Operator Error: A Critical Determinant of False Amikacin and Tobramycin Concentrations Using Fluorescence Polarization Immunoassay Kits and TDX Analyzer

Abstract

Amikacin and tobramycin are aminoglycosides used to treat severe Gram-negative infections. Therapeutic monitoring of both drugs is essential to avoid drug toxicity. Fluorescence polarization immunoassay kits for both amikacin and tobramycin are available from Abbott Laboratories, and assays can be run using the TDx analyzer. The test code for amikacin is 3, whereas the test code for tobramycin is 2. Here the authors report that when the operator mistakenly programmed test code 3 (amikacin code) while using the tobramycin kit, the tobramycin values were falsely elevated. The instrument software does not have any mechanism to detect this error. Similarly, when the amikacin kit was used and the operator mistakenly programmed test code 2 (tobramycin code), the amikacin values were falsely lowered. For example, in a serum sample taken from a patient the true amikacin concentration was 20.9 microg/mL. When the amikacin kit was used correctly but test code 2 was programmed, the observed concentration was falsely lowered to 6.1 microg/mL. Similarly, in another specimen the true tobramycin concentration was 3.1 microg/mL. However, when the tobramycin kit was used correctly but test code 3 was used, the observed concentration was falsely elevated to 14.3 microg/mL. The authors also observed a similar effect with controls and spiked specimens containing either amikacin or tobramycin. They conclude that correct programming of the test code is vital to obtaining useful results in amikacin and tobramycin analysis using the TDx analyzer.

Floating resistivity detector for microchip electrophoresis

“…Close monitoring of the contents of aminoglycosides in patients' sera is essential as elevated levels of aminoglycosides antibiotic can cause adverse or toxic reactions such as nephrotoxicity and ototoxicity. Traditionally, microbiological assays (enzymatic assay and immunoassay) [37][38][39] and chromatographic assays (GC and LC) [40][41][42] were employed for clinical analysis. However, long incubation time, interference caused by nonspecific inhibitors, and poor repeatability and reproducibility prevents the former from becoming the method of choice while the latter is not ideal as well due to the needs for pre/on-column derivatization and incompatible physicochemical properties.…”

Determination of tobramycin in soil by HPLC with ultrasonic-assisted extraction and solid-phase extraction

“…Some analytical techniques such as immunological [6][7][8][9], colorimetric [10], and chromatographic [5,[11][12][13][14][15][16][17][18][19][20][21] methods have already been reported for the quantitative determination of tobramycin. Among these analysis methods, high performance liquid chromatography (HPLC) is the most widely used method for determination of tobramycin in different matrices such as human plasma, urine, serum, and pharmaceutical formulations.…”

Development and validation of HPLC method for the determination of tobramycin in urine samples post-inhalation using pre-column derivatisation with fluorescein isothiocyanate

“…Several analytical techniques have been reported for the analysis of tobramycin in biological fluids [26,32] including radioimmunoassay (RIA) [21], fluorescence polarization immunoassay (FPIA) [4], microbiological assays [8,24], radiochemical assay [9], enzyme immunoassay (EIA) [10,29], and chromatographic methods [13,15,22,26,31]. High-performance liquid chromatography (HPLC) and gas chromatography (GC) have been used to detect the aminoglycosides at low concentrations in biological fluids.…”

“…A number of HPLC pre-column derivatisation methods have been demonstrated with 2,4,6-trinitrobenzenesulfonic acid (TNBS) [11,17,22], 1-fluro-2,4-dinitrobenzene (FDNB) [2,[4][5][6][7]27], ophthaladehyde (OPA) [3,12,[26][27][28] and 1-naphthyl isothiocyanate (NITC) [15]. The limitation of use of TNBS and FDNB is due to their high toxicity, and the main disadvantage of NITC is the length of time to achieve reaction.…”