Instaswab qPCR sensitivity
Leading nasal swab for Covid-19 testing (including Delta variant) by the numbers
Side by side lab study demonstrates OPT’s InstaSwabTM superior qPCR sensitivity over flocked and polyester swabs.
In an experimental study, OPT InstaSwab™ showed significantly improved collection and elution efficiency as compared to both the Copan FLOQSwab and traditional polyester swabs. The enhanced efficiency of InstaSwab™ has the potential to increase the limit of detection and sensitivity of molecular assays up to an order of magnitude thereby improving assay performance and reducing the likelihood of false negatives.
- High efficiency specimen elution at concentrations one order of magnitude lower than conventional swabs
- Boost sensitivity of the PCR assay
- Potential for detecting early stage infection and reduction in false negatives
According to a recent study conducted by Harvard Medical School, the best-in-class PCR assay for detecting COVID needs at least 100 copies of the viral gene in each milliliter of transport media, while the least sensitive one may require 10,000 fold more (over 1,000,000 copies per millimeter). The higher viral gene concentration needed, the higher likelihood that a patient with the virus may be missed, something called a “false negative”.
Nasal swabs, the essential tool for sample collection, have long been missing from the discussion. In a general context, the swabs perform dual functions: to collect specimens from the patients, and to release them into media for the assays. Mishaps in either step will reduce the specimens available for the test, and in turn decrease test sensitivity. As shown in a recent study, inadequate swabbing and specimen elution resulted in low specimen quality and delayed diagnostics of COVID-19, which led to both social and economical costs.
OPT Industries demonstrated this with an_in vitro_test. They placed 150 microliters of liquid droplets into a series of vials. Each droplet had COVID-19 viral gene dissolved in it to mimic specimens from positive patients. The concentrations ranged from 100,000,000 copies per milliliter to 1,000 copies per milliliter in different droplets. The researchers compared polyester swabs, flocked fiber swabs, and InstaSwabs™ when collecting these droplets and placed them in the transport media to have the samples eluted out. The concentrations of viral gene released from the swabs were analyzed by qPCR test.
It was found that across all concentrations, InstaSwabs™ were more effective in collecting and releasing specimens into the detection assay. On average, InstaSwabs™ were able to transfer 63% of the target viral gene into the machine, while flocked fiber swabs transferred 36% and polyester swabs transferred 14%. Flocked fiber swabs and polyester swabs failed to provide enough samples for the assay to detect in extremely low viral concentrations, such as 1,000 copies/mL and less, resulting in false negatives. However, InstaSwabs™ still maintained high efficiency and delivered results, suggesting the possibility of enhancing PCR sensitivity by at least one order of magnitude.
Conventional swabs are made from natural (cotton) or synthetic (polyester, nylon, etc) fibers. Although the dense, fibrous structures are capable of absorbing liquids well, part of the sample often remains trapped in the fibers instead of being fully released into the transport media. This becomes a source of low sample quality and thus, increases the potential of false negatives. Engineers at OPT Industries developed a method of rationally designing and manufacturing swabs with structures that exceed existing swab performance requirements. They removed the dense fibers and replaced them with dedicated mesh-shaped microstructures of 100 micron (0.004’’) resolution. OPT has named these improved collection devices InstaSwab™ for their microstructured bulbs that not only collect samples as efficiently as traditional swabs, but release the sample completely and almost instantly when placed into the transport media.
This study confirms that in terms of diagnostics, the efficiency of the sample collection device matters greatly. Using a high performance device, such as InstaSwab™, it is possible to boost the sensitivity and reliability of an assay by enabling pathogen detection at considerably low concentrations. This is an important enhancer for detecting diseases at their early stages when the pathogen concentration could be extremely low. In a scenario where samples are collected by individuals in a home setting and without medical supervision, InstaSwabs™ can improve the sample recovery and make the test kits more reliable. Fast, efficient elution can also shorten the time to complete an assay, reducing laboratory costs for the testing companies.
This work was a collaboration between OPT Industries and Planobo. PCR tests were performed through the Boston University Medical Center.