J Bras Pneumol. 2018 Mar-Apr; 44(2): 84. PRACTICAL SCENARIOA cross-sectional multicenter study evaluated self-reported adherence to inhaled therapies among patients with COPD in Latin America. 1 Inclusion and exclusion criteria for the study are shown in Chart 1. The authors found that self-reported adherence was low in 20% of the patients, intermediate in 29%, and high in 51%; and that poor adherence was associated with more exacerbations in the past year, a lower smoking history, and a lower level of education. The authors concluded that suboptimal adherence to inhaled therapies among COPD patients was common and that interventions to improve adherence are warranted. Chart 1Inclusion and exclusion criteria for a cross-sectional multicenter study of patients with COPD in Latin America.(1)
BACKGROUNDEstablishing inclusion and exclusion criteria for study participants is a standard, required practice when designing high-quality research protocols. Inclusion criteria are defined as the key features of the target population that the investigators will use to answer their research question. 2 Typical inclusion criteria include demographic, clinical, and geographic characteristics. In contrast, exclusion criteria are defined as features of the potential study participants who meet the inclusion criteria but present with additional characteristics that could interfere with the success of the study or increase their risk for an unfavorable outcome. Common exclusion criteria include characteristics of eligible individuals that make them highly likely to be lost to follow-up, miss scheduled appointments to collect data, provide inaccurate data, have comorbidities that could bias the results of the study, or increase their risk for adverse events (most relevant in studies testing interventions). It is very important that investigators not only define the appropriate inclusion and exclusion criteria when designing a study but also evaluate how those decisions will impact the external validity of the results of the study. Common errors regarding inclusion and exclusion criteria include the following: using the same variable to define both inclusion and exclusion criteria (for example, in a study including only men, listing being a female as an exclusion criterion); selecting variables as inclusion criteria that are not related to answering the research question; and not describing key variables in the inclusion criteria that are needed to make a statement about the external validity of the study results. IMPACT OF THE INCLUSION AND EXCLUSION CRITERIA ON THE EXTERNAL VALIDITY OF THE STUDYIn our example, the investigators described the inclusion criteria related to demographic characteristics (age ≥ 40 years of age and male or female gender), clinical characteristics (diagnosis of COPD, stable disease, outpatient, and current or former smoker); and exclusion criteria related to comorbidities that could bias the results (sleep apnea, other chronic respiratory diseases, and acute or chronic conditions that could limit the ability of the patient to participate in the study). On the basis of these inclusion and exclusion criteria, we can make a judgment regarding their impact on the external validity of the results. Making those judgments requires in-depth knowledge of the area of research, as well as of in what direction each criterion could affect the external validity of the study. As an example, the authors excluded patients with comorbidities, and it is therefore possible that the levels of nonadherence reported would not be generalizable to COPD patients with comorbidities, who most likely would show higher levels of nonadherence due to their more complex medication regimens. REFERÊNCIAS1. Montes de Oca M.Menezes A.Wehrmeister FC.Lopez Varela MV.Casas A.Ugalde L Adherence to inhaled therapies of COPD patients from seven Latin American countries The LASSYC study. PLoS One. 2017;12(11):e0186777. doi: 10.1371/journal.pone.0186777. [PMC free article] [PubMed] [CrossRef] [Google Scholar] 2. Hulley SB, Cummings SR, Browner WS, Grady DG, Newman TB. Designing Clinical Research. PA: Lippincott Williams & Wilkins; 2007. [Google Scholar] Articles from Jornal Brasileiro de Pneumologia are provided here courtesy of Sociedade Brasileira de Pneumologia e Tisiologia (Brazilian Thoracic Society) What is the type of research design that allows the researcher to control the situation?Experimental research allows the researcher to control the situation. In so doing, it allows researchers to answer the question, “What causes something to occur?” Permits the researcher to identify cause and effect relationships between variables and to distinguish placebo effects from treatment effects.
What technique do researchers use to reduce the impact of confounding variables?There are several methods you can use to decrease the impact of confounding variables on your research: restriction, matching, statistical control and randomization. In restriction, you restrict your sample by only including certain subjects that have the same values of potential confounding variables.
What influences the choice of the research design?The selection of a research design is also based on the nature of the research problem or issue being addressed, the researchers' personal experiences, and the audiences for the study. In this book, three types of designs are advanced: qualitative, quantitative, and mixed methods.
Which type of research design looks for cause and effect between variables?Experimental research, often called true experimentation, uses the scientific method to establish the cause-effect relationship among a group of variables that make up a study.
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