnostic accuracy of urine protein electrophoresis and to reduce the volume required for immunoelectrophoresis.
The most sensitive routine method for identifying urinary monoclonal immunoglobulin kappa and lambda light chains, called Bence Jones proteins (BJPs), in clinical laboratories is immunofixation electrophoresis (IFE), but this procedure is time-consuming and expensive. As a result, many laboratories screen for paraproteins with urine protein electrophoresis (UPE), which is insensitive when low concentrations of BJP are present and is difficult to interpret with severe proteinuria. The purpose of this study was to determine whether kappa/lambda ratios can be used in conjunction with UPE to improve diagnostic reliability in identifying paraproteins, and decrease the need for IFE on all samples. Urine specimens from 243 patients were examined by UPE and kappa/lambda ratios, and compared with IFE. Due to poor analytical sensitivity, the urinary kappa or lambda concentrations could not be determined in many cases. As a result, many specimens showed kappa/lambda ratios that were indeterminate. Nevertheless, when both urinary kappa and lambda concentrations were undetectable, a BJP could be ruled out. A urinary kappa/lambda ratio between 0.75-3 also ruled out a BJP. The use of kappa/lambda ratios, in conjunction with UPE, resulted in a 52% decrease in the volume of IFE during the course of this study, with 100% sensitivity for detecting BJP.
Levinson
S S
SS
Department of Pathology, University of Louisville, KY 40206, USA.
D000465:Algorithms; D000686:Amyloidosis / Q000175:diagnosis / Q000652:urine; D001536:Bence Jones Protein / Q000652:urine; D004586:Electrophoresis / Q000379:methods*; D006801:Humans; D007122:Immunoelectrophoresis / Q000379:methods; D007145:Immunoglobulin kappa-Chains / Q000652:urine*; D007146:Immunoglobulin lambda-Chains / Q000652:urine*; D009391:Nephelometry and Turbidimetry; D010265:Paraproteinemias / Q000175:diagnosis / Q000652:urine; D011507:Proteinuria / Q000175:diagnosis / Q000652:urine; D012680:Sensitivity and Specificity
D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D001536:Bence Jones Protein