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Biomedical subjects

S Gallivan

Publications and source records attributed to S Gallivan.

At least 19 recordsLinked to original sources
PubMed1999

Withdrawing low risk women from cervical screening programmes: mathematical modelling study.

OBJECTIVE: To evaluate the impact of policies for removing women before the recommended age of 64 from screening programmes for cervical cancer in the United Kingdom. DESIGN: A mathematical model of the clinical course of precancerous lesions which accounts for the influence of infection with the human papillomavirus, the effects of screening on the progression of disease, and the accuracy of the testing procedures. Two policies are compared: one in which women are withdrawn from the programme if their current smear is negative and they have a recent history of regular, negative results and one in which women are withdrawn if their current smear test is negative and a simultaneous test is negative for exposure to high risk types of human papillomavirus. SETTING: United Kingdom cervical screening programme. MAIN OUTCOME MEASURES: The incidence of invasive cervical cancer and the use of resources. RESULTS: Early withdrawal of selected women from the programme is predicted to give rise to resource savings of up to 25% for smear tests and 18% for colposcopies when withdrawal occurs from age 50, the youngest age considered in the study. An increase in the incidence of invasive cervical cancer, by up to 2 cases/100 000 women each year is predicted. Testing for human papillomavirus infection to determine which women should be withdrawn from the programme makes little difference to outcome. CONCLUSIONS: This model systematically analyses the consequences of screening options using available data and the clinical course of precancerous lesions. If further audit studies confirm the model's forecasts, a policy of early withdrawal might be considered. This would be likely to release substantial resources which could be channelled into other aspects of health care or may be more effectively used within the cervical screening programme to counteract the possible increase in cancer incidence that early withdrawal might bring.

Adult↗
PubMed1997

Mathematical modeling of pharmacy systems.

Mathematical modeling and its potential applications in pharmacy are discussed. A model is a simplified representation of the real world. As an experimental approach, modeling minimizes expense, risk, and disruption, but its validity can be hard to ascertain. Mathematical models describe numerically the relationships among elements of a system and are a powerful tool in making decisions affecting that system. There are two types of mathematical models: analytical models, which directly describe the relationships between system inputs and outputs using mathematical equations (such as pharmacokinetic models), and simulation models, which involve the replication, usually with a computer, of events as they occur in the real world. Analytical models are easier to develop but are not appropriate for describing highly complex systems. In continuous-time simulation, the system is represented as an uninterrupted flow of material; in discrete-event simulation, it is assumed that events occur only at distinct times. Various simulation programs are commercially available. The stages of a mathematical modeling study are (1) formulate the problem, (2) determine the model's structure, (3) collect and analyze initial data, (4) develop the model further, (5) validate the model, (6) experiment using the model, and (7) use the results. There have been many applications of modeling in health care, but relatively few have involved the study of pharmacy systems. Mathematical modeling offers pharmacists a low-risk, low-cost tool for aiding decisions about pharmacy systems by predicting alternative futures.

Models, Organizational↗
PubMed1997

Monitoring the results of cardiac surgery by variable life-adjusted display.

BACKGROUND: Conventional assessment of the outcome of cardiac surgery usually takes the form of retrospective mortality figures and, at best, indicates an average performance over time. Summary tables conceal good and bad runs, and without risk adjustment they are difficult to interpret. We developed a refinement of the cumulative sum method that weights death and survival by each patient's risk status and provides a display of surgical performance over time. METHODS: The variable life-adjusted (VLAD) plot shows the difference between expected and actual cumulative mortality. VLAD shows whether a surgeon's performance is above or below what might be expected. This mortality-scoring system accumulates penalties for each death and rewards for every survivor, based on the inherent risk of perioperative death of each case concerned. FINDINGS: We illustrate the results of three performance reviews, displayed as VLADs. The first shows the results of an individual surgeon for 547 consecutive cardiac-surgical cases. The overall mortality was 36% less than that predicted by the Parsonnet scoring system. The second displays the results for 5000 consecutive patients who underwent cardiopulmonary bypass between 1992 and 1996, divided into six contemporaneous series. The predicted mortality was 9% compared with 6% actual mortality. The third is a plot for a trainee surgeon and clearly shows how a period of poor performance was identified and then substantially improved, which would not have been revealed by conventional tables of summary statistics. INTERPRETATION: VLAD provides a graphical display of risk-adjusted survival figures for individual surgeons or units over time and could be modified to monitor performance over a range of treatments and outcomes.

Cardiovascular Surgical Procedures↗
PubMed1997

Evaluating cervical cancer screening programmes for developing countries.

