A new super-sensitive test developed by scientists spots markers for cancer or AIDS using the naked eye.
As it does not need sophisticated equipment, the test-tube technique should be cheap and simple, making it a a boon for disease detection in poor countries, the team wrote in Nature Nanotechnology on Sunday.
Researchers from Imperial College London used the technology to scan for molecules of p24, a marker for HIV infection, and Prostate Specific Antigen or PSA, an early indicator of prostate cancer.
Their method is used to analyse serum, a light-yellow fluid that is extracted from blood by a centifuge and is commonly used in health tests.
"If the result is positive for p24 or PSA, there is a reaction that generates irregular clumps of nanoparticles, which give off a distinctive blue hue in a solution inside the container," said a statement.
The reaction, in response to the presence of antibodies, occurred even at ultra-low concentrations of p24 or PSA.
"If the results are negative, the nanoparticles separate into ball-like shapes, creating a reddish hue. Both reactions can be easily seen by the naked eye."
Nanoparticles are microscopic clusters of atoms sized between one and 100 nanometres (a billionth of a metre), that are seen as a promising field of research for their potential in delivering medicines, for example.
The team said their visual sensor technology was 10 times more sensitive than existing standard methods for measuring p24 and PSA biomarkers -- molecules that can indicate the presence of disease.
It was able to detect minute levels of p24 in patients with low viral loads that went undetected using some existing tests.
The new method was also 10 times cheaper.
Study co-author Roberto de la Rica said the test would allow people to be diagnosed at an earlier state of disease, and thus treated sooner.
"We also believe that this test could be significantly cheaper to administer, which could pave the way for more widespread use of HIV testing in poorer parts of the world."
But study co-author Molly Stevens told AFP the method had yet to be tested in a large patient trial to confirm its usefulness.
As yet, the technique cannot pinpoint how big the concentration of HIV or cancer markers is.
"It is an 'on-off' test," Stevens cautioned. "It does not say specifically how many biomarkers are in blood, but only if they are present."