Blog | Tuesday, June 11, 2013

What's your problem? What makes a diagnosis

There has been controversy lately over the new edition of the American Psychiatric Association's new version of their Diagnostic and Statistical Manual (DSM 5). Among a number of critiques, the most-forwarded on the Internet seems to be that of the National Institute of Mental Health, which recommended that researchers applying for grants not use the DSM 5 because, rather than classify diseases and diagnoses based on etiology, it does so based on symptomatology.

The narrative that the psychiatrists are trying to write is a triumphal progression from anecdote to empiricism, from Freud's couch to the colorful images of the fMRI.

Unfortunately, the example psychiatrists would like to follow, medicine, is not as simple as all that. When we diagnose, we often apply a heuristic which relies not just on results of tests and images but also on the patients' symptomatic report. Call it "bacterial pneumonia" all you want, but a patient without symptoms can't be diagnosed with pneumonia even if there's an infiltrate on the X-ray. And even if a patient is symptomatic, we don't go and culture the bacteria from the lung tissue except in relatively serious circumstances.

The point here is not the details of what makes a pneumonia, merely that we do not have a magic on-off switch within the body that we can examine when making a diagnosis. Psychiatrists know this as much as we do, which is why (to internists' secret shame) we don't have anything like a unified diagnostic and statistical manual, and if we did, it would be just as controversial as the DSM.

Zackary Berger, MD, ACP Member, is a primary care doctor and general internist in the Division of General Internal Medicine at Johns Hopkins. His research interests include doctor-patient communication, bioethics, and systematic reviews. He is also a poet, journalist and translator in Yiddish and English. This post originally appeared at his blog.