New micro-needle patch to replace standard TB skin test

Scientists have developed a novel patch with tiny, biodegradable needles that can penetrate the skin and accurately diagnose tuberculosis.
The standard diagnostic test for tuberculosis is difficult to give, because a hypodermic needle must be inserted at a precise angle and depth in the arm to successfully check for tuberculosis, researchers said.
Now, a team led by University of Washington engineers has created a patch with tiny, biodegradable needles that can penetrate the skin and precisely deliver a tuberculosis test.
"With a micro-needle test there's little room for user error, because the depth of delivery is determined by the micro-needle length rather than the needle-insertion angle," said senior author Marco Rolandi.

"This test is painless and easier to administer than the traditional skin test with a hypodermic needle," said Rolandi.
A tuberculosis test is a common precautionary measure for health care professionals and international travellers. The bacterial infection usually attacks the lungs and can live in an inactive state for years in the body.

A diagnostic test involves an injection in a person's arm. Within two or three days, a swollen, firm bump will appear if an infection is present.
Rolandi's lab and collaborators at the Infectious Disease Research Institute in Seattle believe this is the first time micro-needles made from biomaterials have been used as a diagnostic tool for tuberculosis.

They say their test will be easier to use, less painful and has the potential to be more successful than the standard tuberculosis skin test.
Researchers tested the patch on guinea pigs and found that after the micro-needles were inserted using the patch, the skin reaction associated with having a tuberculosis infection was the same as using the standard hypodermic needle test.
A micro-needle patch test has potential as a simpler, more reliable option than the traditional tuberculosis test for children who are needle-shy, or in developing countries where medical care is limited, Rolandi said.
"It's like putting on a bandage," Rolandi said.

With the standard test, if a hypodermic needle is inserted at the wrong angle, the solution to check for tuberculosis is injected too deep or too shallow into the skin, and the test fails.
Micro-needles have been used in recent years as a painless alternative to hypodermic needles to deliver drugs to the body.
Micro-needles on a patch can be placed on an arm or leg, which then create small holes in the skin's outermost layer, allowing the drugs coated on each needle to diffuse into the body.
The study was published in the journal Advanced Healthcare Materials.