Scandinavian journal of gastroenterology. Supplement
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The limitations of conventional group comparative therapeutic trials are discussed. They include: the heterogeneity problem (due to biological variations within the sample) and the extrapolation problem (i.e. the problem of external validity). These problems may to some extent be overcome by multiple cross-over studies in a single patients. ⋯ Usually, it is necessary to measure the clinical effect by means of clinical scores, for which reason ranking methods must be used. The statistical significance may be judged by means of a permutation test. The risk of committing a type II error in single patient studies is usually high.
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Scand. J. Gastroenterol. Suppl. · Jan 1988
Comparative StudyExperience with a multi crossover model in dyspepsia.
A multi cross over model (MCOM) has been designed for single case studies. The model which is only partly randomized, implies regular interchanges between treatment periods with active drug and placebo. ⋯ The advantages of the single case approach and the impact of the MCOM is illustrated by the results from a study of the effect of cimetidine in non ulcer dyspepsia. Although there are several statistical objections to the model, the results from the study are reasonable and demonstrate a small degree of violence of preassumptions.
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Scand. J. Gastroenterol. Suppl. · Jan 1988
Comparative StudyStatistical issues in studies of individual response.
We consider intensive studies of individual response to therapy in a controlled experiment. It is helpful to distinguish between strict 'N = 1' studies, which are pragmatic trials intended to draw conclusions concerning only the patient under consideration, and 'N much greater than 1' studies, which are explanatory trials intended to make more general statements about a treatment with highly variable response, for which aggregate measures of effect on groups are inappropriate. Issues of design, measurement, and statistical significance are discussed, and the rule of permutation tests emphasised. Three published examples are used as illustrations.
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Scand. J. Gastroenterol. Suppl. · Jan 1987
Randomized Controlled Trial Clinical TrialTranexamic acid in gastric and duodenal bleeding.
In this prospective, randomized, double-blind study the effect of the antifibrinolytic drug tranexamic acid was compared with that of placebo in 154 patients bleeding from verified benign lesions in the stomach and/or duodenum. Three out of 72 patients receiving tranexamic acid underwent emergency surgery, in contrast to 15 out of 82 in the placebo group (p = 0.010). ⋯ Side effects were seen in six patients, of which an uncomplicated deep venous thrombosis was the most severe. It was concluded that tranexamic acid reduces the blood transfusion requirement and the need for emergency surgery in patients bleeding from a benign gastric or duodenal lesion.
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Scand. J. Gastroenterol. Suppl. · Jan 1987
ReviewTranexamic acid in acute upper gastrointestinal bleeding.
The effect of the antifibrinolytic substance, tranexamic acid, has been studied in 5 double-blind, randomized, placebo-controlled trials in patients with acute upper gastrointestinal bleeding. The results of these trials have varied with regard to blood transfusion requirements and the frequency of operations. All of the studies have shown lower mortality in patients treated with tranexamic acid. Thus tranexamic acid would seem to be indicated in acute upper gastrointestinal bleeding.