Doing More with Less

Human papillomavirus (HPV) DNA testing is regarded as the most sensitive screening method for cervical cancer, but it remains too costly and too complicated for use in resource-limited settings where cervical cancer burden is highest. In an effort to break down this barrier, researchers have  combined DNA amplification and lateral flow detection to create a prototype, sample-to-answer, point-of-care test for HPV16 and HPV18 DNA.

“DNA detection commonly relies on polymerase chain reaction (PCR), which requires extensive sample preparation and complicated instrumentation to cycle through temperatures and measure amplified DNA,” says lead researcher Kathryn Kundrod. “In contrast, isothermal amplification relies on additional enzymes to replicate DNA copies at a single temperature. This means the test can be carried out using a single-temperature heater, which is a much simpler instrument compared with the thermocycler required for PCR. Amplified DNA is then detected by lateral flow strips, which wicks samples down a paper strip to produce either a positive or negative test line, again reducing instrumentation complexity.”

They tested the prototype with synthetic samples, provider-collected clinical samples from the US, and samples collected from Mozambique. “It is critical to evaluate new technologies in diverse settings – including with different levels of resources – early in the development process,” explains Kundrod. “Though the test performed similarly in both settings, we saw false negatives in Mozambique that we did not see in the US. From this, we identified that samples collected in Mozambique had higher levels of cells due to the method of collection, which inhibited the test. This finding informed the need to improve sample preparation.”

The main aim of the prototype was to reduce instrumentation complexity and user steps while keeping costs low – a financial goal they achieved with a projected per-test cost of less than US$5 and an instrumentation cost of less than $1000. “The projected per-test cost was based on off-the-shelf reagent costs purchased at small scale, and we are optimistic that the cost could be further reduced when purchased in bulk. The instrumentation cost is based on the projected manufacturing cost of the heat block and the list price for a benchtop centrifuge,” says Kundrod, adding that, even at such a low cost, the test requires only six simple steps and takes just 45 minutes from sample to answer. “It also matches the sensitivity of commercially available HPV DNA tests and is more sensitive than Pap smears.”

Although HPV16 and HPV18 are responsible for 70 percent of cervical cancers and precancerous lesions (2), there are around 14 high-risk HPV subtypes altogether. Kundrod says they plan to expand the existing test to include additional HPV genotypes, as well as improve the sample preparation protocol for self-collected samples: “We are excited to offer a new approach to HPV testing that, with additional optimization, could expand access to HPV testing in resource-limited settings. Paired with point-of-care diagnostic tools and increased treatment capacity, tests like this could allow for single-visit screen-and-treat.”