Dual‐wavelength recording, a simple algorithm to eliminate interferences due to UV‐absorbing substances in capillary electrophoresis

Abstract

Analytical interferences have been described due to the presence of various exogenous UV-absorbing substances in serum. Iodine-based X-ray contrast agents and various antibiotics have been reported to interfere with interpretation of serum protein pherograms, resulting in false diagnosis of paraproteinemia. In the present study, we have explored the possibility of measuring UV absorbance at two distinct wavelengths (210 and 246 nm) to distinguish between true and false paraproteins on a Helena V8 clinical electrophoresis instrument. This study demonstrates that most substances potentially interfering with serum protein electrophoresis show UV-absorption spectra that are distinct from those of serum proteins. Scanning at 246 nm allows detection of all described interfering agents. Comparing pherograms recorded at both wavelengths (210 and 246 nm) enables to distinguish paraproteins from UV-absorbing substances. In case of a true paraprotein, the peak with an electrophoretic mobility in the gamma-region decreases, whereas the X-ray contrast media and antibiotics show an increased absorption when compared to the basic setting (210 nm). The finding of iodine-containing contrast media interfering with serum protein electrophoresis is not uncommon. In a clinical series, interference induced by contrast media was reported in 54 cases (of 13 237 analyses), corresponding with a prevalence of 0.4%. In the same series, 1631 true paraproteins (12.3%) were detected. Implementation of the proposed algorithm may significantly improve the interpretation of routine electrophoresis results. However, attention should still be paid to possible interference due to presence of atypical proteins fractions (e.g., tumor markers, C3).

Large abnormal peak on capillary zone electrophoresis due to contrast agent

“…desalting samples, charcoal pre-treatment, analysis at two different wavelengths, but they are not routinely available and should not be necessary with good laboratory practice. 5,8,9 This case highlights the importance of laboratories having robust processes in place to interpret serum protein electrophoresis patterns and to sense check results before communicating significant abnormalities. Otherwise, erroneous reporting of the presence of a paraprotein could lead to patients having unnecessary and invasive investigations.…”

“…desalting samples, charcoal pre-treatment, analysis at two different wavelengths, but they are not routinely available and should not be necessary with good laboratory practice. 5,8,9…”

Determination of iohexol and iothalamate in serum and urine by capillary electrophoresis

“…Iodine‐based X‐ray contrast agents are well known as analytical interferences in serum protein electrophoresis. Scanning serum pherograms at 246 nm allows to detect all described interfering agents . In comparison with HPLC, CE is an easier, faster, less labor‐intensive and cheaper method, which is at least as accurate as that provided by HPLC.…”