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Biomedical subjects

J Whitehead

Publications and source records attributed to J Whitehead.

At least 73 records · Page 4Linked to original sources
PubMed1991

Bringing the abusive employee back.

In many health care settings, some dispute resolution process exists which limits the discretion of the employer to simply terminate an employee suspected of inappropriate or abusive behavior. On occasion, the working of such disciplinary processes results in an employee, who is viewed by management as having broken a fundamental trust, being returned to the workplace. In managing the return of these individuals, provider agencies must develop strategies to reduce the likelihood of any future client injury and to increase the chances of returning the employee to a productive functioning level. We surveyed employees returned to work after an abusive incident along with their supervisors to determine what specific supports each group saw as necessary for a successful return. As a result, an individualized, structured program was developed to deal with such returns and piloted. The authors' results indicate that the program might serve as one possible model for wider use.

Aggression↗
PubMed1991

An investigation into the effect of different intakes of vitamin C on drug metabolism in Gambian men.

Hepatic mixed-function oxidase activity was measured in Gambian men during a period of low seasonal vitamin C intake and after vitamin C supplementation. Demethylation of methoxyphenylacetamide (methacetin) was followed using a breath test, in which the exhalation of 13C-enriched CO2 was measured following an oral dose of 13C-methacetin. Vitamin C supplementation, sufficient to increase plasma levels significantly, did not influence methacetin metabolism. However, methacetin metabolism in unsupplemented men appeared normal in the majority of cases. Hepatic tissue may not have been sufficiently depleted of vitamin C to impair the activity of the mixed function oxidase system.

Acetamides↗
PubMed1990

An improved approximation for calculation of confidence intervals after a sequential clinical trial.

A method for the calculation of confidence intervals following a sequential clinical trial is proposed which is more accurate than methods based solely on continuous monitoring assumptions, but is not as computationally laborious as previous methods suggested for group sequential trials. The calculation takes account of the excess of the sample path over the boundary at the final inspection of the trial, which may be substantial after group sequential monitoring, and is ignored when continuous monitoring is assumed. Accuracy of such confidence intervals after a triangular test is investigated by simulation of coverage probabilities, individual confidence limit probabilities and p-value curves.

Clinical Trials as Topic↗
PubMed1989

Comparison of the information in two lung function experiments.

The amount of ventilation relative to perfusion (the ventilation-perfusion ratio) received by the lung is a useful indicator of the efficiency of lung function. Two alternative techniques for recovering the ventilation-perfusion ratio are outlined. While both techniques rely on the use of inert gases, one is well established and the other is only in a developmental stage. This paper focuses on a comparison of the amount of statistical information provided by these two techniques about the ventilation-perfusion ratio. The criterion applied here for measuring amount of information has roots in communication theory and uses ideas inherent to Bayesian inference.

Bayes Theorem↗
PubMed1989

The analysis of relapse clinical trials, with application to a comparison of two ulcer treatments.

Patients cured of ulcers, carcinomas or other recurrent conditions are randomized between two treatments designed to maintain their recovery. Spontaneous reporting of relapse is supplemented by periodic asymptomatic screening. Interest centres on the difference in times to relapse between the two treatments. However, the analysis is complicated by the times to diagnoses at screens being qualitatively different from the times to symptomatic diagnoses between screens. In this paper a number of approaches to the analysis of such data are explored, and one of them is recommended. An extensive example with data on ulcer recurrence is presented to illustrate the method.

Adult↗
PubMed1989

Fungal contamination of mini peak flow meters.

Sixteen peak expiratory flow meters from the Outpatient Department of Solihull Hospital were dismantled for inspection and washing. Fungal contamination was found in all 16 machines with visible contamination in four.

Equipment Contamination↗
PubMed1989

Risk factors for breast cancer by mode of diagnosis: some results from a breast cancer screening study.

