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Biomedical subjects

D Ashby

Publications and source records attributed to D Ashby.

At least 19 recordsLinked to original sources
PubMed1999

An investigation of the effects on children of tooth extraction under general anaesthesia in general dental practice.

OBJECTIVE: To describe the morbidity related to general anaesthesia provided in general dental practices for the extraction of teeth in school children. DESIGN: Observational study supported by structured questionnaires and interviews. SETTING: Three general dental practices in a Lancashire health district and children's homes. SUBJECTS: 80 children aged 5-15 years undergoing extractions under general anaesthesia. MAIN OUTCOME MEASURES: Observed demeanour of the children prior to, during and immediately after the surgical procedures. Reported morbidity during the following 24 hours and 1 month later. RESULTS: 92% of the children complained of symptoms associated with the surgery under general anaesthesia. Distress was noted in 16 (20%) patients during the induction of 26 (33%) during recovery. Continued crying was reported for 24 (39%) during the journey home and for 23 (37%) once home had been reached. Other symptoms included nausea, vomiting, sickness and prolonged bleeding. Six reported psychological trauma 1 month after; three had nightmares, two had continuing bad memories and one was depressed for several days. CONCLUSION: Morbidity following extractions under general anaesthesia in general dental practice is common and has distressing consequences for the young patients and their carers.

Adolescent↗
PubMed1998

Time to publication as full reports of abstracts of randomized controlled trials in cystic fibrosis.

OBJECTIVES: To determine 1) what proportion of abstracts of randomized controlled trials (RCTs) presented at international conferences on cystic fibrosis (CF) are published as full reports, 2) time to publication, and 3) factors that might delay or prevent publication. METHODS: At the end of 1995, the Cochrane CF Group's register of RCTs contained 199 abstracts describing 180 RCTs. Abstracts were identified by handsearching 44 abstract books of three international CF conferences over a 30-year period. We searched the register for subsequent full reports of these RCTs and used survival analysis to investigate time to publication. Using the log-rank test, we examined 1) whether there is a difference in time to publication between reports where the investigators concluded that the test treatment was as effective as or better than the control treatment, and reports where it was not, and 2) whether there is a difference in time to publication according to sample size. RESULTS: Thirty-two percent of the 178 abstracts analyzed were subsequently published in full. Survival analysis indicated that the proportions published before 12 months, 2 years, and 5 years were 8.1%, 29%, and 40% respectively. No difference in time to publication was identified when the abstracts were stratified according to conclusions or sample size; no significant association (P > 0.05) existed between time to publication and both sample size and conclusions together. CONCLUSION: Only a small proportion of abstracts of RCTs presented at international conferences on CF are followed by full publication, and usually only after several years. Therefore, many potentially valuable studies do not reach a wide audience. However, we found no consistent factors which might delay or prevent publication.

Abstracting and Indexing↗
PubMed1997

Tutorial in biostatistics Bayesian data monitoring in clinical trials.

Many clinical trials organizations use regular interim analyses to monitor the accruing results in large clinical trials. In disease areas such as cancer, where survival is usually a major outcome variable, ethical considerations may lead to a stipulated requirement for data monitoring of mortality. This monitoring has frequently taken the form of limiting interim analyses to be few in number, and specifying an extreme p-value of, for example, p < 0.001 or p < 0.01 as grounds for early termination of the trial. Group-sequential methods are also used. However, none of these approaches formally assesses the impact that the results of a clinical trial may have upon clinical practice. Thus a trial might be terminated early because of apparent treatment benefits, but might fail to influence sceptical clinicians to modify their future treatment policy. We discuss the application of Bayesian methods, including the use of uninformative, sceptical and enthusiastic priors, and demonstrate that the necessary calculations are both straightforward to perform and easy to interpret statistically and clinically. Methods are illustrated with interim analyses of a clinical trial in oesophageal cancer.

Bayes Theorem↗
PubMed1997

Respiratory syncytial virus genotypes and disease severity among children in hospital.

