[Critical reading of analytical observational studies]

Analytical observational studies provide very important information about real-life clinical practice and the natural history of diseases and can suggest causality. Furthermore, they are very common in scientific journals. The aim of this article is to review the main concepts necessary for the critical reading of articles about radiological studies with observational designs. It reviews the characteristics that case-control and cohort studies must have to ensure high quality. It explains a method of critical reading that involves checking the attributes that should be evaluated in each type of article using a structured list of specific questions. It underlines the main characteristics that confer credibility and confidence on the article evaluated. Readers are provided with tools for the critical analysis of the observational studies published in scientific journals.

[Key aspects in interpreting clinical trials in radiology]

A clinical trial is an experimental study to evaluate the efficacy and safety of a treatment or diagnostic technique in human beings. To ensure the methodological quality of a clinical trial and the validity of its results, various checklists have been elaborated to identify biases that could invalidate its conclusions. This article focuses on the points we need to consider in the critical evaluation of a clinical trial. We can usually find this information in the "materials and methods" and "results" sections of articles. Randomization, follow-up (or analysis of losses), blinding, and equivalence between groups (apart from the intervention itself) are some key aspects related to design. In the "results" section, we need to consider what measures of clinical efficacy were used (relative risk, odds ratio, or number needed to treat, among others) and the precision of the results (confidence intervals). Once we have confirmed that the clinical trial fulfills these criteria, we need to determine whether the results can be applied in our environment and whether the benefits obtained justify the risks and costs involved.

[The six steps necessary in elaborating critically appraised topics]

Different types of critically appraised topics (CATs) can be elaborated in diagnostic imaging: comparison of diagnostic tests, evaluation of techniques for early detection (screening), economical analyses, or therapeutic aspects, among others. Their design will vary in function of the question they aim to answer. For example, for treatment evaluation, clinical trials are the best, but if there are secondary studies (systematic reviews or meta-analyses) that synthesize information from several studies, the results will be more important and the scientific conclusions will be more relevant. Regardless of the study design used, the elaboration of a CAT will involve six steps: 1) question; 2) systematic and efficient bibliographic search; 3) levels of evidence (choosing the articles that have the best level); 4) critical reading of the articles chosen; 5) applying conclusions to the context, and 6) recommendations. In this article, we will describe these steps and the nuances for different types of studies in each step.

[Critically appraised topics (CATs): a new publishing opportunity in Radiología]

Physicians need fast access to quality information about the best diagnostic tests and treatments in each case. To meet this need, a new publishing format has emerged. Critically appraised topics (CATs) are elaborated following the five steps of evidence-based medicine. CATs are structured summaries of research articles that deal with a specific clinical query, presenting a critical evaluation of the best evidence available to support the validity of the available options. CATs have proven useful in teaching evidence-based radiology and this publishing format is becoming more common. Radiology CATs can be found on medical websites and in journals, including those dedicated to general medicine as well as those specifically dedicated to radiology. Radiología encourages the publication of CATs because we consider that they can be useful for daily decision making.

[Evidence-based radiology for diagnostic imaging: what it is and how to practice it]

Evidence-based radiology is defined as the decision that results from integrating clinical information to select the most appropriate imaging test on the basis of the best available evidence, the physician's experience, and the patient's expectations. The practice of evidence-based radiology consists of five steps: formulating the question, performing an efficient search of the literature, critically evaluating the literature, applying the results of the search and evaluation while taking into account our experience and the patient's values, and evaluating the results obtained within our own practice. In diagnostic imaging, the number of resources available for evidence-based radiology is increasing: apart from books, articles, and web pages on this subject, evidence-based radiology is receiving more attention at diagnostic imaging conferences. The principles of evidence-based radiology will help promote the appropriate use of resources, greatly benefiting patients (decreasing the use of examinations that use ionizing radiation), professionals (less overload), and managers (more efficient use of resources).