In my opinion, the concept of a diagnosis is a greatly overvalued aspect of modern medicine.
The Oxford Dictionary defines a diagnosis as the identification of the nature of an illness or other problem by examination of the symptoms (1). This concept of a diagnosis has its uses, but when it comes to treating the patient, it is a dangerously insufficient concept. Let me explain, using the example of stroke.
In essence, a stroke may be defined as brain tissue death due to a blood vessel blockage or leakage. There are two major types of stroke, ischemic (a blockage in one of the arteries supplying part of the brain) and hemorrhagic (a leakage in one of the arteries supplying part of the brain). Roughly 70-90% of all strokes are ischemic, and 10-30% of all strokes are hemorrhagic, depending on which part of the world we're talking about (2).
It's rarely difficult to make a diagnosis of stroke - the clinical symptoms are often obvious, and combined with medical imaging the diagnosis is often made when the patient arrives at the hospital. When the stroke has completed, knowledge of the diagnosis does not help much as nothing further can be done to salvage the dead brain tissue - instead, the emphasis of treatment turns towards rehabilitation and further stroke prevention.
Most people suffering from an initial stroke will rehabilitate well. Therefore what really matters in the long-term, and in my opinion the main focus of the admission, ought to be further stroke prevention.
Diagnosis Versus Source
In contrast to the diagnosis, the concept of a source is a greatly undervalued aspect of modern medicine.
The source may be defined as the pathological mechanism from which the diagnosis originates. In the example of stroke, discovering the stroke source is what allows the treating doctor to institute targeted prevention against further strokes.
Using the specific example of ischemic stroke, any of the following sources may produce an arterial blockage in the brain:
(1) Large artery atherosclerosis. This occurs when a blood clot forms on a ruptured atherosclerotic plaque in a large artery (such as a carotid artery), detaches, and travels to the brain where it gets stuck in a smaller artery.
(2) Atrial fibrillation. This occurs when the heart contracts chaotically or "fibrillates" thus creating turbulent blood flow, which is a breeding ground for clots that travel to the brain and get stuck in a smaller artery.
(3) Small artery disease. This occurs when the walls of tiny arteries in the brain get too thick and literally close off, depriving the brain tissue they supply of blood and oxygen. (4) Further stroke sources. There are dozens of further possible ischemic stroke sources - these include rips in the arterial wall that create a site for clot formation, heart valve infections that send vegetations to the brain, holes in the heart that allow clots from veins to pass over to the arteries and go to the brain, artery spasms that constrict blood flow to part of the brain, drugs such as amphetamines and cocaine that irritate the arterial walls and make them constrict...plus many more.
To prevent further strokes, the source must be identified before further strokes can be prevented. It's critical to get this right, as the treatment of large artery atherosclerosis (antiplatelet and statin medications, or surgical removal) is not the same as that for atrial fibrillation (anticoagulant medications) is not the same as that for small artery disease (antiplatelet and antihypertensive medications) is not the same as that for all of the other potential stroke sources listed above.
Unfortunately, while the concept of a diagnosis is taught well in medical school, the concept of a source is not. Thus, a proper hunt to identify the stroke source is often not done. However, if we are to think ahead and prevent further strokes, identifying and treating the stroke source is arguably the most important aspect of a patient's admission to hospital.
Thus, I am vexed if another doctor mentions they diagnosed an ischemic stroke without stating the stroke source - to me, it means they're just reacting to the current condition, not proactively thinking ahead to prevention. What they ought to say is that they diagnosed an ischemic stroke secondary to large artery atherosclerosis, atrial fibrillation, small artery disease, or whatever source was responsible; further strokes cannot be optimally prevented without knowing the source.
Altering The Approach
While we've used ischemic stroke as an example, the concept of diagnosis versus source is broadly applicable to most medical conditions. Diagnosing a hemorrhagic stroke is not enough - the source must be identified, which may be high blood pressure, an aneurysm, a weakness in the arterial wall, or something else. Diagnosing a seizure is not enough - the source must be identified, which may be epilepsy, alcohol withdrawal, a brain tumour, or something else. Diagnosing a myocardial infarction (heart attack) is not enough - the source must be identified, which may be coronary artery atherosclerosis, a rip in a coronary artery, inflammation in a coronary artery, or something else. If we're not identifying and treating the source in all these acute conditions, the condition will likely recur, despite getting the diagnosis right.
Beyond preventing a repeat of the acute condition, the identification of the source is even more vital, for it provides a clue to the presence of a chronic disease - and chronic diseases are lifelong producers of myriad diagnoses and sources. Chronic diseases keep coming back at the patient; they're relentless.
Yet as it stands now, even if the chronic disease is identified, the treatment of it is usually glossed over. Consider the case of ischemic stroke secondary to large artery atherosclerosis. If we identify large artery atherosclerosis on imaging, that allows us to institute the correct treatment (antiplatelet and statin medications, or surgical removal) to prevent further strokes. Yet even if that treatment is started, at best it will slow down the chronic disease in the case of medications, or remove a small part of it in the case of surgery - but it will not seriously impede the insidious progression of atherosclerosis throughout the body. Ultimately, both the ischemic stroke and the large artery atherosclerosis are merely end-points of the systemic chronic disease, atherosclerosis, that exists throughout the entire body; this is the real disease we must treat.
Thus, to really tackle chronic diseases, the current approach to medicine must be altered. Right now, medicine is reactive, not proactive. We react to the acute condition by making a diagnosis, sometimes searching for the source, and instituting a treatment against the acute condition. What we ought to do is become more proactive by making a diagnosis, securing the source, instituting a targeted treatment against the acute condition, then initiating a targeted treatment against the chronic disease that was ultimately responsible for the acute condition.
Whilst doctors are distracted and occupied by the tsunami of acute conditions coming at them from all directions, the real culprits go untreated. It is not the strokes, seizures, and heart attacks that are the problem; these are incidental byproducts of the real culprits which include atherosclerosis, cancer, and neurodegeneration. We must direct the bulk of our clinical and research efforts towards atherosclerosis, cancer, and neurodegeneration. Stop reacting to the epiphenomena created by these chronic diseases; start proactively tackling the chronic diseases themselves.
If we do, the human condition will improve tremendously.
References (1) https://en.oxforddictionaries.com/definition/diagnosis. (2) Ikram et al. 2012. International Epidemiology of Intracerebral Hemorrhage. Current Atherosclerosis Reports 14(4), 300-306.