Diagnostic accuracy
How accurate is a 15-minute COVID antigen strip?
Open access · cc by · source: Europe PMC
COVID-19 Ag Respi-Strip was highly specific (99.5%) but only moderately sensitive (57.6%) vs PCR, best when viral load was high (CT <22).
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The proposed use follows from the performance profile rather than from the headline accuracy of 82.6%.
A test can be highly specific and still miss most cases. The COVID-19 antigen strip showed 99.5% specificity, 1.7% between-observer disagreement and no cross-reactivity, with sensitivity of 57.6% and a practical detection limit around CT below 22 — so the authors propose it as a first-line complement to molecular testing, not a replacement.
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How accurate is a 15-minute COVID antigen strip?
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Overall sensitivity 57.6% and specificity 99.5%.
we found an overall sensitivity and specificity of 57.6 and 99.5%, respectively with an accuracy of 82.6%.
Clinical evaluation used 328 nasopharyngeal samples.
The clinical performance study was performed in a retrospective multi-centric evaluation on aliquots of 328 nasopharyngeal samples.
Key findings
Between-observer disagreement 1.7%, robustness 98%, no cross-reactivity with other virus-infected samples. Overall sensitivity 57.6%, specificity 99.5%, accuracy 82.6%; ICT cut-off around CT <22. Authors propose first-line use complementary to molecular tests.
Methodology
Developed a colloidal-gold ICT targeting conserved SARS-CoV nucleoprotein, then measured analytical reproducibility/cross-reactivity and clinical performance on 328 nasopharyngeal aliquots against qRT-PCR.
Limitations
Moderate sensitivity means many PCR-positive cases are missed, especially at higher CT; evaluation was during an ascending epidemic curve and does not replace PCR confirmation.
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