· A wide range of tests are available for detection of viral RNA as well as serological and immunoassays for antibodies developed due to exposure to SARS CoV-2 in infected persons. Despite the emerging research, information about clinical validity of tests is limited.
· Multiple factors affect test performance including the nature of the specific test, type of specimen and its quality, severity and duration of illness at the time of testing. These individual variations hamper assessment of diagnostic accuracy and suggest that a combination of tests on multiple types of specimens at serial time points might be needed to confirm a COVID 19 diagnosis.
· Point of care tests are desirable and needed to scale up testing in low resource settings; however, tests are of variable quality and more research is needed before they can be relied on for clinical decision making.
Notes
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Williams-Roberts, H; Waldener, C. What is the accuracy of diagnostic tests for COVID-19 detection? 2020 May 12; Document no.: EPM051201 RR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. (CEST rapid review report)
Dalidowicz, M; Young, C. How effective is surveillance antigenic testing? 2021 Jan 29; Document no.: EOC012601-01 ESR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. 32 p. (CEST evidence search report).
Howell-Spooner, B. How well does the presence and level of antibodies predict the presence or absence of the disease? 2020 Apr 14; Document no.: LAB041401-01 ESR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. 20 p. (CEST evidence search report)
Moderate to strong grade evidence show the overall sensitivityrangeof IgM, IgG, and combined IgM/IgG are 48.1% to 94.1%, 64.7% to 100%, 83% to 100%, respectively.
IgM/IgG combined assay, with the posterior probability of 99.15%, has greater accuracyand sensitivity than a single IgM or IgG test.
The sensitivity of antibody tests is extremely low (~ 11.1%) in the first week following the onsetof symptoms but increasesrapidlyduring the second week.
IgG and IgM titers in patients with severe disease arehigher than those in the non-severe patients.
Antibody testsmay detect the presence of COVID-19 in asymptomatic individuals with negative rt-PCRresults.
Wang, H; Reeder, B; Howell-Spooner, B. How well does the presence and level of antibodies predict the presence or absence of the disease? 2020 Apr 15; Document no.: LAB041401 RR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. 9 p. (CEST rapid review report)
Badea, A; Reeder, B; Groot, G; Muhajarine, N; Minion, J; Miller, L; Howell-Spooner, B. In real world settings, what is the validity of Rapid Antigen Tests (RATs) in identifying SARS-CoV-2 and how well do they predict disease? 2022 Jan 12, Document no.: EOC211201 RR Table. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2022. (CEST table).
The diagnostic accuracy of Rapid Antigen Tests (RAT) has been widely studied in various applications and in diverse populations.
Sensitivity, in the order of 75% in pooled estimates, is significantly influenced by the presence or absence of symptoms, viral load, and the timing of sampling relative to the onset of symptoms.
Specificity, in the order of 99% in pooled estimates, is consistently high across tests, populations, and sampling methods.
Post-test probability of being an infectious case following a positive test is highest in individuals with a high pre-test probability (population prevalence > 5%), such as those with COVID-19 symptoms, and those in settings with a high level of community transmission. Here, the positive predictive value is in the order of 95%. However, when used in settings with a lower pre-test probability (population prevalence < 0.5%), as in screening asymptomatic individuals, the positive predictive value is considerably reduced, as low as 25%.
Post-test probability of being an infectious case following a negative test is less than 1% (negative predictive value > 99%) in all settings except those with the highest levels of community transmission.
Badea, A; Reeder, B; Groot, G; Muhajarine, N; Minion, J; Miller, L; Howell-Spooner, B. In real world settings, what is the validity of Rapid Antigen Tests (RATs) in identifying SARS-CoV-2 and how well do they predict disease? 2022 Jan 12, Document no.: EOC211201 RR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2022. 15 p. (CEST rapid review report).
Miller, L. & Howell-Spooner, B. In real world settings, what is the validity of RATs in identifying COVID-19 (sensitivity, specificity), and how well do they predict disease (positive and negative predictive values)? 2021 Dec 29, Document no.: EOC211201 ESR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2021. 56 p. (CEST evidence search report).
Dalidowicz, M. Is pooled testing for COVID-19 equally as reliable as individual testing and what are the optimal pool testing sizes? 2020 Aug 12; Document no.: EOC081301-01 ESR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. 8 p. (CEST evidence search report)
· Pool testing for COVID-19 can be equal to individual testing in terms of sensitivity, specificity and positive and negative prediction rates
· Pooled testing is optimal for use when disease prevalence is low, as prevalence increases, optimal pool sizes decrease and efficiency is lost
· At a prevalence of approximately 1%, optimal pool sizes have been found to be up to 13
· Pools of 5 were found to be equally efficient and could be done using 50% less tests up to a prevalence of 5%
· Recommended for use in large scale asymptomatic screening, highest viral load occurs before symptoms so less likely to miss borderline positive in convalescent stage
· Not recommended for clinical diagnostic use
Badea, A; Muhajarine, N; Dalidowicz, M. Is pooled testing for COVID-19 equally as reliable as individual testing and what are the optimal pool testing sizes? 2020 Aug 14; Document no.: EOC081301 RR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. 19 p. (CEST rapid review report)
