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In general, little is known about most rare diseases. A small no of patients with rare disease often results in limited clinical experience within individual treatment centers. The clinical description of disease may be incomplete and medical literature often consists of individual case reports or small case studies limiting the understanding of the natural history of the disease. Both the lack of available treatments and poor understanding of rare disease can be linked to unique challenges that researchers come across for rare disease in clinical trial possesses. The challenges occur across the life cycle of research study design, ethical considerations and subject recruitment and retention.
When designing a rare disease study sometimes it may be difficult to find fundamental information on which study protocol can be designed for eg. Data on disease prevalence and incidence making it difficult to determine the appropriate study site or country. Diagnosis may be complex particularly in case where no definitive tests are available. The development of study data set may be hindered by lack of information on full range of disease symptoms and treatment practices. Selecting appropriate study duration may be difficult particularly where new treatments are extending lifespan. Ethical concerns may also arise in rare diseases, where majority of rare disease affecting children who are considered as vulnerable population. Designing and conducting studies that enroll children may be more complex when designing studies for adults. Rare disease research may also focus on other vulnerable population such as cognitively impaired persons or pregnant women. Rare disease study needs to be sensitive to needs of such population.
Once study is initiated then researchers face challenges with regard to Patient recruitment &retention. By definition, rare disease has limited Patient population. Patient recruitment can become more complicated if there are simultaneous studies .Enrollment in one trial may make patient ineligible for another trial. Patients with these diseases are widely scattered across the globe. For some rare diseases, investigators see a single patient per year or none and also there is no guarantee that the patients will qualify for the study. Therefore, the rare disease studies may involve large no. of physicians, specialty centers and studies may need to include patients from several countries to obtain a sufficient study population. Retention of patients for duration of study is extremely important given small study sizes. Researchers generally need to devote significant effort for following up of these patients as they belong to different locations to keep the patients enrolled in the study.
When you conduct clinical trials involving rare diseases, you face a unique set of medical, scientific and operational challenges. A significant knowledge gaps still remain and Randomized Controlled Trials may be extremely difficult to conduct in rare disease population due to small size and length of follow up limitation. Innovative research methods are needed to overcome barriers of rare disease Clinical trials. Rare disease trials require a customized approach tailored to the specific indication and study goals.