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Biomedical subjects

D L Colbert

Publications and source records attributed to D L Colbert.

At least 19 recordsLinked to original sources
PubMed1994

Detection of phencyclidine in urine using a polarization fluoroimmunoassay.

A polarization fluoroimmunoassay was developed for the detection of phencyclidine in urine and the reagents were adapted for use on the Abbott TDx analyser. The assay was used to look for evidence of phencyclidine abuse, over a 6 month period, amongst patients attending drug abuse clinics in the East End of London. Although over 2000 patients' samples tested negative, the assay successfully detected phencyclidine in an external quality control scheme.

Animals↗
PubMed1994

Drug abuse screening with immunoassays: unexpected cross-reactivities and other pitfalls.

Immunoassays are the only practical means of coping with the increasing demand for drug abuse screening because of their simplicity and ease of automation. However, it is essential that the analyst understands the strengths and weaknesses of such assays to enable correct interpretation of results. This is especially important with the increasing popularity of near-patient testing where assays are liable to be carried out by inexperienced and untrained staff. False-positive and false-negative results, unexpected cross-reactivities and other pitfalls are discussed, together with an attempt to explain the reasons for these problems.

Amphetamine↗
PubMed1993

Experience with cost-effective in-house reagents for the assay of carbamazepine in serum, using the Abbott TDx.

The development of inexpensive in-house reagents for the assay of carbamazepine in serum, using a commercially available derivative and antiserum is described. They were adapted for use on the Abbott TDx as direct replacements for commercial reagents. Comparison with a high-performance liquid chromatography method is discussed together with an evaluation of their performance in an external quality control scheme. They proved robust and reliable and reagent costs were reduced to around 3p per test.

Carbamazepine↗
PubMed1993

Reducing the cost of phenytoin assays with in-house TDx reagents.

The Abbott TDx is frequently used for therapeutic drug monitoring of phenytoin concentrations, but reagent costs are high. In an attempt to reduce these costs, we investigated the preparation of in-house reagents. A commercial antiserum was available at reasonable cost and the fluorescent tracer was easily prepared. We describe the preparation of these reagents and their application to the TDx system. Substantially reduced costs were obtained using the in-house reagents.

Calibration↗
PubMed1992

Urinary cotinine fluoroimmunoassay for smoking status screening adapted to an automated analyser.

A polarization fluoroimmunoassay for cotinine, a major metabolite of nicotine, has been adapted for fully automated screening of urine samples on the Abbott TDx analyser. The method has sensitivity and specificity suitable for the discrimination of active smokers from non-smokers (including passive smokers) by application of a cut-off at 0.5 mg l-1 of total urinary cotinine. Most active smokers' urine gave results over 1 mg l-1, whereas apparent levels in non-smokers were 0.08 mg l-1 or lower. A result for one sample can be obtained in about 5 min and a throughput of 80 samples h-1 can be maintained for large-scale screening applications.

Adult↗
PubMed1992

Cost effective EMIT assays, for drugs of abuse in urine, using the Eppendorf EPOS analyser.

Laboratories with an increasing work load of drug abuse testing require high turnover techniques at low cost. Syva's EMIT system is suitable for modification onto modern automated instrumentation and, with reagent dilution, costs can be significantly reduced. We describe the modification of these assays onto the Eppendorf EPOS analyser which can process 300 samples an hour at a cost of 13p per test.

Cost-Benefit Analysis↗
PubMed1992

Measurement of phenytoin in serum using in-house reagents employing the Syva enzyme-multiplied immunoassay technique principle.

Reagents have been developed for the measurement of phenytoin in serum, using the enzyme-multiplied immunoassay approach first introduced by Syva. The assay uses a commercially available antiserum and phenytoin valeric acid coupled to glucose-6-phosphate dehydrogenase as the tracer. It has been adapted for use on an Eppendorf EPOS analyser, which allows 300 assays/h with high precision. Excellent agreement was achieved with commercial reagents, and costs were reduced markedly.

