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Biomedical subjects

J B Garner

Publications and source records attributed to J B Garner.

At least 19 recordsLinked to original sources
PubMed1994

Deviance estimates of sample size for equivalence tests in vaccine trials.

This paper proposes a sample size procedure for both equivalence and conventional tests for the comparison of two binomial proportions, based on the signed square root of the deviance. When the comparison is based on the odds ratio, I describe an alternate 'close' conditional exact method that gives results that support those given by the deviance method. I summarize the advantages of the deviance-based method and also show that in general equivalence situations the sample size estimate depends upon the measure of comparison selected, odds ratio, risk ratio or risk difference.

Binomial Distribution↗
PubMed1994

Gender differences in the presentation, treatment, and short-term mortality of acute chest pain.

The Halifax County MONICA database was used to estimate the gender bias in presentation, prehospital and in-hospital treatment, and 28-d mortality of patients suffering an episode of acute chest pain. The study population consisted of all county residents aged 25-74, admitted between 1984 and 1990 to a CCU, or suffering a myocardial infarction anywhere in a hospital. The mean age for men was 58.5 (n = 6561), for women 61.5 (n = 3176). Women of all age groups were more likely to have a history of diabetes or hypertension, and below age 55 had a higher prevalence of peripheral vascular disease. Typical symptoms for infarction were present in 30.8% of women and 38.1% of men (p < 0.0001). More women were taking beta-blockers, Ca-antagonists, digitalis, diuretics, and nitrates (p < 0.001), and more men were on antiarrhythmics. A gender difference was observed for coronary arteriography (24% in men, 18% in women) and for the exercise stress test (23% in men, 18% in women). In hospital, men had more episodes of severe arrhythmias (OR = 1.52). Except for aspirin and antiarrhythmics, the difference in hospital medication and 28-d mortality (9.6% in women vs. 7.8% in men) could be explained by the existing clinical conditions.

Adult↗
PubMed1992

A case-control study of unexplained antepartum stillbirths.

OBJECTIVE: To ascertain factors that will identify women who are at increased risk of unexplained antepartum stillbirth. DESIGN: Matched case-control study. The cases and controls were initially analysed as a whole group and again after dichotomizing into those of low birthweight (< 2500 g) and those of normal birthweight (> or = 2500 g). SETTING: Western Australia 1980-1983. SUBJECTS: Unexplained antepartum stillbirths of > or = 1000 g birthweight (cases) and liveborn infants individually matched for year of birth, plurality, sex and birthweight of infant and race of mother (controls). RESULTS: The case pregnancies had more polyhydramnios (OR 10.83, 95% CI 2.41-48.69) and cord problems (OR 6.57 95% CI 1.36-31.75) than the controls but, paradoxically, other obstetric and medical complications were less common in the cases. The association with polyhydramnios persisted when the analysis was confined to those with low birthweight. With normal birthweight fetal distress was more frequent in the cases (OR 3.65 95% CI 1.36-9.80) but there were few other differences. CONCLUSIONS: The clinical and diagnostic systems currently in use are unable to identify many fetuses at risk of death. Decreases in the rate of unexplained antepartum stillbirths await the discovery of new preventable causes, or of innovations in clinical or laboratory aspects of obstetric care.

Birth Weight↗
PubMed1991

The standard error of Cohen's Kappa.

This paper gives a standard error for Cohen's Kappa, conditional on the margins of the observed r x r table. An explicit formula is given for the 2 x 2 table, and a procedure for the more general situation. A parsimonious log-linear model is suggested for the general case and an approximate confidence interval for kappa is based on that model. Numerical illustrations are given comparing the standard results with exact conditional results and those of the present paper. The conclusions are, first, that the standard error of kappa under the null hypothesis (that kappa is zero) should not be used except when the null is plausible; secondly, that the usual formula for the standard error appears appropriate except in the unusual circumstance of kappa taking large negative values; and, thirdly, in small samples the distribution of the estimate of kappa appears very non-symmetric, and it is preferable to base confidence intervals on transformations of kappa. A PC program with source code implementing the suggested procedures is available from the author.

Confidence Intervals↗
PubMed1991

Randomized controlled trial of antenatal social support to prevent preterm birth.

OBJECTIVE: To test the effect of a programme of additional antenatal social support on the occurrence of preterm birth (a birth from 20 to 36 weeks gestation) in women at risk of preterm birth. DESIGN: A prospective randomized controlled trial. The design was one of randomization before consent for a new treatment. SETTING: Three public hospital antenatal clinics in Perth and the offices of 87 obstetricians and general practitioners in Western Australia. SUBJECTS: 1970 pregnant women with poor obstetric histories entered the trial; 983 of these were randomly allocated to the programme group and 987 to the control group. INTERVENTIONS: Normal antenatal care was provided for both groups. In addition, members of the programme group were offered an intervention aimed at providing expressive (emotional) social support, consisting of antenatal home visits and telephone calls by midwives. Of the women allocated to the programme group, 24 refused consent and 69 were not traced before completion of their pregnancies, the remaining 890 women (90.5%) agreed to enter the programme, and each received at least one intervention. MAIN OUTCOME MEASURES: Gestational age at completion of the pregnancy. A pregnancy ending before 20 weeks was labelled a miscarriage. RESULTS: There were 126/981 (12.8%) preterm births in the programme group and 147/986 (14.9%) in the control group. The outcome data for two women in the programme group and one in the control group could not be found. The unadjusted odds ratio for preterm birth in the programme was 0.84 (95% CI 0.65-1.09). The observed relative reduction in preterm births associated with the programme was 13.8% (95% CI -8.2% to +31.5%) and the trial had a 60% power to exclude a true relative reduction of 25%. CONCLUSIONS: The results of this trial and those of other controlled clinical trials provide little evidence for the effectiveness of social support interventions in the prevention of preterm birth in women with poor obstetric histories.

