Diagnostic accuracy of electrophoretic analysis of native or defribrinated plasma using serum as a reference sample

BACKGROUND: Electrophoretic analysis of plasma may provide inaccurate results unless plasma is defibrinated with ethanol. OBJECTIVE: The aim of this study, conducted following the Standards for Reporting of Diagnostic Accuracy (STARD), was to determine whether cellulose acetate (CAE), agarose gel (AGE), and capillary zone (CZE) electrophoresis of native plasma (NP) and defibrinated plasma (DP) provided the same information as serum electrophoretograms. METHODS: Serum, NP, and DP electrophoretograms obtained using the 3 methods were examined visually by 3 observers to identify changes in globulin fractions and provide diagnostic interpretations. Using serum analysis as the reference method, sensitivity, specificity, and positive likelihood ratio of NP and DP electrophoretograms to identify abnormal globulin profiles were calculated. RESULTS: Specimens from 46 dogs were analyzed. Albumin and α(1) - and γ-globulin fractions were lower and β(2) -globulin fractions higher in NP than in serum and DP. Interpretations of NP electrophoretograms were the same as for serum in 54.8% (CAE), 51.2% (AGE), and 51.6% (CZE), revealed an increased β-globulin fraction in 32.3-41.5%, and resulted in misinterpretation, especially for CZE analysis, in 4.7-16.1% of the dogs; all dogs with abnormal serum electrophoretograms were identified correctly using NP. Analysis of DP was similar to serum analysis in about 2/3 of the dogs. In the others, defibrination did not resolve spurious plasma findings or induced additional changes. Up to 75 and 27% of NP and DP electrophoretograms, respectively, were abnormal in dogs with normal serum electrophoretograms. Sensitivity for NP and DP analysis was high, but specificity for NP was poor. CONCLUSIONS: Analysis of NP provides the same information as serum analysis in > 50% of cases, and, despite low specificity, could preliminarily exclude the presence of abnormalities when only plasma is available. If electrophoretograms are not normalized by defibrination, electrophoretic abnormalities are likely present, and electrophoresis should be repeated using serum.