Introduction: Who Should Seek Diagnostic Testing

If you or someone close to you is experiencing memory problems that interfere with daily life, it’s important to seek medical evaluation. Not all memory changes mean dementia is developing. As people age, some degree of forgetfulness is normal, such as occasionally misplacing keys or forgetting someone’s name. However, dementia—a general term describing a decline in mental ability severe enough to interfere with everyday activities—is different and is not a normal part of aging.^[4]

People should consider diagnostic testing when memory loss or confusion begins to affect their ability to function independently. This might include forgetting what keys are used for, getting lost in familiar places, or struggling to complete routine tasks like preparing meals or paying bills. Early symptoms of Alzheimer’s disease, the most common cause of dementia, often include forgetting recent events or conversations.^[6] Over time, these problems worsen and can affect reasoning, language, coordination, mood, and behavior.^[7]

Family members or friends may notice changes before the person experiencing them does. Someone with early dementia might have trouble remembering things or thinking clearly, but at first they may be aware of these difficulties. As symptoms progress, loved ones often become more likely to recognize the issues.^[6] If you notice persistent changes in someone’s memory, thinking, or behavior, encouraging them to see a healthcare provider is an important first step.

Getting an early diagnosis has several benefits. It allows people to understand what is causing their symptoms, access appropriate treatments, and make important decisions about their care and future while they are still able to participate fully. Early diagnosis also opens the door to clinical trials and support services that can improve quality of life.^[12]

Diagnostic Methods for Identifying Dementia

Diagnosing Alzheimer’s disease and other forms of dementia involves multiple steps. Because dementia can have many underlying causes, healthcare professionals use a combination of approaches to identify the specific disease affecting the brain and to rule out other conditions that might cause similar symptoms.

Medical History and Physical Examination

The diagnostic process typically begins with a detailed conversation between the patient, their family members, and a healthcare provider. The doctor will ask about the symptoms being experienced, when they started, and how they have changed over time. Understanding the person’s medical history, including any chronic conditions like high blood pressure or diabetes, is also important because these can affect brain health.^[12]

Input from close family members or friends is especially valuable during this stage. They can provide information about changes in the person’s daily functioning that the patient may not notice or remember. This might include details about difficulties with work tasks, household chores, or social interactions.

A physical examination helps the doctor assess overall health and identify any medical problems that could be contributing to cognitive symptoms. For example, thyroid problems or medication side effects can sometimes cause dementia-like symptoms that are actually reversible.^[7]

Tests of Memory and Thinking Skills

Healthcare providers use specialized assessments to evaluate how well a person’s brain is functioning. These tests, often called cognitive tests, measure memory, attention, problem-solving, language skills, and other mental abilities. During these evaluations, a person might be asked to remember lists of words, draw shapes, follow instructions, or answer questions about current events.^[12]

These assessments help doctors understand which areas of thinking are affected and how severe the impairment is. They also provide a baseline that can be used to track changes over time. The results help distinguish between normal age-related memory changes and the more significant decline seen in dementia.

Laboratory Tests

Blood tests are a routine part of dementia diagnosis. These tests check for conditions that can affect brain function, such as vitamin deficiencies, thyroid disorders, or infections. By identifying and treating these underlying problems, doctors can sometimes reverse or improve cognitive symptoms.^[12]

Recently, blood tests have become available that can detect specific proteins associated with Alzheimer’s disease. These biomarker tests measure substances in the blood that indicate whether certain disease-related changes are happening in the brain. Blood biomarker tests have become accurate enough to show if someone is likely to have amyloid—a protein that builds up in the brain in Alzheimer’s disease—without needing more invasive procedures.^[12]

Brain Imaging

Imaging tests create pictures of the brain’s structure and can reveal changes associated with dementia. Magnetic resonance imaging (MRI) and computed tomography (CT) scans show detailed images of the brain and can help identify problems like strokes, tumors, or bleeding that might be causing symptoms. They can also show whether parts of the brain have shrunk, which is common in Alzheimer’s disease.^[12]

More specialized imaging called positron emission tomography (PET) scans can show how the brain is functioning and detect the presence of abnormal proteins. Amyloid and tau PET scans can reveal whether plaques and tangles—hallmark features of Alzheimer’s disease—are present in the brain. These scans have traditionally been used mainly in research settings but are increasingly being used in clinical practice to support diagnosis.^[12]

Analysis of Cerebrospinal Fluid

In some cases, doctors may recommend testing the fluid that surrounds the brain and spinal cord, called cerebrospinal fluid. This fluid is collected through a procedure called a lumbar puncture or spinal tap. Laboratory analysis of this fluid can measure levels of proteins like amyloid and tau, providing information about whether Alzheimer’s-related changes are occurring in the brain.^[12]

Before newer blood tests became available, cerebrospinal fluid analysis was one of the main ways to detect these biomarkers. While still valuable, it is a more invasive procedure compared to a simple blood draw.

