New ultra-sensitive test for cancer, HIV developed

A new ultra-sensitive test designed to detect diseases including HIV and cancer may prove 10,000 times more effective than current diagnostic tools, Stanford scientists say.
When a disease - whether it is a cancer or a virus like HIV - begins growing in the body, the immune system responds by producing antibodies.
Fishing these antibodies or related biomarkers out of the blood is one way that scientists infer the presence of a disease.
This involves designing a molecule that the biomarker will bind to, and which is adorned with an identifying "flag."
Through a series of specialised chemical reactions, known as an immunoassay, researchers can isolate that flag, and the biomarker bound to it, to provide a proxy measurement of the disease.

The new technique, developed in the lab of Carolyn Bertozzi, a professor of chemistry at Stanford University in US, augments this standard procedure with powerful DNA screening technology.

The chemists have replaced the standard flag with a short strand of DNA, which can then be teased out of the sample using DNA isolation technologies that are far more sensitive than those possible for traditional antibody detections.
"This is spiritually related to a basic science tool we were developing to detect protein modifications, but we realised that the core principles were pretty straightforward and that the approach might be better served as a diagnostic tool," said Peter Robinson, a graduate student in Bertozzi's group.

The researchers tested their technique, with its signature DNA flag, against four commercially available, US Food and Drug Administration (FDA)-approved tests for a biomarker for thyroid cancer.
It outperformed the sensitivity of all of them, by at least 800 times, and up to 10,000 times, researchers said.
By detecting the biomarkers of disease at lower concentrations, physicians could theoretically catch diseases far earlier in their progression.
"The thyroid cancer test has historically been a fairly challenging immunoassay, because it produces a lot of false positives and false negatives, so it was not clear if our test would have an advantage," Robinson said.

A clinical trial underway in collaboration with the Alameda County Public Health Laboratory will help evaluate the technique as a screening tool for HIV, researchers said.
Early detection and treatment of the virus can help ensure that its effects on the patient are minimised and reduce the chance that it is transmitted to others.
"In contrast to many new diagnostic techniques, this test is performed on pre-existing machines that most clinical labs are already familiar with," said Cheng-ting Tsai, a graduate student in Bertozzi's group.
The research was published in the journal ACS Central Science.