Guideline Examines Diagnostic Accuracy of CSF 14-3-3 Protein in sCJD

September 19, 2012

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Testing for the 14-3-3 protein in spinal fluid may support the clinical diagnosis and other diagnostic tests used to diagnose sporadic Creutzfeldt-Jakob disease (sCJD) in patients who present with rapidly progressive dementia and are suspected of having sCJD. This is the primary finding in “Diagnostic Accuracy of CSF 14-3-3 Protein in Sporadic Creutzfeldt-Jakob Disease,” a new guideline from the AAN that was published electronically ahead of print on September 19, 2012, and appears in the October 2, 2012, print edition of Neurology®.

While the test may help when used in cases where doctors suspect sCJD may be present, the test is not accurate enough either to diagnose the disease or to rule out the disease with absolute certainty.

The usefulness of the 14-3-3 test will largely depend on a clinician’s judgment of the pretest probability of sCJD for a given patient. “Our analysis found that a pretest probability of about 20 percent to 90 percent for diagnostic accuracy should cue the physician that testing may be helpful,” said Taim Muayqil, MBBS, FRCPC, lead author of the guideline. Such judgments will reasonably consider the rarity of sCJD (incidence 1 per million per year), the patient’s clinical presentation, and the results of already obtained ancillary tests such as brain MRI. However, how the test should be used in conjunction with EEG and MRI findings suggestive of sCJD needs further investigation.

The authors also contend that only physicians experienced in dementia diagnosis should determine whether the 14-3-3 protein test is needed and how results should be understood. For circumstances wherein the physician thinks the likelihood of sCJD is extremely low or extremely high, testing for 14-3-3 would not be useful regardless of the result.  Further, the test results will not importantly change the probability of sCJD in patients who are unlikely to have sCJD to begin with. “Analyzing test results and understanding them in the context in which they are applied are key to making an accurate sCJD diagnosis,” said Muayqil. “A positive 14-3-3 assay result in patients who are unlikely to have sCJD should not distract the investigator from considering a different dementing illness, or, more important, a reversible cause of dementia.”

Read the guideline and access PDF summaries for clinicians and patients, a slide presentation, and a clinical example. For more information, contact Julie Cox at jcox@aan.com or (612) 928-6069.