CovidNudge: a rapid 90 minutes test for COVID-19 diagnosis

Having efficient testing methods in place is crucial to control the spread of COVID-19 pandemic. Testing and early diagnosis of the disease can not only help in controlling the spread of the virus but can also be helpful in managing the symptoms of the disease from an early stage by providing the right treatment and care to the patients. Current testing method for SARS-CoV-2 in laboratory involves the use of a technique called RT-PCR 1. This technique essentially looks for the presence of viral genetic material in the patient sample, which is commonly obtained in the form of a nasal or throat swab. Recently, a new test called CovidNudge has been trialed for detecting SARS-CoV-2 in patient samples in UK and has proven to deliver much quicker results when compared to standard laboratory testing, introducing the potential for point of care testing i.e. testing outside of clinical laboratories and at the patient's bedside1. This article aims to provide some insight into this new testing method, its current applications and potential future use as a point-of-care test for diagnosing COVID-19.

CovidNudge test developed by the scientists at DnaNudge and Imperial College London © Imperial College London

What is CovidNudge and how does it work?

CovidNudge is a rapid test for diagnosing COVID-19, developed by DnaNudge, an Imperial College London spinout company2. The test can deliver results in just about 90 minutes. Moreover, the device can directly process swab samples, saving the time and effort of initial sample preparation in laboratory2. The device is made up of two components- DnaCartridge and the NudgeBox (the processing unit). The nasal or throat swab is placed in the swab chamber of the DnaCartridge where the swab is broken and its tip with the sample on it undergoes some reactions wherein the RNA is extracted from the sample1. The barcode on the cartridge is then scanned and the cartridge is placed in the Nudgebox for processing where a real-time RT-PCR reaction takes place which tests the presence of viral genes in the sample. This is tested by analysing the amplification of 7 target viral genes. Even if one of the target gene amplifies in two or more reaction wells in the device, then the test result comes out as positive1. Another major advantage of using this device is that each CovidNudge device is connected to a cloud-based database via WiFi which further aids quick analysis and delivery of results to the patients. The results can be delivered directly to a patient's electronic health record or their smartphone app1.

How accurate is the test?

According to a study published in The Lancet journal, that evaluated the performance of CovidNudge and compared it with laboratory testing, CovidNudge test was found to be 94% sensitive and 100% specific1. Sensitivity is the ability of the test to correctly identify the positive cases whereas the specificity of the test is its ability to correctly identify the negative cases. In the study, out of 386 samples tested, CovidNudge gave 67 positive test results while 71 positive results were obtained on laboratory testing. However, all the negative cases were correctly identified1. Meaning, the test is likely to give a few false negatives (about 6%) but is very unlikely to give any false positives.

CovidNudge vs standard laboratory testing

Although this test may seem like a useful alternative to laboratory testing, it has its advantages and limitations. The table below compares the two tests highlighting the pros and cons of each.

CovidNudge Test	Standard Laboratory Testing
The test is fully automated and samples can be used directly without the need to undergo manual processing in laboratory1.	Traditional RT-PCR technique is used which requires the samples to be processed in laboratory before carrying out the process1.
The whole process takes just about 90 minutes to give results for a single sample. The patient can access results shortly after as they are sent directly to their electronic health record1.	The process takes about 4-6 hours to be completed1 and it can take upto 3 days for the patient to receive their results after the test3.
The enzyme human RNase acts as a control to help ensure that sufficient sample is being put into the device for analysis. So, it is easy to detect an insufficient sample in which case, the sample can be retaken1.	An insufficient sample in a laboratory RT-PCR process gives a negative result. This increases the chances of getting a false negative result as it can be difficult to predict when the result is negative due to sample insufficiency1.
Currently, only a single sample can run on one testing device1. This limits the testing capacity of the device to just about 15 tests per day2.	High throughput testing is available as multiple samples can be run in a machine simultaneously1.
No laboratory work experience required1.	Laboratory experience required and hence can only be performed by trained personnel1.