Diagnosing Alzheimer's: The Problem With Medicine
In my last Alzheimer's blog we asked, "Why is it that sometimes health professionals disagree about the diagnosis of Alzheimer's disease in a specific patient?" For example, today in our group meeting (Where a group of us review the patients that we have seen during the week), we discussed a patient who was told by a previous physician that she did not have Alzheimer's disease, but our group agreed that she probably did. Why does such a thing happen?
There are a few reasons why this might be the case.
We reviewed the first three steps used by a clinician when making the diagnosis of Alzheimer's disease. The clinician takes a history, performs an examination, obtains some tests and draws a conclusion. There is the possibility of different opinions arising at each of these steps. We reviewed taking a history, performing and examination and obtaining tests. We now need to review how a clinician draws a conclusion about a possible diagnosis. In doing this we attempt to determine if there are ways that two clinicians, using the same history, the same examination, and the same test results can arrive at different conclusions.
In a perfect world in which all clinicians have perfect knowledge (which certainly does not exist), all clinicians would arrive at the same conclusions given the same information. However, ours is an imperfect world and clinicians are part of that.
When making a diagnosis, decisions are influenced by a clinician's background. For example, clinicians who diagnosis patients may have very different training and experience. Clinicians with different types of training may include, just to name a few, family physicians, general internists, geriatricians, general neurologists, nurse practitioners and physician assistants. In addition, members within each of these groups may have special training in dementia.
Thus, clinicians approach the diagnosis with a background that will be, in part, dependent on their training. It also may be dependent on their own personality. One clinician may see a need to diagnose dementia in anyone whom he believes might have it. This clinician may believe that the research definitely indicates that an early diagnosis is important, and that early treatment is necessary, because it helps prevent certain things, such as ending up in a nursing home.
A second clinician may see a need to make the diagnosis only if such a diagnosis is important in the given circumstance. The second clinician may believe that the research is not definite and that early treatment raises risks of medication side effects and may not help the patient. Both of these positions can probably be justified by what we know about treatment in Alzheimer's disease.
A second reason why two clinicians may arrive at different diagnoses may be the degree to which they weigh the information that they have. For example, let us consider a hypothetical patient with the following features. The patient has had a previous heart attack and now has a history that includes a problem with thinking and memory that apparently has been slowly getting worse. That patient also has difficulty with daily functioning. The examination demonstrates that the patient has trouble with memory and with another ability, such as writing.
Therefore, based on the first two steps used in diagnosing patients, this patient does have a dementia. A slow progression would be typical for Alzheimer's disease. After the history and examination, this hypothetical patient has an MRI (a test that shows normal and abnormal features of the brain). The report of this test indicates that the MRI shows evidence of more than one stroke. In the setting of a previous heart attack (a disorder that is known to commonly be associated with stroke), the MRI result might make a clinician believe that the patient has dementia because of stroke, so called "vascular dementia."
At this point there is conflicting evidence. Does the patient have Alzheimer's disease, vascular dementia, or both? It is not possible to answer this question. Consequently, physicians of equal background and ability may arrive at different diagnoses, even when they are in total agreement on the available information, both from the patient and from the available research studies.
In summary this blog and my most recent blog before this one have attempted to illustrate a fundamental issue in medicine. It is not an exact science. The field of medicine knows much about people and the diseases that affect them. However, no clinician can have all of this knowledge. Even if a clinician does, there are still major gaps in our knowledge. This makes the field an inexact science. In this setting, it is quite possible for two clinicians to arrive at different conclusions about a diagnosis of Alzheimer's disease.