Evaluation of Theophylline, Valproic Acid and Phenytoin by the CEDIA Method

Kim, Moon Hee; Shin, So Young; Kwon, Gye Cheol; Koo, Sun Hoe; Park, Jong Woo

Abstract

BACKGROUND
CEDIA is a newly developed method for therapeutic drug monitoring (TDM) and has some merits such as easy application to routine chemical analyzers, rapid and precise quantitation even in low concentrations and less cross reactivity. We evaluated the CEDIA(epsilon) (Microgenics Co., CA, USA) in measurement of theophyllin, valproic acid and phenytoin levels using 502X(epsilon) (A & T, Tokyo, Japan) and compared the results to those of the TDx(epsilon) (Abbott Laboratories, IL, USA) in order to assess the utility of the CEDIA(epsilon).
METHODS
We evaluated the performance of 502X(epsilon) in the aspects of the within-runs and the between-runs precision, linearity, and carry-over. We compared the results of the CEDIA(epsilon) reagent with those of TDx(epsilon). The control materials (Bio-Rad TDM control level 1 and level 3; Bio-Rad laboratories, CA, USA) and clinical specimens were used for these studies.
RESULTS
The coefficients of variation (CV) for the within-run and the between-run imprecision of 502X(epsilon) were 2.0-7.6% and 4.0-6.5%, respectively. The carry-over rate for theophyllin, valproic acid and phenytoin was 1.33%, 0.45% and 0.53%, respectively. The linearity (r(2)) of theophyllin, valproic acid and phenytoin was 0.9941, 0.9983 and 0.9947, respectively. The correlation coefficients (r) of theophyllin, valproic acid and phenytoin levels of CEDIA(epsilon), with those determined by the TDx(epsilon), were 0.9730, 0.9703 and 0.9695, respectively (P<0.001).
CONCLUSIONS
The recentlydeveloped CEDIA(epsilon) proved to be highly precise and linear for quantitative analysis of theophyllin, phenytoin and valproic acid. Correlations with TDx(epsilon) were significantly high. CEDIA(epsilon) was thought to be clinically useful for TDM.