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Biomedical subjects

A Donner

Publications and source records attributed to A Donner.

At least 73 records · Page 4Linked to original sources
PubMed1997

Factors affecting the comparability of meta-analyses and largest trials results in perinatology.

The objective of this report is to provide a new methodology for evaluating the performance of meta-analysis (MA) in corroborating results of large trials (LT) and to identify factors that could explain lack of similarity in the results. We used two criteria to judge the degree of similarity between a MA and the LT: (a) the ratio of the relative risk of the MA to the relative risk of the LT; and (b) the 95% confidence interval about this ratio. Furthermore, this degree of similarity was cross-tabulated with the presence or not of evidence of selective inclusion of positive studies (e.g., publication bias) as judged from "funnel plots" and statistical indicators. Depending on which of our two criteria was used, we found that between 20% and 53% of the 30 MAs studied have high or very high degree of similarity with the LT. We also found strong evidence that factors influencing asymmetrical funnel plots of MA, such as publication bias, may play an important role in this degree of similarity. There was a sizeable proportion of meta-analyses that did not agree with large trial results. We recommend that funnel plots be used as a tool for identifying which MAs can mislead. However, the statistical indicators at hand are unlikely to be of use in many area of medicine considering the regrettably small number of randomized controlled trials per topic available.

Bias↗
PubMed1997

Tubeless laryngotracheal surgery in infants and children via jet ventilation laryngoscope.

We present the first use of tubeless superimposed combined high- and low-frequency jet ventilation (SHFJV) with a jet laryngoscope in laryngotracheal surgery in infants and children. Twenty-eight patients underwent 53 operative procedures. The average age of the patients was 7.3 years. The most common diagnoses were laryngeal papillomatosis and subglottic stenosis. The duration of jet ventilation averaged 33 min. The gas exchange was sufficient in each case. The advantages of SHFJV in the surgery of the laryngotracheal area in infants and children are optimal view at the larynx and trachea, maximum space for the handling, application of the laser without risks, no time limitation, suitability for stenosis, and neither anesthetic nor surgical complications.

Adolescent↗
PubMed1997

Non-alcoholic duct destructive chronic pancreatitis.

BACKGROUND: The pathology of non-alcoholic chronic pancreatitis has not yet been sufficiently studied. AIMS: To identify the major changes of pancreatic tissue in patients surgically treated for non-alcoholic chronic pancreatitis. PATIENTS: Pancreatectomy specimens from 12 patients with non-alcoholic chronic pancreatitis, including four patients with autoimmune or related diseases (Sjögren's syndrome, primary sclerosing cholangitis, ulcerative colitis, and Crohn's disease), were reviewed. METHODS: Morphological changes were studied histologically and immunohistochemically (to type inflammatory cells) and compared with the pancreatic alterations found in 12 patients with alcoholic chronic pancreatitis. RESULTS: In patients with non-alcoholic chronic pancreatitis, with or without associated autoimmune or related diseases, pancreatic inflammation particularly involved the ducts, commonly resulting in duct obstruction and occasionally duct destruction. None of these features was seen in alcoholic chronic pancreatitis which, however, showed pseudocysts and calcifications. CONCLUSION: The pancreatic changes in patients with non-alcoholic chronic pancreatitis clearly differ from those with alcoholic chronic pancreatitis. The term chronic duct destructive pancreatitis is suggested for this type of pancreatic disease.

Adolescent↗
PubMed1997

The HELLP syndrome.

Explore the source record for details and available documents.

Analgesia, Obstetrical↗
PubMed1996

Randomised study of n of 1 trials versus standard practice.

