Insufficient data were available to investigate the effect of symptom status or time after symptom onset.ДЄntigen tests vary in sensitivity. For Xpert Xpress, the average sensitivity was 100% (95% CI 88.1% to 100%) and average specificity 97.2% (95% CI 89.4% to 99.3% 2 evaluations 100 samples, 29 cases). Using data from evaluations following the manufacturerвЂ™s instructions for use, the average sensitivity of ID NOW was 73.0% (95% CI 66.8% to 78.4%) and average specificity 99.7% (95% CI 98.7% to 99.9% 4 evaluations 812 samples, 222 cases). Most of the data relate to the ID NOW and Xpert Xpress assays. Sensitivities varied according to test brand. Thirty studies reported 33 evaluations of five different rapid molecular tests. No studies assessed the accuracy of repeated lateral flow testing or selfвЂђtesting.

At 0.5% prevalence applying the same tests in asymptomatic people would result in PPVs of 11% to 28% meaning that between 7 in 10 and 9 in 10 positive results will be false positives, and between 1 in 2 and 1 in 3 cases will be missed. Average specificities were high in symptomatic and asymptomatic participants, and for most brands (overall summary specificity 99.6%, 95% CI 99.0% to 99.8%).ДЄt 5% prevalence using data for the most sensitive assays in symptomatic people (SD Biosensor STANDARD Q and Abbott Panbio), positive predictive values (PPVs) of 84% to 90% mean that between 1 in 10 and 1 in 6 positive results will be a false positive, and between 1 in 4 and 1 in 8 cases will be missed. Using data from instructions for use (IFU) compliant evaluations in symptomatic participants, summary sensitivities ranged from 34.1% (95% CI 29.7% to 38.8% Coris Bioconcept) to 88.1% (95% CI 84.2% to 91.1% SD Biosensor STANDARD Q). Sensitivity was high in those with cycle threshold (Ct) values on PCR в‰¤25 (94.5%, 95% CI 91.0% to 96.7% 36 evaluations 2613 cases) compared to those with Ct values >25 (40.7%, 95% CI 31.8% to 50.3% 36 evaluations 2632 cases).

Average sensitivity was higher in the first week after symptom onset (78.3%, 95% CI 71.1% to 84.1% 26 evaluations 5769 samples, 2320 cases) than in the second week of symptoms (51.0%, 95% CI 40.8% to 61.0% 22 evaluations 935 samples, 692 cases). There were differences between symptomatic (72.0%, 95% CI 63.7% to 79.0% 37 evaluations 15530 samples, 4410 cases) and asymptomatic participants (58.1%, 95% CI 40.2% to 74.1% 12 evaluations 1581 samples, 295 cases). Estimates of sensitivity varied considerably between studies. Nearly all studies (97%) defined the presence or absence of SARSвЂђCoVвЂђ2 based on a single RTвЂђPCR result, and none included participants meeting case definitions for probable COVIDвЂђ19.ДЇortyвЂђeight studies reported 58 evaluations of antigen tests. Characteristics of participants in 35 (45%) studies differed from those in whom the test was intended to be used and the delivery of the index test in 39 (50%) studies differed from the way in which the test was intended to be used. Studies of antigen tests were of a higher methodological quality compared to studies of molecular tests, particularly regarding the risk of bias for participant selection and the index test. We considered risk of bias to be high in 29 (37%) studies because of participant selection in 66 (85%) because of weaknesses in the reference standard for absence of infection and in 29 (37%) for participant flow and timing.

Studies were mainly from Europe (n = 39) or North America (n = 20), and evaluated 16 antigen and five molecular assays. SeventyвЂђeight study cohorts were included (described in 64 study reports, including 20 preвЂђprints), reporting results for 24,087 samples (7,415 with confirmed SARSвЂђCoVвЂђ2).

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