Figure - available from: Journal of Clinical Laboratory Analysis
This content is subject to copyright. Terms and conditions apply.
A case misdiagnosis of selective proteinuria in urine protein electrophoresis by Sebia SDS‐AGE. A, Urine protein electrophoresis at the initial clinic visit. B, Urine protein electrophoresis at the second visit. Lanes 1 and 5 are the misdiagnosed “albumin” protein tested in two consecutive samples, which is indicated by the triangle. Lane 2 is a kappa‐type FLC, lane 3 is a mixed proteinuria, and lane 4 is a glomerular proteinuria in an identical gel. C, Markers. Lane 6 is glomerular proteinuria; lane 7 is a positive sample that shows the position of the FLC monomer, dimer, and albumin. D, Serum electrophoresis (SPE) demonstrates a monoclonal M spike in the R region. E, Serum immunofixation (IFE) shows an IgG lambda monoclonal type. F, Urine immunofixation shows a lambda monoclonal type
Source publication
Background
Monoclonal free light chains (FLC) commonly exist in monomeric or dimeric forms but rarely as larger molecules. Little is known about whether polymeric molecules can affect urine protein electrophoresis (UPE) results.
Methods
Urine samples were collected from 72 multiple myeloma (MM) patients with Bence Jones protein (BJP). Urine protei...
Citations
... In renal failure, a monoclonal band may be detectable on SPEP when a patient has only a light chain myeloma. The likelihood of a detectable monoclonal band on SPEP is enhanced with lambda light chain myelomas due to higher tendency of lambda monoclonal light chains to dimerize (22). ...
Background
Laboratory methods for diagnosis and monitoring of monoclonal gammopathies have evolved to include serum and urine protein electrophoresis, immunofixation electrophoresis, capillary zone electrophoresis, and immunosubtraction, serum-free light chain assay, mass spectrometry, and newly described QUIET.
Content
This review presents a critical appraisal of the test methods and reporting practices for the findings generated by the tests for monoclonal gammopathies. Recommendations for desirable practices to optimize test selection and provide value-added reports are presented. The shortcomings of the serum-free light chain assay are highlighted, and new assays for measuring monoclonal serum free light chains are addressed.
Summary
The various assays for screening, diagnosis, and monitoring of monoclonal gammopathies should be used in an algorithmic approach to avoid unnecessary testing. Reporting of the test results should be tailored to the clinical context of each individual patient to add value. Caution is urged in the interpretation of results of serum-free light chain assay, kappa/lambda ratio, and myeloma defining conditions. The distortions in serum-free light chain assay and development of oligoclonal bands in patients‘ status post hematopoietic stem cell transplants is emphasized and the need to note the location of original monoclonal Ig is stressed. The need for developing criteria that consider the differences in the biology of kappa and lambda light chain associated lesions is stressed. A new method of measuring monoclonal serum-free light chains is introduced. Reference is also made to a newly defined entity of light chain predominant intact immunoglobulin monoclonal gammopathy. The utility of urine testing in the diagnosis and monitoring of light chain only lesions is emphasized.
Human serum albumin (HSA) has pseudoesterase activity. So far on gel specific detection of such property of HSA is never reported. Moreover, protein binding dyes are non-specific for albumin. However, many of such dyes are used for HSA detection. So, dye-based albumin detection on the gel is expected to generate false-positive results for HSA. In this context, we have discovered that Fast Blue BB (FBBB, 0.12%) stains specifically HSA pseudoesterase activity with 2 Naphthyl acetate (2NA) as an ester substrate. Further, neostigmine has not inhibited the pseudoesterase activity associated with HSA.
Neostigmine is a known inhibitor of many true esterases like acetylcholinesterase. So, neostigmine addition offers specificity to the method developed for staining of HSA. Additionally, 2NA stains HSA better than bovine serum albumin (BSA). Exploring all these novel findings, we have devised a simple method of HSA detection on the gel, accurately where other esterases are not detected. To the best of our knowledge, our method is the first to detect HSA pseudoesterase activity specifically on gel without getting interfered by any other esterase activity. The method detects HSA better than BSA. We feel that this method will go a long way for the specific detection of HSA on the gel. It is also relevant for understanding the purity of donor human milk matrix and pharmaceutical preparation of HSA. Our method can detect 7 μM of added HSA in human urine. Therefore, our method can be proceeded further for microalbuminuria detection in days to come.
