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Biomedical subjects

J Windeler

Publications and source records attributed to J Windeler.

At least 19 recordsLinked to original sources
PubMed2006

[Benefit and benefit assessment].

The term value denotes the effect(s) of an intervention which will improve, by more than just a little, prognosis and/or symptoms and/or quality of life of the patient. The value of a medical intervention has to be assessed in a way that the patient can be adequately informed and believable promises and pronouncements of such an intervention are made. The decisive and only relevant question when assessing value is to what extent the patient profits. The assessment of value is connected with the question about clinically or patient-relevant (i. e. relevant) end points, which for the patient means decisive and perceived events that as a rule have an effect on him/her. It is the aim of value assessment to ensure quality of an individual treatment and of medical practice in a wider sense.

Germany↗
PubMed2005

[Post-marketing surveillance studies].

Approval of a drug on the market is typically considered as the successful endpoint of a long development phase. This often leads to reduced interest in further research for the indication approved, while in contrast the patient's as well as physician's interest in further research increases. This paper discusses the main areas of effectiveness, safety and post-marketing practice regarding sensible study types for the specific area and the potential gain of knowledge.

Aged↗
PubMed2001

Intention-to-treat: methods for dealing with missing values in clinical trials of progressively deteriorating diseases.

Since it came up in the 1960s, the principle of intention-to-treat (ITT) has become widely accepted for the analysis of controlled clinical trials. In this context the question of how to perform such an analysis in the presence of missing information about the main endpoint is of major importance. Uncritical use of several ad hoc strategies for dealing with missing values is common in the practice of clinical trials. On the other hand, little is known about possible dangers and problems of applying these strategies. We therefore performed a detailed investigation of different methods for dealing with missing values in order to develop recommendations for their practical use. A simulation study was performed investigating possible consequences on type I error and power of applying different methods for dealing with missing values. The simulations were based on a clinical trial of osteoporosis, a progressively deteriorating disease. The strategies examined can be roughly classified into numerical imputation strategies (last observation carried forward, mean and regression based methods) and non-parametric strategies (rank and dichotomization based methods). Different drop-out mechanisms and different types of progression of disease are considered. The type I error increases drastically for the different strategies, especially if the courses of disease vary between treatment groups. The loss in power can be substantial. There is no strategy which is adequate for all different combinations of drop-out mechanisms, drop-out rates and courses of disease over time. For drop-out rates less than 20 per cent and similar courses of disease in the treatment groups, missing values might be replaced by the mean of the other group, or counted as treatment failures after dichotomization of the endpoint. For larger drop-out rates or less similar courses of disease, no adequate recommendations can be given. Because of the drastic consequences of increasing drop-out rates, it has to be a primary goal in clinical trials to keep missing values to a minimum. Unobserved information cannot be reliably regained by any methodological resources. As there are no strategies for universal use, reasons for the choice of a certain method have to be provided when designing and analysing clinical trials.

Computer Simulation↗
PubMed2001

Postprandial blood glucose latency after oatmeal is a valid screening test for diabetic gastropathy in type 1 diabetes, but not in type 2 diabetes.

Disordered gastric motility occurs frequently in diabetes mellitus. Gastric emptying time is abnormal in about 50% of diabetic patients and delayed emptying time is known as an important cause for brittle diabetes in type 1 diabetes. We compared the rise in blood glucose after a standardized meal (oatmeal test) as a noninvasive screening test for diabetic gastropathy with the noninvasive measurement of gastric emptying time with ultrasound in type 1 and type 2 diabetic patients. The test result was considered pathological if the rise of blood glucose after an initial steady state did not reach 20 mg/dl in the first 20 min after the meal (prolonged blood glucose latency). We found a sensitivity of 90% (58.7-99.8) and a specificity of 100% (71.5-100) for the oatmeal test in type 1 diabetes in the gastropathy screening. In type 2 diabetes we found a sensitivity of 13% (1.5-38.3) and a specificity of 78% (60-90.7) (95% CI). In conclusion, the oatmeal test seemed to be a good, noninvasive screening test in diabetic gastropathy in type 1 diabetes, but has no diagnostic value in type 2 diabetes. The causes for such a difference may be due to a different postprandial blood glucose regulation in type 2 diabetes compared to the beta-cell-depleted type 1 diabetes.

Adult↗
PubMed2001

[Rapid reviews for evidence-based decision support. (Restricting) requirements].

