The precision and accuracy studies for theophylline (TP) determinations with Seralyzer System (S. S.) applying apoenzyme reactivation immunoassay were performed and clinical evaluations of the S. S. were also examined. Within-and between-day precision studies of S. S. using the samples of TP spiked in normal human plasma showed a good reproducibility having less than 7 % as the coefficient of variation. TP plasma samples, which were obtained from 6 healthy volunteers, were determined by S. S. and the results were compared with those obtained by high-performance liquid chromatography (HPLC). A good correlation between HPLC and S. S. was obtained (n=42, y= 0.942x+ 0.902, r =0.986, p<0.001).
The specificity of S. S. for TP determination was assessed by measuring TP spiked plasma samples including 4 different metabolites or 6 analogues each, and the effect of ascorbic acid (AA) which has a reducing activity was also examined. The cross reactivity of S. S. was somewhat larger, compared with that of commercially available TP immunoassays. It was found that AA decreases TP levels, however, normal AA concentration range in plasma may not affect TP determination.
On the other hand, it was revealed that S. S. was affected by the concentration of protein in the sample, the lower results were obtained in the low protein concentration. These findings were supported in the case of ultrafiltered plasma or saliva. The TP levels were observed significantly low with S. S. than those with the other method. Based on those observations, S. S. might be a useful method for clinical routine or emergent plasma TP determinations.
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