Biomedical subjects

A O'Hagan

Publications and source records attributed to A O'Hagan.

8 recordsLinked to original sources

PubMed2001

Bayesian cost-effectiveness analysis from clinical trial data.

A key tool for assessing the relative cost-effectiveness of two treatments in health economics is the incremental C/E acceptability curve. We present Bayesian computations for this curve in the case where data on both costs and efficacy are available from a clinical trial. Analysis is given under various formulations of prior information. A case study is analysed in which reasonable prior information is shown to strengthen substantially the posterior inference, leading to a more conclusive assessment of cost-effectiveness. Calculations can be performed using readily available Bayesian software.

Anti-Asthmatic Agents↗

PubMed2001

A framework for cost-effectiveness analysis from clinical trial data.

We present a general Bayesian framework for cost-effectiveness analysis (CEA) from clinical trial data. This framework allows for very flexible modelling of both cost and efficacy related trial data. A common CEA technique is established for this wide class of models through linking mean efficacy and mean cost to the parameters of any given model. Examples are given in which efficacy may be measured as a continuous, binary, ordinal or time-to-event outcome, and in which costs are modelled as distributed normally, log-normally, as a mixture or non-parametrically. A case study is presented, illustrating the methodology and illuminating the role of prior information.

Bayes Theorem↗

PubMed2000

Inference for the cost-effectiveness acceptability curve and cost-effectiveness ratio.

The aim of this article is to consider Bayesian and frequentist inference methods for measures of incremental cost effectiveness in data obtained via a clinical trial. The most useful measure is the cost-effectiveness (C/E) acceptability curve. Recent publications on Bayesian estimation have assumed a normal posterior distribution, which ignores uncertainty in estimated variances, and suggest unnecessarily complicated methods of computation. We present a simple Bayesian computation for the C/E acceptability curve and a simple frequentist analogue. Our approach takes account of errors in estimated variances, resulting in calculations that are based on distributions rather than normal distributions. If inference is required about the C/E ratio, we argue that the standard frequentist procedures give unreliable or misleading inferences, and present instead a Bayesian interval.

Antirheumatic Agents↗

PubMed1999

Intestinal obstruction after lung transplantation in children with cystic fibrosis.

BACKGROUND/PURPOSE: Distal intestinal obstruction syndrome (DIOS) occurs in 15% of patients with cystic fibrosis (CF). The authors reviewed their experience to determine the incidence, risk factors, and natural history of adhesive intestinal obstruction and DIOS after lung transplantation. METHODS: Eighty-three bilateral transplants were performed in 70 CF patients between January 1990 and September 1998. All were on pancreatic enzymes preoperatively, and none had preoperative bowel preparation. Fifty-six patients (80%) had prior gastrostomy (n = 54) or jejunostomy (n = 2). Eighteen patients (25.7%) had a previous laparotomy for meconium ileus (n = 8), fundoplication (n = 4), liver transplant (n = 1), jejunal atresia (n = 1), Janeway gastrostomy takedown (n = 1), pyloromyotomy (n = 1), free air (n = 1), or appendectomy (n = 1). RESULTS: After lung transplantation, 7 patients (10%) required laparotomy for bowel obstruction (6 during the same hospitalization, and 1 during a subsequent hospitalization). The causes of obstruction were adhesions only (n = 1), DIOS only (n = 2), and a combination of DIOS and adhesions (n = 4). Adhesiolysis was performed in the 5 patients with adhesions, and a small bowel resection was also performed in 1 patient. DIOS was treated by milking secretions distally without an enterotomy (n = 3) with an enterotomy and primary closure (n = 1) or with an end ileostomy and mucus fistula (n = 2). Five had recurrent DIOS early postoperatively. One resolved with intestinal lavage, 2 were treated successfully with hypaque disimpaction, and 2 underwent reoperation; 1 required an ileostomy. The most important risk factor for posttransplant obstruction was a previous major abdominal operation. Obstruction occurred in 7 of 18 (39%) who had undergone a prior laparotomy versus 0 of 52 who had not (P < .001, chi2). CONCLUSIONS: (1) The incidence of intestinal obstruction is high after lung transplantation in children with CF. (2) Previous laparotomy is a significant risk factor. (3) Recurrent obstruction after surgery for this condition is common. (4) Preventive measures such as pretransplant bowel preparation and early postoperative bowel lavage may be beneficial in these patients.

Adolescent↗

PubMed1990

Practical Bayesian analysis of a simple logistic regression: predicting corneal transplants.

The Bayesian analysis of a logistic regression model is described using an example of predicting the need for a corneal transplant in keratoconus. Controversy over the use of subjective prior information in Bayesian methods is avoided by a formulation representing negligible prior information. Simple computational procedures are described, and it is argued that the results are more accurate, clearer and make fuller use of the information contained in the data. Analysis of more complex models is considered. In particular, it is argued that classical methods as implemented in the computer package GLIM can be used as approximations to Bayesian methods, particularly at the initial stage of model selection.

Bayes Theorem↗

PubMed1990

Predictors for likelihood of corneal transplantation in keratoconus.

A group of 70 patients who had attended the Keratoconus Clinic at Moorfields Eye Hospital over a 10-year period were analysed retrospectively. At the end of this period 23 eyes had undergone corneal transplantation. This gave an overall probability of 16%, various information obtained at the initial visit was then analysed for a possible relationship with the probability of needing a transplant within ten years. The only significant relationship found was the initial corneal radius as determined by the back optic radius of the first contact lens. A graph was constructed plotting probability of corneal transplant against each radius at the first visit, which could assist clinicians in advising patients.

Adult↗

PubMed1986

Factors influencing post-operative hospital stay after transurethral resection of the prostate gland.

The influence of 12 clinical and social factors on the length of post-operative stay in hospital after transurethral resection of the prostate was investigated in 100 patients. Using a multiple binary regression analysis, the factors significantly associated with a post-operative stay exceeding 6 days were: patient's age greater than 70 years (P less than 0.005), the presence of existing cardiovascular disease (P less than 0.005) and the weight of the prostate gland resected greater than 10 g (P less than 0.005). The first two factors are useful in providing a prediction of prolonged post-operative stay. The results indicate that those factors associated with a prolonged post-operative stay are beyond the control of the clinician.

Age Factors↗

PubMedDate not supplied

Bayesian assessment of sample size for clinical trials of cost-effectiveness.

The authors present an analysis of the choice of sample sizes for demonstrating cost-effectiveness of a new treatment or procedure, when data on both cost and efficacy will be collected in a clinical trial. The Bayesian approach to statistics is employed, as well as a novel Bayesian criterion that provides insight into the sample size problem and offers a very flexible formulation.

Bayes Theorem↗