Background

CKMB is an antiquated cardiac marker due to its limited clinical utility. Current guidelines recommend cardiac troponin testing as the biomarker of choice for myocardial injury due to its superior specificity and sensitivity. Additionally, co-testing with CKMB and troponin adds no incremental value.  

This is supported by the American College of Cardiology (ACC), European Society of Cardiology (ESC), Association for Diagnostics & Laboratory Medicine (formerly AACC), American Society for Clinical Pathology (ASCP), Cleveland Clinic’s Cardiovascular Medicine Division, Clinical Biochemistry Section, and Laboratory Stewardship Committee. 

References

• Fourth Universal Definition of Myocardial Infarction (PMID: 30571511) 
• Eliminating CKMB Testing in Suspected ACS: A Value-Based Quality Improvement (PMID: 28806444) 
• ESC Study Group on Cardiac Biomarkers of the Association for Acute CardioVascular Care: A Fond Farewell at the Retirement of CKMB (PMID: 33486520)

Test Name

Alzheimer’s Disease Biomarker Panel, Cerebrospinal Fluid

Test Code

ALZCSF

CPT Codes

83520 – QTY (3)

Methodology

Electro Chemiluminescence Immunoassay (ECLIA)

Specimen Requirements

Type:
Cerebrospinal fluid (CSF)

Volume:
2.5 mL

Container:
CSF Transport Tube, 2.5 mL (Sarstedt)

Collection Instructions

1. Confirm that the tube type is correct – only a specimen collected in the Sarstedt CSF Transport Tube [ref. 63614.625] is acceptable.
2. Perform a lumbar puncture using the gravity drip collection method (preferred). Do not use the first 2 mL of CSF.
3. Collect CSF directly into the tube up to the fill line.
4. Inspect the sample for the presence of blood. Do not use CSF samples that appear reddish. Instead, collect additional clear (non-hemolytic) CSF in a new CSF tube.
5. Do not process the sample before sending it to the laboratory (i.e., do not invert, transfer, or aliquot).

Rejection Criteria

CSF collected in polystyrene or glass tubes

Bloody or hemolyzed specimens.

Unfilled tubes.

Stability

Ambient:
5 days

Refrigerated (preferred):
14 days

Frozen:
8 weeks (-20⁰C)

Days Performed

Days Performed
Once a week

Reported
1-8 days

Reporting

Component

p-Tau181/Abeta42

Total-Tau/Abeta42

p-Tau181

Total-Tau

Abeta42

Reference Interval

≤0.0230

≤0.280

≤31.3 pg/mL

≤375.4 pg/mL

≥564.2 pg/mL

Clinical Information

A negative p-Tau181/Abeta42 ratio and/or Total-Tau/Abeta42 ratio is consistent with a negative amyloid positron emission tomography (PET) scan and reduces the likelihood that a patient’s cognitive impairment is due to Alzheimer’s disease.

A p-Tau181/Abeta42 ratio and/or Total-Tau/Abeta42 ratio elevated above the cut-off is consistent with biological changes associated with Alzheimer’s disease (AD) and a positive amyloid positron emission tomography (PET) scan. A positive result does not establish a diagnosis of AD or other cognitive disorders and should be interpreted as an adjunct to other clinical diagnostic information.

The ratios will not be calculated in samples with an Abeta42 concentration >2,500 pg/mL. This result is consistent with a negative amyloid positron emission tomography (PET) scan and reduces the likelihood that a patient’s cognitive impairment is due to Alzheimer’s disease.

The p-Tau181, Total-Tau, and Abeta42 tests are not intended to be used as a stand-alone test in spinal fluid. For interpretation of results, refer to the p-Tau181/Abeta42 and Total-Tau/Abeta42 ratios.

The test method is the Elecsys electrochemiluminescence immunoassay manufactured by Roche Diagnostics. Values determined by different assay methods cannot be used interchangeably.

The validity of this test interpretation requires strict adherence to the specimen collection and preparation instructions detailed in the Cleveland Clinic’s Test Directory.