Current best evidence for clinical care (more info)
The sensitivity of the BinaxNOW coronavirus disease 2019 (COVID-19) Ag Card test (BinaxNOW) was 51.6% among asymptomatic healthcare employees relative to real-time reverse transcriptase polymerase chain reaction (rRT-PCR). The odds of a positive BinaxNOW test decreased as cycle threshold value increased. BinaxNOW could facilitate rapid detection and isolation of asymptomatically infected persons in some settings while rRT-PCR results are pending.
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Having a test that can quickly identify some patients with Covid would be useful in managing the flow in EDs.
This is a single centre study aimed to evaluate the performance of the BinaxNOW (rapid test) for detecting asymptomatic SARS-CoV-2 positive persons in relation with traditional RT-PCR test. Results showed a specificity of 97%. However regarding sensitivity, the rates were 83% for symptomatic and 51% for asymptomatic patients. Although the test is reliable to identify actual covid-19 positive symptomatic patients early, there is no benefit to its application for screening asymptomatic individuals.
This is valuable information. The test being slightly more than 50% accurate is disappointing and seems marginally better than a coin toss. It is surprising to see the authors suggest that this test may be used as a screening tool. Clinical evaluation may be significantly better.
Antigenic tests have a known reduced sensitivity as compared to RT-PCR for SARS-CoV-2. Their utility rests with a result much faster than RT-PCR, suitable for point-of-care use.