We have investigated factors affecting the probability that a woman with breast cancer participating in a mammographic screening programme will be diagnosed by the screen. Data from a large American case-control study, with subjects drawn from women participating in an annual screening programme, were used. During the screening programme, 409 cases were identified, the mode of diagnosis being screen detection for 331 and interval detection for 78. No significant relationships were found between mode of diagnosis and age, age at menarche, oral contraceptive use, age at first live birth, age at menopause or history of maternal breast cancer. There was a non-significant trend for particular mammographic patterns to be associated with interval detection. However relative risk of breast cancer and probability of interval detection were observed to increase about the time of the menopause. These results suggest that the 3 yearly mammography programme being introduced in the UK might be improved if an extra examination was included around the time of the menopause.

Breast Neoplasms↗
PubMed1988

Prospective epidemiological studies involving paired organs.

Standard methods for analysing survival data or case-control data normally concern factors affecting a subject as a whole. However, in a study of a condition that might develop in one or both of a pair of bodily organs information on response and on covariates may be available for each separately. This information can be used to investigate whether the presence of a factor on one side is associated with the condition on that same side, and thus leads to more direct evidence concerning aetiology. In this paper methods of analysing data on paired organs are described. The techniques are illustrated using data from a case-control study of breast cancer, in which the role of breast calcifications was of interest.

Breast Diseases↗
PubMed1988

Systemic mycotic disease of captive crocodile hatchling (Crocodylus porosus) caused by Paecilomyces lilacinus.

The sudden death occurred of a captive Estuarine crocodile hatchling (Crocodylus porosus). On autopsy, granuloma-like lesions were seen in the liver, left lung and spleen, and branching, septate fungal hyphae were observed in sections of liver and spleen. The fungus isolated from the liver showed characteristics of both Paecilomyces lilacinus and Paecilomyces marquandii but was closer to the former species. This is apparently the first report of the isolation of this fungus from a reptile in Australia.

Alligators and Crocodiles↗
PubMed1986

Methotrexate and cyclosporine compared with cyclosporine alone for prophylaxis of acute graft versus host disease after marrow transplantation for leukemia.

We treated 93 patients who had acute nonlymphoblastic leukemia in the first remission or chronic myelocytic leukemia in the chronic phase (median age, 30 years) with high-dose cyclophosphamide and fractionated total-body irradiation, followed by infusion of marrow from an HLA-identical sibling. To evaluate postgrafting prophylaxis for graft versus host disease, we studied these patients in a sequential, prospective, randomized trial that compared the effect of a combination of methotrexate and cyclosporine (n = 43) with that of cyclosporine alone (n = 50). All patients had evidence of sustained engraftment. A significant reduction in the cumulative incidence of grades II to IV acute graft versus host disease was observed in the patients who received both methotrexate and cyclosporine (33 percent), as compared with those who were given cyclosporine alone (54 percent) (P = 0.014). Seven patients who received cyclosporine alone acquired grade IV acute graft versus host disease, as compared with none who received both methotrexate and cyclosporine. Thirty-five of the 43 patients given both methotrexate and cyclosporine and 31 of the 50 patients given cyclosporine are alive as of this writing, at 4 months to 2 years (median, 15 months); the actuarial survival rates in the two groups at 1.5 years were 80 percent and 55 percent, respectively (P = 0.042). We conclude that the combination of methotrexate and cyclosporine is superior to cyclosporine alone in the prevention of acute graft versus host disease after marrow transplantation for leukemia, and that this therapy may have a beneficial effect on long-term survival.

Acute Disease↗
PubMed1986

Diffusion-related differences in elimination of inert gases from the lung.

Partial pressures of intravenously infused acetylene, Freon 22, and isoflurane (gases with similar solubilities in blood but differing molecular weights) were compared in arterial and mixed venous blood and mixed expired gas of 13 anesthetized mongrel dogs to determine whether gas molecular weight influenced gas exchange. Analysis of covariance was used to account for the variables of ventilation-perfusion ratio, partition coefficient, and experimental run before individual gas effects were sought. A gas effect difference was observed such that the arterial fractional retention of isoflurane (mol wt 184.5) would be 12% higher than that of acetylene (mol wt 26) if the two gases had identical partition coefficients. This effect was neither significantly increased by positive end-expiratory pressure nor decreased by high-frequency oscillatory ventilation. To test whether the individual gas effect was greater with gases with disparate erythrocyte and plasma partition coefficients, the exchange of ethyl iodide (erythrocyte-to-plasma solubility ratio 8.1) and diethyl ether (solubility ratio 0.95) was compared in five dogs. A larger difference between the elimination of the two gases was observed than predicted from the differences in molecular weight. The observed individual gas effect appears to be diffusion related, influenced both by the molecular weight of a gas and its erythrocyte-plasma partition coefficient ratio.

