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Chapter 9 : Clinical Indications and Applications of Serum and Urine Protein Electrophoresis
This chapter reviews basic principles of electrophoresis, the types of apparatus that are available, quality control and quality assurance procedures, and costs involved with the procedure and provides a wide variety of patterns with recommended interpretations. Electrophoresis of serum and urine in the clinical laboratory takes advantage of the fact that each protein has its own unique structure. The first studies of serum protein electrophoresis were performed entirely in a fluid-based system devised by Arne Tiselius, winner of the 1948 Nobel Prize in Chemistry, called moving boundary electrophoresis. An early-morning void collected into a container without preservative is adequate for screening for the presence of monoclonal free light chains. Each protein electrophoresis gel should have an internal control sample run on it. The percentage of protein in each fraction should be recorded and compared day to day. Good quality assurance requires coordination of all available laboratory information for the patient. A file is set up for the patient the first time that an M protein is detected in the serum or in the urine. In patients with cirrhosis, synthesis of hepatocyte-derived proteins such as albumin and transferrin is decreased. In protein-losing enteropathy, damage to the gastrointestinal tract such as occurs in gluten-losing enteropathy (celiac disease), the serum demonstrates findings similar to those of the nephritic syndrome with hypoalbuminemia, hypogammaglobulinemia, and occasionally elevated levels of α2 macroglobulin. The urine immunofixation is compared to the urine protein electrophoresis to determine which band is the monoclonal free light chains (MFLC).
General structure of an amino acid.
Peptide bond formation between two amino acids.
Serum electropherogram for a patient who is heterozygous for α1 antitrypsin (PIMS). Rel, relative; TP, total protein; A/G, albumin-to-globulin ratio.
Serum protein electrophoresis on the semiauto-mated Sebia Hydragel 30 β1-β2 gel demonstrating sharp bands and a crisp separation of the β1 (transferrin) band from the β2 (C3) band. Samples 6, 13, 14, 24, and 25 have suspicious bands that all proved to be M proteins by immunofixation. In sample 24, the M protein (an IgA κ) migrated in the same location as the C3 (β2) band. By comparing this band to the other C3 bands on this gel, the increase becomes more obvious.
Levey Jennings charts for albumin for the month of September 2004 (top) and the α1 fraction for the same run (bottom). More variation is seen in the α1 fraction because of the smaller percentage of proteins present in this fraction. Nonetheless, no sample is beyond 2DS (2 standard deviations) and no trend of high or low values is evident. VM., median value.
A complex electropherogram pattern with a normal pattern underlaid to show the normal positions of the β-region bands. The abnormal serum shows hypoalbuminemia and anodal slurring of albumin, and the four peaks in the β region are labeled. The fibrinogen was identified by immunofixation, and the radiocontrast dye was indicated by both the lack of a band in that region by immunofixation for IgG, IgA, IgM, κ, and λ and a telephone call indicating that the patient had been given a radiocontrast dye ( Table 1 ). Ref, reference; T.P., total protein; A/G, albumin/globulin.
Results for three serum samples. For each sample, there are two lanes; the lane on the left is a serum protein electrophoresis fixed with acid, and the lane on the right is an immunofixation with antipentavalent antisera (anti-IgG, IgA, IgM, κ, and λ). The sample in lane 8 shows a band (arrow) that does not react with antipentavalent antisera; it is fibrinogen.
An electropherogram with a prominent M-protein spike and suppression of the normal gamma globulin. The spike measures 1.9 g/dl, and the total gamma globulin is 2.0 g/dl. Only 0.1 g/dl is accounted for by the gamma globulin not measured in the M-protein spike. T.P., total protein; A/G, albumin/globulin; Ref, reference.
Serum electropherogram with major protein bands noted, as well as globulin regions.
Serum protein electrophoresis gel with three samples. The middle sample is deficient in α1 antitrypsin (a ZZ variant). This can be seen by the lack of the α1 antitrypsin band compared to the samples above and below it. The electropherogram is the CZE pattern from the same case. Note that while the α1 antitrypsin band is absent, the measurement of the α1 region shows a normal amount of α1 globulin. This reflects the measurement of proteins involved with α1 lipoprotein and orosomucoid. Rel, relative; TP, total protein; A/G, albumin/globulin.
Electropherogram demonstrating a massive polyclonal increase in IgG4 subclass (arrow) (proven by immunofixation). Ref., reference; T.P., total protein; A/G, albumin/globulin.
Electropherogram demonstrating a cirrhosis pattern. Ref., reference; L, low value; H, high value; T.P., total protein.
Electropherogram demonstrating a protein loss pattern. TP, total protein; A/G, albumin/globulin; Rel, relative.
Electropherogram demonstrating a tiny M protein (0.11 g/dl). This tiny M protein turned out to indicate λ light-chain disease with a massive monoclonal FLC in the urine. Rel, relative.
Several urine protein electrophoretic patterns for concentrated urine samples.
Locations of radiocontrast spikes in CZE a
Comparison of serum protein intervals by agarose gel electrophoresis and CZE a