Microfluidic chip to quickly diagnose the flu

Researchers miniaturize a more expensive diagnostic test into a single-use microfluidic chip roughly the size of a miscroscope slide.

During the H1N1 flu pandemic of 2009, which spread across more than 200 countries and killed more than 18,000 people, it became clear that flu diagnosis was often taking too long and resulting in frequent false negatives.

Roughly the size of a standard microscope slide, the chip currently costs $10 and produces results in a few hours. Boston University

Today, researchers from Boston University, Harvard, and the Beth Israel Deaconess Medical Center are reporting in the journal PLoS ONE that they have built a microfluidic chip that rivals in accuracy the gold-standard diagnostic test known as RT-PCR but is faster, cheaper, and disposable.

For their four-year study, which involved 146 patients with flu-like symptoms and was funded by the National Institutes of Health, researchers essentially miniaturized the RT-PCR test into a chip the size of a standard microscope slide and analyzed two types of nasal specimens as accurately as the lab-scale method.

"We wanted to show that our technique was feasible on real-world samples," Catherine Klapperich, an associate professor who led the study, said in a news release. "Making each chip single-use decreases the possibility of cross-contamination between specimens, and the chip's small size makes it a good candidate for true point-of-care testing."

The chip is made of a top column that extracts RNA from signature proteins associated with the influenza A virus, a middle chamber that then converts the RNA into DNA, and a climate-controlled lower channel that replicates the DNA enough times to be detected by an external reader.

The team found that their chip not only rivals RT-PCR, they say it also outperformed other common flu diagnostic tests, including viral culture (which typically takes days to a week for results), rapid immunoassays (imagine a pregnancy test that is only 40 percent accurate), and DFA (direct fluorescent antigen testing, which is lab-intensive).

"The new test represents a major improvement over viral culture in terms of turn-around time, over rapid immunoassay tests in terms of ... the ability to detect the virus from minimal sample material, and over DFA and RT-PCR in terms of ease of use and portability," Klapperich said.

The team is currently working to further improve its chip so that it costs just $5 and can produce results in an hour.

Many people with the flu don't actually seek out medical care, according to the Centers for Disease Control and Prevention, but the small number who do are tested and often at greater risk of serious complications and even death. A faster, more affordable test with fewer false negatives could help stem outbreaks and ultimately save lives.

 

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