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. 2021 Sep 17;224(6):976-982.
doi: 10.1093/infdis/jiab337.

Longitudinal Assessment of Diagnostic Test Performance Over the Course of Acute SARS-CoV-2 Infection

Rebecca L Smith  1   2   3 , Laura L Gibson  4 , Pamela P Martinez  1   5   6 , Ruian Ke  7 , Agha Mirza  8 , Madison Conte  8 , Nicholas Gallagher  9 , Abigail Conte  10 , Leyi Wang  11 , Richard Fredrickson  11 , Darci C Edmonson  1 , Melinda E Baughman  1 , Karen K Chiu  1 , Hannah Choi  1 , Tor W Jensen  1   12 , Kevin R Scardina  1 , Shannon Bradley  1 , Stacy L Gloss  1 , Crystal Reinhart  1 , Jagadeesh Yedetore  1 , Alyssa N Owens  13 , John Broach  14   15 , Bruce Barton  16   17 , Peter Lazar  16 , Darcy Henness  18 , Todd Young  18 , Alastair Dunnett  18 , Matthew L Robinson  8 , Heba H Mostafa  9 , Andrew Pekosz  10 , Yukari C Manabe  8 , William J Heetderks  19 , David D McManus  20 , Christopher B Brooke  1   5
Affiliations

Longitudinal Assessment of Diagnostic Test Performance Over the Course of Acute SARS-CoV-2 Infection

Rebecca L Smith et al. J Infect Dis. .

Abstract

Background: Serial screening is critical for restricting spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by facilitating timely identification of infected individuals to interrupt transmission. Variation in sensitivity of different diagnostic tests at different stages of infection has not been well documented.

Methods: In a longitudinal study of 43 adults newly infected with SARS-CoV-2, all provided daily saliva and nasal swabs for quantitative reverse transcription polymerase chain reaction (RT-qPCR), Quidel SARS Sofia antigen fluorescent immunoassay (FIA), and live virus culture.

Results: Both RT-qPCR and Quidel SARS Sofia antigen FIA peaked in sensitivity during the period in which live virus was detected in nasal swabs, but sensitivity of RT-qPCR tests rose more rapidly prior to this period. We also found that serial testing multiple times per week increases the sensitivity of antigen tests.

Conclusions: RT-qPCR tests are more effective than antigen tests at identifying infected individuals prior to or early during the infectious period and thus for minimizing forward transmission (given timely results reporting). All tests showed >98% sensitivity for identifying infected individuals if used at least every 3 days. Daily screening using antigen tests can achieve approximately 90% sensitivity for identifying infected individuals while they are viral culture positive.

Keywords: RT-qPCR testing; SARS-CoV-2; antigen testing; diagnostic testing; test sensitivity.

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Figures

Figure 1.
Figure 1.
Daily sensitivity of each test platform relative to the day of first positive viral culture result. Shaded areas represent the 95% confidence interval around the observed proportion. Abbreviation: RT-qPCR, quantitative reverse transcription polymerase chain reaction.
Figure 2.
Figure 2.
Status sensitivity of each test platform relative to viral culture positivity. Bars indicate the 95% confidence interval around the observed proportion. Prepositive (n = 31) refers to samples taken on days before the first viral culture-positive sample collected from each individual. Positive (n = 153) refers to samples taken on days for which viral culture results were positive. Postpositive (n = 126) refers to samples taken on days with negative viral culture results that occur after the first positive culture result. Abbreviation: RT-qPCR, quantitative reverse transcription polymerase chain reaction.
Figure 3.
Figure 3.
Protocol sensitivity of each test platform to detect an infected person (A) at any time over a 14-day testing period or (B) before or on days where nasal samples were viral culture positive, relative to the frequency of testing. Bars indicate 95% confidence interval around the observed proportion. Abbreviation: RT-qPCR, quantitative reverse transcription polymerase chain reaction.
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