Currently there is no easy test available for this rare but fatal brain condition.
Instead, doctors have to take a sample of spinal fluid or brain tissue, or wait for a post-mortem after death.
What they look for is tell-tale deposits of abnormal proteins called prions, which cause the brain damage.
Building on earlier US work, Dr Graham Jackson and colleagues, from University College London, have now found it is also possible to detect prions in urine.
This might offer a way to diagnose CJD rapidly and earlier, they say, although there is no cure.
Creutzfeldt-Jakob disease (CJD):
CJD is a rare, but fatal degenerative brain disorder caused by abnormal proteins called prions that damage brain cells.
There are several forms of the disease:
- sporadic, which occurs naturally in the human population, and accounts for 85% of all CJD cases
- variant CJD, linked to eating beef infected by bovine spongiform encephalopathy (BSE)
- iatrogenic infection, caused by contamination during medical or surgical treatment
In the 1990s it became clear that a brain disease could be passed from cows to humans.
The British government introduced a ban on beef on the bone.
Since then, officials have kept a close check on how many people have become sick or died from CJD.
There is no known cure.
The study looked at urine samples from 162 people. Of these:
- 91 were healthy controls
- 34 had neurological disease that was not thought to be caused by CJD
- 37 had a diagnosis of CJD (20 of these were sporadic CJD)
The urine test gave no "false-positive" results - meaning it did not falsely suggest there was CJD in any of the patients known not to have the disease.
But it was less reliable when it came to detecting actual cases.
It accurately detected just under half of the sporadic CJD patients and even fewer of the vCJD patients.
The researchers hope they will be able to improve the test further so it can reliably detect all types of CJD.
Dr Jackson said: "Although there is currently no cure for this disease, an accurate and early diagnosis is extremely important for patients and their families.
"In the future, as trials of potential therapies become available, the earlier a patient can be diagnosed the more effective any treatment is likely to be.
"This test could be a critical step forward."
To date, more than 2,000 UK people are thought to have died from CJD.
In the UK, a person`s lifetime risk for developing sporadic CJD is about one in 5,000.
The government spends £5.5m a year on CJD surveillance and research.
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