Antibodies↗
PubMed1992

An in-house opiate enzymoimmunoassay based on the Syva EMIT principle.

Many laboratories involved in drug-abuse screening use enzymoimmunoassays such as Syva's EMIT system. Although automation has been extensively used to reduce assay costs, further reductions can be achieved by the development of in-house reagents. We have developed our own reagents for the detection of opiates in urine by using the Syva EMIT principle and adapted it for use on an Eppendorf EPOS analyzer. The immunogen was produced from 3-carboxymethylmorphine, and morphine-3-glucuronide attached to glucose-6-phosphate dehydrogenase was used as the tracer. Excellent agreement with Syva's commercial assays was obtained.

Antibody Specificity↗
PubMed1991

The effect of fluorescein labels on the affinity of antisera to small haptens.

Small haptens such as methylamphetamine (MW 149) cannot, on their own, induce an immune response. It is also unlikely that they fill the binding site of any antibody that recognises them. Under such circumstances any attached label might be expected to enter the area of the binding site and exert an influence on overall binding. To investigate the possible influence of the label on binding, a range of fluorescein-labelled derivatives, differing in bridge length, were prepared. Antiserum binding of these labelled derivatives was then compared to that of the unlabelled drug. Evidence is presented which suggests that, with small haptens, the closeness of the fluorescein molecule can markedly influence antibody binding. Significant differences were found in titre, sensitivity, and assay kinetics. These overall effects appear to be brought about by the change in affinity of the antibody for the labelled hapten.

Amphetamines↗
PubMed1991

A broad spectrum immunoassay using fluorescence polarization for the detection of amphetamines in urine.

Rapid immunoassays are widely used to screen for amphetamine abuse. Broad spectrum immunoassays are the most useful for this purpose followed by physicochemical techniques for verification and identification of particular drugs. We describe the production of an antiserum with a broad specificity for the amphetamine group of drugs. The antiserum was produced in a sheep using an immunogen linking amphetamine to keyhole limpet haemocyanin via an N-aminobutyl bridge. This antiserum was used to develop a fluorescence polarization immunoassay for application to urine samples. A limited investigation into the use of saliva as an alternative sample was also performed. The effects of chemical modifications to the basic amphetamine structure on antibody binding are discussed.

Amphetamines↗
PubMed1988

Development of fluoroimmunoassays for the specific detection of morphine in urine.

Two fluoroimmunoassays for the specific detection of morphine in urine are described based on the use of ovine antibodies and fluorescein-labelled normorphine. The first, a polarisation fluoroimmunoassay, is performed by adding 10 microliter of urine to 1.5 ml of a single-reagent, comprising premixed antiserum and tracer, incubation for a few minutes at ambient temperature and measurement of fluorescence polarisation. The assay gives results which compare well with those by thin-layer chromatography, EMIT d.a.u., and the Boehringer opiate drug test. Although adequate for routine screening for drug abuse, the technique is not as sensitive as some radioimmunoassays. Therefore, a second fluoroimmunoassay was developed based on the use of the same antibodies covalently coupled to magnetisable particles to facilitate both the separation of the bound and free fractions and the removal of non-specific interfering substances. Thus, larger sample volumes could be employed and greater sensitivity achieved.

Chromatography, Thin Layer↗
PubMed1988

Development of a single reagent polarisation fluoroimmunoassay for the detection of opiates in urine.

The design, development, and optimisation of a simple polarisation fluoroimmunoassay to detect the opiate group of drugs, in urine, is described. Urine (10 microL) is added to 1.5 mL of a single reagent, prepared by mixing ovine anti-opiate serum with fluorescein-labelled morphine. After incubation for 30 min at 30 degrees C, or 60 min at room temperature, fluorescence polarisation is measured. The assay can be used as a "stat" test or automated for large batch screening and detects the commonly abused opiates, heroin (through its metabolite morphine), codeine, and dihydrocodeine.

Antibody Specificity↗