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Diagnosis

CSF proteins 130 and 131 were specific for diagnosing Creutzfeldt-Jakob disease

ACP J Club. 1997 Mar-Apr;126:44. doi:10.7326/ACPJC-1997-126-2-044

Related Content in this Issue
• Companion Abstract and Commentary: Brain protein 14-3-3 was a sensitive test for Creutzfeldt-Jakob disease


Source Citation

Zerr I, Bodemer M, Otto M, et al. Diagnosis of Creutzfeldt-Jakob disease by two-dimensional gel electrophoresis of cerebrospinal fluid. Lancet. 1996 Sep 28;348:846-9.


Abstract

Objective

To assess the usefulness of proteins 130 and 131, detected by 2-dimensional gel electrophoresis (2-DE) of cerebrospinal fluid (CSF), in the diagnosis of Creutzfeldt-Jakob disease.

Design

Blinded comparison of 2-DE of proteins 130 and 131 with clinical, electroencephalographic (EEG), and neuropathologic criteria.

Setting

Germany.

Patients

182 patients (age range 25 to 85 y, 68% women) who were suspected of having Creutzfeldt-Jakob disease.

Description of tests and diagnostic standard

Serum, plasma, and CSF samples were obtained from patients. 2-DE was done on CSF samples, and gels were assessed for the presence or absence of proteins 130 and 131. Concentrations of neuron-specific enolase (NSE) were also measured in CSF; a concentration of > 35 ng/mL was the cutoff for a positive test result. The diagnostic standard was based on clinical, EEG, and neuropathologic criteria, according to which patients' diagnoses of Creutzfeldt-Jakob disease were classified as definite (neuropathologic verification); probable (progressive dementia < 2 y, periodic sharp-wave complexes on EEG, and 2 of 4 neurologic findings); possible (clinical criteria for probable disease without the EEG results); and other (longer duration of dementia, 1 of 4 neurologic findings, no EEG abnormalities). The 2-DE was assessed by 2 evaluators blinded to the clinical diagnosis.

Main outcome measures

Sensitivity and specificity of 2-DE and NSE.

Main results

Diagnoses of Creutzfeldt-Jakob disease were classified as definite in 58 patients, probable in 46 patients, and possible in 34 patients. 44 patients were considered to have a diagnosis other than Creutzfeldt-Jakob disease. Proteins 130 and 131 were detected in 47 of the 58 patients with definitive diagnoses (sensitivity 81%, 95% CI 68% to 90%) and in none of the 44 patients with other diagnoses (specificity 100%, CI 93% to 100%). {The likelihood ratio [LR] of a positive test result approached infinity, and the LR of a negative test was 0.19.}* The sensitivity of NSE > 35 ng/mL was 79% (CI 66% to 88%), and the specificity was 91% (CI 77% to 97%). {LR+ was 9 and LR- was 0.23.}* Proteins 130 and 131 and NSE > 35 ng/mL were both present in 45 patients (78%) with definite Creutzfeldt-Jakob disease.

Conclusions

2-dimensional gel electrophoresis for proteins 130 and 131 in cerebrospinal fluid was specific and moderately sensitive for the diagnosis of Creutzfeldt-Jakob disease. Elevated concentrations of neuron-specific enolase correlated with the presence of proteins 130 and 131.

Source of funding: Bundesministerium für Gesundheit.

For article reprint: Dr. T. Weber, Neurologische Klinik, Marienkrankenhaus, Alfredstrasse 9, D-22087 Hamburg, Germany.

*Numbers calculated from data in article.


Commentary

What does the practicing clinician need to know about the transmissible neurodegenerative diseases caused by prions? Prions, or proteinaceous infectious particles, are not viruses. They are smaller than viruses and are resistant to the usual methods that inactivate nucleic acids. They do not induce an immune response. The gene encoding for the human prion particle has been identified on the short arm of chromosome 20. Yet to be determined is the normal function of human prion protein in cellular metabolism or the mechanism of transformation of this protein to its pathologic isoforms and the subsequent clinical expression of neurodegenerative disease (1).

In humans, prions are responsible for Creutzfeldt-Jakob disease and the recently important bovine spongiform encephalopathy (BSE) found in cattle in Great Britain. 10% of cases of Creutzfeldt-Jakob disease can be familial and can be transmitted by an autosomal dominant pattern related to a point mutation of the encoding gene. Evidence exists for a protective effect of heterozygosity of the prion protein gene against the more common sporadic form and the fearsome iatrogenic transmission. Accidental spread by contaminated corneal transplants and neurosurgical grafting procedures has been well documented. Cadaveric sources of growth hormone and human gonadotropins have also been described as sources of the disease.

Clinically, Creutzfeldt-Jakob disease is characterized by rapidly evolving dementia, myoclonus, and a highly suggestive EEG pattern. Pathologic features are a severe loss of neurons, vacuolization, and an absence of inflammatory cells. It is intriguing how Creutzfeldt-Jakob disease prions aggregate to form amyloid filaments and plaques.

A definitive diagnosis of Creutzfeldt-Jakob disease still depends on histologic examination of brain tissue. Recently reported cases of a variant of Creutzfeldt-Jakob disease (absence of the periodic sharp-wave complexes on EEG) and its potential link to BSE have increased the urgency for a rapid and easily applied method with which to diagnose Creutzfeldt-Jakob disease (2). An accurate and practical premortem diagnostic test would be useful in identifying Creutzfeldt-Jakob disease for organ and blood donation screening. Zerr and colleagues have modified a previously described method with which to confirm and further define the sensitivity and specificity of testing for the concentration of 2 proteins (130 and 131) in the CSF of affected patients by 2-DE.

Hsich and colleagues have been able to use the simpler and more practical immunoassay of 14-3-3 proteins. They first showed that proteins 130 and 131 in CSF are in fact 14-3-3 proteins. They then showed an 88% specificity (which improves to 99% when patients with recent strokes and herpes encephalitis are excluded) of the immunoassay in the diagnosis of Creutzfeldt-Jakob disease. In animal studies, the overall specificity was an impressive 99%.

Hence, we now have an accurate CSF immunoassay to help diagnose transmissible spongiform encephalopathy in animals and humans. However, a clinical caveat is that 14-3-3 proteins may represent leakage from neuronal disruption of any cause (e.g., strokes or encephalitis); therefore, in patients with other neurologic disorders, clinical interpretation must be done with this in mind.

Clinicians may find this immunoassay useful in the proper clinical setting. Classic Creutzfeldt-Jakob disease may not be a diagnostic dilemma. However, in atypical cases, a positive immunoassay of 14-3-3 proteins may help to diagnose Creutzfeldt-Jakob disease. If it is shown that a breach can occur in the species barrier that prevents the transmission of BSE between cattle and humans, the most practical application of immunoassay of protein 14-3-3 may be to identify diseased animals and humans who are exposed to BSE.

Charles V. Guida, MD
Southampton HospitalSouthampton, New York, USA

Charles V. Guida, MD
Southampton Hospital
Southampton, New York, USA


References

1. Prusiner S. Molecular biology of prion disease. Science. 1991;252:1515-22.

2. Collinger J. New diagnostic tests for prion disease. N Engl J Med. 1996;335:963-5.