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Biomedical subjects

A C Deacon

Publications and source records attributed to A C Deacon.

At least 19 recordsLinked to original sources
PubMed2003

International air travel: a risk factor for attacks in acute intermittent porphyria.

Five patients are reported with acute intermittent porphyria in whom attacks were apparently precipitated by international air travel. In four subjects this was the initial presenting attack and in a fifth the cause of an acute relapse in a patient requiring regular haem arginate prophylaxis. Multifactorial precipitants implicated include, dehydration, missed meals, alcohol use, infection, chronic hypoxia, premenstrual syndrome and stress. Acute intermittent porphyria should be suspected in individuals presenting with unexplained acute abdominal pain following international air travel. Appropriate precautions may reduce the incidence of attacks in known porphyrics.

Abdominal Pain↗
PubMed2001

ACP Best Practice No 165: front line tests for the investigation of suspected porphyria.

The porphyrias are uncommon disorders of haem biosynthesis and their effective management requires prompt and accurate diagnosis. This article describes methods for the determination of urinary porphobilinogen, urinary and faecal total porphyrins, and total porphyrins in erythrocytes and plasma that are suitable for use in non-specialist laboratories. The selection and interpretation of these methods, and the indications for further, more specialised, investigation are discussed.

Biomarkers↗
PubMed1998

Identification of acute porphyria: evaluation of a commercial screening test for urinary porphobilinogen.

A commercial semi-quantitative kit (Trace) for urinary porphobilinogen (PBG) in which urine is pre-treated with ion-exchange resin and the colour of the Ehrlich-PBG adduct matched against a set of surrogate standards was compared with qualitative screening methods (Watson-Schwartz) in common use. Twenty samples in which PBG had been quantitated were blindly tested by both methods in each of 13 typical user laboratories. For urine samples with raised PBG, 123 out of 129 results were positive when tested with the Trace kit. Using qualitative tests routinely in use in the various laboratories only 45 out of 119 results were unequivocally positive. Sixteen out of 91 results for pigmented urine samples with normal PBG were reported as positive using qualitative screening tests, but only one using the Trace kit. Therefore, the Trace method is far more sensitive and specific than the qualitative screening tests. It is recommended that Watson-Schwartz-type screening tests should be abandoned and, ideally, all urine samples analysed by quantitative methods. However, the Trace method is a convenient alternative which is adequate for the initial screening of symptomatic patients.

Acute Disease↗
PubMed1994

Indian herbal remedies for diabetes as a cause of lead poisoning.

Herbal remedies from the Indian subcontinent have been found to have high concentrations of heavy metals and unsupervised treatment may result in toxicity. We report the case of an Indian patient with hepatitis who was found to have lead poisoning where the source was traced to ethnic remedies he had been taking for diabetes.

Adult↗
PubMed1994

Acute intermittent porphyria: diagnostic conundrums.

Acute intermittent prophyria is a genetic disorder of haem biosynthesis caused by defects in the gene encoding hydroxymethylbilane synthase on the long arm of chromosome 11. Every effort should be made to identify gene carriers amongst the relatives of patients known to have acute intermittent porphyria as they are at risk of developing potentially fatal neurogenic attacks if exposed to precipitating factors. Erythrocyte hydroxymethylbilane synthase activity was determined in 46 members of two large well characterised families by assaying enzyme activity by both high performance liquid chromatography (HPLC) and fluorimetric assays. Additionally, hydroxymethylbilane synthase immunoreactivity was determined by a sandwich-type ELISA. Statistically significant correlations were observed between erythrocyte hydroxymethylbilane synthase activity assayed by HPLC and by the fluorimetric assay, and enzyme protein concentration (r = 0.85, p < 0.001 and r = 0.80, p < 0.001, respectively). The assay of hydroxymethylbilane synthase immunoreactive concentration in erythrocytes was useful in excluding acute intermittent porphyria in one patient in whom unequivocal assignment of porphyric status was not possible by assaying enzyme activity alone. Erythrocyte hydroxymethylbilane synthase activity assayed by HPLC and fluorimetry showed approximately equal diagnostic performances, both giving rise to a dichotomic distribution of values, with overlap zones of 6% (1/16) and 22% (2/9), respectively, at the "cut off" applied.

