Published on: July 27, 2013
by Tele Management:
Short of examining brain tissue at autopsy, presently no single test can definitively diagnose Alzheimer’s disease (AD). However, a knowledgeable physician can clinically diagnose the disease with an accuracy of up to 90% by methodically ruling out other illnesses with similar symptoms.
The work-up basically includes three levels of assessment, ranging through patient history, physical and neurological examination, laboratory and neuropsychological tests, and brain imaging. The first level of assessment is geared towards patients who may be showing early signs and/or symptoms of dementia and includes a patient and family interview, a physical and neurological examination, and laboratory tests.
During the patient interview, the provider elicits a complete medical history, beginning with current mental and physical conditions. Specifically, the provider wants to know about issues with body systems as well as memory or other cognitive problems.
The patient’s past health, social history as well as family health history are important to note. From this information, the physician can learn about risk factors, previous head trauma and neurological conditions. The provider will need a list of current medications, both prescription and over-the-counter (OTC).
The patient’s family is also interviewed separately from the patient to verify the information given by the patient and to get the family’s observations of the patient’s cognitive and behavioral symptoms.
The doctor then conducts a complete physical and neurological examination. The physical examination consists of a hearing and vision screen and a blood pressure reading. During the neurological check-up, the physician tests muscle strength and tone as well as reflexes and balance. The patient’s current mental status is determined by using the Mini-Mental State Examination, or MMSE, which consists of questions to assess the patient’s awareness of time and place, and ability to recall and understand information.
Results from blood and urine laboratory tests can also help the provider to rule out other diseases. For level one assessment, the provider is likely to order a complete blood cell count, glucose (sugar), serum electrolytes, thyroid function tests and drug levels. With these tests, a physician can rule out anemia, chronic infection and medication intoxication.
Level two assessment is performed on all patients with signs and symptoms of dementia/AD unless information from the level one assessment allows the physician to make a diagnosis with relative confidence. Further laboratory tests are indicated in this level and include liver function tests and vitamin deficiency tests, such as B12 and folate. At this level of evaluation, a doctor may order some tests based on the patient’s risk factors. These include screening for syphilis or HIV, urinalysis for heavy metals and genetic testing for diseases other than AD. Screens for syphilis or HIV may be appropriate depending on the patient’s age, past sexual history, or regional prevalence of either disease. If a patient worked in an environment with heavy metal exposure, a 24-hour urinalysis to screen for this toxicity may be warranted. Genetic testing may be indicated for patients who have a significant family history.
Brain imaging is also indicated at this level of assessment. The American Academy of Neurology recently published practice guidelines on the use of brain imaging to aid in the diagnosis of AD/dementia. While no imaging method can detect AD, these tools are used to rule out stroke, brain tumor, or abscess. Imaging options include noncontrast computed tomography (CT) and magnetic resonance imaging (MRI).
The third level of assessment includes tests and imaging that are not routinely warranted. These evaluations are generally required for patients who have an atypical course of disease or if the physician remains substantially unsure of the diagnosis. This level of evaluation may also be useful in patients who have early onset dementia/AD.
Evaluations at this level include neuropsychological tests, which are given by psychologists with special training. Neuropsychological assessments help clinicians differentiate psychological illness from dementia/AD. Additional imaging may also be indicated and includes functional brain imaging (PET, SPECT). This type of imaging is ordered to find out if the brain is working as it should. Other tests such as lumbar puncture are used only in patients with certain diseases, including metastatic cancer or if a central nervous system infection is suspected.
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