ABSTRACT
A homogeneous spectrophotometric EMIT immunoassay kit for the quantitation of theophylline in serum or plasma has been modified to produce a rapid, amperometric immunoassay requiring a 50 microliters whole blood sample. The basis of the detection system for the assay is the electrochemical oxidation of NADH produced by G6PDH-labelled theophylline at a potential of +150 mV vs Ag/AgCl using platinised activated carbon (PACE) electrodes. Comparison of the amperometric whole blood method with the conventional spectrophotometric plasma assay produced a reasonable correlation: y = 0.90x - 1.01, (r = 0.98, n = 12). The advantage of the new method is that simple and robust instrumentation can rapidly determine theophylline in whole blood with no sample pre-treatment or separation steps.
Subject(s)
Enzyme Multiplied Immunoassay Technique , Theophylline/blood , Biosensing Techniques , Blood Chemical Analysis/instrumentation , Blood Chemical Analysis/methods , Electronics, Medical , Enzyme Multiplied Immunoassay Technique/instrumentation , Evaluation Studies as Topic , Humans , NAD , Oxidation-Reduction , SpectrophotometryABSTRACT
Traditional, less sensitive simple immunoassays ('Placentex' and 'Pregnosis') were performed concurrently with newer, more sensitive, but simple immunoassays ('Sensitex' and a capillary tube pregnancy test) and radioimmunoassays for beta-HCG from two commercial sources (Roche Diagnostics and Monitor Science Corporation). Generally these various assays agreed, but of particular importance for the early screening of urinary HCG (prior to the first missed but expected period) was that the commercial half-unit tube test ('Sensi-tex') gave early positive results comparable to the half-unit research capillary tube test previously reported. These sensitive simple immunoassays (SSIA) may improve the management of patients very early in pregnancy and following termination of pregnancy.
