Agarose Gel Electrophoresis versus Capillary Zone Electrophoresis: a Comparative Analysis for Monoclonal Protein Detection in Blood.

Abstract

Background: Serum protein electrophoresis (SPE) is the first-line test for the diagnosis of monoclonal gammopathies. While agarose gel electrophoresis (AGE) has been the traditional gold standard, capillary zone electrophoresis (CZE) offers potential advantages in terms of resolution and sensitivity. This study aimed to compare the diagnostic accuracy of these two techniques in detecting monoclonal gammopathies.

Methods: A retrospective study was conducted on 10,909 adult patients without a prior diagnosis of monoclonal gammopathy who underwent SPE between 2017 and 2019. All patients received both AGE using the HYDRASIS 2 SCAN (Sebia, Issy-les-Moulineaux, France) and CZE using the CAPILLARYS 2 instrument (Sebia). Additional laboratory tests, including immunofixation electrophoresis and free light chain quantification in serum and urine, were performed. The final diagnosis was established one year after the initial diagnostic workup.

Results: The sensitivity of AGE was 87.6% (95% confidence interval (CI: 86.9 - 88.2), with a specificity of 99.5%. In contrast, CZE demonstrated a sensitivity of 94.2% (CI: 93.8 - 94.6) and a specificity of 98.9%.

Conclusions: CZE is a valuable tool for the diagnosis of monoclonal gammopathies, offering improved sensitivity over AGE. However, CZE may struggle to detect certain monoclonal immunoglobulins due to their insolubility in the CZE buffer, leading to precipitation and undetected results on electrophoretic tracings, even at high serum levels. SPE should be used in conjunction with complementary tests to ensure comprehensive detection of monoclonal immunoglobulins.