Potential Consequences of Changing Disease Classifications

This Viewpoint discusses the potential harms that can emerge from changing disease classifications, generally to broaden criteria for diagnosing greater numbers of patients, and calls for a balanced and systematic evaluation of the benefits and risks of shifting illness thresholds before formalizing changes.

[Extract] Clinicians tend to think of diseases as being immutable, existing in nature like elements of the periodic table or the planets. The medical literature reinforces this myth, implying that changes are a result of increasing scientific knowledge moving medicine toward better and more accurate descriptions of these natural kind concepts. In fact, diseases are not fixed, and even with common diseases (such as diabetes, depression, and anemia), their definitions have changed considerably over time, with significant, but often unrecognized harmful, potential consequences for patients. What constitutes a disease may change in 1 of 3 ways: (1) a change in the formal definition, (2) a change of tests, or (3) a shift of the implicit threshold.