Adolescent↗
PubMed1988

Performance of screening tests for porphyria.

The clinical utility of screening tests for porphyria has been assessed in 201 cases referred to Northwick Park Hospital. Routine screening in the referring laboratories was unreliable giving both false negative and positive results. Only 43% of porphyrics were correctly identified, apparently due to poor analytical sensitivity. Evidence is presented to show that the adoption of alternative semiquantitative tests for porphyrins employing spectrophotometric scanning of acidified urine or of faecal extracts will overcome many of these problems.

Clinical Laboratory Techniques↗
PubMed1987

Estimation of whole body bone resorption rate: a comparison of urinary total hydroxyproline excretion with two radioisotopic tracer methods in osteoporosis.

In 37 female patients with primary osteoporosis, urinary hydroxyproline excretion, determined in 18 24-h consecutive complete urine collections was compared with two radioisotopic measurements of bone resorption rate measured simultaneously using 85Sr. A somewhat better fit was obtained when the kinetically determined bone resorption rate was corrected for long-term exchange processes within bone. Regression analysis showed that the intercept of the regression of hydroxyproline excretion on resorption rate, corrected or uncorrected for exchange, was significantly higher than zero at about 100 mumol/day. This is consistent with a substantial fraction of urinary hydroxyproline arising from non-bony sources. Fifteen paired studies were analysed and the results suggested that intra-individual variability in these relationships (when studies were separated by a year or more) were similar to inter-individual variability. We calculated the precision with which an estimate of bone resorption could be determined based on the calculated regressions. As a means of non-invasive quantitation of whole body bone resorption rate, the excretion rate of hydroxyproline, measured over 5 days, for example, appeared competitive with isotopic methods making no correction for exchange and relatively little worse than our exchange corrected method.

Aged↗
PubMed1984

Trends in trabecular and cortical bone in the radius compared with whole body calcium balance in osteoporosis.

Mean linear attenuation coefficients for trabecular bone (T) in the distal radius and total absorption coefficients (TA) in the radial mid-shafts of 22 patients with crush fracture osteoporosis were measured serially for a year by using computed tomography. After approximately 6 months, each patient was admitted to a metabolic ward for an 18-day calcium balance study. The rate of change (trend) in trabecular bone (T) in the distal radius was a better predictor of calcium balance than the trend in mid-shaft cortical bone (TA). The scatter in the regressions of the trends of T and TA on calcium balance could be accounted for by known methodological uncertainties.

Absorptiometry, Photon↗
PubMed1982

The Hycel-M multichannel analyzer--a model for evaluation.

We evaluated the Hycel-M Multichannel Analyzer on behalf of the British Department of Health and Social Security. The purpose of the evaluation was to determine the precision of the instrument over a prolonged period of time, to compare its results with those of well-tried laboratory procedures, and to determine how the instrument would perform under the rigors of routine analysis. In addition, experiments were designed and carried out to test specifically certain new features of the instrument. Some new approaches to the analysis of the data generated have been examined and are discussed. The findings are presented as a demonstration of an evaluation procedure.

Autoanalysis↗
PubMed1979

Enzymic assay of total cholesterol involving chemical or enzymic hydrolysis--a comparison of methods.

Manual procedures for estimating serum total cholesterol by use of cholesterol oxidase (EC 1.1.3.6) and the phenol--aminophenazone--peroxidase chromogenic system are described, in which cholesteryl esters are hydrolyzed either by use of pancreatic cholesterol ester hydrolase (EC 3.1.1.13) or saponification by ethanolic potassium hydroxide. Both methods are linear up to a cholesterol concentration of 12 mmol/L and are reproducible (between-run CV, about 1.1%). The chemical hydrolysis method yields results that are about 10% lower than those obtained by enzymic hydrolysis, because of incomplete removal of interfering thiols generated during the saponification of serum. The chemical hydrolysis procedure is much less susceptible to interferences, particularly by bilirubin, but the enzymic hydrolysis system is simpler to perform and therefore has a greater potential for mechanization.

Cholesterol↗