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Biomedical subjects

A R Walker

Publications and source records attributed to A R Walker.

At least 19 recordsLinked to original sources
PubMed1992

Screening for colorectal carcinoma: an analysis of the sensitivity of haemoccult.

The sensitivity of Haemoccult for asymptomatic colorectal carcinoma has been estimated in a large randomized controlled trial of mass population screening, with a minimum follow-up of 2 years. A total of 111 cancers were diagnosed in those who completed the screening tests; of these, 36 appear to have been missed by Haemoccult and 75 were detected by the test, giving an overall sensitivity of 67.6 per cent. Haemoccult was shown to be significantly more sensitive for carcinoma of the sigmoid and descending colon than for rectal or right-sided cancers (81 versus 45 and 47 per cent, respectively). The sensitivity was higher when tests were completed over 6 rather than 3 days (74 versus 65 per cent), but this difference was not statistically significant. There was no evidence for a detrimental effect on tumour stage of a false-negative Haemoccult test; indeed, a higher proportion of the interval cancers were Dukes' A tumours than cancers in the control group.

Aged↗
PubMed1992

Cost savings in mass population screening for colorectal cancer resulting from the early detection and excision of adenomas.

The widely-accepted hypothesis of a development sequence from colorectal adenoma to carcinoma is felt by clinicians to legitimate adenoma excision during routine colonoscopic investigation. Using published data on adenoma development, and adenoma prevalence data derived from the Nottingham colorectal cancer screening trial, the number of carcinomas prevented by early excision as a result of screening is predicted. The cost-effectiveness of early excision is then evaluated with reference to the expected treatment costs saved. These cost savings are found to represent a discount on the overall costs of mass population screening for colorectal cancer.

Adenoma↗
PubMed1992

Effect of subject age on costs of screening for colorectal cancer.

STUDY OBJECTIVE: The aim was to estimate costs and yields of faecal occult blood screening and rescreening for colorectal cancer, for differing age cohorts. DESIGN: Cost and clinical data were used as the basis for modelling the expected costs, and cost savings, resulting from the treatment of screen detected cancers, as compared with cancers detected by symptomatic presentation. SETTING: Data were derived from the MRC screening trial currently in progress in Nottingham. PARTICIPANTS: Approximately 140,000 subjects, age 50-79 years, were randomly allocated to a test (screened) and a control (unscreened) group. MAIN RESULTS: The net costs of detecting and treating a cancer following colorectal screening fall as the age of the target population increases, owing principally to the increasing incidence of the disease with age. Generally, the marginal detection and treatment costs falls for all age groups with the first screening round, but rises considerably with the second. If allowance is made for cancers prevented as a result of early detection and excision of adenomas, the costs of screening are substantially reduced for all age groups. CONCLUSIONS: Assuming a cost per QALY (quality adjusted life year gained) equivalent to that derived for the breast cancer screening programme, and a QALY gain from colorectal screening of one year, three screens, each separated by two years, appear economically justified for populations aged 60 years and above. Expected gains from cancer prevention make two screens justifiable for those between 45 and 59 years of age.

Age Factors↗
PubMed1992

Perplexing features in the occurrence of dental caries and its relationship to sugar intake.

Epidemiologically, there are numerous perplexing features, insufficiently appreciated, in the occurrences of degenerative diseases, and in the roles of their risk factors. This applies particularly to dental caries, the commonest of all diseases, and the risk factor, sugar intake. In some contexts, caries scores are much lower, or are much higher, than expected. Moreover, even in contexts where outwardly the same risk factors are widespread, ranges of scores are much wider than would be expected. In all contexts, among groups and more especially among individuals, the association of caries experience and dietary intakes, particularly that of sugar intake, is limited. Accordingly, caution must be exercised in the over-blaming of sugar and in the overclaiming of benefits to be derived from reducing intake.

Adult↗
PubMed1992

Cost-effective screening strategies for colorectal cancer.

This paper models a range of feasible strategies for mass population screening for colorectal cancer. It uses both clinical and economic data derived from the major colorectal cancer screening trial currently under way in Nottingham, supplemented by data from concurrent Scandinavian trials. Costs and yields for 12 strategies are modelled, and optima are identified according to a number of evaluation criteria. The cost-effectiveness condition for the desirability of introducing a programme of colorectal screening is also established.

Aged↗
PubMed1991

Malabsorption of carbohydrate foods by urban blacks.

Prevalences of non-infective bowel diseases are very low in South African urban blacks compared with the white population. In seeking elucidation, using breath hydrogen measurements in series of black and white subjects, small-bowel transit time was determined, and the malabsorption of maize, wheat, and rice investigated. Median transit times in both ethnic groups were similar. Rice was fully, but wheat incompletely absorbed by both groups. Maize, the staple food of blacks, was incompletely absorbed by them, although completely absorbed by the white subjects. Carbohydrate consumption is high in the black population (60-65% of total energy intake). It is probable that in blacks, despite their now eating a low-fibre diet, an expected increase in large-bowel diseases has been inhibited in part by the protective mechanism of fermentation of malabsorbed maize and wheat.

Adult↗
PubMed1991

Glycaemic responses to different carbohydrate foods in healthy and diabetic blacks in Soweto.

Diabetes mellitus is uncommon in rural southern African blacks. With urbanisation and lifestyle changes, incidence rises to that in western populations. To assess associated changes in carbohydrate metabolism, glycaemic responses to glucose, refined maize, refined rice and bread were studied in 8 healthy and 8 non-insulin-dependent diabetic urban blacks. Additionally, in the healthy group serum insulin responses were measured. In the healthy, maize (the staple food of blacks) elicited the highest glucose response (207 mmol/l/min) and bread the lowest (107 mmol/l/min). The glycaemic indices of maize and glucose were similar. Serum insulin responses to maize were significantly lower than that of bread at 90 minutes (maize 66 muU/ml; bread 93 muU/ml; P = 0.02). In diabetics, maize and glucose elicited similar glycaemia (928 mmol/l/min and 921 mmol/l/min respectively). The high glucose response to maize could relate to its processing and physical form. The low insulin secretion could be due to inadequate stimulation by the 'entero-insular' axis. Moreover, variability in glucose insulin responses could stem from ethnic or genetic reasons. In the dietary management of black diabetics, refined maize should be replaced by other cereals.

Adult↗