OBJECTIVES: To determine the spectrum of N and G genotypes of respiratory syncytial virus (RSV) causing respiratory tract infection and whether particular genotypes are associated with severity of infection. PATIENTS AND METHODS: Nasopharyngeal aspirates (NPAs) were obtained from 114 infants with acute respiratory tract infection due to RSV over two seasons. Viral mRNA was extracted from NPAs or cultured virus, reverse transcribed, and the cDNA amplified by the polymerase chain reaction using primers directed to parts of the N and G gene respectively. Amplicons were separately digested with four different restriction endonucleases for each gene. The fragments were separated by agarose gel, electrophoresis, and the electrophoretic patterns used to assign the various genotypes. Disease severity was assessed as very mild (upper respiratory tract signs only), mild (coryza and signs of lower respiratory tract infection), moderate (requiring nasogastric or intravenous fluids), and severe (requiring oxygen or ventilation). RESULTS: Five of the six known N genotypes were detected, but NP4 and NP2 were found most frequently. There was no association between N genotype and disease severity. Six G (SHL) genotypes were detected. Significantly (p = 0.04) more of the infants infected with the SHL2 genotype had severe or moderate disease. CONCLUSIONS: During the seasonal peaks of RSV respiratory tract infection at least 10 different RSV genotypes cocirculated. While there is no association between N genotypes and disease severity, infection with the SHL2 G genotype appears to result in moderate to severe disease.

Acute Disease↗
PubMed1996

A Bayesian approach to Weibull survival models--application to a cancer clinical trial.

In this paper we outline a class of fully parametric proportional hazards models, in which the baseline hazard is assumed to be a power transform of the time scale, corresponding to assuming that survival times follow a Weibull distribution. Such a class of models allows for the possibility of time varying hazard rates, but assumes a constant hazard ratio. We outline how Bayesian inference proceeds for such a class of models using asymptotic approximations which require only the ability to maximize the joint log posterior density. We apply these models to a clinical trial to assess the efficacy of neutron therapy compared to conventional treatment for patients with tumours of the pelvic region. In this trial there was prior information about the log hazard ratio both in terms of elicited clinical beliefs and the results of previous studies. Finally, we consider a number of extensions to this class of models, in particular the use of alternative baseline functions, and the extension to multi-state data.

Bayes Theorem↗
PubMed1996

An analysis of papers published in the British and European Journals of Orthodontics.

UNLABELLED: The aims of this study were to assess the type, subject, setting and methods of papers published in British Journal of Orthodontics (BJO) and European Journal of Orthodontics (EJO) between 1989 and 1993 to allow all published randomized controlled trials (RCTs) to be identified and a comparison of the papers published in the journals to be made. A hand search of all papers published in BJO and EJO between 1989 and 1993 was performed, and the type, subject, setting, and methods of each paper were classified and recorded. Of the studies, 59.3 per cent related to clinical orthodontics, but only three RCTs were identified in each journal. This comprised 2.8 per cent of the clinical research papers which were analysed. The remaining studies used non-randomized controls or were uncontrolled. Significant differences were found between the type (P < 0.001), subject (P < 0.001), setting (P < 0.01) and methods (P < 0.05) of papers published in the two journals. Relatively more papers in BJO were case reports, clinical opinions and update articles, reported on orthodontic materials or assessed methods of measuring the outcome of treatment. Ninety per cent of papers in EJO reported the results of research projects and relatively more papers, than in BJO, were related to animal studies, and were laboratory based or epidemiological. OBJECTIVES: To identify all randomized controlled trials (RCTs) and compare papers published in two orthodontic journals. DESIGN: A retrospective, observational study. SETTING: The British Journal of Orthodontics (BJO) and European Journals of Orthodontics) (EJO). DATA SOURCE: Papers published between 1989 and 1993. METHOD: A hand search of all papers was performed. The type, subject, setting and methods of each paper were classified and recorded. RESULTS: 200 papers were identified in BJO and 275 in EJO. Six RCTs were identified which represents 2.8 per cent of clinical research papers. Significant differences were found between the type (P < 0.001), subject (P < 0.001), setting (P < 0.01), and methods (P < 0.05) of papers published in the two journals. More papers in BJO were case reports, clinical opinions, and update articles, and reported on orthodontic materials or assessed methods of measuring the outcome of treatment. Ninety per cent of papers in EJU reported the results of research projects. More papers were related to animal studies; were laboratory based on epidemiological. CONCLUSION: Despite the RCT being regarded as the 'Gold Standard' for the evaluation of therapeutic interventions and materials only six (5.1 per cent) of such studies used this method. Significant differences in the type, setting and subject of papers published in BJO and EJO between 1989 and 1993 were found.

Animals↗
PubMed1995

Fibrosing colonopathy in cystic fibrosis: results of a case-control study.

