Evaluation of a new capillary zone electrophoresis system for the identification and typing of Bence Jones Protein

Abstract

Objectives Capillary electrophoresis has recently emerged as a new sensitive technique for the separation of urinary proteins. We evaluated a new method for Bence Jones Protein (BJP) detection and characterization on native urine samples by the Paragon CZE™ 2000 system. To avoid interference in electrophoretic separation, urine samples were preliminarily treated for the selective removal of interfering salt particles. Design and methods The evaluation was done on a total of 350 fresh 24-h urine samples. The salt particle removal consisted of a manual chromatographic separation, optimized in the course of our evaluation. Capillary zone urinary protein electrophoresis (CZ-UPE) was compared with conventional high-resolution electrophoresis on an agarose gel, while capillary immunosubtraction (CZU-IFE) was compared with agarose gel immunofixation. Results After finding a consistent protein loss in eluates, the preanalytical treatment was optimized by changing sample dilution and eluate collection. The within- and between-run imprecision values for monoclonal peaks corresponding to BJP ranged from 0.4–12.2% to 3.3–6.3%, respectively. The detection limit for BJP, defined as the lowest measurable monoclonal peak on CZ-UPE, was 0.0012 g/L for κ BJP and 0.0007 g/L for λ BJP. CZ-UPE and CZU-IFE sensitivities were significantly lower in urine samples with a total protein level ≤ 100 mg/L (67% and 78%, respectively) compared to those with total protein > 100 mg/L (92% and 94%, respectively). Comparison between BJP measurements obtained from densitometric scanning with those from absorbance tracing showed a correlation coefficient of 0.994 and a bias of 29.8 mg/L. Conclusions Paragon CZE™ 2000 can be introduced in routine for screening and typing of BJP; in urine samples with a total protein level > 100 mg/L, the performance is consistent with results from published validation studies on CZE applied to serum samples.