Diagnosing Alzheimer's: Lab Tests

Reviewed by: HU Medical Review Board | Last reviewed: June 2019 | Last updated: November 2019

When a person suspects they might have Alzheimer’s, getting an accurate diagnosis is crucial. There are a variety of illnesses and complications that can mimic the neurological symptoms of Alzheimer’s disease, and it’s important to rule those out in order to find the actual cause of the symptoms. Although Alzheimer’s disease can only be definitively diagnosed after death with tissue from an autopsy; while a person is living, the diagnosis is made from a combination of tests, observations, and lab work.1

There is no single diagnostic test for Alzheimer’s disease, so a doctor uses a variety of things to make a diagnosis. Laboratory testing is often one of the tools used to aid in making a diagnostic decision.

Exploring symptoms

When a person goes to the doctor for possible Alzheimer’s disease, along with a physical exam, the doctor will typically do a medical and symptom history. They will collect information about the physical and mental health of the person, along with information about what kinds of symptoms are occurring. Alzheimer's symptoms can include memory impairment, poor judgment and decision-making, difficulty completing everyday tasks, losing or misplacing familiar items, mood or personality changes, and trouble with planning and organizing.2 The severity of symptoms can change as the disease progresses, so it’s important for the doctor to get an accurate picture of the symptoms and how they’ve changed over time.

Various symptoms of Alzheimer’s can also be symptoms of other illnesses or conditions, including nutritional deficiencies, abnormal thyroid function, excess alcohol consumption, sleep apnea, other types of cognitive disorders, stroke, brain tumors, medication interactions or side effects, and more. It’s important to get as much information as possible from a variety of tests in order to get an accurate diagnosis.

Different kinds of laboratory tests

Blood and urine tests might be done to check for vitamin deficiencies, thyroid disorders, anemia, infection, inflammation, electrolyte imbalance, drugs that may influence cognition. chemicals, hormone levels, and deficiencies. Sometimes these laboratory tests are done routinely for older adults because of risk for various illnesses, including2:

  • CBC (for example, white blood cells that may indicate infection, hemoglobin and hematocrit which measures red blood cell count and could indicate anemia)
  • Electrolyte panel
  • Glucose testing
  • Vitamin B12 (check for deficiency)
  • T4 and TSH (thyroid defects)
  • Liver function tests (for example, bilirubin, albumin
  • Kidney function (for example, creatinine, blood urea nitrogen)

Medications can interact with each other in a variety of ways, and adverse interactions can cause symptoms similar to those of Alzheimer’s disease. Laboratory tests can show if there is a potentially treatable condition that can reverse symptoms. If laboratory tests come back normal, then various ailments can be ruled out, narrowing down the diagnosis even further.

Further testing

If the lab work shows nothing notable, the person may be referred to a specialist who can do more tests to determine whether or not the symptoms are due to Alzheimer’s disease. Additional testing that might be done can include physical and neurological exams, brain imaging tests, genetic testing (not recommended for everyone), and mental status testing. All of these kinds of tests can help piece together a broader picture for the doctor of a person’s mental status, cognitive abilities, symptom presentation over time, and overall functioning – all of which can help them make a confident diagnosis of Alzheimer’s, if need be.

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