Mass Solution

Existing antibody-based tests for infectious diseases such as malaria are fairly cheap, but even a dollar per test can be prohibitively expensive if the target population comprises millions of people in the world’s poorest countries. Now a better screening tool is coming to the fore: mass spectrometry, a common chemistry tool that precisely identifies molecules on the basis of their atomic weight. A portable machine built at Johns Hopkins University is more sensitive than antibody-based tests, covers all four kinds of malaria, and costs very little to operate.

That could make it a perfect tool for initial malaria screening of large populations, says Andrew Feldman, the physicist who developed the test at the Johns Hopkins University Applied Physics Laboratory in Laurel, MD. “My guess is we are going to be the gold standard for that kind of screening analysis,” says Feldman, who is planning clinical trials. He found that a malarial by-product known as heme-an iron-containing molecule thrown off by the malaria-causing Plasmodium parasite as it “eats” hemoglobin-has a clear signature, which a mass spectrometer can recognize easily.

Unfortunately, although it is cheap to operate, the briefcase-size, 13-kilogram instrument currently costs about its weight in gold. Johns Hopkins has created a startup, Matrix Instrument, to manufacture it, but Feldman estimates that even produced in quantity, each unit would would tip the scales at $25,000. That sum, however hefty, might still be affordable for a mass-screening project.

Malarial screening is just one likely use for the new diagnostic tool. Using mass spectrometry, “you can detect many, many things with one instrument,” says physical chemist Wayne Bryden, leader of the Johns Hopkins project that built the machine. Doctors who use the instrument don’t even need to know what they are looking for; everything weighs something. Bryden hopes the malaria application will be the first step toward an all-purpose diagnostic device for hospital and health clinic settings-not to mention military applications such as sensing chemical- and biological-warfare agents.