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Test ID: P1433    
14-3-3 Protein, Spinal Fluid

Useful For Suggests clinical disorders or settings where the test may be helpful

Supporting, in conjunction with other tests, a diagnosis of Creutzfeldt-Jakob disease in patients with rapidly progressive dementia when other neurodegenerative conditions have been excluded

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

The 14-3-3 proteins are a group of highly conserved proteins composed of several isoforms that are involved in the regulation of protein phosphorylation and mitogen-activated protein kinase pathways. They exist in vivo as dimers of the various isoforms with apparent molecular mass of 30 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and 60 kDa on gel chromatography. Sequence homology among the various isoforms ranges from 22% to100%. The beta, gamma, and theta isoforms are found in tissues of the nervous system.

 

Detectable 14-3-3 protein in cerebrospinal fluid (CSF) specimems is indicative of substantial, relatively rapid, neuronal destruction. Increased CSF concentrations of 14-3-3 proteins have been described in patients with various forms of Creutzfeldt-Jakob disease (CJD), some other rapidly progressive dementias, and a large range of other vascular, inflammatory, neoplastic, and metabolic central nervous system (CNS) disorders (see Cautions), which can be associated with significant and rapid neuronal destruction.

 

The main clinical use of 14-3-3 measurements is in the differential diagnosis of dementia, in particular to distinguish CJD and its variants from other dementias. The most common forms of dementia (progressive multi-infarct dementia and Alzheimer disease) are uncommonly associated with elevated CSF levels of 14-3-3, presumably because of their slow pace of progression.

 

CJD is an incurable neurodegenerative disease caused by accumulation of self-catalytically misfolded endogenous prion proteins in the CNS. Its cause is most commonly sporadic, but it can be inherited (variations that predispose to misfolding) or acquired (iatrogenic transmission by infected human tissues or tissue extracts, surgical procedures, or by ingestion of some animal products that contain misfolded prion proteins).

 

The diagnosis of CJD is highly complex and involves clinical history and neurologic examination, electroencephalographs (EEG), magnetic resonance imaging (MRI), and exclusion of other possible causes of dementia, in addition to CSF examination. Several, slightly different scoring systems are in use to integrate these parameters into a final diagnosis of possible, probable, or definite CJD. The most widely accepted of these scoring systems is the WHO set of diagnostic criteria for sporadic CJD from 2018 (see Interpretation).

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Normal: < or =2.0 ng/mL

Elevated: >2.0 ng/mL

Interpretation Provides information to assist in interpretation of the test results

In cerebrospinal fluid (CSF) specimens, a  14-3-3 protein concentration of 2.0 ng/mL or higher supports the diagnosis of Creutzfeldt-Jakob disease (CJD) in patients who have been carefully preselected based on various diagnostic criteria. CSF 14-3-3 measurement is particularly helpful in sporadic CJD, where it is used as one of several diagnostic criteria.

 

Sporadic CJD World Health Organization (WHO) diagnostic criteria from 2018:

1. Definitive CJD: Diagnosed by standard neuropathological techniques; and/or immunocytochemically; and/or Western blot confirmed protease-resistant PrP; and /or presence of scrapie-associated fibrils.

 

2. Probable CJD: Neuropsychiatric disorder plus positive RT-QuIC in cerebrospinal fluid (CSF) or other tissues OR

rapidly progressive dementia; and at least 2 of the following clinical features:

-Myoclonus

-Visual or cerebellar signs

-Pyramidal/extrapyramidal signs

-Akinetic mutism

AND a positive result on at least 1 of the following laboratory tests

-A typical EEG (periodic sharp wave complexes) during an illness of any duration

-A positive 14-3-3 CSF assay in patients with a disease duration of less than 2 years

-High signal in caudate/putamen on magnetic resonance imaging (MRI) brain scan or at least 2 cortical regions (temporal, parietal, occipital) either on diffusion-weighted imaging (DWI) or fluid attenuated inversion recovery (FLAIR)

AND without routine investigations indicating an alternative diagnosis.

 

3. Possible CJD: Progressive dementia; and at least 2 of the following clinical features:

-Myoclonus

-Visual or cerebellar signs

-Pyramidal/extrapyramidal signs

-Akinetic mutism

AND the absence of a positive result for any of the 4 tests above that would classify a case as “probable”
AND duration of illness less than 2 years
AND without routine investigations indicating an alternative diagnosis.