Female↗
PubMed1990

Mathematical analysis of multisolute renal flow in a single nephron model of the kidney.

A single nephron model, which includes the Bowman's space, Cortical interstitium, and Pelvis as well-stirred baths, is investigated. A boundary value problem, which allows for pelvic reflux, is established for the fluid-multisolute flow in the nephron. The implicit function theorem is used to establish the existence and uniqueness of a solution of the boundary value problem for the case of small permeability coefficients and transport rates.

Animals↗
PubMed1989

The effects of propranolol, phentolamine, and atropine on canine coronary vascular gradients.

The objective of this study was to measure pressure gradients in the coronary circulation following the administration of three receptor-blocking drugs, propranolol, phentolamine, and atropine when administered singly and in sequence. As well, we examined the responses of these gradients to eight interventions: left stellate ganglion or left vagosympathetic trunk stimulation, administration of isoproterenol, acetylcholine, noradrenaline, adenosine, phenylephrine, or adrenaline. Using a multiple linear regression model we examined the actions and interactions of the receptor-blocking agents on hemodynamic variables and vascular gradients. Propranolol reduced heart rate as expected and blocked the responses to isoproterenol administration. As well, it abolished the epicardial coronary artery diastolic gradient. The gradient was restored when propranolol was the second receptor blocker administered but was abolished when it was the third. Phentolamine induced vasodilation with a decrease in coronary small vessel gradients. This effect persisted without regard to the sequence of administration. When it was the second or third agent it decreased the microcirculation and small vein gradients, an action it did not manifest when given singly. Atropine singly did not alter pressures or gradients; but as the second agent it altered the transmural, outflow tract, epicardial diastolic, and microcirculation and small vein diastolic gradients; and as the third agent the changes were in the transmural, epicardial systolic and diastolic, and small artery systolic and diastolic gradients. The pattern of responses was not predictable and that indicates that unique changes occur in the responses of the coronary circulation when multiple receptor-blocking agents are employed. Adrenergic control tends to dominate in the coronary arterial circulation, and muscarinic control in the coronary microcirculation and veins with considerable overlap.

Adenosine↗
PubMed1988

Existence and uniqueness of solutions in general multisolute renal flow problems.

This paper considers systems of differential equations that describe flows in renal networks. The flow geometry is of the type that occurs in modelling the renal medulla. The unknowns in the system include the flow rate, the hydrostatic pressure, and the concentrations of the various solutes. Existence and uniqueness of solutions of the appropriate boundary value problems are established, in the case of small permeability coefficients and transport rates, or large diffusion coefficients and small resistance to flow constants.

Kidney Medulla↗
PubMed1987

Coronary circulatory pressure gradients.

The pressure gradients of the canine coronary circulation were measured in 37 dogs during control and following eight interventions: left stellate ganglion or left vagosympathetic trunk stimulation, as well as isoproterenol, acetylcholine, noradrenaline, adenosine, phenylephrine, or adrenaline infusions. During control, pressure gradients in the epicardial coronary arteries (measured from the aorta to coronary artery branch) were 15.2 +/- 1 mmHg (1 mmHg (1 mmHg = 133.32 Pa) during systole and 10.6 +/- 1.5 mmHg during diastole. Adrenaline increased this systolic gradient, while acetylcholine and phenylephrine decreased it. In contrast, the pressure gradients in the small coronary arteries (from the branch of an epicardial artery to the pressure in an obstructed coronary artery) were 56 +/- 1.3 mmHg during systole and 63.7 +/- 1.3 mmHg during diastole. These gradients were increased by phenylephrine during both systole and diastole, noradrenaline and adrenaline during diastole and decreased by isoproterenol (systolic), left vagosympathetic trunk stimulation (diastolic), acetylcholine (systolic and diastolic), and adenosine (diastolic). The microcirculation and small vein gradients during control were 16.4 +/- 1.2 mmHg during systole and 8.5 +/- 0.8 mmHg during diastole. Decreases in this gradient were produced by isoproterenol, acetylcholine, and adenosine during systole and adenosine during diastole. These observations are consistent with the concept that the coronary circulation has considerable regulatory capacity in all of its component parts. Specifically, epicardial arteries appear to function as both conduits and as resistance vessels, small arteries as major resistance vessels, and the microcirculation and small veins as both capacitors and resistors.

Acetylcholine↗
PubMed1987

Prevalence of major mental retardation and associated disabilities in the Canadian Maritime Provinces.

