This document compares different electrophoretic methods for detecting monoclonal proteins in patients with multiple myeloma. Capillary electrophoresis is more sensitive than agarose gel electrophoresis at detecting monoclonal proteins, especially those migrating in the beta region, but is less specific. Immunofixation electrophoresis is less sensitive than agarose gel electrophoresis or capillary electrophoresis at detecting monoclonal proteins, especially at low concentrations. Measuring the kappa to lambda free light chain ratio can help detect monoclonal proteins and improve the sensitivity of electrophoretic methods. Capillary electrophoresis may detect subtle peaks not seen on gel electrophoresis, but some minor abnormalities detected only by capillary electrophoresis could be false positives.

1. Comparison of Electrophoretic Methods
in Multiple Myeloma Patients
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2. Terms and Definitions
• Capillary electrophoresis (CE): a liquid-based protein separation
system, having advantage of quick and automated.
• Subtraction immunotyping electrophoresis (IT): seperates serum
proteins using antisera for each of the heavy and light chains.
• Agarose gel electrophoresis (AGE): One of the most commonly used
clinical method for protein electrophoresis.
• Immunofixation electrophoresis (IFE): is used to confirm the
presence of monoclonal bands and to identify the type of paraprotein
Am J Clin Pathol. 2008;129:451-458.

3. A Clinical Question
• Is the capillary electrophoresis appropriate methods
as good as gel electrophoresis
to detect monoclonal protein in the serum or urine
in following-up multiple myeloma patients?
▶so that, we can reason the observed phenomenon in the 2 cases.
• Articles reviewed includes
• McCudden et al. Am J Clin Pathol. 2008;129:451-458.
• Cho and Jeon et al. Ann Clin Lab Sci. 2013;43:285-288.
• Cho et al. Clin Lab. 2013;59(3-4):445-448. (abstract only)

4. McCudden 2008
• CE is more sensitive than AGE
• Avoidance of application artifacts
• Superior detection of β-region migrating monoclonal proteins
• CE is less specific than AGE
• Direct photometric detection of proteins during electrophoresis, resulting in
minor abnormalities in the electrophoretogram not typically observed in
those derived from scanning densitometry.

5. McCudden 2008
• The IT method was less sensitive than AGE or CE for the detection of
monoclonal immunoglobulins.
• In particular, specimens contained monoclonal immunoglobulins at low
concentrations (<0.3 g/dL),
• Monoclonal free light chains,
• multiple (oligoclonal) bands
were often incorrectly typed by interpreters using IT.

6. Cho and Jeon 2013
• Small peaks in capillary electrophoresis could be important findings as
precursors to large and clear monoclonal peaks in the future.
• K/L ratio by the sFLC assay is highly useful as an auxiliary method for
electrophoresis, because where the K/L skewing results significantly
improved monoclonality detection.
Ann Clin Lab Sci. 2013;43:285-288.

7. Free Light Chain (FLC) Assay
• A sensitive antibody-based system that can detect
low concentrations of monoclonal free light chains.
• FLC kappa – 22.5 kDa, monomer
FLC lambda – 45 kDa, dimer
FLC kappa to lambda in serum = 1:1.6
• Free serum kappa light chains – 3.3 to 19.4 mg/L
Free serum lambda light chains – 5.7 to 26.3 mg/L
Kappa to lambda ratio – 0.26 to 1.65
Lancet. 2003;8;361(9356):489-91.

8. Conclusion
• Subtle peak in UPEP by capillary method in the case 1 (M/72), which
is not visible in GE, might be a false positive results in CE.
• However, since small peaks in the CE could possibly predict future
huge increase in M-protein, the interpretation better to be conducted
with FLC assay results.
• The case 2 (F/66), which did not show peak in subtraction
immunotyping, but did in gel immunofixation, might be explained by
detection limit of the capillary electrophoresis method.

9. 백승민
감사합니다.