Since evidence-based decision making is increasingly gaining acceptance among German health care authorities the need for evidence-based support for time-critical decisions becomes obvious. The best method to identify and summarize the available evidence is the conduct of systematic reviews of the literature. However, generally systematic reviews are not applicable in matters of urgency, because of their time consuming preparation. Concepts for "rapid reviews" are urgently required which ensure that these reviews still produce reliable results. The article proposes strategies to accelerate the preparation of a systematic review and discusses their possible influences on the conclusions of the review. Research efforts are needed to clarify which of the accelerations actually yield valid results.

Delivery of Health Care↗
PubMed2001

[Evidence-based scientific analysis of fundamental Medical Services of Statutory Health Insurance internal principle assessment].

In Germany, the increasing relevance of Evidence-based medicine (EbM) is not only a consequence of growing economic limitations in the health care system but of a changed jurisdiction, too: liability of the statutory health insurances (SHI) to pay for medical care depends on the proof of its effectiveness. This is of special importance for the Medical Services in their role as an advisor of the SHI. The article depicts the basic assignments of the Medical Services of the Statutory Health Insurance, their legal frame and the role of EbM in sociomedical expertising. The way of fundamental sociomedical expertising, its internal and external effects, the personnel and technical/logistic requirements are described as well as potential of improvement.

Delivery of Health Care↗
PubMed2001

[Evidence-based medicine in the further development of health care systems. Comments on a current discussion].

The concept of evidence-based medicine is applicable also in the field of guiding health care systems to overcome deficits in adequate patient care. EbM has already been used in this field and has passed first tests of its practical application. There are some obstacles against the future esteem of EbM. These include some misunderstanding concerning the concept itself, missing routine where external evidence has to be put into practice, and some general resistance. Details are presented and an adequate usage of EbM is argued for.

Delivery of Health Care↗
PubMed2001

[How much is "evidence-based"? An overview of the state of the art in research].

The proportion of evidence-based health care gives rise to controversy. Estimates range from 4%-20%. Studies trying to ascertain the proportion of evidence-based healthcare show wide variations in the results depending on design, setting, subject, main outcome measures, methodology and definition of evidence from 11-82%. The results should not be generalized to community health care and should not be misused in public discussions.

Delivery of Health Care↗
PubMed2000

[CONSORT--What is to be expected from a reputable scientific publication].

The publication of the CONSORT Statement was aimed at the improvement of the quality of research reports of randomized controlled clinical trials. It contains the most important standards of high quality research. Although originally meant for randomized studies only most aspects of this statement can be applied to other kinds of clinical studies. The following--and last--article of this series on medical biostatistics presents and comments the most important criteria.

Clinical Trials as Topic↗
PubMed2000

[Factors modifying frequency of publications of clinical research results exemplified by medical dissertations].

BACKGROUND AND OBJECTIVE: The problem of so-called "publication bias"--distortion of statements about an event by selective publication--is receiving growing attention. Assessment of the results of a given study can be affected by knowing the factors that favour or inhibit the publication of its results. METHODS: The data were based on an analysis of 371 medical doctoral dissertations on clinical research. Characteristic features of the dissertations were obtained by questionnaire, supplemented by MEDLINE search and, additionally, by personal enquiry about the publications. Bivariate and multivariate analysis of the characteristic features was used to evaluate the factors that influenced publication of a dissertation. RESULTS: There were mainly three factors that influenced the decision whether or not a dissertation was published: (1) a positive result of the study (odds ratio 2.5, 95% confidence interval 1.12-5.75); (2) the publishing activity of the dissertation's referee (odds ratio 3.8, 95% confidence interval 1.77-7.97; and (3) the quality of the statistical analysis of the dissertation's data (odds ratio 1.67, 95% confidence interval 0.99-2.80). CONCLUSION: A distinct publication bias can be demonstrated also in the case of doctoral dissertations in that positive results are clearly published more often than negative ones.

Academic Dissertations as Topic↗
PubMed2000

[Neurological scales as endpoints in stroke studies. Aspects of statistical evaluation].

Even after publication of ECASS II, the latest paper in a series of large, placebo-controlled studies on thrombolysis in acute ischaemic stroke, there is still uncertainty as to what the best clinical endpoint(s) is (are) in trial design for reliably identifying significant differences between treatment groups. If the expected treatment difference as measured by a neurological outcome scale like the Modified Rankin Scale corresponds more to a shift in dispersion (on average a majority of patients profits greatly) rather than to a shift in location (on average each patient profits much), then the power of the odds ratio test is much higher than that of the Wilcoxon test and therefore the clinical outcome parameters should be dichotomised. With respect to the time window of 0-6 hrs from symptom onset of an acute ischaemic stroke, for example, a dichotomisation of 0-2 vs. 3-6 for the Modified Rankin Scale is reasonable. In the case of multiple endpoints, a global (multivariate) test should be used, but the correlation between these endpoints must not be too high, which means that the various manifestations of the complex stroke disease should be considered.

