ABSTRACT
BACKGROUND: We evaluated the Vitros 950 (Johnson & Johnson Clinical Diagnostics, Inc., NY, USA) in the measurement of digoxin and theophylline levels and compared its results to those of the TDxFLx II (Abbott Laboratories, IL, USA) used for therapeutic drug monitoring (TDM) world-widely in order to assess the utility of the Vitros 950 as a TDM instrument. METHODS: From June 1997 to August 1997, 125 and 135 candidates for TDM were randomly chosen to measure digoxin and theophylline, respectively, using the Vitros 950 and TDxFLx II. The relationship between its results and those of TDxFLx II were determined. The within-run and between-run precisions of the Vitros 950 were determined using two controls (Vitros Performance Verifier I and II; J & J Clinical Diagnostics, Inc., NY, USA). The high-concentration control (Vitros Performance Verifier II) was diluted in Vitros 7% BSA to 5 dilutions. And linearity for quantitative analysis of digoxin and theophylline were determined. RESULTS: The coefficients of variation (CV) for the within-run of the Vitro 950 were 0.8% - 4.4%. And the CV for between-run precision of the Vitro 950 were 1.7% - 12.3%. The linearity of digoxin and theophylline were relatively good. The correlations (r) of digoxin and theophylline levels with those determined by the Abbott TDxFLx II were 0.95 and 0.93, respectively (P <0.001). CONCLUSIONS: The recently developed dry slide method of the Vitros 950 proves to good precision and linearity for quantitative analysis of digoxin and theophylline. Its results correlate well with those of the TDxFLx II. The Vitros 950 does not require an elaborate preparatory protocol for the sample, and is easy to use and maintain.So it is considered a highly feasible instrument for stat test.