iPhone Microscope Yields Modest Results in Worm Diagnosis

Larry Hand

March 11, 2013

A mobile telephone transformed into a microscope yielded "only modest" accuracy and sensitivity but holds future promise when used to diagnose soil-transmitted helminths compared with traditional light microscopy, according to an article published online March 11 in the American Journal of Tropical Medicine and Hygiene.

Isaac I. Bogoch, MD, from the Divisions of Internal Medicine and Infectious Diseases, Toronto General Hospital, Ontario, Canada, and colleagues conducted a proof-of-concept study that was integrated into a clinical trial on the safety and efficacy of anthelmintic drugs against helminth infections in school-aged children on Pemba Island, Tanzania. All patients were treated with 400 mg albendazole at the end of the study.

Mobile phone microscope. Photo credit: Isaac Bogoch

The researchers mounted a 3-mm ball lens to the camera of an iPhone 4S (Apple) with double-sided tape. They punctured a small hole in the tape and centered the lens over the telephone camera lens. They placed smear slides of stool samples close to the tape, so that less than 1 mm of space separated the slide and lens. The lens captured the stool sample from atop the slide, which was illuminated from below (estimated equivalence of 50 - 60× magnification). A cellophane strip over the stool prevented lens contamination.

The researchers assessed 199 smears by using both mobile telephone microscopy and conventional microscopy. They found that the mobile telephone microscope captured a sensitivity of 69.4% and a specificity of 61.5% in detecting helminth infections compared with light microscopy. Although detection was high for some helminth species (81.0% for all Ascaris lumbricoides), the mobile microscope only captured 14.3% of hookworms compared with light microscopy. On 26 slides with no visualized helminth eggs, the mobile microscope had a 61.5% concordance rate with light microscopy, the researchers write. In addition, the mobile telephone microscope had several false-positive results compared with none for the light microscope.

"Compared with conventional light microscopy, our simple mobile phone microscope achieved only modest diagnostic yield," the researchers write. "However, we feel that the mobile phone microscope holds promise as a novel point-of-care test for intestinal helminth diagnosis, because it is portable, easy to construct and use, and relatively inexpensive. More importantly, mobile phones have become ubiquitous worldwide."

When sensitivities reach or exceed 80% in future testing, the mobile telephone microscope would likely be of clinical use, the researchers write. "[A]lthough it is not sensitive enough for immediate application, it is getting close to acceptable diagnostic characteristics," they write. "For example, if a clinical decision rests on whether a patient has a soil-transmitted helminth infection, seeing an egg, regardless of the species, should prompt clinicians to treat with an anthelmintic drug with broad spectrum of activity."

Soil-transmitted helminths are a major public health issue in developing countries, especially in rural areas with inadequate sanitation, and affect about 2 billion people worldwide.

This research was supported by the Medicor Foundation. One author is financially supported by the Swiss National Science Foundation. The other authors have disclosed no relevant financial relationships.

Am J Trop Med Hyg. Published online March 11, 2013.