Fibrosing colonopathy was first described in cystic fibrosis (CF) children in 1994. We have done a nested case-control study to identify possible associations with this condition. A case ascertainment within the UK CF population to identify any cases that occurred between January, 1984, and April, 1994, found 14 cases, all under 14 years and confirmed by independent histopathological review. All had presented since April, 1993; 12 were boys and six had received some or all of their care in Liverpool. Each case was matched, by date of birth, with four controls from the UK CF Registry. Information was obtained about cases and controls from their case records and by a structured interview with the families. In the 12 months before surgery, there was an association between the occurrence of fibrosing colonopathy and use of high-strength pancreatic enzyme preparations. This association was dose related. Odds ratio per extra 1000 high-strength capsules was 1.45 (95% CI 1.14-1.84). For use of protease, the odds ratio per million extra units per kg was 1.55 (1.19-2.03). For usage of individual high-strength products at any time during the 12 months before surgery some differences were observed; for Creon 25000 the odds ratio was 0.38 (0.10-1.42), for Nutrizym 22 43.4 (2.51-751), and for Pancrease HL 8.4 (1.95-36.1). These last two confidence intervals are extremely wide and compatible with these two products having the same odds ratios. Laxative use was independently predictive (odds ratio 2.42 [1.20-4.94]). We conclude that there is a dose-related association between high-strength pancreatic enzyme preparations and fibrosing colonopathy.

Adolescent↗
PubMed1995

Conversations in ethics: exploring the literature.

Because of changes in the healthcare industry, many questions have surfaced concerning ethical dilemmas. We, on the ethics committee, thought it a good idea to publish some updated and informative literature concerning these dilemmas.

Ethics, Nursing↗
PubMed1994

Simple Bayesian analysis in clinical trials: a tutorial.

In this tutorial paper we give a simple Bayesian analysis of data that arise in clinical trials. We consider the case when there are two treatment groups and the response in each group can be assumed to be binomially distributed. We also assume that prior beliefs about the rate parameter in each group can be adequately expressed by a Beta distribution. Using such a model approximate posterior inferences can then be made about the odds ratio between the two groups. We illustrate this methodology by analyzing a randomized trial to assess the benefits of treating patients with carcinoma of the pelvic region (rectum, bladder, colon, cervix) using high-energy fast neutrons as opposed to conventional megavoltage x-rays (photons). In this trial there was prior information about the relative efficacy of neutron therapy based on the beliefs of 10 clinicians. Some of the deficiencies of this simple approach are high-lighted and other approaches to analysis indicated. The paper facilitates practical consideration of a Bayesian approach without the complexities that a fuller analysis necessitates.

Bayes Theorem↗
PubMed1994

Axial length biometry in infants with retinopathy of prematurity.

Ultrasound axial length measurements were obtained on infants under a birthweight of 1500 g or 32 weeks gestation undergoing screening for retinopathy of prematurity (ROP). A total of 496 readings were obtained on 171 infants between 32 and 41 weeks post-conceptual age. Other details recorded were maximum stage of acute ROP, birthweight, gestational age, sex, and biparietal and occipitofrontal head diameters. The relationship of these variables to axial growth of the eye was examined using analysis of covariance with a repeated measures approach. Mean axial length increased from 15.27 mm to 16.65 mm in the left eye during this period. Following adjustment for repeated readings a growth rate of 0.18 mm/week was obtained for both eyes. Male infants were found to have longer axial lengths despite correction for birthweight, gestation and head size (p < 0.0001 right and left). Higher stages of acute ROP were also associated with shorter axial length (p < 0.05 for all stages of both eyes) but the rate of growth during the study period did not demonstrate significant differences between stages. Stage 3 infants reaching the threshold for cryotherapy had shorter axial length than stage 3 infants not receiving treatment. The effect of prematurity on the growth of the eye and the significance of these findings with respect to the subsequent development of refractive errors in premature infants are discussed.

Analysis of Variance↗
PubMed1994

A brief sensitive screening instrument for depression in late life.

Data collected with the depression scale (DEP) of the Brief Assessment Scale (BAS) at interviews with 811 elderly subjects were analysed to determine which of its 21 individual items could be selected to produce a short screening scale for depression which would have less than 10 items and a Cronbach's alpha above 0.8. Eight items which fulfilled these requirements were selected to form the Even Briefer Assessment Scale for Depression (EBAS DEP). The validity of the scale was assessed against psychiatric diagnoses made on a subset of 211 subjects. The EBAS DEP had a sensitivity and specificity for a diagnosis of a DSM-III-R mood disorder (depressed) of 0.91 and 0.72, respectively. The EBAS DEP could be useful as a brief screen for depression in busy hospital and primary care settings where a full assessment of mood for every patient is impractical. The EBAS DEP is presented, together with instructions for its use, to enable independent study of its reliability and validity in other populations.