This study evaluates cervical screening programmes for regions of the world where resources are scarce and little screening currently takes place. It investigates infrequent screening and programmes in which as many women as possible are screened just once in their lifetime. It also compares the effectiveness of cytology and human papillomavirus (HPV) testing for primary screening. Different programmes are evaluated by a stochastic model of the progression of pre-cancer, its relationship to papillomavirus infection and the diagnostic accuracy of alternative screening methods. These are compared in terms of the impact on the incidence of invasive cancer and resource use. Important factors that determine the suitability of different screening programmes are the available resources and the expected population coverage. Blanket screening for women aged 30-59 years, with the aim of covering all just once in their lifetime, could reduce the incidence of invasive cancer by up to 30%. A 10-year programme would require about 50% more routine screening tests to bring about the same reduction in incidence and a 5-year programme about 2.5-3 times as many. With either approach it would be more effective for resource use to concentrate on screening women aged 30-59 than a wider age group. Whether HPV testing would be more effective as a primary screening method than cytology depends on the underlying prevalence of HPV infection, the accuracy of cytology, the cost and the suitability of the testing procedure under field conditions.

Adult↗
PubMed1997

Use of the short form 36 (SF36) for health status measurement in rheumatoid arthritis.

The patient-administered Health Assessment Questionnaire (HAQ) is widely used in rheumatology studies. Another health quality assessment technique commonly used for other non-rheumatological conditions is the 'Short Form 36' (SF36). This has questions designed to assess eight aspects of health ranging from physical limitations to general perceptions of vitality and mental well-being. This study presents information on the health status of 137 patients with rheumatoid arthritis (RA) assessed by both the SF36 and HAQ. Summary statistics are given for the elements of the SF36 according to age, gender, disease measures of RA and the presence of co-morbidity. There were significant associations between the physical functioning score of the SF36 and the HAQ score. with other measures of disease activity and severity, and with co-morbidity, although there was considerable inter-patient variability. These findings suggest that future applications of health status questionnaires are possible.

Adult↗
PubMed1997

Telemedicine: evaluation or stagnation.

Telemedicine is attracting attention as a new means of delivery health care, but research indicates a low level of useful analysis of projects. This paper reviews the potential of telemedicine and suggests the use of appropriate evaluation techniques can enable that potential to be realised. The importance of quantifying benefits and introduction of wider perspectives is discussed and advocated.

Europe↗
PubMed1996

Can papilloma virus testing be used to improve cervical cancer screening?

This report investigates different options for using human papillomavirus (HPV) testing in cervical cancer prevention. These options are evaluated by a stochastic model of the progression of pre-malignancy and its relationship to HPV infection. Three screening policies are compared: 2 based on cytological screening, with or without HPV testing, and 1 in which HPV testing is the primary screening method. A policy of HPV testing for women with mildly abnormal smears would have little effect on the overall incidence of invasive cancer when compared with a policy of repeat cytology, provided follow-up is efficient. Moreover, the potential value of HPV testing as a primary screening method is strongly dependent on the proportion of neoplasias that are HPV-negative. Important factors in assessing the future role of HPV testing would be cost-effectiveness and benefits from improved compliance.

Adult↗
PubMed1996

Women's involvement with the decision preceding their caesarean section and their degree of satisfaction.

OBJECTIVE: To assess the extent to which women contribute to the decision for caesarean section and their satisfaction with the decision and procedure. DESIGN: Observational study of women undergoing caesarean section who were interviewed using a standard proforma. SETTING: University College Hospital, London. PARTICIPANTS: One hundred and two consecutive women undergoing caesarean section. RESULTS: The women's perceived reason for the caesarean section agreed with the doctors' reason in 91 cases (89.2%). Only 2/29 women having elective sections stated they had no contribution, compared with 22/73 women having emergency sections (P = 0.018, two-tailed Fisher's exact test). Twenty out of 29 women (69%) having elective procedures and 37/73 women (51%) having emergency sections recorded medium or more contribution. All women except one were 50% or more satisfied with the decision. Women's satisfaction with the operation was high in the immediate post-operative period and remained so over the following six weeks. Forty-three women (49%) said they would prefer an elective section in the next pregnancy given the choice. CONCLUSIONS: Women undergoing caesarean section were well informed and took a considerable part in the decision-making process. This suggests that women's wishes may be playing a role in increasing caesarean section rates. High levels of satisfaction with both the decision and the procedure itself indicate that caesarean section is an acceptable method of delivery, particularly when an elective procedure.

Cesarean Section↗
PubMed1995

Survival and quality of life in patients with protracted recovery from cardiac surgery. Can we predict poor outcome?

