Testing for SARS-CoV-2, What is New
Our friends at Imperial describe their novel, lab free, point of care test for SARS-CoV-2 known as COVID nudge in The Lancet September 17. This was based on work done by Gibani and Toumazou.
Between April and May 2020 they obtained two nasal pharyngeal swab samples from individuals in three hospitals in London and Oxford. Samples were collected from three groups: Self-referred healthcare workers with suspected COVID-19; patients attending emergency departments with suspected COVID-19; and hospital inpatients with or without suspected COVID-19. For the COVID nudge test the nasopharyngeal swabs were inserted directly into a cartridge which contained all reagents and components required for RT PCR reactions, including multiple technical replicates of seven SARS-CoV-2 gene targets and human ribonuclease P as a sample adequacy control. Swab samples were tested in parallel using the COVID nudge platform and the standard laboratory RT PCR using swabs in viral transport medium for processing in a central laboratory. The primary analysis was to compare the sensitivity and specificity of the point of care COVID nudge test with laboratory based testing.
The overall sensitivity of the point of care test compared with laboratory based testing was 94% with an overall specificity of 100%. The sensitivity of the test varied by group, self-referred healthcare workers 93%, patients in the emergency department 100% and hospital inpatient admissions 100%. Specificity was consistent between groups. Point of care testing performance was similar during a period of high background prevalence of laboratory positive tests and low prevalence in an inpatient screening setting.
They concluded that the COVID nudge platform was a sensitive, specific and rapid point of care test for the presence of SARS-CoV-2 without laboratory handling or sample pre-processing and went on to say that this would enable rapid decisions for clinical care and testing programmes. This new point of care test which works on PCR will be a substantially important fast test to help eradicate this dreadful virus.
CRISPR technology is being used as a simple test for detection of SARS-CoV-2. It has been found that the sensitivity of this test is similar to that of the PCR assay and stop Sherlock testing in one pot is a streamlined assay with combined simplified extraction of viral RNA with isothermal amplification and CRISPR mediated detection. This test can be performed at a single temperature in less than an hour and with minimal equipment. Integration of isothermal amplification with CRISPR mediated detection requires the development of common reactive buffer that could accommodate both steps and the sensitivity was 93% and specificity was 98.5%.
The London General Practice awaits with anticipation for commercial availability of this test so that it can be included in every single family practice, both private and National Health Service.