Test Details
Methodology
See individual test components.
Test Includes
This test includes Metabolic Panel (14), Comprehensive; Vitamin B12 and Folates; Thyroid-Stimulating Hormone (TSH); Elecsys® pTau-181, Plasma; and Complete Blood Count (CBC) With Differential, Reflex to Peripheral Smear Review.
Use
This test is used to assess and rule-out potential reasons for clinically observed cognitive impairment.
Special Instructions
This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.
Custom Additional Information
The laboratory evaluation of cognitive impairment aims to identify reversible or treatable conditions that may mimic or exacerbate neurodegenerative disease. Current guidance from the American Academy of Family Physicians (AAFP), American Academy of Neurology (AAN), American Geriatrics Society (AGS) and the Alzheimer's Association supports a focused tier 1 panel consisting of a complete blood count (CBC), comprehensive metabolic panel (CMP), thyroid-stimulating hormone (TSH) and vitamin B12 and folate levels.1
The CBC evaluates for anemia and infection, both of which can contribute to impaired cognition. Anemia may reduce cerebral oxygen delivery and lead to fatigue and decreased attention, while leukocyte abnormalities may indicate infection or systemic inflammation associated with delirium or cognitive decline.2
The CMP assesses electrolyte balance, renal and hepatic function and glucose levels. Electrolyte disturbances such as hyponatremia or hypercalcemia are recognized reversable causes of cognitive dysfunction. Abnormal renal or hepatic function may result in metabolic encephalopathies, while glucose dysregulation can impair cognition in both acute and chronic seetings.2
Measurement of TSH is essential due to the neuropsychiatric manifestations of thyroid disorders. Hypothyroidism may present with memory impairment and slowed cognition, whereas hyperthyroidism can produce agitation and reduced concentration. Routine screening for thyroid dysfunction is recommended because it is common and potentially reversible.3
Vitamin B12 and folate deficiencies are well-established reversible contributors to cognitive impairment. Vitamin B12 deficiency, in particular, is associated with neurologic and psychiatric symptoms that may occur even in the absence of anemia.3
The inclusion of Elecsys® pTau-181 is intended to be used in a primary care setting as an aid in the initial rule-out assessment for Alzheimer's disease. A negative test result is consistent with a negative amyloid positron emission tomography (PET) scan result and reduced likelihood that a patient's cognitive impairment is due to amyloid pathology.4
Specimen Requirements
Specimen
Serum, plasma, whole blood
Volume
3 mL serum, 1 mL plasma, 4 mL whole blood
Container
Gel-barrier tube, transfer tube, lavender-top (EDTA) tube
Footnotes
1. Kramer ES, Johnson MN, Winslow B. Evaluation of suspected dementia. Am Fam Physician. 2025 Dec;112(6):657-667. PubMed 41533411
2. American Academy of Neurology; Alzheimer's Association. Laboratory tests for diagnosing dementia. Published 2025. Accessed June 2026 at https://www.droracle.ai/articles/276134/what-laboratory-test s-are-recommended-for-diagnosingdementia.
3. GeriGuides. Dementia: Work up-labs, imaging, and consults. GeriGuides website: https://www.geriguides.com/2022/04/dementia-work-up-labs-imaging-and-consults/ Published April 11, 2022. Accessed June 2026.
4. Elecsys Phospho-Tau (181P) Plasma: Instructions for use [method sheet]. Version 1.0. Roche Diagnostics; published 2023-2025 (exact version dependent). Accessed June 2026 at https://elabdoc-prod.roche.com/eLD/api/downloads/1ff55446-7ec1-f011-3191-005056a71a5d?countryIsoCode=us.