Of all the 2256 adult cardiac surgical patients operated upon during a 12-month period from 1st February 1992 in three units, only 162 (7.2%) spent more than 48 h in the intensive care unit (ICU) (median 6 days, range 3-90). There were 47 deaths in ICU, 7 more before hospital discharge, and a further 10 before the study end-point of one year after surgery. All 98 1-year survivors were at home with 86 of them reporting their quality of life, on formal evaluation, to be within the reference range which we have established for a less complicated cohort of cardiac surgical patients. Prospectively collected physiological measurements were used in a mathematical model to test how well we could predict which patients will die and which of the survivors have a poor quality of life. The algorithm performs well for cardiac surgery patients with a specificity of 98%. If treatment had been withdrawn when death or poor quality of life became predictable, the maximum number of ICU bed days that could be freed was of the order of 2%. The plight of these patients is distressing, but most survive and do well and they are infrequent compared with the large majority who survive to leave hospital after a short ICU stay.

Adult↗
PubMed1995

Fetal size and growth in Bangladeshi pregnancies.

A longitudinal study of 20 uncomplicated pregnancies in Bangladeshi women was undertaken. Fetal growth was investigated by serial ultrasound scans performed between 26 and 38 weeks of pregnancy. Repeated measurements of abdominal circumference and estimates of fetal weight were best described by a log quadratic equation. The coefficients were not significantly different from those obtained from a previously reported study of fetal growth in 67 uncomplicated pregnancies with healthy outcomes in white Anglo-Saxon women. Further comparison between the two groups showed that the mean abdominal circumference and estimates of fetal weight of the Bangladeshi fetuses were smaller at 28, 32 and 36 weeks' gestation. These results suggest that, although Bangladeshi fetuses appear to be smaller than Anglo-Saxon fetuses, they grow at a similar rate during the third trimester.

Abdomen↗
PubMed1995

Displaying the long-term progression of patients with coronary artery disease.

Cardiac clinicians are often faced with the problem of trying to assimilate details of a patient's long-term history. Case notes are often lengthy, making this process difficult if not impossible in the time available during an outpatient examination. A computer system has been developed to assist with this task. This generates a graphical summary of the principal features of a patient's long-term progression. It gives an overview of how the patient's anginal status has changed, his or her drug treatment and any surgical interventions. The system also allows the clinican to display summaries of diagnostic tests carried out. The system can be used to assist clinical management and speed up outpatient examination. It can also be used to facilitate case conference sessions and has potential for being used in medical education.

Coronary Disease↗
PubMed1995

Liver biopsy in the diagnosis of malignancy.

In a National Audit of 1500 liver biopsies, 38% were for suspected malignancy. To measure their contribution to clinical decisions, the initial diagnoses, biopsy diagnoses, final diagnoses, and outcomes were coded by computer and compared. Most patients (92%) were investigated for advanced malignancy. The accuracy of clinical diagnosis was 78% against final diagnosis. Liver biopsy was seen as 'confirming' clinical diagnosis overall. This was achieved in 67% (75% with ultrasound guidance), and specificity was almost 100%. However, hepatocellular cancer was confirmed by biopsy in only 32% and haematological malignancy in 13% of suspected cases. Within 3 months, 44% of patients with histological malignancy had died. Histological tumour type was not used in 36% of final diagnoses. Of patients with a malignancy-negative liver biopsy--showing reactive hepatitis, normality, or cholangitis/cholestasis--25%, 47% and 60%, respectively, had final malignant diagnoses. In 6% of patients, biopsy showed chronic liver disease. Only 12% of deaths were autopsied. Liver biopsy contributes very high specificity to the diagnosis of malignancy, and detects non-malignant disease. Failure to use tumour type may result in sub-optimal therapy. Improving diagnostic practice requires more information on outcomes, including autopsies.

Biopsy↗
PubMed1994

Which patients will not benefit from further intensive care after cardiac surgery?

In intensive care units, a predictive model that identified patients who are certain to die would spare suffering and free resources for more productive work. In a prospective study to determine factors which might predict the outcome of a protracted stay in intensive care units, information was collected for 162 patients who remained in intensive care longer than 48 hours after cardiac surgery. Of these patients, 21% presented as emergencies, 35% as urgent cases, and 44% as elective cases. They were drawn from 2256 adult patients operated upon during a 12-month period in three UK centres. 115 patients (71%) who were in intensive care for more than 48 hours survived to be discharged. The median duration of stay was 6 days (range 3-90 days) and the median duration of hospital stay was 21 days (7-111 days). An existing algorithm developed and calibrated to predict outcome for general patients in intensive care was applied to forecast outcomes. Contrary to expectations, the algorithm performed well for patients after cardiac surgery. In identifying deaths in intensive care and before hospital discharge, the specificities for death at various intervals after admission were all 97% or more. There is little scope for improving the algorithm's ability to forecast longer term outcome. Furthermore, if it were to be introduced to aid decisions about withdrawal of treatment, the potential saving in intensive care bed-days would be small--less than 3% overall.

APACHE↗