A cross-sectional survey of the prevalence of major mental retardation in 7- to 10-year-olds in the three Canadian Maritime provinces was carried out in 1980. Case ascertainment from multiple sources was considered to be virtually complete and resulted in a study group of 307 children, for whom 72% of the parents consented to personal data collection. The overall regional prevalence of major mental retardation was 3.65/1,000. Variation in county prevalence rate (based on parental residence at the time of birth) was associated, by regression analysis, with maternal age, areas of greater population concentrations, and number of physicians per capita. These associations were still present when children with Down syndrome were excluded from the analysis. Speech and behavior disorders and epilepsy were the major associated disabilities.

Canada↗
PubMed1986

Associations of body mass index and waist:hip ratio with hypertension.

Canada Fitness Survey data for people aged 20 to 69 years were analysed by means of linear discriminant analysis to determine the effect of age, weight relative to height (body mass index) and weight distribution (waist:hip ratio) on hypertension (defined as diastolic blood pressure of 90 mm Hg or more) for both sexes separately. All three variables had independent effects on hypertension, but partial correlation coefficients indicated that the contribution of waist:hip ratio was secondary to that of body mass index. The association of measurements of body fat (five skinfold measurements) with hypertension was also examined; overall these measurements gave no advantage over the more simply measured body mass index. The results confirm the importance of assessing the predominant location of body fat and the body mass index when examining excess weight in relation to disease.

Adipose Tissue↗
PubMed1986

Causal origins of major mental handicap in the Canadian Maritime provinces.

From a retrospective epidemiological survey, the prevalence of major mental handicap among seven- to 10-year-old children in the Maritime region of Canada in 1980 was estimated to be 36.5 per 10,000 children. Based on information obtained for 221 of the 307 children ascertained by the survey, prenatal origins dominated (58 per cent), followed by perinatal (10 per cent) and postnatal (4 per cent). No specific cause could be determined for 27 per cent of the children, but 41 per cent of this group had epilepsy and/or cerebral palsy in addition to major mental handicap. Significant differences were found in the causal spectrum between the Maritime region of Canada and regions studied in other developed countries. The results of this survey have implications for planning prevention programs, and for epidemiological surveillance and monitoring of adverse reproductive outcomes.

Birth Weight↗
PubMed1985

Acid neutralization capacity of Canadian antacid formulations.

A study was designed to determine the acid neutralization capacities (ANCs) of the new Canadian antacid formulations and to compare these products with standard antacid products in terms of lot-to-lot consistency, ANC, sodium and "calorie" contents, and price to the pharmacist. Twenty-three liquid and 18 tablet antacids were tested. The concentrated liquid antacids (Mylanta-2 Extra Strength, Amphojel 500, Gelusil Extra Strength, Maalox TC and Diovol Ex) were found to have the highest ANCs. Six of the tablet antacids (Amphojel, Amphojel Plus, Camalox, Gelusil-400, Maalox and Mylanta-2) were found to have greater ANCs than 15 of the liquid antacids. Between-lot variation exceeded that of within-lot variation in 10 of the 14 liquid antacids for which this variation could be tested. The concentrated liquid antacids provide the highest ANCs with the lowest dosage volume and sodium and calorie contents. Some tablet antacids have the potential to be used as alternatives to liquid antacids because of their high ANC and patient convenience. The inclusion of ANC on the labels of antacid products would assist in the rational determination of the dose of these products.

Antacids↗
PubMed1985

Spontaneous intracerebral haemorrhage: an analysis of factors affecting prognosis.

A retrospective study of 100 patients with spontaneous intracerebral haemorrhage was carried out, to identify clinical factors which have a predictive value for outcome. Numerical equivalents for the admission level of consciousness (the Glasgow Coma Scale), ventricular rupture, partial pressure of oxygen in the blood, the electrocardiogram, clot location, and clot size were combined into equations predicting outcome. The best single parameter for prediction was the Glasgow Coma Scale.

Cerebral Hemorrhage↗
PubMed1984

A proportional hazards analysis of the clinical characteristics of infertile couples.

Evaluated were methods of ordering the many possible predictors of infertility outcome. The clinical characteristics of infertile couples were studied with respect to the occurrence of pregnancy during follow-up, by means of the methods of survival analysis. Among 1,297 couples who were infertile for 12 months or more, the cumulative pregnancy rate at 36 months with 95% confidence limits was 49% +/- 4%. The proportional hazards analysis identified three independent predictors of the occurrence of pregnancy from the couple's history (with P values in brackets): a history of pregnancy in the partnership (0.0001); shorter duration of infertility (0.0001); and shorter length of marriage (0.005). The predictors arising from the diagnostic process (with P values in brackets) were: fewer infertility diagnoses (0.0001); a favorable primary clinical diagnosis (0.001); and the presence of any tubal disease, regardless of the primary clinical diagnosis (0.001). The analysis selected an economical set of significant predictor variables and demonstrated that a longer period of contraception was associated with a lower pregnancy rate among infertile couples. Also, three simple questions from the history were nearly equivalent to the entire diagnostic process as predictors of the outcome.

Adult↗