BLOG: What does ‘rare’ actually mean when communicating with patients?
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When you tell a patient that complications for their upcoming surgery are “rare” or that it is “uncommon” for their disease to result in blindness, do you know what you’re actually telling them?
Many doctors do not realize that the language of medical risk is precisely defined and that using the incorrect adjective could result in a communication failure or poor medical decision.
A “very common” condition affects more than one in 10 people, or the risk is greater than 10%. The incidence of new dry eye symptoms 3 months after LASIK surgery is 27%, so this risk is very common (Eydelman M, et al.).
A “common” condition affects between one and 10 people in 100. In the developed world, a patient with glaucoma has a 6% chance of going bilaterally blind by the end of their life, so this outcome is common among all patients diagnosed with glaucoma (Chen PP, et al.).
“Uncommon” refers to an outcome that affects between one and 10 people in 1,000, or between 0.1% and 1%. Decreased visual acuity due to strabismus strikes 0.5% of all infants and so is uncommon.
“Rare” affects between one and 10 people in 10,000, or the risk is between 0.01% and 0.1%. Retinal detachments have an annual incidence of just a little more than one in 10,000, so your chance of getting one this year is rare.
“Very rare” affects less than one in 10,000 people, or less than 0.01%. The risk for endophthalmitis after cataract surgery is thought to be roughly one in 12,000 cases, so, fortunately, very rare.
In the United States, a “very rare disease” is defined differently, as one that strikes fewer than one in 200,000. This is a strict definition that affects congressional funding.
The “vast majority” is not a precisely defined phrase and tends to be used indiscriminately to reinforce a loose argument. Recent examples of its use in peer-reviewed texts have referred to percentages between 55% and 99%.
It’s one thing to use words precisely, but if your patient doesn’t understand these definitions, your precision is wasted. If possible, it is preferable to give patients exact numbers (Rozen JE).
As doctors, one of our primary jobs is to tell patients their level of risk for adverse events; this is a foundation of informed consent. Using words accurately is crucial to this aspect of the job.
References:
- Chen PP, et al. Ophthalmology. 2003;doi:10.1016/S0161-6420(02)01974-7.
- Eydelman M, et al. JAMA Ophthalmol. 2017;doi:10.1001/jamaophthalmol.2016.4587.
- Rozen JE. Perceptions of treatment risk vary based on how surgeons communicate risk information to patients. Presented at: American College of Surgeons Clinical Congress; Oct. 23-27, 2021 (virtual meeting).
For more information:
Oliver Kuhn-Wilken, OD, is a staff optometrist at Pacific Cataract and Laser Institute’s Tualatin Clinic in Oregon.
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