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Zebras do exist: the diagnostic odyssey of rare disease patients


A Rare Patient Voice Case Study

think horses not zebras

​In medical school, students are trained to look for common ailments and not rare illnesses, hence the saying, “When you hear hoofbeats, think horses, not zebras.” However, doctors should not ignore the possibility of an illness being a “zebra.” Those who do risk putting their patients’ health at risk. 

However, doctors should not ignore the possibility of an illness being a “zebra.” Those who do risk putting their patients’ health at risk. 

At Rare Patient Voice, the experiences and viewpoints of patients and caregivers are valued as vital components in progress towards new treatments and cures. A recent RPV case study on rare disease patients’ diagnostic “odyssey” — a long, complicated journey that inches forward towards a goal — was undertaken with the goal of revealing the effects of delayed and inaccurate diagnoses of rare diseases. Researchers surveyed 3,471 patients and caregivers across 436 rare diseases. Some of the questions asked were how often they had to undergo testing, how many physicians they needed to see, how long they waited to receive a diagnosis, and whether they were misdiagnosed. The results are not representative because of the respondents’ different experiences, but they reveal common issues in the diagnostic process.

Summary of the study:

Recognising the highly varied experiences of the respondents, the researchers focused on the commonalities of their experiences instead of making a conclusive statement about rare disease patients. The study’s key findings:

The average waiting period before patients received a diagnosis is 4.4 years.

The median waiting period is 1.1 years

This data means that half of the survey participants received their diagnosis after just over a year. Many, however, waited for a much longer period, which explains why the average (mean) waiting period skewed to 4.4 years. Other important findings are:

  • Patients took an average of seven tests before getting diagnosed.
  • Patients saw an average of four physicians before diagnosis.
  • Forty-six percent received a misdiagnosis.
  • Forty-seven percent believed they received delayed treatment.
  • One-third or 30.5% underwent genetic testing. Of this population, 66.9% believed the test helped find the correct diagnosis.

To find the common experiences of the patients surveyed, the researchers analysed the data of 61 diseases that had 10 diagnosed patients. The patients eventually diagnosed with primary immunodeficiency illnesses, ankylosing spondylitis, celiac disease, depression, Ehlers-Danlos syndrome, Fabry disease, mastocytosis, and Pompe disease had a median waiting period of five years and an average waiting period of 10 years. Researchers identified a couple of factors for the long wait:

Multiple testing was necessary

Patients needed to see many physicians

Some were misdiagnosed

The bottom-line:

The Zebras Do Exist case study highlights some common roadblocks to timely and correct diagnosis: allowing preconceptions about a disease to influence the direction of the diagnostic process, gender biases, lack of awareness about a specific disease, late consultations with knowledgeable specialists, and lack of insurance, among others. 
Patients must overcome their fear and avoid being in denial of their condition. They must be vocal when they feel that physicians are inattentive about their symptoms, given the latter’s inclination to “look for horses instead of zebras.” Physicians must be proactive in learning more about rare diseases, their symptoms, and diagnostic procedures.

think horses not zebras

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