Currently, an irrefutable diagnosis of Alzheimer’s disease (AD) is only possible by autopsy. The diagnosis of Alzheimer’s and other types of dementia while patients are still alive is not yet an exact science, but doctors do have an arsenal of tests that can narrow down the underlying reason(s) for a patient’s memory problems and changes in behavior. However, it is important to keep in mind that these mental and physical tests are conducted to rule out all other possible causes, not to confirm the presence of AD.

“Clinicians are about 80 percent accurate in determining whether someone has AD, but a lot of cases aren’t black and white,” explains David Morgan, MD, CEO and director of the Byrd Alzheimer’s Institute at the University of South Florida. While this figure may not seem reassuring, it is still crucial for patients to undergo testing once they begin exhibiting symptoms. The results will help physicians provide a diagnosis and appropriate treatment suggestions, which will enable patients and their families to make plans and prepare for the future.

Read: A Dementia Diagnosis: Bane or Blessing?

So, when should one seek medical attention for suspected Alzheimer’s? “When anything happens that makes someone raise their eyebrow, it should also raise a red flag,” states Amanda Smith, MD, Medical Director of the Byrd Alzheimer’s Institute. For instance, if someone you love is always punctual and never forgets an appointment but suddenly misses several over the course of a few weeks, it’s time to see the doctor, urges Dr. Smith.

Tests Used to Diagnose Alzheimer’s Disease

There are many different tests that doctors use to get a well-rounded picture of a patient’s health and determine if Alzheimer’s disease is a concern. These are some of the most commonly used diagnostic tools.

Medical History

As with the treatment of any medical condition, physicians will ask for a rundown of a patient’s past and current health issues and all medications they are currently taking. The doctor will also take a brief family medical history to assess the patient’s risk of developing certain conditions due to genetic, lifestyle and environmental factors. For example, if a patient’s parent had early-onset Alzheimer’s disease, it increases the likelihood that the patient will also develop this disease.

Physical Testing

A family or primary care physician can perform a physical exam and conduct laboratory tests to rule out conditions like vitamin deficiency, thyroid issues, diabetes, kidney disease, or even drug side effects and interactions that can cause dementia-like symptoms. A physical screening may include blood and/or urine testing, measurement of vital signs, and an in-depth discussion about symptoms and lifestyle choices.

Cognitive Testing

If the cause of memory loss still hasn’t been determined, the doctor may perform mental status testing. There are two different tests used to assess a patient’s status, the Mini-Mental State Exam (MMSE) and the Mini-Cog.

The MMSE will determine if the patient is aware of their symptoms, if they can remember a short list of words and instructions, and measure the strength and range of their everyday mental skills. According to the Alzheimer’s Association, the maximum MMSE score is 30 points. Lower scores suggest mild (20-24), moderate (13-20) or severe dementia (12 or less).

The Mini-Cog is a very brief test that measures mental functioning through word recall and a patient’s ability to accurately draw a clock. The maximum score on a Mini-Cog is five points. A score of four points or less typically indicates the need for further cognitive evaluation.

While cognitive tests are helpful, Dr. Morgan admits that, physicians don’t have clear instructions for detecting the earliest stages of Alzheimer’s. “The problem with early detection is that different people have different mental capacities,” he notes. To complicate matters further, all of us—whether we have a diagnosis of Alzheimer’s or not—have good and bad days.

Even if some sort of dementia is suspected and these tests do not yield clear results, it is important for them to be repeated yearly, at minimum, to track changes in a patient’s mental state. In fact, it is wise to begin annual testing after a certain age rather than waiting until noticeable cognitive symptoms arise.

Neuropsychological Testing

During this kind of testing, a physician will assess a patient’s reflexes, eye movements, speech and coordination to see if other neurological disorders may be causing dementia-like symptoms. These culprits may include brain tumors, an accumulation of fluid around the brain known as hydrocephalus, a stroke or Parkinson’s disease.

“I think they are somewhat effective, but for the earliest stages, they aren’t sensitive enough,” Dr. Morgan says of neuropsychological exams. He believes these tests are best for patients who are already showing clear symptoms of dementia.

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Brain Imaging

Brain imaging is perhaps the most significant testing method currently available to help diagnose AD. MRI (magnetic resonance imaging) and CT (computed tomography) scans can rule out other conditions that have similar symptoms to Alzheimer’s and reveal tumors, evidence of damage from a stroke or excess fluid on the brain.

For the average healthy person, neurons in the brain die as we get older, causing the organ to shrink about one percent each year. In a person with AD, that amount increases to roughly three percent annually. Only through brain imaging can doctors see how the mass and structure of one’s brain changes over time.

However, one thing that CT and MRI scans cannot do is show how well (or poorly) a patient’s brain is functioning. For that, doctors use positron-emission tomography (PET) scans because they provide a look at the chemistry of the brain. PET scans enable doctors to determine whether different areas of brain tissue are living or dead and detect abnormalities in cellular activity, which can usually be seen before symptoms of dementia arise.

During a PET scan, a slightly radioactive glucose-based solution is injected into the body. A PET machine (which looks like MRI and CT machines) then takes three-dimensional images of the brain that illustrate which areas are functioning correctly and which ones are not using the glucose solution as fuel. Certain PET scan solutions can also detect the presence of beta-amyloid protein clusters—a biomarker of Alzheimer’s disease. Depending on the patterns of brain function and the presence of amyloid clusters in the resulting images, a physician can determine if Alzheimer’s disease, another type of dementia or another condition altogether is responsible for cognitive symptoms.

Experts at the Alzheimer’s Association believe that this specialized PET scan can be helpful in certain situations but not others. For instance, a positive scan that confirms the presence of amyloid plaques does not mean that a person definitely has Alzheimer’s. The plaque build-up could be due to something else. Conversely, a negative scan would be useful only in excluding AD from the list of possible reasons for an elder’s memory loss and altered behavior. This is why Medicare does not cover amyloid PET imaging except for patients participating in clinical studies that meet specific criteria and have been approved by the Centers for Medicare and Medicaid (CMS).

Genetic Testing

Researchers know that certain genes increase the risk of developing AD or one of the rare forms of AD, called autosomal dominant Alzheimer’s disease (ADAD), which tends to run in families. With ADAD, symptoms often occur earlier in life, but this form of the disease accounts for less than five percent of all cases.

Possession of a gene called APOE E4, poses the strongest risk of developing AD. A blood test is available to determine whether a person has this gene. However, having the gene does not mean one will develop AD, only that one is at greater risk. Knowing this could encourage lifestyle changes to slow down the onset of Alzheimer’s, but genetic testing is highly controversial and it usually is not covered by insurance plans.

Next Steps Following Diagnosis

Right now, there is no available treatment that can effectively halt or reverse the progression of Alzheimer’s disease. Certain medications and therapeutic interventions have been shown to help dementia patients maintain their physical and mental functionality for as long as possible, but none of these options represent a cure. Doctors hold out hope that, if they can catch the disease earlier, they may be able to develop more successful treatment plans that will change this fact. In the meantime, the best thing for people to do is embrace a healthy lifestyle and be proactive when it comes to medical testing.