Distinguishing Between Types of Dementia

Because there are many types of dementia, part of the diagnostic process involves figuring out which disease is causing the symptoms. Alzheimer’s disease accounts for 60 to 80 percent of dementia cases, but other conditions like vascular dementia, Lewy body dementia, and frontotemporal dementia can also cause similar problems with thinking and memory.^[4]

Each type of dementia is caused by different changes in the brain. In Alzheimer’s disease, abnormal deposits of proteins form amyloid plaques and tau tangles throughout the brain. In vascular dementia, problems with blood flow—such as from strokes—damage brain tissue. Lewy body dementia involves abnormal deposits of a protein called alpha-synuclein, which form structures called Lewy bodies. Frontotemporal dementia results from the buildup of abnormal amounts of tau or other proteins in the frontal and temporal lobes of the brain.^[3]

The pattern of symptoms, results of cognitive testing, and findings from imaging and biomarker tests all help doctors determine which type of dementia is present. This is important because different types of dementia may progress differently and may respond to different treatments.

Diagnostics for Clinical Trial Qualification

Clinical trials are research studies that test new ways to prevent, detect, or treat diseases. For people with early Alzheimer’s disease or those at risk of developing it, participating in clinical trials offers the opportunity to access experimental treatments that may slow the disease’s progression. However, enrolling in these studies requires meeting specific criteria, and diagnostic testing plays a central role in determining eligibility.

Confirming the Diagnosis and Disease Stage

Most clinical trials for Alzheimer’s disease focus on people in the early stages of the disease. To qualify, participants typically need to have either mild cognitive impairment—a condition where memory or thinking problems are noticeable but don’t significantly interfere with daily life—or mild Alzheimer’s disease. Cognitive testing is used to confirm that a person’s level of impairment matches the study’s criteria.^[11]

Trials testing disease-modifying treatments, particularly newer drugs that target amyloid protein in the brain, require proof that amyloid is actually present. This is a critical eligibility requirement because these treatments are designed specifically to remove or reduce amyloid buildup.

Biomarker Testing for Trial Enrollment

To confirm the presence of amyloid in the brain, clinical trials often require participants to undergo biomarker testing. This can be done through a PET scan that shows amyloid deposits in the brain, or through analysis of cerebrospinal fluid obtained via lumbar puncture. Both methods provide direct evidence of Alzheimer’s-related brain changes.^[11]

Before prescribing certain FDA-approved treatments like lecanemab or donanemab—drugs that were tested in clinical trials and are now available—doctors may order PET scans or cerebrospinal fluid analysis to confirm that amyloid deposits are present. These same requirements often apply when enrolling in trials testing similar therapies.^[11]

Blood-based biomarker tests are increasingly being used in clinical trial screening as well. These tests are less invasive and more convenient than PET scans or spinal taps, making them useful for identifying potential participants who are likely to have amyloid in their brains. If a blood test suggests amyloid is present, more definitive testing may follow to confirm eligibility.

Baseline Health Assessments

Before joining a clinical trial, participants undergo comprehensive medical evaluations to ensure they are healthy enough for the study and to establish a baseline for comparison. This typically includes blood tests, physical examinations, and sometimes imaging studies to check for other health conditions that might affect participation or safety.

For trials testing anti-amyloid drugs, monitoring for side effects is particularly important. Some of these medications can cause changes in the brain that show up on MRI scans, such as temporary swelling or small areas of bleeding. Because of this, participants in such trials typically need MRI scans at the beginning and at regular intervals throughout the study to watch for these effects.^[11]

Ongoing Monitoring During Trials

Once enrolled in a clinical trial, participants undergo regular assessments to track how the disease is progressing and whether the experimental treatment is having an effect. This includes repeated cognitive testing to measure changes in memory and thinking, as well as periodic biomarker testing to assess changes in the brain.

These ongoing evaluations serve two purposes: they help researchers determine whether the treatment is working, and they allow the medical team to monitor for any safety concerns. Participants and their families receive detailed information about what to expect during the trial and what tests will be performed.