Back to EPIDEMIOLOGYA problem constantly faced by physicians and medical students is how to choose literature without wasting time or losing important information. Nowadays, medical practitioners are involved in many activities, such as clinical assistance and research projects. These activities expend most part of doctor’s day, so that rarely a doctor or a student can read all the articles he judges necessary. As if it was not enough, medical research is being enormously increased, and it would be impossible to read all the articles about every important subject, in order to maintain a correct clinical policy. These facts lead to a dilemma, in which every medical student or practitioner should know certain rules to choose the right articles and obtain useful information about the subject of interest. There are different kinds of literature, each one has importance because carries characteristics that allow us to take some conclusions of great use in clinical decisions, to direct future researches or even to review important matters. Due to the pivotal importance of getting the right information, doctors should not worry about advances in specific areas, except in their preferred areas. On the contrary, they should read mainly literature that is important to develop or change clinical policy, and this includes reading only scientifically important articles.
The medical literature is composed by many kinds of articles, such as review articles, original articles, case reports and editorials. Review articles, editorials and book chapters are of great interest because they are extremely easy to read and synthetic. Yet, the scientific value and contribution of these articles are questionable, because these papers are written by specialists to describe what is thought to be the truth, but the authors always have their own point of view, so that the articles can be affected by personal opinions. Case reports are merely observation of interesting clinical cases, they are useful to focus interest on cases, or series, and their characteristics ( prognosis, diagnosis, treatment and etc. ). They are extremely important to describe rare events, because in these events it would be difficult to find more cases. However, further studies are often necessary to determine whether the achieved results are accurate. All the aforementioned studies have their uses, but usually cannot allow us to make clinical decisions.
On the other hand, there are some observational studies of greater value to guide clinical choices, such as case-control, cohort and clinical trials. Case-control studies compare cases ( patients with a certain disease and studied factor ) with a control group that should contain people from the same population, with the same possible risk-factors. The only factor that must differ between the groups is the studied factor. These characteristics of controls are essential to obtain the expected results of a case-control study, because if there are many differences between the groups, other than the studied factor, they can influence on the final conclusions. This kind of study is more “powerful” than the previously described, because it can compare the disease group with a similar group, and then determine whether a characteristic ( risk-factor ) is responsible for certain disease. The cohort study has the same purpose of the case-control, but differ because in cohorts the evaluation of risk-factors antecedes the event of interest. Whereas a case-control study starts from this event and then risk factors are evaluated. Cohorts confer the most powerful basis among the mentioned studies, but as this kind of study needs time, money and many patients, sometimes, case-control studies are preferred to determine causality.
In order to determine whether a medical procedure is useful in the treatment of certain disease, clinical trials are carried out. Using this study, its possible to measure the benefits of a drug, a surgery or any intervention, in comparison with another intervention, drug or placebo. This comparison allow medical practitioners to make decisions based on scientific information. Yet, in this studies, the compared groups must be similar in as much characteristics as possible, because the main difference must be the studied factor. Statistical analysis is applied in all the studies described above, and indicate if the difference between the interventions is significant, or if a habit ( such as smoking ) is a risk-factor to any clinical condition .
The results of these studies must be evaluated in relation to bias, selected population, statistical analysis and many other important parts of a medical article. The value of a certain article, regarding to its characteristics, will be discussed in the next edition of this paper.
If a doctor knows what grade of sure he needs and what kind of article he is looking for, he can make a searching strategy and search in any medical files or library. The strategy must content the most important words linked to the searched subject ( keywords ), and this words should be selected in order to match with words from all the articles that contents the needed subject. If a subject is expressed by more than one word, both should be selected. For example, if you are searching for radiotherapy in patients with esophageal cancer, you could search by esophageal, oesophageal, esophagus, oesophagus, cancer, carcinoma and radiotherapy. This would increase the sensibility of your search. The thesaurus function of the computer programs can also be used, but some articles that uses different words, such as esophageal and oesophageal, may be lost. Then you would have a lot of articles, from which you should read the title and in case it fits in your objectives, you should read the abstract. Reading the abstracts, you can exclude the unnecessary articles by using a proper criteria, such as language, number of patients, design of the study, bias and others. Now, all the articles you have are at least interesting and deserve attention. What is more, one of the most used medical files is MEDLINE, which contents thousands of articles with their title, authors, language and abstract, so that the mentioned strategy becomes easy. After searching the articles you should make a critical reading, make your own decisions and develop your clinical policy.
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