Acetylene↗
PubMed1986

Bone marrow transplantation experience for children with aplastic anemia.

From May 1971 through December 1981, 81 children (22 months to 17 years of age) received allogeneic bone marrow grafts for severe aplastic anemia. All donors were HLA-identical family members. Fifty-seven of the 81 (70%) are still alive. Twenty-three untransfused patients were conditioned with cyclophosphamide, 50 mg/kg/d, for four days, and 19 (83%) have survived from 5 to 12 years. All 58 transfused patients were conditioned with cyclophosphamide, 50 mg/kg/d, for four days, 11 received additional immunosuppression, and 19 received posttransplantation donor buffy coat cells. Thirty-eight (65%) have survived from 3 to 13 years (P = .1). In a multivariate analysis, the only factor significantly associated with increased survival among patients with sustained grafts was the absence of significant graft v host disease (P less than .0001). The factors significantly related to increased rejection were low bone marrow cell dose (P less than .05) and positive relative response in mixed leukocyte culture (P less than .0001), but the addition of buffy coat cells did not significantly influence graft rejection. The development of grades II to IV acute graft v host disease was associated with random donor platelet refractoriness (P less than .05) and donor/recipient sex differences (P less than .05). Patients at highest risk for chronic graft v host disease were those patients who developed significant acute graft v host disease (P less than .01) and who received buffy coat infusions (P less than .025). All patients who were untransfused had a negative relative response and were not refractory to random donor platelets.

Acute Disease↗
PubMed1986

Supplementary analysis at the conclusion of a sequential clinical trial.

Suppose that a clinical trial has been carried out using a sequential design. Any analysis that neglects the monitoring of the trial is potentially biased, and this holds for analyses of responses not directly used to determine whether the study should be stopped. Although valid methods exist to deal with the responses actually used in the sequential design, little has been written about secondary analyses of further responses. In this paper, two approaches to secondary analyses are explored. One is a conditional approach that avoids the problems of bias, the other an unconditional approach that allows for the sequential nature of the trial. The two methods are illustrated by application to three examples, each concerning a different type of response variable.

Biometry↗
PubMed1985

Wolfe mammographic parenchymal patterns. A study of the masking hypothesis of Egan and Mosteller.

Wolfe defined four different classes of breast parenchymal patterns and claimed that they were associated with different risks for the subsequent development of breast cancer. Egan and Mosteller suggested that these patterns did not constitute a true risk factor, rather the effect was caused by the greater difficulty of detecting breast cancers in the dense (P2, DY) patterns compared with the fatty (N1, P1) patterns. Similarly, Mendell believed that a bias was introduced into Wolfe's work by requiring a negative mammogram before a patient entered the study. This study of 221 prevalent and 706 incident cancers followed for up to 10 years indicates that a masking effect does exist, but that it operates in addition to a difference in risk of breast cancer within the four Wolfe classes. Wolfe's hypothesis is found to be valid.

Breast Neoplasms↗
PubMed1985

A FORTRAN program for the design and analysis of sequential clinical trials.

Clinical scientists are becoming increasingly aware of the need to monitor clinical trials in progress, and to validate their procedure by the use of a formal sequential design. An interactive program, written in FORTRAN 77 and called "PEST: Planning and Evaluation of Sequential Tests," is introduced. The program can be used to design trials based on the sequential probability ratio test, the triangular test, and the restricted procedure, among others. Furthermore, from the observed terminal values of the test statistics, the program will provide an analysis which includes the significance level and point and interval estimates of the parameter of interest. The computations are based on large-sample theory which encompasses many types of patient response, including binary and ordinal outcomes as well as survival times.

Clinical Trials as Topic↗