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Blood Tests Used in the Diagnosis of Alzheimer's Disease

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Updated June 14, 2008

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(LifeWire) - Although science is getting closer, there's still no simple diagnostic test for Alzheimer's disease. Instead, physicians who suspect the condition basically start by ruling out other causes of the symptoms, which include memory loss, confusion, and problems with executive functioning.

This diagnostic process almost always includes blood testing for everything from infections to vitamin deficiencies. The goal is to uncover other possible conditions that might be causing or worsening the symptoms.

Blood Tests Used in Diagnosing Alzheimer's Disease

Although there are numerous tests, physicians generally request them all at once, so you don't need to worry about going through repeated blood draws and needle pricks. Different physicians may prefer different tests, and which ones are ordered depends on your medical history and other physical symptoms. Don't worry if one listed here wasn't ordered. If you have questions, don't be afraid to talk to your doctor about the results or how he or she interprets them.

Thyroid Functioning
This test evaluates thyroid functioning. Hypothyroidism (an underactive thyroid) can cause forgetfulness and fatigue. A thyroid disorder is treatable under the care of a physician.

White Blood Cell Count
Increased white blood cell counts can indicate infection. In rare cases, a bacterial or viral infection can reach the brain, causing symptoms similar to Alzheimer's disease.

Red Blood Cell Count
Low levels of red blood cells suggest anemia (iron deficiency). Symptoms of anemia include weakness, forgetfulness, mental confusion and loss of sex drive.

Screening Tests for Syphilis Antibodies
Syphilis, a sexually transmitted disease, can cause mental confusion if left untreated.

Kidney Function Screening
Poor kidney function means more waste products in the blood. It can produce disorientation, confusion and difficulty expressing simple thoughts.

HIV Testing
HIV is a virus that can result in forgetfulness and mental confusion.

Erythrocyte Sedimentation Rate (ESR)
Erythrocyte is another term for a red blood cell. The test measures how quickly red blood cells settle to the bottom of a thin tube containing the blood sample. Higher measurements could reflect various things, including inflammation, infection or some other disorder (such as cancer or an autoimmune disease), or even a pregnancy.

Serum Glutamic Pyruvic Transaminase (SGPT) Testing
SGPT is an enzyme concentrated in the liver. If the liver is damaged, high levels of this enzyme will be found in the blood. This may indicate problems with the liver's ability to detoxify the blood, which could impair brain functioning.

Toxic Screening
As its name suggests, this test measures toxic substances in the blood -- anything from street drugs to excessive levels of prescription medications. The test helps physicians determine if a medication or drug might be causing dementia symptoms.

A True Diagnostic Test?

Researchers at Stanford University are closing in on a diagnostic test that they believe will identify Alzheimer's disease two to three years before the appearance of symptoms, which should work for about 90% of patients. In a November 2007 study published in the journal Nature Medicine, researchers examined the blood plasma of individuals who were either symptom-free or exhibiting Alzheimer's symptoms, and they isolated 18 proteins that might serve as markers for early recognition and diagnosis of Alzheimer's disease.

Although more research is needed before any such assay will be available for general use, an effective diagnostic test could revolutionize not only the diagnosis of Alzheimer's disease, but potentially its treatment as well. This could allow the disease to be recognized before any cognitive damage has occurred.

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LifeWire, a part of The New York Times Company, provides original and syndicated online lifestyle content. Betsy Lee-Frye is an independent journalist living in Kansas City, Mo. Her work has appeared in The Dallas Morning News, Better Homes and Gardens Special Interest Publications and Kansas City Magazine.

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