It is inevitable to miss a diagnosis

The author is an emergency physician and former chief of emergency medicine at the Montreal Heart Institute. A professor at the University of Montreal, he teaches and participates in research in emergency medicine and intervenes frequently on health issues.

All doctors miss diagnoses, even serious and urgent ones—especially in the emergency room. The very nature of medicine means that, no matter how much time, diligence and energy one puts into treating a patient, even without doing anything wrong. Since this reality can surprise, disappoint and worry you, I will try to explain it to you simply.

Diagnosis should be seen as a finding based on an analysis of known facts. This analysis, which takes place in the doctor’s brain, makes it possible to identify the appropriate health problem better with Variety of signs and symptoms.

In emergency medicine, it may also surprise you, the emergency physician’s first responsibility is not to find it, that famous diagnosis, to miss as few serious diagnoses as possible. This corresponds to two primary outcomes: the ‘confirmation’ of the diagnosis and the ‘elimination’ outcome.

In many cases, the situation is too obvious to require any diagnostic approach, and the important thing above all is to treat the patient quickly. For example during cardiac arrest, which is rare. In this line we also find acute infarction, obvious stroke, clearly visible fracture, severe asthma attack or serious allergic reaction.

Except that, for the majority of other emergency room consultations, diagnoses are not written clearly on the front. The clinician’s strategy then aims to ‘confirm’ or ‘eliminate’ one or more diagnoses consistent with the clinical presentation.

At the end of this process, the doctor will inevitably miss some of them, even among the most serious ones. Rarely cardiac arrest, apparent fracture or major allergic reaction. But often more subtle symptoms, such as a mild infarction, a mild stroke, a small clot in the lungs – called a pulmonary embolism – or even a rupture of the aorta, which is often fatal.

The reason is simple: in general, the examinations carried out never allow 100% of health problems to be detected, so that a certain percentage of diagnoses are always missed. To describe this phenomenon, we also say that tests have sensitive incomplete.

For example, screening, which is the best screening for pulmonary embolism, will always miss about 10% of cases, according to studies on the subject. These normal results are then classified as a ‘false negative’. ».

If we want to avoid all false negatives and identify 100% of serious and urgent cases of pulmonary embolism, we will have to recheck or perform a large number of additional tests, which is unthinkable, except in the case of the objective severity of the embolism case. The patient is required to find the answer completely.

Doubling up on tests to detect more pulmonary embolisms, therefore, would beget another equally serious problem, the problem of “false positives”: even the best tests regularly point to diagnoses that do not, in fact, exist.

These “lies” this time are associated with their imperfection Quality tests. To continue with the example, let’s say that about 1 in 20 scans (5%) give a diagnosis of pulmonary embolism… even though it doesn’t exist.

When these tests are repeated unnecessarily so as not to miss a diagnosis, the number of false positives increases by the same amount. This is not without consequences, as the treatments taken, and anticoagulants, also have their share of risks.

In emergency medicine, the right balance is struck when the majority of pulmonary embolisms, especially the most severe ones, are found without this resulting in a high rate of false positives. This implies the loss of a certain number, in our example up to 10%.

By multiplying this percentage by the assumed number of blockages in Quebec per year, roughly 6,500, we can estimate that perhaps 650 blockages pass under the radar one way or another each year, which is 2 per day. Rest assured, these often present the lowest risks.

The whole art – and science – of medicine is about striking a delicate balance between detecting the most serious medical problems and accepting, both physician and person treating, that some diagnoses will be missed.