Geographic Distribution of Potential Rare Disease Patients’ Residences

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Among Medicare Fee-for-Service (FFS) beneficiaries, potential rare disease patients' residences have a median distance of over 200 miles to a relevant clinical trial site.

The identification of patients with rare diseases can be a challenge, especially when the conditions have not been assigned diagnosis codes. Avalere explored two algorithms to identify the locations of potential patients with rare autoimmune diseases without diagnosis codes in 2018–2021 claims data. Avalere then mapped the distance from these locations to likely sites of care to gain insights into potential barriers to diagnosis and treatment. The analysis found the median distance from the location of a potential patient with a rare disease to the most frequently visited provider was about 10 miles, while the median distance to a potential clinical trial site studying the relevant rare disease was over 200 miles.

The first algorithm identified patient locations based on the presence of at least one medical claim of a high likelihood disease-related diagnosis code in addition to having claims for at least one of the blood tests or a relevant biopsy used to test for rare autoimmune diseases. This method identifies potential patients’ home ZIP code, which can then be compared to sites of care. The second algorithm leveraged disease manifestation diagnosis codes and additional clinical inclusion, and exclusion criteria to find potential patient locations. This algorithm was more targeted and complemented the broader analysis of algorithm one.

By using the two algorithms above to search for potential patient locations, Avalere conducted an analysis of the distance to sites of care. First, Avalere plotted the ZIP codes of identified residences on a heatmap and found that patient residences are distributed similarly to the US national population distribution, with concentrations in major US cities. Then, we measured the distance between a patient’s home ZIP code and that of their most frequently visited provider and a rare autoimmune disease clinical trial site.

The result of the analysis shows that patient residences are generally close to their most frequently visited healthcare provider, with a median distance of 10 miles. The bottom quartile has a distance of about 4 miles, while the top quartile has a distance of about 20 miles. However, the analysis identified some outlying residences with a distance of roughly 2,500 miles to the most frequently visited provider. Hypotheses include that some patients go across the country to receive specialized treatment and or that some patients’ permanent address may not be the only residence at which they receive care.

Due to the small number of rare autoimmune clinical trial sites in the US, potential patients’ locations are over 200 miles to a clinical trial site by median. The bottom quartile has over 100 miles to a trial site, while the top quartile has over 500 miles to a trial site. The maximum distance to a trial site was roughly 1,500 miles. Compared to the distance to the most frequently visited provider, these results may indicate potential travel barriers for patients with rare diseases. All findings were consistent among the two algorithms.

As stakeholders aim to increase access to care for patients with rare diseases, carefully considering the number and location of clinical trial sites and potential mechanisms and support for patients who may need to overcome geographic barriers to care will be important.


Avalere performed this analysis using 100% Medicare FFS claims, accessed by Avalere via a research collaboration with Inovalon, Inc., and governed by a research-focused Center for Medicare & Medicaid Services data use agreement. This includes the 100% sample of Medicare Part A and Part B Medicare FFS claims data.

To learn more about factors that affect patient access to case, connect with us.

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