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Dementia, Secondary Causes

Test code(s) 91410

Question 1. Why order the Dementia, Secondary Causes panel?

This panel is designed to evaluate patients for the presence of potentially reversible (ie, secondary) causes of dementia such as vitamin B12 deficiency, hypothyroidism, hypoparathyroidism, anemia, hypoxia or hypercapnia, hepatic and renal encephalopathies, diabetes, and dehydration.

The panel includes a complete blood count (including differential and platelets; test code 6399), TSH, vitamin B12, folate, and a comprehensive metabolic panel (test code 10231). It is modeled after the recommendations of the American Academy of Neurology (AAN), a National Institutes of Health Consensus Panel, the European Federation of Neurological Societies (EFNS), and others.1-5

Question 2. What other tests can be performed to evaluate a patient for secondary causes of dementia?

Guidelines recommend screening for syphilis and HIV in patients with suggestive clinical features.1,2,4 Urinalysis, urine culture, and heavy metal screening may also be added as needed based on clinical suspicion.4 Finally, cerebrospinal fluid testing may be helpful in patients highly suspicious for neurosyphilis, HIV, cerebral Lyme disease, or vasculitis.2,3  

Question 3. When should these tests be performed?

Simmons et al suggest ordering blood testing at the time of the initial assessment if cognitive impairment screening test results are abnormal or if there is clinical suspicion of another disease (Figure 1).4

Question 4. Are genetic and biomarker tests helpful in the differential diagnosis of dementia?

At this time, dementia diagnosis is primarily based on clinical observation. Biomarker tests, however, may enhance the specificity of the diagnosis in research settings.5 Genetic tests may also enhance the specificity in such settings.

Athena Diagnostics, a Quest Diagnostics company, offers testing for total tau (T-tau), β-amyloid1-42 (Aβ42), and phosphorylated tau 181 (P-tau) protein biomarkers. Athena Diagnostics also offers mutation testing of the APOE, PSEN1, PSEN2, and APP genes. For more information, visit AthenaDiagnostics.com or call 1-800-394-4493.

References

  1. Knopman DS, DeKosky ST, Cummings JL, et al. Practice parameter: diagnosis of dementia (an evidence-based review). Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2001;56:1143-1153.
  2. Consensus conference. Differential diagnosis of dementing diseases. JAMA. 1987;258:3411-3416.
  3. Sorbi S, Hort J, Erkinjuntti T, et al. EFNS-ENS Guidelines on the diagnosis and management of disorders associated with dementia. Eur J Neurol. 2012;19:1159-1179.
  4. Simmons BB, Hartmann B, DeJoseph D. Evaluation of suspected dementia. Am Fam Physician. 2011;84:895-902.
  5. McKhann GM, Knopman DS, Chertkow H, et al. The diagnosis of dementia due to Alzheimer’s disease: recommendations from the National Institute on Aging-Alzheimer’s Association workgroups on diagnostic guidelines for Alzheimer’s disease. Alzheimers Dement. 2011;7:263-269.
This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.
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