Cerebral Infarction↗
PubMed2000

Short- and long-term results after laparoscopic vs conventional colon resection in a tumor-bearing small animal model.

BACKGROUND: We designed a study to evaluate the short- and long-term outcome of laparoscopic vs conventional colonic resection in a tumor-bearing small animal model. METHODS: We operated on male BD X rats (260-300 g), performing either laparoscopic (n = 9) or open colon resection (n = 9) in order to evaluate stress and immunological response to laparoscopic vs conventional colon resection. A third group (n = 9) underwent anesthesia only. Immediately before and after surgery, as well as at 1, 7, and 21 days postoperatively, a sample of 1 ml blood was taken from the retrobulbar venous plexus. Stress (corticosterone) and immune parameters (neopterine and IL-1 beta, IL-6) and body weight as a parameter of postoperative recovery were measured to identify short-term alterations. Long-term changes were evaluated in terms of survival time and at autopsy by measuring the tumor weight and the number of tumor infiltrated nodules (histology). RESULTS: The analysis of variance (ANOVA) showed significant differences between the three groups over a period of 1 week (p < 0.001 for corticosterone, p = 0.009 for neopterine, p = 0.04 for IL-1 beta, p = 0.024 for IL-6). Additionally, significant differences by t-test were found between the laparoscopic (minor alteration) and conventional (major alteration) group regarding corticosterone (p = 0.0015), neopterine (p = 0.0024), IL 1-beta (p = 0.033), and IL-6 (p = 0.015) at the end of the operation. One week after the operation, the body weight was different depending on the type of operative procedure: 7 days postoperatively the rats lost 8% of their body weight after open surgery but only 4.3% after laparoscopic surgery. After anesthesia only, body weight increased by approximately 4.8%. The medium survival time for the lap group was 44 days, whereas it was 44.1 days for the conventional group and 46 days for the anesthesia group (ANOVA p = 0.625). The number of nodules was 13.5 in the laparoscopic group 10.5 in the open group, and 7.4 in the anesthesia group, (ANOVA p = 0.119). The tumor weight was 6.8 g in the laparoscopic group, 6.4 g in the open group, and 5.04 g in the anesthesia group (ANOVA p = 0.874). CONCLUSION: In a tumor-bearing small animal model, laparoscopic colon resection alters the stress and immune system less than open colon resection. This observation has no implications for the long-term results as measured by survival time and at autopsy. Therefore, laparoscopic colon resection has a short-term benefit and has no negative effect on long-term results compared to conventional operative procedures.

Adenocarcinoma↗
PubMed2000

Effect of pressure and gas type on intraabdominal, subcutaneous, and blood pH in laparoscopy.

BACKGROUND: According to the literature, the number of port-site metastases in laparoscopic surgery varies considerably depending on the type of gas used for the pneumoperitoneum. In order to investigate this observation we studied the changes in blood, subcutaneous, and intra-abdominal pH during laparoscopy with helium, CO(2) and room air in a rat model. In addition, we looked at the influence of intra-abdominal pressure and duration of pneumoperitoneum on the pH during the laparoscopy. METHODS: pH was measured by tonometry, intra-abdominally and subcutaneously. A pH electrode was additionally placed into the subcutaneous tissue and the results compared to those measured by tonometry. Blood samples were taken from a catheter in the carotid artery. The intra-abdominal pressure was 0, 3, 6, 9 mm Hg for 30 min in each case. We investigated the effect of pneumoperitoneum with CO(2), helium and air in randomized groups of 5 rats. In an additional series the pressure was held constant at 3 mm Hg and the pH was measured every 30 min. RESULTS: Due to the different absorption capacity of the peritoneum, laparoscopy with CO(2) decreases the subcutaneous pH from 7.35 to 6.81. Blood pH is reduced from 7.37 to 7.17 and the intra-abdominal pH from 7.35 to 6.24. Other, less absorbable gases induce smaller changes of blood and subcutaneous pH (only 10% of CO(2)). In a variance analysis the p value is less than 0.001. The influence of duration of laparoscopy (30 min vs. 90 min) on the subcutaneous pH is less compared to the influence of intra-abdominal pressure (0, 3, 6, 9 mm Hg). CONCLUSIONS: Depending on the type of gas (CO(2), air, helium) used for laparoscopy blood, subcutaneous and intra-abdominal pH are influenced differently. Because lower pH is known to impair local defense mechanisms, these results may be one explanation for the higher incidence of port-site metastasis in laparoscopy with CO(2) than with other gases, as reported in the literature.

Abdomen↗