Michael Harper for redOrbit.com – Your Universe Online
Engineers from the University of Washington (UW) have developed what they believe to be an accurate and effective skin test for diagnosing tuberculosis.
Current tests are difficult to administer and can often yield inaccurate results. Using a patch with an array of embedded microneedles, doctors and nurses could one day administer a tuberculosis (TB) test as easily as they could place a bandage on a small wound. Doctors, teachers and those who travel to other countries are often given a TB test to ensure they’re free of the respiratory infection. As TB can live dormant in a person’s lungs for years, it’s important that any skin test get accurate results every time.
A recent study shows one-third of the global population may carry latent TB, an inactive variety of the disease. This latent TB will turn active in about five to ten percent of those who carry the inactive disease, according to the Philippines Star.
According to senior author and UW assistant professor of materials science and engineering Marco Rolandi, the current method of administering a TB skin test requires a steady hand. A small amount of a substance called PPD tuberculin is injected into the dermis of the forearm, or the layer beneath the skin. If a hard and red bump appears in two to three days after the injection, it’s likely a TB infection is present. The size of the bump can determine the severity of the infection.
This test isn’t always accurate, however, and those administering the test could inject the PPD in the wrong area. For instance, the PPD could be administered too high and into the skin or too low and past the dermis. Moreover, if the needle isn’t inserted at the right angle, the PPD may not be injected properly.
Rolandi says his team’s microneedle patch eliminates potential error by placing an array of tiny, biodegradable needles on a single piece of material.
“With a microneedle test there’s little room for user error, because the depth of delivery is determined by the microneedle length rather than the needle-insertion angle,” explains Rolandi.
This test is painless and easier to administer than the traditional skin test with a hypodermic needle.
Rolandi’s UW team partnered with the Infectious Disease Research Institute in Seattle to develop the microneedle patch and say they believe this is the first time such a patch has ever been developed.
“It’s like putting on a bandage,” Rolandi said. “As long as the patch is applied on the skin, the test is always delivered to the same depth underneath the skin.”
The UW team first tested the patch on guinea pigs and found the test gave the same results as a standard and correctly-administered hypodermic needle test. Rolandi also says the patch could be more affordable to those living in areas where health care is expensive.
Microneedles have been used in other medical and therapeutic applications before, delivering drugs to people’s arms or legs. These patches are often made of metals or silicon, but the UW and Infectious Disease Research Institute felt it important to develop a biodegradable option. Their patch, therefore, is made of silk and chitin, a main component in the exoskeleton of crabs, lobsters, shrimp, and cicadas. This material has proven strong enough to break the skin and deliver the PPD tuberculin used in TB tests.
Rolandi and paper co-author Derek Carter say they hope the patch will prove successful enough to one day be a commercially available product.