Diagnosing TB on the Cheap

An inexpensive microscope, a cell phone and the Internet are the main ingredients in a promising method to diagnose tuberculosis in the poorest and most remote areas of the world.

The system is the work of a Peru-based research team led by Mirko Zimic, PhD '08, MHS '01, MSc, a professor at the Universidad Peruana Cayetano Heredia (UPCH), and Patricia Sheen, PhD '08. Zimic describes the technology as a "complement" to microscopic-observation drug-susceptibility (MODS).

That innovative TB diagnostic was developed in 2000 by Luz Caviedes, MHS '10, under the supervision of International Health professor Robert Gilman, MD, researchers from UPCH and others.

MODS is a cheaper, faster and more sensitive alternative to standard TB culture tests that can take as long as four months to detect multidrug-resistant tuberculosis (MDR-TB). Especially vulnerable are patients with a dual diagnosis of HIV and MDR-TB, Gilman says. Half of them may die within two months without appropriate treatment.

The breakthroughs of MODS, which can diagnose TB within 7 to 14 days, centered on the discoveries that Mycobacterium tuberculosis grows in liquid media faster than in solid media and that the rod-shaped TB colonies can be viewed microscopically. But the method presents formidable challenges for remote, low-resource regions in developing countries. It requires an inverted microscope, which costs about $5,000, as well as trained technicians, says Zimic.

Despite the benefits of MODS, which is in place in several developing countries, a critical shortage of TB diagnostics suitable for use in areas with few health services hampers efforts to control the disease, experts say. "You can't treat well if you can't diagnose well," says Gilman, who has conducted infectious disease research in Peru for more than 25 years.

To bring MODS technology to areas in need, Zimic's team set out to build a more affordable—and digitalized—inverted microscope. Parts include a $1 halogen lamp and stock optical components. Total cost: about $400.

In this model, a technician places the MODS assay plate containing a patient's sputum samples on the microscope and takes a digital photo. He then sends it, via Internet or cell phone, to a computer server at UPCH that analyzes the image using a mathematical algorithm. Within 15 seconds, the diagnosis is delivered by text message or email to the lab.

Studies on proof-of-principle experiments, published in PLoS ONE and the Journal of Microscopy, confirmed the method's accuracy.

Now, Zimic's research team is at work on a pilot project in the Trujillo region of northwest Peru to test TB telediagnostics based on MODS. The goal is to bring the system to low-resource areas with high TB burdens. His lab is also working on image-analysis diagnostics to analyze Pap smears and skin lesions.

Says Zimic: "If you have an algorithm to interpret the images remotely, then you can use the same method."