Fig. 3.

Longitudinal study. The findings of the longitudinal study are summarized comparing Ct values of the N gene in breath (breath test N), nasopharyngeal swab (NP Swab N) and saliva (saliva N) to a rapid antigen test on nasopharyngeal swab (Abbott AG). (A) Individual graphs of the 11 participants followed up over the course of their infection, day 0 being the first day any diagnostic test turned positive. The period in which the breath test is positive is shaded. As shown, 3/11 participants were positive on all tests concurrently, while 8/11 had discrepant results on the first day of testing positive. In the latter cases, the breath test turned positive before NP swab on two occasions (subject 121 and 169) and after in two others (subject 147 and 156). The Abbott AG test turned positive 0–3 days after a PCR test (mean 1.4 days). (B) A summed graph in which the Ct values of all tests performed in the 11 participants on a particular day are averaged for one particular sample type. A trend towards an earlier peak in the breath test N in comparison to NP Swab N and saliva N is shown on top. Median and 95%CI were calculated using the bootstrap method. Lastly, as shown and more clearly visible in Fig. S7, the breath test turns negative before RT-qPCR on other respiratory samples.