Rapid COVID-19 Detection with NP Swabs Using miDiagnostics PCR Test
An NP (nasopharyngeal) swab is a diagnostic test commonly used to detect respiratory infections. It involves inserting a long, flexible swab through the nostril along the nasal passage towards the back of the nasopharynx. The swab has a brush or cotton tip that rubs against the tissue, collecting mucus and secretions. The sample collected on the swab is then tested in a lab for the presence of viruses, bacteria, or other microbes.
NP swabs allow doctors to diagnose illnesses such as influenza, COVID-19, respiratory syncytial virus (RSV), whooping cough, and viral pharyngitis. They can also detect Group A Streptococcus, which causes strep throat. Although passing the swab to the back of the nose and throat can be uncomfortable, NP swabs provide an important sample to identify pathogens causing respiratory infections.
The COVID-19 pandemic has placed immense pressure on healthcare systems to rapidly diagnose or exclude SARS-CoV-2 infection. The current gold standard is laboratory-based reverse transcriptase PCR (RT-PCR) testing, which is accurate but often has long turnaround times of 24-48 hours. Rapid antigen tests are faster but have lower and more variable sensitivity. There is a need for accurate point-of-care COVID-19 testing that provides results in under 30 minutes.
A new rapid PCR test developed by miDiagnostics aims to address this need. In a recent prospective study published in Journal of Clinical Microbiology, researchers evaluated the clinical performance of the miDiagnostics COVID-19 PCR test using nasopharyngeal (NP) swabs.
The study enrolled 770 participants at a mobile COVID-19 testing center in Belgium from March to April 2022. Most participants were symptomatic. Three NP swabs were collected from each participant in randomized order - one for the index miDiagnostics PCR test, one for the reference laboratory PCR test (ThermoFisher TaqPath), and one for additional discordance testing with a third PCR kit.
The miDiagnostics test detects two N gene targets of SARS-CoV-2 using an ultrafast PCR chip in a compact reader device. Minimal sample preparation is required, with direct introduction into the test card after heat inactivation. Results are available in under 30 minutes.
The miDiagnostics PCR test showed 95.5% positive percent agreement (PPA) and 94.9% negative percent agreement (NPA) compared to the TaqPath laboratory reference PCR. Performance was even higher in symptomatic individuals, with 98.6% PPA and 96.5% NPA. Two minor adverse events occurred during NP swabbing - one nosebleed and one painful swabbing.
Sensitivity was lower in asymptomatic participants (74.4% PPA) likely due to lower viral loads. Retesting was required in 7.4% of tests due to technical errors. Freeze-thaw cycles did not significantly impact results. The PCR run time was under 13.5 minutes.
The study demonstrates excellent clinical performance of the miDiagnostics COVID-19 PCR test using NP swabs, with fast turnaround times. The rapid and reliable results could allow for prompt clinical decision making and better COVID-19 management. However, the more invasive NP sampling can rarely cause minor complications. Further studies on less invasive sampling methods are warranted.
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Bos DAG, Lagrou K, Verbakel JY. Prospective Performance Evaluation of the miDiagnostics COVID-19 PCR Test for Rapid SARS-CoV-2 Detection on Nasopharyngeal Swabs. J Clin Microbiol. 2023 May 23;61(5):e0187122. doi: 10.1128/jcm.01871-22. Epub 2023 Apr 24. PMID: 37093001; PMCID: PMC10204629.