How Accurate Are Nasal Swab Rapid Tests For COVID-19?
With the COVID-19 pandemic ongoing, rapid and accurate testing remains critical for case identification and controlling spread. Polymerase chain reaction (PCR) tests are sensitive but slow and resource-intensive. Can rapid antigen testing play a complementary role? A study in 2022 evaluated the accuracy of nasal antigen testing for mild COVID-19 cases.
What did the study do?
Researchers in Bahrain collected paired nasal and nasopharyngeal samples from 4,183 people with mild COVID-19 symptoms. The nasal samples were tested using a rapid Abbott antigen test. The nasopharyngeal samples were tested by PCR, the gold standard. They then compared the results to evaluate the antigen test's accuracy.
What were the main findings?
The rapid antigen test had 82.1% sensitivity and 99.1% specificity compared to PCR. Cases missed by antigen testing had higher PCR cycle thresholds, indicating lower viral loads. When excluding PCR results above cycle threshold 24, antigen test sensitivity improved to 87.9%.
What are the limitations?
The study compared nasal antigen testing to nasopharyngeal PCR rather than using nasal samples for both tests. The sample size for repeat testing after discrepant results was small. Detailed clinical symptom data was not collected.
What do the results mean?
Despite limitations, the findings support nasal antigen testing as a useful screening tool for mild COVID-19 cases, especially those with higher viral loads. Though PCR remains the gold standard, antigen testing can play a complementary role in COVID-19 testing strategies. More research is still needed on antigen test accuracy in different populations.
In summary, rapid nasal antigen testing shows promise for screening mild symptomatic COVID-19 cases when paired with PCR confirmation. More evidence is needed to guide expanded implementation as part of integrated testing strategies for controlling the pandemic.
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Reference
Alqahtani M, Abdulrahman A, Mustafa F, Alawadhi AI, Alalawi B, Mallah SI. Evaluation of Rapid Antigen Tests Using Nasal Samples to Diagnose SARS-CoV-2 in Symptomatic Patients. Front Public Health. 2022 Jan 14;9:728969. doi: 10.3389/fpubh.2021.728969. PMID: 35096725; PMCID: PMC8795669.
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