When I use a word . . . . Too much healthcare—overdiagnosis

Overdiagnosis

Recognition of the phenomenon of overdiagnosis is older than you might think, although the meaning of the word has changed over the years.

Trying to trace the concept back, and to determine what it means, I start with the Merriam-Webster online dictionary (at https://www.merriam-webster.com/dictionary). It defines “overdiagnosis” as “the diagnosis of a condition or disease more often than it is actually present” and gives “diagnose” as a secondary entry, implying that it’s a back-formation. It also states that the first known use of overdiagnosis was in 1971, in the meaning defined. It doesn’t give the 1971 quote, but it might be in the title of a paper in the Journal of the Canadian Association of Radiologists: “Potential over-diagnosis of pancreatic islet cell adenoma.”1

Perhaps the Oxford English Dictionary (OED) can do better. And it does—to an extent. It defines “overdiagnosis” as “Excessively frequent (and hence occasionally incorrect) diagnosis of a particular disease, etc.” and gives the earliest instance as dating from 1955: “The authors’ opinion inclines to the possibility of underdiagnosis of lung cancer rather than to its overdiagnosis in the two bronchitic series.”2 The OED dates “overdiagnose” a little earlier, back to 19503: “These studies show that malaria is probably over-diagnosed, especially in areas where its prevalence seems to be decreasing.” This suggests that “overdiagnose” is not a back-formation at all.

Even earlier instances of “overdiagnose” can be found in the British Medical Journal. Here, for example, is an instance from 15 January 19384: “Dr. PAUL WOOD said that the cardiac complications of major abdominal surgery were ‘over-diagnosed’ by many surgeons.” The use of inverted commas around the word here suggests that the author thought that the term was relatively new. But here is an even earlier instance, from 31 January 19255: “Dr. J. G. Soutar ... thought that encephalitis was over-diagnosed at the present time.” In this case, the hyphen occurs at the end of a line and it is not clear whether it is a soft hyphen (for “overdiagnosed”) or a hard one (for “over-diagnosed”), probably the latter. Hyphens, however, tend to disappear from compound words, as in “health[-]care.”

So, did “overdiagnose” come first? Well, perhaps not, since there is an even earlier instance of “overdiagnosis,” in the title of a paper published in the Canadian Medical Association Journal in 1924, tending to confirm that it is the source of “overdiagnose” and not the other way round: “Over-diagnosis of pulmonary tuberculosis.”6

And there is an even earlier instance, the earliest that I have found, from 1913: “Overdiagnosis is also a possibility in the presence of elusive signs, as is well illustrated by a case ... in which quite extensive tuberculosis of the right lung was diagnosed, all the signs being due to obliteration of the pleural cavity by slight adhesions without appreciable thickening, the lung perhaps suffering from slight passive congestion.”7

It is now becoming clear that “overdiagnosis” has two different meanings. The early meanings imply incorrect diagnosis of a condition rather than the one that is actually present. In those cases the word that perhaps should have been used was “misdiagnosis” (e.g. pleural adhesions instead of tuberculosis). “Misdiagnosis” was available, even in 1913, for although the OED’s earliest example is from 1946, it is antedated by the British Medical Journal, in a report of a discussion in Parliament in 19118: “But if I [Mr Burns] were not a Minister I would retort on these simple facts that I doubt if we would have had a single death, vaccinated or unvaccinated, had it not been that there was a misdiagnosis of a case of small-pox as chicken-pox.” In fact, the data that John Burns, then Minister for Health, quoted—deaths among 58 individuals, two of 42 vaccinated and seven of 16 unvaccinated (P=0.0002)—suggested that vaccination reduced the risk of death from smallpox, contrary to what he preferred to believe.

However, in recent years “overdiagnosis” has acquired a different meaning. Definitions that have been suggested include:

• “… when individuals are diagnosed with conditions that will never cause symptoms or death.”9

• “Diagnosis of a condition that, if unrecognized, would not cause symptoms or harm a patient during his or her lifetime.”10

• “Making people patients unnecessarily, by identifying problems that were never going to cause harm or by medicalising ordinary life experiences through expanded definitions of diseases.”11

The last of these definitions comprises the two major factors that together constitute overdiagnosis, although not synonymous with it, overdetection12 and overdefinition.13

An extended definition

Every so often the National Library of Medicine adds new terms to its collection of Medical Subject Headings (MeSH). Last year they added 227 new terms, including “overdiagnosis,”14 defined to include the two points made above, plus a third, the medicalisation of ordinary experiences. The entry also includes an explanatory codicil, not strictly speaking part of the definition, but detailing the possible harmful outcomes:

• “The labeling of a person with a disease or abnormal condition that would not have caused the person harm if left undiscovered, creating new diagnoses by medicalizing ordinary life experiences, or expanding existing diagnoses by lowering thresholds or widening criteria without evidence of improved outcomes. Individuals derive no clinical benefit from overdiagnosis, although they may experience physical, psychological, or financial harm.”15

What overdiagnosis is not11

Although overdetection, due not only to widespread screening, but also to diagnostic overtesting or by paying attention to incidentalomas, is one of the major factors that contribute to overdiagnosis, false positives as a result of testing, which can lead to further investigations and potential harms, do not in themselves constitute overdiagnoses, because there is nothing to diagnose by the test being used. As an example of the problem consider the results of an analysis by the Canadian Task Force on Preventive Health Care of data from lung cancer screening.16 Of every 1000 individuals screened there were 40 true positive tests and three fewer deaths from lung cancer as a result of treatment; however, of 351 individuals with false positive tests, three had major complications and one died from invasive follow-up tests. Not a great trade-off, especially considering the cost of the screening programme. Nevertheless this was an example not of overdiagnosis in the modern sense of the word, but of misdiagnosis followed by unnecessary further investigations.

Nor, by the same token, is overdefinition the same as overdiagnosis; it merely contributes to it.

Nor is overdiagnosis the same as overtreatment, although it can lead to it.

And one more thing overdiagnosis is not. In Willy Russell’s play Educating Rita (1980), her Cambridge tutor, Frank, explains to Rita the meaning of assonance by an example from a poem by W B Yeats, in which he rhymes the word ‘swan’ with the word ‘stone’. “Oh,” says Rita, “it means getting’ the rhyme wrong.” Misdiagnosis is not the same as overdiagnosis; it means getting the diagnosis wrong.

Concluding thoughts

So now, to be explicit, we have a comprehensive definition of “overdiagnosis,” encompassing three different ways of making people patients:

1. by labelling them with a condition of some sort that would not have caused them harm if left undiscovered; this relates to the heterogeneity of many conditions, resulting in a spectrum of conditions within the category, not all of which need attention; this has been referred to as the fuzziness within the disease category17;

2. by expanding the definition of a disorder to encompass more individuals; this has been attributed to what has been called the fuzziness of the outer boundary of a disease definition17;

3. by labelling them with a disease category that medicalises ordinary experience, such as pregnancy, the phenomenon known as disease mongering.

Note that in discussing overdiagnosis, some do not include the last of these categories, which has been linked to overselling of therapeutic interventions,11 and it is one that requires separate consideration.

Finally, since there may be some who seek a simpler summary of what overdiagnosis, or rather one of its major outcomes, is, I suggest the subtitle of Overdiagnosis by Welch, Schwarz, and Woloshin9: “Making people sick in the pursuit of health.”