OBJECTIVE: To compare outcomes between groups of patients with irreversible chronic airflow limitation given theophylline by n of 1 trials or standard practice. DESIGN: Randomised controlled study of n of 1 trials versus standard practice. SETTING: Tertiary care center outpatient department. SUBJECTS: 31 patients with irreversible chronic airflow limitation who were unsure that theophylline was helpful after an open trial. INTERVENTIONS: n Of 1 trials (single patient randomised multiple crossover comparisons of theophylline against placebo) followed published guidelines. For standard practice patients theophylline was stopped and resumed if their dyspnoea worsened; if their dyspnoea then improved theophylline was continued. For both groups a decision to continue or stop the drug was made within three months of randomisation. MAIN OUTCOME MEASURES: Exercise capacity as measured by six minute walking distance, quality of life as measured by the chronic respiratory disease questionnaire at baseline and six months after randomisation, and proportions of patients taking theophylline at six months. RESULTS: 26 patients completed follow up. 47% fewer n of 1 trial patients than standard practice patients were taking theophylline at six months (5/14 versus 10/12; 95% confidence interval of difference 14% to 80%) without differences in exercise capacity or quality of life. CONCLUSIONS: n Of 1 trials led to less theophylline use without adverse effects on exercise capacity or quality of life in patients with irreversible chronic airflow limitation. These data directly support the presence of a clinically important bias towards unnecessary treatment during open prescription of theophylline for irreversible chronic airflow limitation. Confirmation in a larger study and similar studies for other problems appropriate for n of 1 trials are needed before widespread use of n of 1 trials can be advocated in routine clinical practice.

Aged↗
PubMed1996

Lipids and stroke: a paradox resolved.

BACKGROUND: Although dyslipidemia is a well established risk factor for coronary artery disease, its relationship to ischemic cerebrovascular disease has remained unclear, perhaps because of the heterogeneous nature of strokes. METHODS: In a case-control study, we measured the serum concentrations of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, serum triglycerides, and lipoprotein(a) levels and determined the apolipoprotein E phenotype and serum ferritin level in 90 consecutive systematically investigated patients with stroke or transient ischemic attack of atherothrombotic origin. Ninety age-, sex-, and community-matched subjects served as controls. RESULTS: Plasma total cholesterol (5.99 vs 5.45 mmol/L [232 vs 211 mg/dL], P=.003), low-density lipoprotein cholesterol (3.96 vs 3.45 mmol/L [153 vs 133 mg/dL], P=.004), and serum triglyceride (2.09 vs 1.82 mmol/L [8] vs 70 mg/dL], P=.03) levels were significantly higher among the patients with atherothrombotic strokes and transient ischemic attacks than among the control subjects. The inverse was true for high-density lipoprotein cholesterol (1.07 vs 1.18 mmol/L [41 vs 46 mg/dL], P=.02) levels. No significant differences were found in lipoprotein(a) levels or in the distribution of apolipoprotein E phenotypes or allele frequency. Serum ferritin levels did not differ significantly between patients and control subjects. CONCLUSIONS: Elevated low-density lipoprotein cholesterol and triglyceride levels are significant independent risk factors in patients with proven atherothrombotic cerebrovascular disease manifesting as stroke or transient ischemic attack. The level of stored serum iron, as reflected by serum ferritin levels, does not correlate with the presence of atherothrombotic cerebrovascular or coronary disease.

Aged↗
PubMed1996

Statistical considerations in the design and analysis of community intervention trials.

Community intervention trials are often characterized by the allocation of intact social units to different intervention groups. The assessment of adequate sample size for such trials must take into account the statistical dependencies among responses observed within an allocated unit. However, the small numbers of units typically involved in such trials imply that many methods of analysis that have been proposed for analyzing correlated data, particularly in the case of a dichotomous outcome variable, are not applicable to such designs. In this article we investigate this issue and determine the minimum number of units required per group, for the case of both a dichotomous and a continuous outcome variable, needed to provide adequate statistical power for detecting various levels of treatment effect. The use of significance testing as a method of detecting intracluster correlation is also investigated, and, in general, discouraged.

Adolescent↗
PubMed1996

The statistical analysis of kappa statistics in multiple samples.

Methods are presented for assessing and comparing the results of k > or = 2 independent samples of measured agreement or concordance, where in each sample a given member of a pair of observations is classified according to the presence or absence of a binary trait. Examples include the assessment of interobserver agreement across different groups of patients in a clinical study, investigations of sibling concordance across different genetic groups, and meta-analyses of observer agreement across different studies. The methodology described is based on application of goodness-of-fit theory to testing hypotheses concerning kappa statistics. Partitioning methods allow a variety of hypotheses to be tested, including an assessment of the degree of agreement within each sample, a testing procedure based on the pooled data, and a test of heterogeneity that may be used to assess the validity of pooling across samples. Three examples are given.

