Mathematics professor and author Manil Suri and physician and professor Daniel Morgan discuss false positives in diagnostic tests, the impact of rarity on accuracy, prenatal testing for rare diseases, and the lack of statistical education in medical schools.
False positive results from lab-developed tests (LDTs) have led to panic and even the abortion of healthy fetuses, prompting the FDA to propose closing the oversight loophole.
Understanding the mathematical limitation of false positives is crucial for effective testing, especially for rare conditions, and communicating risk accurately to patients is essential.
Deep dives
The Problem with Lab-Developed Tests
Lab-developed tests (LDTs) have been exempt from FDA oversight, but the agency proposed to close this loophole due to false positive results. False positive prenatal diagnoses have caused panic for expecting parents and even led to the abortion of healthy fetuses. LDTs have also caused problems in genetic testing and cancer treatments. The FDA is considering whether to withdraw, revise, or finalize the rule.
The Mathematical Limitation of Testing
All tests, not just LDTs, have the risk of false positives. This risk becomes more significant when the tested condition is rare. For rare conditions, tests should only be used when additional risk factors or symptoms are present. Understanding this mathematical limitation is crucial for effective testing.
The Importance of Communicating Risk to Patients
Communicating risk accurately to patients is essential. Genetic counselors are often better at conveying risk than doctors. It is important to use risk-based language when discussing test results with patients, and to consider the individual patient's situation and preferences. Trusting the math and focusing on the patient's best interests can help navigate the complex landscape of testing and decision-making.
Manil Suri and Daniel Morgan are an unusual team: Manil is a mathematics professor and author, while Daniel is a physician and professor of epidemiology, public health, and infectious diseases. But they recently teamed up for a First Opinion essay, “Diagnostic tests for rare conditions present a mathematical conundrum,” in which they write about how the more rare a disease ease, the more likely a test will return a false positive. Host Torie Bosch spoke with Manil and Daniel about how false positives can cause major problems, how both physicians and patients misunderstand statistics, and how their work plays out in their own lives.
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