The buffer liquid is also called antigen extraction solution and is not toxic. It’s composed of
- 97.9031% Water
- 1.0% Non-Toxic Detergents
- 0.85% NaC
- 0.0346% NaH2PO4
- 0.2123% Na2HPO4
The short answer is it’s highly unlikely.
Ethylene oxide is a gas that is commonly used to sterilize many different types of medical devices, including swabs used in test kits.
The sterilization process consists of a number of highly controlled and monitored stages, including removing ethylene oxide after treating the swabs. The amount of residual EO that is allowed has been set (by the international standard ISO 10993-7:2008) according to contact time of the medical device with the person. Contact time is divided into 3 categories: limited, prolonged, and permanent duration.
The swabs used in lateral flow test kits fall under the category of limited contact time. These limits are not further divided by body weight and therefore the limits set are also applicable for children.
These allowable limits were selected to ensure that any residual levels present on the medical device after sterilization pose minimal risk.
The average time of contact for a single test (around 20 seconds) and the current testing regimen (twice a week), means that each person is exposed to any residue on the swab for around 40 seconds per week. Calculating from the allowed residues, a person would need to be tested twice a week for over 40 years for the total contact time to be in a higher contact category. Therefore, the manufacturer’s original calculations that these swabs are in the ‘limited’ contact category are still valid for the current testing regimen.
There are two main reasons that cause Innova LFD test kits failure.
- Not enough sample volume loaded to the test cassette (need 2 drops).
- Sample viscosity is too high.
The UK real-world practice indicates the estimated false positive rate is low as 3/10,000. While there is a very rare chance that individual nasal specimen contains materials that can cross-react with the test kit agent, our internal studies have found that samples with low ph values generally can produce false positive results.
LFD’s false negative results is often identified by comparing to PCR results.
LFD detects the infectious and PCR detects the infected. The LFD false negative rate rises when compared with PCR results because PCR tests detect not only individuals currently considered to be infectious but also individuals who are no longer considered infectious but still carry residual viral RNA.
While PCR has been used as the gold standard in detecting COVID infections, more and more studies have pointed out the flaws in PCR results. For example, a recent study published on Journal of Infection has found that “more than half of individuals with positive PCR test results are unlikely to have been infectious, RT-PCR test positivity should not be taken as an accurate measure of infectious SARS-CoV-2 incidence. Our results confirm the findings of others that the routine use of ‘positive’ RT-PCR test results as the gold standard for assessing and controlling infectiousness fails to reflect the fact that 50-75% of the time an individual is PCR positive, they are likely to be post-infectious.”
Independent studies have demonstrated that the Innova rapid antigen test detects 99.8% of infected individuals who are infectious to others and has a specificity of 99.9% to 99.97% from over 1.7 million tests. In summary, the false negative rate for Innova LFD is very low in identifying infectious individuals.