Assay of theophylline: in vivo and in vitro evaluation of dry chemistry and immunoassay versus high-performance liquid chromatography.
In the last decade, kits using dry chemistry have been introduced for analysis of theophylline in biological fluids. We investigated the performance of Ames Seralyzer and Kodak Ektachem 700XR. They were compared to an enzyme immunotechnique (Syva EMIT) and high-performance liquid chromatography (HPLC). Mixed sera from theophylline-treated patients at concentrations of 20, 50, and 80 mumol/L were used. We also investigated the performance of the various methods when assaying theophylline concentrations obtained from individual patients treated or intoxicated with theophylline (n = 35 patients). In within-day analysis, the EMIT method deviated +1- + 9%. the Ektachem 700XR method deviated +2- + 8%, and the Seralyzer method deviated at least + 18% compared to HPLC. Within-day variability was low for all 4 methods. A similar pattern was seen during between-day assay. In five intoxicated patients, EMIT, Seralyzer and Ektachem 700XR deviated at least + 10% compared to HPLC. The Ektachem 700XR method deviated +16- + 36% compared to HPLC, when samples of 240 mumol/L and above were analyzed. Our study shows that theophylline assay kits cannot be recommended in drug analytical laboratories unless specific backup methods are available. EMIT showed the best performance compared to HPLC. Ektachem 700XR gave good results at therapeutic drug concentrations, but was not reliable in intoxicated patients or in those with decreased kidney function.
Department of Clinical Chemistry, Södersjukhuset, Stockholm, Sweden.
H
H
Wallinder
L L
LL
Gustafsson
K
K
Angbäck
P
P
Höglund
A
A
Magnusson
L
L
Arvanius
D000328:Adult; D002623:Chemistry Techniques, Analytical / Q000379:methods; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003404:Creatinine / Q000097:blood; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D006932:Hyperbilirubinemia / Q000097:blood; D007124:Immunoenzyme Techniques; D007668:Kidney / Q000502:physiology; D008297:Male; D011933:Reagent Kits, Diagnostic; D013806:Theophylline / Q000097:blood*
D011933:Reagent Kits, Diagnostic; D003404:Creatinine; D013806:Theophylline