Today, a paper available online reinforced concerns that the Abbott ID NOW, a rapid molecular (genetic) detection test for COVID-19 viral RNA, is significantly less sensitive than traditional genetic assays employing the polymerize chain reaction.
The major advantage for the Abbott test is that it is a small device that can be transported to testing sites and get a result from a swab of the back of the throat within five minutes. This allowed for “drive through” testing to identify people who are actively infected with COVID-19.
New data from NYU Medical School have now reinforced concerns about this assay. As compared to traditional genetic testing using PCR (Cepheid Xpert Xpress SARS-CoV-2 system) the Abbott ID NOW using swabs with viral transport media missed 33% of samples detected as positive by Cepheid’s PCR, and when using Abbott’s preferred dry swab technique the ID now missed 48% of positive samples.
These results are disastrous as they will result in unsuspecting infected people spreading the virus because they have received a negative result. This defeats the entire reason for virus screening.
Previously, studies have suggested that the Abbott assay was much less sensitive than other genetic techniques. False negatives have also been reported from screening centers in NYC. However, Abbott dismissed these concerns saying that the use of viral transfer media resulted in a less sensitive result than using dry nasal swabs. In this paper the investigators documented that viral transfer media was actually better than the dry nasal swabs, resulting in a miss of only a third of the samples whereas traditional dry nasal swab samples failed to detect virus in almost half of the subjects.
The reasons for this are not entirely clear, but the Abbott ID NOW uses a different type of genetic amplification and detection system, where all the components to amplify the genetic material are mixed together and run simultaneously. This may be less efficient than PCR techniques and also be disturbed by contaminants in the patient samples. The fact that the results where better with the viral transfer media may support this because it can stabilize samples.
Also, this device is used in all sorts of settings, such as drive throughs and factories. The conditions are difficult, temperatures and humidity vary, and technicians are under stress. The Abbot device needs to be field tested in these conditions.
There is great enthusiasm for the Abbott test given it can provide an answer within five minutes as compare to 45 minutes (at best) for a PCR test. However, even if a much lower number of infections are missed, like the 20% reported by the Cleveland Clinic, it is unacceptable as a screening test. If you miss 1 in 5 infected individuals you would have to confirm all negative test results using a traditional PCR assay.
Regardless of the preliminary nature of this report the onus is now on Abbott to have this device validated in an independent, blinded field study. This is would have been done if this device was fully approved by the FDA and not simply approved under the Emergency Use Approval (EUA).