Aged↗
PubMed1994

Prognostic value of ambulatory ST segment monitoring compared with exercise testing at 1-3 months after acute myocardial infarction.

The relative value of ambulatory ST segment monitoring for assessing prognosis following acute myocardial infarction is currently uncertain. Ambulatory monitoring was performed in 177 patients at a mean of 38 days (range 22-93) post-myocardial infarction and its prognostic value was compared with exercise treadmill testing (n = 170). Cardiac events (myocardial infarction, cardiac death or coronary revascularisation) were noted during at least 1 year of follow-up. The presence or absence of ST depression on ambulatory monitoring did not predict increased fatal or non-fatal cardiac events although more severe ST depression had some predictive power: after adjusting for clinical variables and coronary prognostic indices, the duration/24 h (P = 0.03) and magnitude (P = 0.007) of ST depression had independent value. ST deviation on exercise testing was associated (P < 0.05) with increased events (19/90; 21% vs 7/80; 9%) and in patients with a positive exercise test ST depression on ambulatory monitoring did not identify any additional events (8/41; 20% vs 11/49; 22%). No factor available from ambulatory monitoring was predictive of outcome once variables from exercise testing were taken into account. Ambulatory ST segment monitoring performed in the late recovery phase (1-3 months) after acute myocardial infarction is inferior to exercise testing for predicting prognosis and does not increase the predictive power of an exercise test. Ambulatory monitoring may only be indicated in patients unable to perform an exercise test.

Electrocardiography, Ambulatory↗
PubMed1993

Prognostic significance of transient myocardial ischemia on ambulatory monitoring after acute myocardial infarction.

The prognostic value of ambulatory ST-segment monitoring after myocardial infarction was prospectively assessed in 203 patients both early (mean 6 days, n = 201) and late (38 days, n = 177). During at least 1 year of follow-up there were 21 cardiac deaths and 44 cardiac events (death, reinfarction or coronary revascularization). ST depression was seen less often during early than late monitoring (29 of 201 [14%] vs 56 of 177 [32%]). Early ST depression was significantly associated with increased mortality (7 of 29 [24%] vs 14 of 172 [8%]) (< 0.05) and increased cardiac events (13 of 29 [45%] vs 30 of 172 [17%]) (p < 0.001) and had independent value after allowing for clinical factors and coronary prognostic indexes (adjusted relative risks 3.40 and 2.70, respectively). ST depression on late monitoring was only associated with increased cardiac events when it was: (1) frequent (e.g., > or = 3 episodes/day [10 of 31 patients, 32% vs 18 of 146, 12%]) (p < 0.01); (2) prolonged (e.g., > or = 20 minutes/day [8 of 25, 32% vs 20 of 152, 13%]) (p < 0.05); or (3) severe (e.g., maximum of > or = 1.5 mm [8 of 28, 29% vs 20 of 149, 13%]) (p < 0.05). Thus, ST depression occurs less frequently during ambulatory monitoring before discharge than during late monitoring, but is a more specific prognostic indicator; however, it is more benign during late monitoring. Ambulatory ST-segment monitoring can be used to predict prognosis in the first year after myocardial infarction, although its relative value as a screening test compared with exercise testing remains to be established.

Electrocardiography, Ambulatory↗
PubMed1993

Tuberculin testing in residential homes for the elderly.

BACKGROUND: Evidence from the United States has shown that tuberculin sensitivity increases with length of stay among residents in homes for the elderly, implying an increasing risk of infection. There is no evidence as to whether or not residents in homes in the United Kingdom have a similar risk. METHODS: A study was undertaken to determine whether residence in a home for the elderly increases the risk of tuberculosis infection. Over a six month period all residents in homes for the elderly in Liverpool received a tuberculin test. A health questionnaire was completed by the field team for each resident. A total of 2665 residents in homes for the elderly were surveyed. RESULTS: Heaf test grade positivity declined with age, the odds ratio being 0.71 for each 10 year period. Adjusting for age, there was no change in Heaf test grade with length of stay in the home. Heaf test positivity was stronger in smokers (odds ratio 1.59) than ex-smokers (odds ratio 1.20) and non-smokers. Heaf test grade positivity was directly related to pack years. Allowing for age and smoking, the odds ratio for men compared with women for a positive test was 1.62 (95% confidence interval 1.32 to 1.99). CONCLUSIONS: Heaf test positivity declines with age. Residence in a home for the elderly is not associated with increased rate of tuberculosis sensitivity. Smoking and male gender is associated with increased Heaf test positivity.

Adult↗