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Urine protein electrophoresis

Fluid Proteins

Clinical Chemistry

Mr Jean Deenmamode, EPS laboratory, Biochemistry, Homerton University Hospital, London

The characteristics of glomerular and tubular proteinuria can be defined by urine electrophoresis. In the UK, the majority of laboratories use urine protein electrophoresis, together with immunofixation, for the detection and characterisation of Bence Jones protein (monoclonal free light chains, MFLC).

Agarose gel electrophoresis and high sensitivity stains encouraged the use of unconcentrated urine samples. Urine capillary electrophoresis was introduced as a fully automated method, but procedural limitations might have minimised its use.

Certain external quality assessment (EQA) scheme reports have indicated a variety of standard procedures for MFLC detection suggesting that laboratories might not have satisfactorily optimised their procedures for best sensitivity and might not be following best practice.

The installation of a semi-automated gel system in 2001 initiated us to use unconcentrated urine samples. In 2004, a capillary electrophoresis system provided the opportunity to investigate this procedure for urine samples. Furthermore, serum FLC assays using a bench top analyser were evaluated.

The higher sensitivity of capillary electrophoresis serum patterns allowed MFLC, in some instances, to be qualitatively confirmed by immunofixation with free light chains antisera. Quantitative serum FLC might not have been appropriate as part of our reflex testing service.

The levels of best practice in laboratories might be dependent on urine sample type, age, storage, following published guidelines and EQA recommendations and turnaround times. Also, the cost of appropriate tests, inadequate staff numbers, interpretation skills and sample processing time constraints might influence best practice. In spite of these challenges we are providing a reliable qualitative urine service.