Researchers from Washington State University have come up with a diagnostic rig that can use a smartphone, a prism, and an ELISA plate to detect cancer. In the controlled settings of their lab, with the high-purity reagents they had to work with, the researchers were able to detect the cancer marker interleukin-6 (IL-6) with 99% accuracy.

Obviously results in the field will not reflect the near-ideal conditions of lab work. The concepts, though, are solid. The rig consists of a backlit ELISA assaying plate with 96 wells, a “microprism array,” and a 3D printed cradle that holds a smartphone with a camera. The diagnostician using the rig would take samples from a patient, put them in the assay plate, and turn on the backlight. Light would then shine up through the samples in the plate, through the prism, and into the smartphone’s camera — from where the technician can use an app to analyze the light from each individual well in the ELISA plate by its color. Which colors turn up tell the results of the ELISA test.

The whole thing rests on the idea that IL-6 is “closely linked” to a variety of cancers of the lung, liver, breast, and skin. And it is. IL-6 is a protein that the human body produces in response to an alert in the immune system; it induces B cells to make more antibodies, which (when they’re working correctly) glom onto “non-self” invaders and tag them for destruction and disposal. Everyone should have a little IL-6 circulating in their bloodstream. In patients with advanced or metastatic cancers, though, there tends to be a lot. It’s just that IL-6 is also linked to depression and mood disorders, so you can’t rightly look at a patient’s blood, see lots of IL-6, and say with certainty “You have cancer.” But you can look at a patient’s blood, see lots of IL-6, and say “You probably have a condition activating your immune defenses, and you ought to go get a more detailed blood panel done.” For a patient who’s come in worried that their symptoms could be cancer, it would be a useful adjunct to the office visit, just because antibody reactions are fast, so immune assays are relatively quick.

This type of assay isn’t limited to cancer diagnostics, either. Because it has the capacity to tell with confidence whether a thing is present or absent in a sample, all of a sudden the immune-system diagnostics of the ELISA assay can be used for something other than allergies or HIV. To test for a protein, you need an antibody or something else that complexes with that protein. Put the antibody in the ELISA wells, add the person’s fluid sample, and read the wavelengths of light it puts off. It would be almost instant, and with the right housing and disposable accessories, it could be an in-office diagnostic triage tool bar none.

The science is solid. Everything will depend on the physical execution of the science, and the corners they have to cut to get it manufactured. But since the rig they used was built out of Mag-Lite bulbs as the backlight and the cradled iPhone’s stock camera was sufficient to reliably focus the light out of the prism, clearly consumer-grade equipment is sufficient to get results.

Also, this is another step toward an actual consumer tricorder. What’s the tally now? By my count, Geiger counters, CCD cameras that can see in the infrared, a variety of laser options, zoom lenses, projector lenses, and now spectrometry and bioassay analysis can be packed into a handheld no larger than the phablets people are still clearly willing to use. And this is with today’s consumer tech. Imagine how sleek tricorders are going to be when they actually get built.