How Are Rare Disease Studies Conducted?

Why are rare disease studies so important? Rare diseases impact people from all walks of life, all over the world. In the United States (USA), a rare disease is defined as a disease that impacts less than 200 thousand people2. Currently, there are roughly 359 million people living in the USA1. Thus, if you do the math there are approximately 0.00055% of people suffering from rare diseases in the USA at any given time. For this reason, the research of rare diseases often lacks funding. Nonetheless, rare disease studies are critical as they can lead to not only cures for the rare diseases under investigation, but potentially common diseases.

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The Significance of Case-Control Studies 

Case-Control Research is one of the most powerful methods of investigation regarding rare disease studies. Case-Control Studies are unique because they are typically observational3. A principal investigator would find a group of people with the outcome of interest (disease), then observe a second group of people who are similar but do not have the desired outcome of interest. The researcher would examine both groups, especially looking into historical factors, in an attempt to identify some common exposure that may have led to the outcome in question3

Here is an example of this type of rare disease study. A researcher may be looking into a rare cancer. They would, therefore, examine two groups of patients. The first group would consist of people who have the rare cancer that is being studied, and the second group of people would be similar to the first group, however, they would not have rare cancer. The researcher would then examine various historical factors and exposures to determine the cause leading to one group suffering from this rare disease. The researcher may conclude for example, that HIV is a similar factor among the people with that rare cancer, thus it is a risk factor for this rare disease3

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Collaborative Efforts in Rare Disease Studies

Funding has been a limitation when it comes to rare diseases for quite some time as rare diseases do not impact many people overall when it comes to the entire world population. Nonetheless, when it comes to rare disease studies, and moving forward in terms of research as well as investigation, collaboration is key4. Recently we have seen significant partnerships between the public and private sectors coming together to come up with treatments and therapies for rare diseases. This niche market has been picking up interest, and the result has been various cures and treatments for numerous rare diseases across the world4. What’s more renewed interest in rare diseases has doubled the NIH budget from $13 billion in 2007 to roughly $30 billion in 20114

Alternative Clinical Trials in Rare Disease Studies

Rare disease studies can often be challenging, due to the small population sizes associated with these diseases. For this reason, researchers are encouraged to be creative when utilizing conventional study methods such as clinical trials. Researchers may use what is referred to as alternative clinical trials when it comes to rare disease studies. Alternative clinical trials include randomized placebo-phase designs, enriched enrollment, or randomized withdrawal designs. It is critical that researchers be innovative and creative when it comes to the study of rare diseases, as conventional approach methods will often not be applicable to this sort of research, nor the statistical analysis with small population samples.

The Importance of Zebrafish in Rare Disease Research

Zebrafish have proven to be a great tool in the study and advancement of rare disease research

Zebrafish have a uniquely similar genetic structure to that of human beings. In addition, they share more than 70% of their genes with human beings. Also, 84% of human genes known to be associated with diseases have a complement in zebrafish. In addition, they can obtain 200-300 larvae per adult couple and week, which increases the sample size a lot, allowing higher statistical power, at least in preclinical trials. Gene editing technologies, such as CRISPR-Cas, allow generating disease models to design the best preclinical trials for the best candidate selection before human trials. Therefore, zebrafish provide a more time and cost-efficient way to conduct rare disease research.


  1. Worldometer,‘United States Population’ date accessed on 6/26/2022:
  2. RDR, ‘Rare Disease Research’ date accessed on 6/26/2022
  3. NIH, ‘Case Control Studies’ date accessed on 7/27/2022
  4. NIH, ‘Rare Diseases Research’ date accessed on 7/27/2022
  5. NIH, ‘Alternative designs for clinical trials in rare diseases’ date accessed on 7/27/2022

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