BOX 12.4 Selected Types of Research Studies23,24
Descriptive Study Design Research that examines and describes a group of patients, a situation, or an area of interest in a systematic manner; usually as a precursor to a quantitative study (which includes an intervention or randomization).
Types of descriptive research include qualitative studies, case studies, and survey research. Examples:
» The nutritional status of patients who are critically ill (malnourished vs at risk for malnutrition) upon admission (descriptive)
» Use of a focus group of individuals with celiac disease to understand their perceptions about the etiology of their gastrointestinal complaints and how they manage them (qualitative)
» Nursing staff’s beliefs about the value of measuring gastric residual volumes in patients who are enterally fed (survey)
Correlational Study Design Research that predicts the association or correlation between two or more variables. Note that correlation and causation are very different, and a correlational study cannot imply a causal relationship.
Types of correlational research include case-control and cohort studies:
» In case-control studies, researchers compare two groups of patients; one group has an outcome condition or disease and the other group does not. The researchers retrospectively study the effect of a predictor or exposure to a risk factor on the development of the disease. Cases with the disease are matched to controls who do not have the disease.
Example of a case-control study: Comparison of the influence of a high-fiber diet (predictor) on the development of colon cancer (outcome). Two groups, one with colon cancer and one without colon cancer, are compared (development).
» In cohort studies, which can be prospective or retrospective, researchers follow patients either over time or back in time to assess the association between identified risk factors and an outcome.
Example of a retrospective cohort study: Comparison of the complication and readmission rates of patients with head and neck cancer who receive nutrition support with a percutaneous endoscopic gastrostomy tube vs rates for those who do not receive nutrition support via a feeding tube.
Experimental or Analytic Study Design Research involving application of an intervention to establish a cause and effect.
Types of experimental or analytic research include randomized controlled trials (RCTs), and randomized crossover trials. In RCTs, study participants are randomly assigned to one or more groups exposed to a treatment or intervention or to a control group that is not exposed to the treatment or intervention. Randomized crossover trials are another type of experimental or analytical study. In this study design, the subjects are assigned one treatment or another (or a placebo), then undergo a washout period before they receive the alternate treatment (eg, the treatment they did not receive during the first phase of the study). Subjects in randomized crossover trials serve as their own controls.
Examples:
» Differences in hospitalization rates for exacerbation of congestive heart failure (CHF) for individuals with CHF who are randomly assigned to receive nutrition counseling from a registered dietitian nutritionist or receive an educational handout only (RCT)
» Incidence of diarrhea as measured by frequency and stool consistency in patients who are enterally fed a standard isotonic formula and randomly assigned to receive a probiotic, fiber supplement, or placebo (RCT)
» In individuals with irritable bowel syndrome, two types of fiber are evaluated for their effect on abdominal pain, constipation, and diarrhea. Half of the participants are randomly assigned to an insoluble fiber
supplement for 1 month and the other half are assigned to take a soluble fiber supplement over the same time period. After a 1-month washout period, the two groups receive the other type of fiber for an additional month. (randomized crossover design)
252 EFFECTIVE LEADERSHIP & MANAGEMENT IN NUTRITION & DIETETICS
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