Pilot studies represent a fundamental phase of the research process. The purpose of conducting a pilot study is to examine the feasibility of an approach that is intended to be used in a larger scale study. The roles and limitations of pilot studies are described here using a clinical trial as an example. A pilot study can be used to evaluate the feasibility of recruitment, randomization, retention, assessment procedures, new methods, and implementation of the novel intervention.A pilot study is not a hypothesis testing study. Safety, efficacy and effectiveness are not evaluated in a pilot. Contrary to tradition, a pilot study does not provide a meaningful effect size estimate for planning subsequent studies due to the imprecision inherent in data from small samples. Feasibility results do not necessarily generalize beyond the inclusion and exclusion criteria of the pilot design.A pilot study is a requisite initial step in exploring a novel intervention or an innovative application of an intervention. Pilot results can inform feasibility and identify modifications needed in the design of a larger, ensuing hypothesis testing study. Investigators should be forthright in stating these objectives of a pilot study. Grant reviewers and other stakeholders should expect no more.

Emerging results of recent studies comparing the outcome of major depressive disorder patients with comorbid major depressive disorder and substance use disorders suggest that there are fewer differential effects based on comorbidity than previously anticipated by older assumptions from smaller, less methodologically rigorous studies.

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Background: People with known risk factors for chronic obstructive pulmonary disease (COPD) are important targets for screening and early intervention. We sought to measure the prevalence of COPD among such individuals visiting a primary care practitioner for any reason. We also evaluated the accuracy of prior diagnosis or nondiagnosis of COPD and identified associated clinical characteristics. Methods:We recruited patients from three primary care sites who were 40 years or older and had a smoking history of at least 20 pack-years. Participants were asked about respiratory symptoms and underwent postbronchodilator spirometry. COPD was defined as a ratio of forced expiratory volume in the first second of expiration to forced vital capacity (FEV 1 /FVC) of less than 0.7 and an FEV 1 of less than 80% predicted. Results:Of the 1459 patients who met the study criteria, 1003 (68.7%) completed spirometry testing. Of these, 208 were found to have COPD, for a prevalence of 20.7% (95% confidence interval 18.3%-23.4%). Of the 205 participants with COPD who completed the interview about respiratory symptoms before spirometry, only 67 (32.7%) were aware of their diagnosis before the study. Compared with patients in whom COPD had been correctly diagnosed before the study, those in whom COPD had been overdiagnosed or undiagnosed were similar in terms of age, sex, current smoking status and number of visits to a primary care practitioner be cause of a respiratory problem.Interpretation: Among adult patients visiting a primary care practitioner, as many as one in five with known risk factors met spirometric criteria for COPD. Underdiagnosis of COPD was frequent, which suggests a need for greater screening of at-risk individuals. Knowledge of the prevalence of COPD will help plan strategies for disease management. AbstractPreviously published at www.cmaj.ca

In clinical trials and clinical practice, several time points in treatment may provide opportunities to engage and encourage populations at higher risk for attrition and populations with high-risk presentation of illness. Additionally, more aggressive forms of treatment implemented earlier in the treatment process in order to increase the likelihood of more rapid efficacy may reduce dropout rates.

clinicaltrials.gov Identifier: NCT01421342.

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