Scientists have developed a handheld device that enables a smartphone to perform lab- grade medical diagnostic tests which typically require large, expensive instruments.

The USD 550 spectral transmission-reflectance-intensity (TRI) Analyzer attaches to a smartphone and analyses patient blood, urine, or saliva samples as reliably as clinic-based instruments that cost thousands of dollars.

"Our TRI Analyzer is like the Swiss Army knife of biosensing," said Brian Cunningham, professor at the University of Illinois at Urbana-Champaign in the US.

"It is capable of performing the three most common types of tests in medical diagnostics, so in practice, thousands of already-developed tests could be adapted to it," Cunningham said.

Researchers used the TRI Analyzer to perform two commercially available assays – a test to detect a biomarker associated with pre-term birth in pregnant women and the phenylketonuria (PKU) test for newborns to indirectly detect an enzyme essential for normal growth and development.

Their test results were comparable to those acquired with clinic-grade spectrometer instrumentation.

"The TRI Analyzer is more of a portable laboratory than a specialised device," said Kenny Long, lead author of the research published in the journal Lab on a Chip.

Among the many diagnostic tests that can be adapted to their point-of-care smartphone format is an enzyme-linked immunosorbent assay (ELISA), which detects and measures a wide variety of proteins and antibodies in blood and is commonly used for a wide range of health diagnostics tests.

The system is capable of detecting the output of any test that uses a liquid that changes colour, or a liquid that generates light output (such as from fluorescent dyes).

The TRI Analyzer operates by converting the smartphone camera into a high-performance spectrometer.

Specifically, the analyzer illuminates a sample fluid with the phone's internal white light-emitting diode (LED) flash or with an inexpensive external green laser diode.

The light from the sample is collected in an optical fibre and guided through a diffraction grating into the phone's rear-facing internal camera.

These optical components are all arranged within a three-dimensional (3D) printed plastic cradle.

The TRI Analyzer can simultaneously measure multiple samples by using a microfluidic cartridge that slides through an opening in the back of the cradle.

This ability to analyse multiple samples quickly and reliably makes the Analyzer suitable for patients who lack convenient access to a clinic or hospital with diagnostic test facilities or for patients with urgent health situations requiring rapid results.