In order to determine whether a person is infected with Mycobacterium tuberculosis, the Mantoux tuberculin skin test (TST) remains the standard method worldwide. This test is a common precautionary measure to screen the teachers, health care professionals and international travelers for tuberculosis (TB). However, reliable administration and reading of the TST requires standardization of procedures, training, supervision, and practice. It is performed by intradermally injecting 0.1 ml of tuberculin purified protein derivative (PPD) into the inner surface of the forearm. The injection should be made with a tuberculin syringe, with the needle bevel facing upward and inserted as a precise angle and in to depth in the arm to successfully test for TB.
A team of researchers from University of Washington has created a patch with tiny, biodegradable needles that can penetrate the skin and precisely deliver a tuberculosis test. Since the depth of delivery is determined by the length of microneedle, rather than the needle-insertion angle, there is little room for individual user error. This test method is painless and relatively easier to administer.
The researchers tested the patch on guinea pigs and found that after the microneedles were inserted using the patch, the skin reaction associated with having a TB infection was the same as when using conventional hypodermic needle. A microneedle patch which is just like putting on a bandage, has potential as a simpler, more reliable option than the traditional Mantoux test, especially for children who are needle-shy, or in developing countries where medical care is limited,
The image shows the comparison of a microneedle tuberculosis test with a traditional test administered with a hypodermic needle. The lower images show needle-depth problems that can occur with the conventional test. Image courtesy: Marco Rolandi, UW