Clinical Trials

Clinical Trials: A Practical Guide ■❚❙❘A fundamental consideration in patient selection is to enroll patients who arelikely to comply with the study procedures. Patients must be willing to participate,and it is essential to take the time to discuss the risks and benefits of the study,to explain to the patient what is expected from them, and for them to have theopportunity to ask questions. Where possible, it is suggested that patients discussthe study with their family, friends, or primary care physician. Generally, patientsmust provide written informed consent to be enrolled in the study [4], except forin emergency situations where intended or verbal assent is allowed. Ensuring thepatient is adequately informed will minimize dropout rates (patients who choosenot to complete the trial) (see Chapter 9).Reasons why eligible patients are not selectedEligible patients might not be selected to enter a trial because of administrativereasons. For example:• The patient is unavailable during the screening process.• Study personnel are unavailable to screen the patient.• The study drug or intervention is unavailable (eg, if the drug has exceededits shelf life or if the pharmacist is unavailable to formulate an infusion).• The study procedure is unavailable (eg, faulty echocardiography instrument).• The patient may not be able to attend follow-up visits.These reasons can usually be avoided by careful planning and organization.If large numbers of patients are being excluded due to a particular eligibilitycriterion, it is worth considering making small changes to the criteria. This canmake a large difference to recruitment without necessarily affecting outcome orgeneralizability. Any changes to the eligibility criteria must, of course, be submittedas a protocol amendment for ethical review before being implemented.ConclusionWhen designing a clinical trial, careful consideration must be given not only to thesource of patients and the investigators who are going to select the patients, butalso to the disease under consideration and any ethical issues regarding patientparticipation. A specific set of eligibility criteria should be used to define thepatient population under study. These eligibility criteria should ensure that thepatients included in the study are representative of patients with a particulardisease or condition. This will ensure that the study findings can be applied totreat future patients in clinical practice.53