For people living with rare and puzzling medical symptoms, getting a diagnosis is often a long and frustrating process punctuated by many tests and few results. The Washington University School of Medicine in St. Louis Undiagnosed Diseases Network (UDN) Diagnostic Center of Excellence was established in 2019 to solve the trickiest medical mysteries in Missouri and nearby states. It is one of 11 sites in the national UDN funded by the National Institutes of Health (NIH). In the past five years, the center’s team of WashU Medicine geneticists, bioinformaticians, and pediatric and adult medicine specialists have taken on 189 such cases and cracked 56 of them, a success rate on par with the national network.
Now, the center is expanding. Buoyed by the renewal of the center’s five-year, $3.8 million grant, the UDN leadership team plans to increase outreach to medically underserved communities and increase capacity from 30 to 50 patients a year. The center has established a collaboration with the St. Louis Integrated Health Network, an organization dedicated to improving the quality, accessibility and affordability of health care. Together, they will work to identify people with mysterious illnesses in underserved communities who could benefit from its advanced diagnostic capabilities and help them access its services.
Because most rare, mysterious illnesses have a genetic component, genetic testing is a key part of the approach at the UDN, along with a thorough clinical evaluation by WashU Medicine pediatricians and other clinicians with expertise in rare diseases. Sometimes, a genetic change is found with unclear significance. In those cases, UDN researchers use simple organisms — specifically, nematode worms (C. elegans) and zebrafish — to study the effects of the genetic change, and ascertain whether it is likely to be the cause of the patient’s symptoms.
Each case is unique and complex, and can take months to years to solve. Obtaining a diagnosis can be critical for guiding care decisions, establishing eligibility for precision medicine therapies and clinical trials, and connecting patients and their families with communities of people living with the same condition. Sometimes the diagnostic odyssey ends without a diagnosis. Those cases are frustrating and disappointing to patients and doctors alike, but at least the patient and his or her family know that everything possible has been done to get them an answer.
Breaking down barriers to genetic testing
An estimated 3 million people in the U.S. live with undiagnosed diseases, defined as medical conditions without a known cause despite extensive efforts to find one. Members of medically underserved communities — typically high-poverty areas where primary care providers are in short supply and access to medical care is limited — find it particularly hard to get a diagnosis.
One reason is that most undiagnosed diseases turn out to be genetic in origin. Genetic testing can be expensive – ranging from a few hundred dollars to over $5,000, depending on the specific test – and it isn’t always covered by insurance. Studies have shown that people who are uninsured or underinsured have less access to genetic testing.
“A patient’s insurance status is one factor that can impact whether they are referred for and receive genetic testing,” said Brett Maricque, PhD, an assistant professor of genetics at WashU Medicine and the leader of the center’s community engagement team. “Where they get their care also matters. Community health clinics have few financial resources to pay for genetic testing. That’s why we’re focused on expanding access to cutting-edge diagnostics, including to those that are underinsured or uninsured.”
Studies also have shown that genetic diseases are less likely to be identified and accurately diagnosed in people of color. This is partly because genetic test results are compared against reference databases to identify the significance of the results. These databases are mostly composed of people of European descent, which means that people of other ancestral backgrounds are more likely to receive inconclusive results.
With such issues in mind — as well as a nudge from the national UDN — director Patricia Dickson, MD, the Centennial Professor of Pediatrics and a professor of genetics at WashU Medicine, assessed the demographics of the center’s patient population.
“We take on the hardest-to-solve cases,” Dickson said. “These are people who have spent years fruitlessly searching for a diagnosis. Admittedly, we don’t always solve them. But everyone deserves the chance to get an answer. It shouldn’t be limited by who you are, where you live or how much money you have.”