In designing your question, make sure that you have selected one for which you have the adequate resources-access to an adequate number of the clinical patients of interest being paramount. Otherwise, you may find yourself a victim of Lasagna’s Law: The incidence of patient availability sharply decreases when a [clinical study] begins and returns to its original level as soon as the trial is completed.1 Define your patient population carefully, specifying inclusion and exclusion criteria for participating in the study-inclusion criteria that are too strict will make it very difficult to recruit sufficient numbers of subjects; criteria that are too broad will result in including subjects who have comorbidities or other factors that may confound the results of the study.
Explore This IssueApril 2008
Having defined your area of interest and narrowed that down to a specific, focused research question, you are ready to define the scope of the project. This will require making several decisions related to numbers, time, and complexity.
How many patients do you want to recruit for your study? It is important to specify a number at the beginning, and this number should not be selected randomly. The sample needs to be large enough to provide some assurance that if an effect is found, either between two groups or before and after treatment, they represent a real effect and not samples drawn at random from the same statistical population. If the sample is too small, you may fail to detect a clinically important difference; too large, and the study will be longer and more expensive than necessary. An excellent method for determining sample size can be found in Norman and Streiner’s PDQ Statistics.2 The gold standard, however, is to invest in several hours of consulting time with a biostatistician from a local university or medical school. Based on the question you want to investigate, the statistician will reinforce your choice of design (or suggest options); calculate the appropriate sample size needed based on the population variance, effect size, and desired power; and, if you have established a satisfactory working relationship, can assist with statistical analysis of the data at the conclusion of the study.
For the time parameters, decide for how long you will actively recruit patients into your study, and how long the follow-up period for each will be, if you have decided on a design other than a cross-sectional study. For the newcomer to clinical research, designing and undertaking a simple, straightforward study with a limited number of variables that can be quantified and measured objectively is always a better way to start.
Foundation and Framework for the Study
To be successful, any clinical research project needs a strong infrastructure; the heart of that infrastructure is a project coordinator. Although the physician conceptualizes the project and has ultimate responsibility for it, the project coordinator-usually a nurse or other health care professional in the office-brings together all the skills and resources to carry out the project. He or she serves as a task manager and liaison among clinicians, clinical staff, and patients, and must have superb interpersonal communication skills. Invite someone to serve in this role who has not only the skills, but also the willingness, enthusiasm, and dependability to see the project through.