Fig. 4

Comparison of SARS-CoV-2 viral concentration in SS-AN-PCR1. A Average Ct of nose and throat versus nose only swabs in SARS-CoV-2–positive individuals. B Correlation of Ct between nose and throat versus nose only swabs in all individuals. SS-AN-PCR1: SS of the anterior nares using PCR. A The average Ct value was taken across the three genes (ORF1ab gene, N gene, and S-gene) in all concordant and discordant SARS-CoV-2–positive individuals; the boxplot shows a comparison between the SS and AS samples. There was a statistically significant difference in Ct values for nose and throat swabs versus nose-only swabs: mean − 0.99; 95% CI − 1.3, − 0.6; p < 0.001. B There was a strong correlation (Spearman’s rho correlation co-efficient = 0.87; p < 0.001) between the average Ct values of the nose and throat, and nose-only samples. AN, anterior nares; CI, confidence interval; Ct, cycle threshold; NT, nose and throat; PCR, polymerase chain reaction; SS, self-swabbing