Humans↗
PubMed1996

The Pittsburgh randomized trial of tacrolimus compared to cyclosporine for hepatic transplantation.

BACKGROUND: Tacrolimus (formerly FK506) was first used clinically in 1989 to successfully replace cyclosporine in hepatic transplant recipients who were experiencing intractable rejection or as the baseline drug from the time of operation. After extensive pilot experience, an institutional review board-mandated clinical trial comparing cyclosporine with tacrolimus was performed. STUDY DESIGN: From February 16, 1990 to December 26, 1991, 154 patients were recruited. The competing drugs were combined with equal induction doses of prednisone in both arms of the study for the first 81 patients and with subsequently higher doses of prednisone in the remaining 35 patients who received cyclosporine and were entered into the trial. Drug crossover was permitted for lack of efficacy or adverse events. End points were rejection confirmed by biopsy and treatment failure leading to retransplantation or death. RESULTS: Seventy-nine patients were randomized to the tacrolimus arm and 75 to the cyclosporine arm during 1990 and 1991. All patients were available for follow-up throughout the trial, which terminated on May 30, 1995. The mean duration of follow-up was four years. Patients randomized to the tacrolimus arm were less likely to experience acute rejection than were those receiving cyclosporine, with 36.2 percent of the patients receiving tacrolimus and 16.8 percent of the patients receiving cyclosporine showing freedom from rejection at one year (p = 0.003, likelihood ratio test). Survival of patients over the course of the study was virtually the same in the two groups.

Adolescent↗
PubMed1996

Application of SHFJV for surgical procedures.

Using SHFJV in combination with the jet laryngoscope it is possible to ventilate patients for laryngeal surgery with out the necessity for any kind of endotracheal tube or catheters. This technique can also safely be applied in patients with underlying pulmonary or cardiac disease or in obese patients. Patients with laryngeal stenosis can be ventilated from above the stenosis eliminating the danger of barotrauma. The laser can be used at any time the surgeon desires without any additional protective measures. The SHFJV can be used for tracheobronchial stent insertion. Only in cases were the glottis can not be visualized through the jet laryngoscope sufficient ventilation is not ensured and therefore transtracheal high frequency ventilation is the technique of choice.

Adolescent↗
PubMed1996

High frequency ventilation techniques in ARDS.

High frequency ventilation techniques are not applied as routine measures but are still regarded as lastditch efforts in treating patients with severe ARDS or with extensive bronchoplural fistula when conventional mechanical ventilation is not capable in providing sufficient gas exchange. High frequency ventilation techniques can be used in patients with septicemia or recent cerebral bleeding, which is a contraindication for ECMO, or in patients with increased ICP. We believe that high frequency ventilation techniques provide an important therapeutic tool in the treatment of pulmonary insufficiency since the hardware requirement is minimal and, after a brief explanation, the application is easy.

Adult↗
PubMed1996

Testing the homogeneity of kappa statistics.

Procedures are compared for testing the homogeneity of k > or = 2 independent kappa statistics in the case of two raters and a dichotomous outcome. One of the procedures is based on the estimated large sample variance derived under a model frequently adopted for inferences concerning interobserver agreement. The other is based on a goodness-of-fit approach to this model. The results of a Monte Carlo simulation show that the two approaches have similar properties if the number of subjects in each sample is large (> 100), and the prevalence of the underlying trait of interest is not extreme, while the goodness-of-fit approach is recommended for comparisons involving smaller numbers of subjects or in which the prevalence of the underlying trait is small (< 0.3).

Analysis of Variance↗
PubMed1995

Statistical methodology for estimating twin similarity with respect to a dichotomous trait.

Statistical methodology is presented for the estimation of twin similarity with respect to a dichotomous trait. The methodology focuses on the intraclass correlation as the parameter of interest and is analogous to methodology commonly applied to continuous outcome data. For inference problems involving a single sample, confidence interval construction and significance testing are discussed. For two sample problems, test procedures are provided that are an alternative to an approach recently presented by Ramakrishnan et al. [(1992) Genet Epidemiol 9:273-287 (1)]. Two examples based on published data sets are given to illustrate the proposed techniques.

Confidence Intervals↗