Figure 3.

Kinetics of RT-PCR cycle thresholds, virus culture, and oral fluid SARS-CoV-2 antibodies in mild–moderate COVID-19. A, Longitudinal Abbott m2000 SARS-CoV-2 RT-PCR cycle threshold values from nasal-OP swab study samples (blue circles and triangles in Figure 2) by day from symptom onset are shown in gray. Longitudinal oral fluid antispike (Mt. Sinai) IgG mean fluorescence intensity shown in purple. Lines connect values from the same participant. Each sample with a positive RT-PCR result was assessed for propagation of SARS-CoV-2 on VeroE6-TMPRSS2 cells. Samples with positive virus culture are indicated by red circles. The cutoff for positive anti-S IgG is shown with a purple dotted line (see the “Methods” for cutoff calculation). B, The subset of 59 participants with a nasopharyngeal swab collected within 7 days of symptom onset and run on the NeuMoDx SARS-CoV-2 RT-PCR platform is shown by day from symptom onset. The line connects cycle threshold means. C, The subset of nasal-OP swab samples with a cycle threshold <20 is grouped according to whether virus culture of the sample was positive or negative. Means with 95% CIs are shown. *P < .00001 by 1-tailed Student t test. D, The subset of samples shown in (B) that had a simultaneous adequate oral fluid sample is shown here. Filled diamonds represent study time points at which oral fluid contained detectable IgG antibodies to Mt Sinai S-RBD, and open diamonds represent study time points at which oral fluid was negative for anti-S-RBD IgG. Abbreviations: Ab, antibody; COVID-19, coronavirus disease 2019; Cult, culture; IgG, immunoglobulin G; OP, oropharyngeal; RT-PCR, reverse transcription polymerase chain reaction; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; S-RBD, spike receptor binding domain.