Clinical Chemistry, Vol 33, 130-132, Copyright © 1987 by American Association for Clinical Chemistry

The theophylline method of the Abbott "Vision" analyzer evaluated

KM Chan, J Koenig, KG Walton, TA Francoeur, BW Lau and JH Ladenson

We evaluated the analytical performance of the Abbott "Vision" analyzer for theophylline measurement. The within-day precision (CV) was 1.8% and 3.1% at theophylline concentrations of 15.2 and 25.2 mg/L, respectively; between-day precision was 3.5% and 4.8% at 14.9 and 24.4 mg/L, respectively. Bilirubin (143 mg/L) and triglyceride (7.4 g/L) did not interfere, but hemoglobin caused lower values for apparent theophylline, the magnitude of the decrease being proportional to the hemoglobin concentration. At the cutoff concentration of 1 g/L programmed into the instrument by the manufacturer, hemoglobin reduced the theophylline value by less than 10%. Results by the Vision method (y) compared well with those by the "TDX" procedure (x): r = 0.98, y = 0.978x - 0.270 mg/L. The Vision method gave comparable theophylline values for serum, plasma, and whole-blood samples. We also validated analytically and clinically that capillary blood samples collected by finger stick can be used interchangeably with blood samples collected by venipuncture for monitoring theophylline therapy.