For such complicated medical tests, the basic hardware is strangely simple. Many diagnostics—from pregnancy to blood sugar tests—rely on sticky paper that captures molecules on its surface. But the typical type of material used, nitrocellulose, is expensive, limiting the global potential of paper-based diagnostic tests. It can also only capture large molecules.
Now, researchers have created a sticky paper that could open up the developing world to many new types of tests. They used a cheap industrial solvent and diluted it in water, then controlled the acidity of the solution, poured it into a Ziploc bag with some paper, let it sit, rinsed the paper and let it dry. The solvent is sometimes used as an adhesive, so the resulting paper is incredibly sticky and catch all types of molecules.
The researchers then used a special inkjet printer to print out the different markers on the paper that will indicate the presence of harmful molecules The group is opening up their methods to anyone who wants to print tests, so that there will be easily created tests for anyone who needs them, for any disease or disorder.
"We want to develop something to not just ask a single question but ask many personal health questions," the lead researcher said in a press release. "‘Is there protein in the urine? Is this person diabetic? Do they have malaria or influenza?’"
Other printable tests have become cheaper in recent months. A Cambridge-based nonprofit called Diagnostics For All has started printing a test for liver enzymes that costs just pennies to produce. Liver function tests are important for HIV patients. They are also working on a malaria and dengue fever test, and tests that farmers could use to check for food-borne pathogens in their crops. The test results could be interpreted through a smartphone app or a clinician.
Tests can make a big difference in treatment and outcomes. The World Health Organization estimated that in 2008 only 20% of patients with suspected malaria were being subjected to diagnostic tests; the rest were clinically diagnosed based on their symptoms. For malaria, a mistaken clinical diagnosis can lead to over-prescription of malaria treatment and increased drug resistance among malaria parasites as well as waste of limited drug supplies. We better get some stickier paper printed fast.