A new diagnostic test could help doctors better identify prion diseases in living humans. Reporting online yesterday in Nature Medicine, researchers described a simple assay for detecting prions in cerebrospinal fluid taken from people suspected of suffering from Creutzfeldt-Jakob disease (CJD) that is more accurate and sensitive than existing tests that rely on post-mortem brain tissue.

“This technique allows definitive ante-mortem confirmation of CJD,” Ryuichiro Atarashi, a microbiologist at Nagasaki University in Japan who led the study, told Nature News.

The test involves using a shaking assay known as ‘real-time quaking-induced conversion’, which, if prions are present in the sample, causes other proteins to become misfolded. By adding a dye, researchers can then assess whether the number of abnormal proteins has increased.

In pilot studies involving 18 people with CJD, Atarashi and his colleagues showed that the prion disease was correctly diagnosed in 15 of the subjects. And in subsequent blind trials on 30 cerebrospinal fluid samples, the technique correctly pinpointed close to 90% of the CJD cases. The test also created no false positives in people confirmed not to suffer from the prion disease, the researchers found. By comparison, tests for levels of a CJD-specific protein known as 14-3-3 created far more incorrect diagnoses.

Steven Collins, director of the Australian National Creutzfeldt-Jakob Disease Registry and a co-author on the study, says that the new assay is “much more aligned to the actual disease” the previous diagnostics. “The hope is if we can more accurately and confidently say that the illness is CJD, then patients won’t be subjected to unnecessary invasive tests,” he told ABC.

Image of brain from CJD patient via Wikimedia