RESUMO
Interim analysis of data accumulated in clinical trials is one aspect of the monitoring of the study progress. It is usually done to assess whether there are significant differences in efficacy between the experimental and control treatment groups, in order to decide whether to stop or no the trial prematurely. Among many reasons for early interruption of a trial is the ethical consideration that subjects should not be exposed to an unsafe, inferior or ineffective treatment. Statistical methods suited for doing interim analysis, that allow to control the probability of incorrectly rejecting the null hypothesis of no treatment differences, are often not well understood by researchers. In this article we present an intuitive, non-mathematical explanation and review of the statistical methods for doing interim analysis in clinical trials along with an illustrative example of the application of the methods on a hypothetical dataset.
Assuntos
Ensaios Clínicos como Assunto/métodos , Interpretação Estatística de Dados , Projetos de Pesquisa , Protocolos Clínicos , Fatores de TempoRESUMO
OBJECTIVE: To audit appropriate use of blood products in adult patients. DESIGN: A cross-sectional study with pre-set criteria. SETTING: Ciudad Hospitalaria 'Dr. Enrique Tejera', the main public tertiary-care hospital in Valencia, Venezuela. STUDY PARTICIPANTS: We studied 700 adult patients from the Medicine, Surgery, Emergency and Obstetrics departments. MAIN OUTCOME MEASURE: Appropriate use of blood products. RESULTS: Seven hundred patients who had an average of 2.45 transfusions (95% confidence interval = 2.28-2.62) were studied. Prevalence of appropriate use was 51.3% for all departments. Prevalence by department was: 72% for Medicine, 36% for Surgery, 56% for Emergency, and 47% for Obstetrics. The average number of transfusions per subject in each department was: Medicine, 3.41; Surgery, 1.75; Obstetrics, 2.09; and Emergency: 2.81 (F-test: P=0.005). Using the department of Medicine as the reference group, it was found that the departments of Surgery, Emergency and Obstetrics had a higher 'risk' of inappropriate use of transfusions, showing odds ratios of 4.4, 1.38 and 2.79 respectively. CONCLUSION: The main conclusions of this study are: (i) the prevalence of the appropriate use of blood products was 51%; (ii) packed red cells and fresh frozen plasma were the blood products with the lowest prevalence of appropriate use; and (iii) none of the departments showed rates of appropriate use of transfusions greater than 80%, implying a higher cost in health care and putting patients at a higher risk for acquiring a transfusion-transmitted disease.