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Letters |
1
Laboratory Medicine, Immunology and
2
Internal Medicine, University Hospitals Leuven, Katholieke Universiteit Leuven, Herestraat 49, B-3000 Leuven, Belgium
aAuthor for correspondence. E-mail xavier.bossuyt{at}uz.kuleuven.ac.be.
To the Editor:
Over the last 5 years, capillary zone electrophoresis (CZE) has emerged as an automated technique for the separation of serum proteins in clinical laboratories (1)(2)(3)(4)(5). In conventional methods, quantification of the protein fractions is based on dye binding, whereas CZE uses ultraviolet detection at 214 nm for direct protein quantification via the peptide bonds. Any substance or drug that is present in serum and that absorbs at 214 nm potentially can interfere with CZE analysis. It has been reported that radio-contrast media, which absorb at 214 nm, interfere with CZE and can simulate a monoclonal component (6)(7)(8). In the present report, we describe that the antibiotic piperacillin-tazobactam (Tazocin®; Wyeth Lederle) produces a small peak at the anodal site of the ß-globulin fraction.
In Fig. 1
, panels A and C show the ß and 
fractions of CZE electropherograms (Beckman Paragon CZE 2000, software version 2.21) of two samples obtained from patients who received piperacillin-tazobactam (4 g of piperacillin/500 mg of tazobactam three times per day). In the sample shown in panel C, there was a small monoclonal protein in the region. The antibiotic was given intravenously over a 30-min period. The samples were obtained 10 min (Fig. 1A
) and 30 min (Fig. 1C
) after administration of the antibiotic. In each case, a small but distinct peak was observed at the anodal site of the transferrin peak in the ß-globulin fraction. Such a peak is absent in a normal CZE electropherogram and was not seen in the CZE electropherogram of a specimen from the same patient as in Fig. 1A
collected 2 days after piperacillin-tazobactam administration (Fig. 1B
). After this time period, the antibiotic had been cleared from the blood stream. The elimination half-life of piperacillin-tazobactam is 0.7–1.2 h in patients with normal kidney function. Protein binding for piperacillin is 16% at serum concentrations of 200–300 mg/L; for tazobactam, protein binding is 20–23%. Addition of piperacillin-tazobactam to a normal serum led to the appearance in the CZE electropherogram of an abnormal peak in the same location as the extra peak observed in the electropherogram from patients receiving the antibiotic (Fig. 1D
). Parenteral administration of vancomycin (Vancocin®, 1 g twice per day; Eli Lilly) or ceftazidim (Glazidim®, 1 g three times per day; Glaxo Wellcome) did not lead to the appearance of an abnormal peak on CZE (data not shown).
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Collectively, intravenously administered piperacillin-tazobactam produces a small peak in the ß region in CZE. Such peaks might simulate a small monoclonal protein.
References
The following articles in journals at HighWire Press have cited this article:
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  S. Neale, A. Brown, J. Jeffery, and R. M Ayling Drug Monitoring and Toxicology (DMT) Clin. Chem., January 1, 2008; 54(1): 218 - 220. [Full Text] [PDF]
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X. Bossuyt, J. Verhaegen, G. Marien, and N. Blanckaert Effect of Sulfamethoxazole on Clinical Capillary Zone Electrophoresis of Serum Proteins Clin. Chem., February 1, 2003; 49(2): 340 - 341. [Full Text] [PDF]
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