Getting the Diagnosis Right
by Danielle Ofri
New York Times
Recently I had one of those bursting-at-the-seams types of days in clinic. Every scheduled patient showed up, plus a few extras. Everybody seemed to have burning concerns that needed immediate attention. One patient had newly diagnosed thyroid disease but the medication was making her feel worse rather than better. Another was having strange twinges in his lower abdomen. One woman had muscle aches in her arms for the past month and now had the same aches in her legs. Another patient was experiencing drilling-type pain in his lower back that spread up to his neck and scalp. One man had a cough that just wouldn’t leave. A woman was concerned because the soles of her feet felt like they were on fire. Another patient said that she simply had no energy and could hardly get through her day.
For each of these presenting symptoms there is a gamut of possible causes—what doctors call the “differential diagnosis”—that range from the prosaically benign to the concerningly urgent to the immediately life-threatening. The name of the game is to come up with a broad differential for each symptom, then prioritize them by likelihood and by severity. Testing for every possible diagnosis is not feasible, so the doctor needs to ask the right questions, listen carefully to the answers, do the right kind of physical exam, and pay attention to the clinical cues.
If you had the luxury an hour with each patient, you would have the time to carefully sort through the possibilities. But the reality is that you have 5-10 minutes to push the majority of diagnoses to the bottom of the list, come up with the most likely few at the top—being careful, of course, to keep in the rare but life-threatening possibilities—and then explain to the patient what you think. You can order labs, X-rays and the like, but those results won’t come until later. You need to offer to the patient the most likely diagnoses and a plan for how to start treatment and/or investigate more.
It’s a tall order, and an incredibly stressful one. As I raced through my day to trying to avoid falling too woefully behind schedule, I was also struggling to be as thorough as possible. The ulcer gnawing at the pit of every doctor’s stomach is, “What if I miss something serious?”
Patients, of course, have a parallel thought-process going on. Before they even get to the doctors’ office, they’ve thought about the symptoms that ail them, considered what might be causing them, maybe asked a family member’s opinion, and probably have done a web search to get some answers. There are now dozens of “symptom checkers” on the internet that allow you to enter your symptoms and come up with your own differential diagnosis. But are they accurate?
A group of researchers in Boston set out to find out. Using the presenting symptoms from 45 case vignettes from a medical school curriculum, they entered the symptoms into 23 different online symptom checkers. One-third of the programs got the correct diagnosis on the nose. When looking at the differential diagnosis, 58% of the programs had the right diagnosis listed in their top 20 possible diagnoses.
Much of the media coverage of this study focused on how lousy these symptom checkers are—they only got it exactly right a third of the time. But Ateev Mehrotra, the lead author on the study made a different observation. “It made me realize just how hard this task is. What we are asking symptom checkers to do is an extremely difficult task.”
His words make me reflect on my overwhelming day in clinic. Each and every patient presented a wide chasm of possibilities that could be nothing or something or something horrible. Was the patient with no energy just not getting enough sleep? Or was she anemic, or hypothyroid, or depressed, or suffering from pancreatic cancer or experiencing domestic violence? Was the patient with muscle aches having a medication side effect or exhibiting the onset of a systemic inflammatory disease? Did the gentleman with abdominal twinges have vascular compromise to his intestines or was he a hypochondriac? Or was he taking a Slavic weight loss concoction he’d purchased on the internet?
General practitioners like internists, family doctors, pediatricians and emergency doctors face the biggest challenges because the diagnostic field is so wide open. We all want to get it right, but don’t want to over-order tests that can be harmful (and expensive). We may want to allow some observation time to see if the symptoms self-resolve or progress, but we are worried about missing a serious illness, harming a patient or getting sued. Some days it feels shocking that we get it right at all.
And we do, on average, get it mostly right. Doctors’ diagnostic accuracy is estimated to be in the range of 80-90%. That, of course, implies a 10-20% error rate, but on days when it feels like you are being pelted with diagnostic possibilities from cell of the body and that imminent death is lurking everywhere you turn and that you have only minutes to make those decisions, that 80-90% number is comforting.
On cooler-headed days, though, that 10-20% error rate is disturbing. It’s a definite cut above the online symptom checkers, but is it really good enough? Luckily, the Institute of Medicine has taken on the topic of diagnostic error, exploring how errors occur, how they can be measured, and how they can be minimized. Look for the report coming soon.