Lab Med Online.  2014 Oct;4(4):187-190. 10.3343/lmo.2014.4.4.187.

Performance Evaluation of the Syva EMIT Methotrexate Assay on the Toshiba 200FR NEO

• Lim J
• Kim J
• Sohn YH
• Koo SH
• Kwon GC

• KMID: 2312254
• DOI: http://doi.org/10.3343/lmo.2014.4.4.187

Abstract

BACKGROUND
Methotrexate (MTX) is an antifolate antagonist that is widely used for treating various malignancies and non-malignant diseases. MTX levels should be monitored when used in high concentration to determine when to start leucovorin rescue. In this study, we evaluated the analytical performance of the EMIT Methotrexate Assay on a 200FR NEO Chemistry Analyzer (Toshiba Medical System Co., Japan) and compared it with Viva-E Drug Testing System (Siemens Healthcare, Germany).
METHODS
According to the Clinical Laboratory and Standards Institute (CLSI) Evaluation Protocol (EP) 5-A2, three concentrations of the Liquichek Therapeutic Drug Monitoring Control (Bio-Rad Laboratories, USA) were analyzed twice a day for 20 days to monitor assay precision. The 200FR NEO and Viva-E instruments were compared using 40 patients' sera, according to CLSI EP9-A2. The linearity and carry-over rate were also evaluated.
RESULTS
Between-run CVs for low-, medium-, and high-level controls were 4.9%, 0.9%, and 2.0%, respectively, whereas between-day CVs for low-, medium-, and high-level controls were 8.1%, 1.3%, and 3.5%, respectively. In the linearity test, the coefficient of determination (R2) was 0.98 (0.06-1.92 micromol/L). In the comparison study, R2 was 0.955, showing good correlation between the 200FR NEO and Viva-E instruments. The carry-over rate was 0.9%.
CONCLUSIONS
The EMIT assay showed good precision, linearity, and carry-over rate on the Toshiba 200FR. An excellent correlation was observed when comparing results obtained using the Toshiba and Viva-E instruments. In conclusion, the Syva EMIT MTX assay can be readily used for MTX monitoring on the Toshiba 200FR NEO.

Keyword

Methotrexate; EMIT; Therapeutic drug monitoring

MeSH Terms

Chemistry
Delivery of Health Care
Drug Monitoring
Leucovorin
Methotrexate*
Leucovorin
Methotrexate

Figure

• 

  Fig. 1 Comparison of MTX level determinations measured by the Viva-E and the Toshiba 200FR NEO. Differences in results from either instrument are shown in (A) a scatter plot with an ordinary linear fit (blue line), (B) a Bland-Altman difference plot, or (C) a Bland-Altman percent difference plot.

• 

  Fig. 2 Linearity of MTX values using the Syva EMIT Methotrexate Assay on the Toshiba 200FR NEO.

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