Here's a test that detects the presence of abnormal proteins indicative of a deadly prion disease known as Creutzfeldt-Jakob Disease (CJD).
Known formally as transmissible spongiform encephalopathies (TSEs), prion diseases are rare and deadly diseases of the brain. Once infected, the prion particles self-propagates and converts other proteins to be malformed, leading to irreversible destruction of brain material. CJD is among diseases known to be caused by prions - “proteinaceous infectious particles.”
Among CJD cases, the majority (around 85 percent) is sporadic, meaning they occur randomly. The other cases come from inherited mutations, or contamination with infected surgical equipment. Around 70 percent of patients diagnosed with CJD die within one year of diagnosis.
The test, known as RT-QuIC (real-time quaking-induced conversion), amplifies any presence of prions to detectable levels. In some cases, the test requires cerebrospinal fluid; however in some cases, a nose swab may be sufficient for detection.
"Our results suggest that the application of RT-QuIC testing will improve the accuracy and speed of sporadic CJD diagnosis," the authors wrote in their publication. In particular, they reported the test had 100 percent sensitivity and specificity in a population of patients that had CJD and a healthy control population.
This accuracy is quite astonishing consider that most CJD diagnosis may not be made, or validate, until a post-mortem analysis of the brain can be done. Current testing methods can give indication that CJD is the right diagnosis, however, the accuracy of the diagnosis remains spotty. Some tests are designed to look for proxy proteins, such as tau proteins. These are associated with CJD but, as they aren’t actual prions, the diagnosis may not be 100 percent accurate.
In the worst case scenario, patients may be subject to a battery of tests only to be wrongly diagnosed with CJD and missing the opportunity to be appropriately treated by an available therapy. So while there are no current treatments for CJD, RT-QuIC can drastically reduce the number of false positives and misdiagnoses that occur. This means patients with CJD-like symptoms may have an opportunity to seek and receive the correct treatment on the first screening. Such efficiency could reduce the stress and burden on the patients, caretakers, and the healthcare system.
The new diagnostic test is limited in its ability to accurately detect the inherited form of CJD. In addition, since all of the patients in the validation had already shown clinical signs of CJD, the team can’t say if the test would be as accurate in people who are asymptomatic.
Additional sources: Live Science