 

This criteria is based on a Global surveillance, diagnosis, and therapy of human transmissible spongiform encephalopathies: Report of a WHO consultation, February 9-11, 1998, Geneva, Switzerland; b) Zerr I, Kallenberg K, Summers DM, et al: Updated clinical diagnostic criteria for sporadic Creutzfeldt-Jakob disease. Brain 2009;132;2659-2668; and c) National CJD Research and Surveillance Unit at https://www.cdc.gov/prions/cjd/diagnostic-criteria.html assessed 3/17/2020

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Hemolyzed specimens will be rejected. Hemolysis causes falsely elevated 14-3-3 results. The 14-3-3 concentrations in 82 visibly blood-tinged cerebrospinal fluid (CSF) specimens were up to 281 ng/mL, with 74 specimens (90.2%) showing levels above the cutoff.

 

In addition, specimens may be determined to be unsuitable for testing if any of the following conditions are observed(1,2):

-Macroscopically hemolyzed

-Xanthochromic

-RBC counts >500 cells per mcL

-WBC counts >10 cells per mcL

 

The Mayo Clinic 14-3-3 assay is a quantitative assay for 14-3-3 theta/tau isoforms. All other assays are currently based on qualitative or semi-quantitative assessment of 14-3-3 by Western blot of CSF specimens. 14-3-3 results obtained by Western blot can't be compared directly with the Mayo Clinic 14-3-3 results. However, the published literature suggests comparable sensitivity and specificity ranges between the Mayo assay and Western blot assays.

 

Regardless of the method used, measurement of 14-3-3 protein in CSF should not be relied upon exclusively to establish the diagnosis of Creutzfeldt-Jakob disease (CJD). Increased concentrations of 14-3-3 protein in CSF have been described in a variety of central nervous system (CNS) diseases other than CJD that are associated with relative rapid (days to months, rather than months to years) destruction of significant amounts of CNS neuronal tissue. Elevation of 14-3-3 could be found in patients with viral encephalitis, paraneoplastic disorder, or a recent stroke. 14-3-3 protein can also be identified in a small subset of patients with diseases that can temporarily mimic CJD, such as Hashimoto encephalitis, metabolic encephalopathy and amyotrophic lateral sclerosis. Furthermore, false-positive 14-3-3 results are also found in patients with other types of dementia that have an unusual rapid evolution of the disease of less than 1 year.

 

In addition, severe acute CNS episodes of multiple sclerosis, cerebral vasculitides and angiopathies, mitochondrial encephalomyelopathies, CNS storage diseases, widespread or rapidly growing primary or secondary CNS and leptomeningeal tumors might result in 14-3-3 elevations.

Supportive Data

A total of 950 cerebrospinal fluid (CSF) specimens, including 14 from patients with definite (autopsy-proven) Creutzfeldt-Jakob disease (CJD), were tested for 14-3-3 protein. Using the cutoff from receiver operating characteristic curve (ROC) analysis, the sensitivity was 78.6% and specificity was 96.7%. This compares to neuron-specific enolase (NSE), which at a cutoff of 43 ng/mL had sensitivity of 78.6% and specificity of 94.0%. In another group of 30 clinically highly possible or probable CJD cases without histological confirmation, NSE was elevated in 25 (83.3%) and 14-3-3 in 21 (70.0%).

 

In 235 CSF specimens sent in for RBC and WBC counting (CJD was not suspected) the specificity was 94.5%. The 13 specimens that had elevated 14-3-3 results were from patients with disorders known to elevate CSF 14-3-3, such as Guillain-Barre syndrome and viral encephalitis.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Collins S, Boyd A, Fletcher A, et al: Creutzfeldt-Jakob disease: diagnostic utility of 14-3-3 protein immunodetection in cerebrospinal fluid. Clin Neuroscience 2000;7:203-208

2. Burkhard PR, Sanchez JC, Landis T, et al: CSF detection of the 14-3-3 protein in unselected patients with dementia. Neurology 2001;56:1528-1533

3. Aksamit AJ, Preissner CM, Homburger HA: Quantitation of 14-3-3 and neuron-specific enolase proteins in CSF in Creutzfeldt-Jakob disease. J Neurol 2001;57:728-730

4. Castellani RJ, Colucci M, Xie Z, et al: Sensitivity of 14-3-3 protein test varies in subtypes of sporadic Creutzfeldt-Jakob disease. Neurology 2004;63:436-442

5. Llorens F, Villar-Pique A, Hermann P, et al: Diagnostic Accuracy of Prion Disease Biomarkers in Iatrogenic Creutzfeldt-Jakob Disease. Biomolecules 2020 Feb 12;10(2):290