Evaluation and clinical implications of the time to a positive results of antigen testing for SARS-CoV-2

Akashi, Yusaku; Kiyasu, Yoshihiko; Takeuchi, Yuto; Kato, Daisuke; Kuwahara, Masaki; Muramatsu, Shino; Ueda, Atsuo; Notake, Shigeyuki; Nakamura, Koji; Ishikawa, Hiroichi; Suzuki, Hiromichi

doi:10.1016/j.jiac.2021.10.026

Cited by 12 publications

(13 citation statements)

References 17 publications

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“…The results of our investigation evidenced that the viral load in routinely collected nasopharyngeal samples is highly correlated with the positivization time of a rapid SARS-CoV-2 antigen test, displaying AUC as high as 0.82 and overall agreement at high viral load threshold (i.e., Ct <20) of nearly 71%. A similar study has been previously conducted by Akashi and colleagues, using the QuickNavi™-COVID19 Ag (Denka Co., Ltd., Tokyo, Japan) (21). Briefly, the authors found that the time to obtain positive results was also positively correlated with Ct values (p<0.001), such that specimens with higher Ct values of SARS-CoV-2 N2 gene were significantly associated with a longer time to obtain a positive reaction and vice versa, ultimately displaying up to 91% concordance for identifying SARS-CoV-2 RNA positive specimens.…”

Section: Discussionmentioning

confidence: 69%

Association between viral load and positivization time of a SARS-CoV-2 rapid antigen test in routine nasopharyngeal specimens

et al. 2022

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Background: Rapid SARS-CoV-2 antigen tests are potentially useful tools for screening carriers with high viral load. This study was aimed to assess the potential association between viral load and positivization time of a manual SARS-CoV-2 commercial antigen test in routine nasopharyngeal specimens. Methods: In a sample of subjects undergoing routine diagnostic testing, SARS-CoV-2 positivity of nasopharyngeal samples was assayed with both molecular (Altona Diagnostics RealStar SARS-CoV-2 RT-PCR Kit) and antigenic (Roche SARS-CoV-2 Rapid Antigen Test) tests. Positivization time of rapid antigen test was correlated and compared with viral load expressed as mean of SARS-CoV-2 E/S genes cycle threshold (Ct) values. Results: The study sample consisted of 106 patients (median age 48 years, 55 women) with positive results of rapid SARS-CoV-2 antigen testing. A highly significant Spearman’s correlation was found between mean SARS-CoV-2 E/S genes Ct values and positivization time of manual antigen test (r= 0.70; p<0.001). The positivization time of rapid SARS-CoV-2 antigen test displayed an area under the curve of 0.82 (95%CI, 0.74-0.89) for predicting nasopharyngeal samples with high viral load (i.e., mean Ct <20). A positivization time cut-off of 32 sec had 94.9% sensitivity and 58.2% specificity for detecting specimens with high viral load. The overall agreement between mean Ct value <20 and positivization time <32 sec was 70.8%. Conclusions: Positivization time of rapid SARS-CoV-2 antigen tests may provide easy and rapid information on viral load, thus making this type of manual assay potentially suitable for quick and reliable detection and isolation of super-carries.

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Section: Discussionmentioning

confidence: 69%

Association between viral load and positivization time of a SARS-CoV-2 rapid antigen test in routine nasopharyngeal specimens

et al. 2022

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“…Between our results with two home tests and those of others, who measured time-to-positivity in eight other visual read LFTs versus actual or surrogates of viral load, it is likely that most, if not all, of the COVID-19 LFTs will behave similarly. [7][8][9][10]19 Accurate quantification requires first establishing a standard curve with known concentrations of the virus with each LFT before using it to estimate the viral load in a sample. Ideally this would be performed using artificial mucus spiked with the protein or virus rather than UTM as used in this study.…”

Section: Discussionmentioning

confidence: 99%

“…Additionally, two groups reported that the time-to-positive SARS-CoV-2 antigen result was inversely correlated with the Ct values. [8][9][10] In order to determine whether the utilization of timeto-positivity after application of nasal swab samples in two popular home SARS-CoV-2 antigen tests could be used to quantify actual viral load, we investigated the dose-response relationship between time-to-positive result by visual assessment in the antigen tests with purified nucleocapsid protein (NP), chemically inactivated WA1 and Omicron XBB.1.5 viral strains, and Ct values with dilutions of the viruses and in clinical samples. We also examined the feasibility of using time-to-positive result to predict the Ct values in clinical samples from patients with COVID-19.…”

Section: Introductionmentioning

confidence: 99%

Quantification of SARS‐CoV‐2 viral load in patients using time‐to‐results in antigen lateral flow tests

Braunstein,

Vail,

et al. 2024

Clinical Translational Sci

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Based upon clinical observations and recent reports, we anticipated there would be an inverse dose–response relationship between the severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2) viral load and the time‐to‐positivity after application of the nasal swab sample in two popular home coronavirus disease 2019 (COVID‐19) antigen tests, BinaxNOW COVID‐19 Antigen Self‐Test and Flowflex COVID‐19 Antigen Home Test, both of which are sensitive to the nucleocapsid protein (NP). The relationship among the concentration of NP, WA1, and Omicron XBB.1.5 viral strains and the time‐to‐positive result by visual assessment in the tests was examined. The correlation between reverse transcription‐polymerase chain reaction cycle threshold (Ct) values and time‐to‐positivity in clinical samples (training set) also was determined. Strong inverse correlations were obtained between the concentration of the NP, WA1, XBB.1.5, Ct values for dilutions of both WA1 and XBB.1.5, as well as Ct values from the clinical samples and time‐to‐positivity in both antigen tests. The correlation between the actual and predicted Ct values interpolated from the training set was high with both tests in a second set of clinical samples. These results, together with those of other investigations with similar tests, suggest that the time‐to‐positive visual result in most, if not all, lateral flow COVID‐19 antigen tests can be utilized to estimate SARS‐CoV‐2 viral concentrations.

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“…When the positive line appears within the reaction time, a judgement can be made before completing the reaction time. Because the time to positive results can be viral load-dependent [ 12 ], the rapid clinical response to those results can lead to the appropriate infection control and treatment.…”

Section: Discussionmentioning

confidence: 99%

Analytical sensitivity of six lateral flow antigen test kits for variant strains of SARS-CoV-2

Morinaga¹,

Yamada²,

Yoshida³

et al. 2023

Journal of Infection and Chemotherapy

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Evaluation and clinical implications of the time to a positive results of antigen testing for SARS-CoV-2

Cited by 12 publications

References 17 publications

Association between viral load and positivization time of a SARS-CoV-2 rapid antigen test in routine nasopharyngeal specimens

Association between viral load and positivization time of a SARS-CoV-2 rapid antigen test in routine nasopharyngeal specimens

Quantification of SARS‐CoV‐2 viral load in patients using time‐to‐results in antigen lateral flow tests

Analytical sensitivity of six lateral flow antigen test kits for variant strains of SARS-CoV-2

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