Figure. Cycle Thresholds (Ct) for Home Self-collected Midnasal Swabs and Clinician-Collected Nasopharyngeal (NP) Swabs.

Home self-collected midnasal swab (n = 28) Ct values were positively associated with the paired clinician-collected nasopharyngeal swab (n = 30) Ct value (correlation coefficient, 0.81; P = 5.1 × 10⁻⁶). The Ct values were calculated from a severe acute respiratory syndrome coronavirus 2 reverse transcriptase–polymerase chain reaction assay that targets 2 distinct regions of the virus, using Centers for Disease Control and Prevention primers and probes for the virus nucleocapsid (N) gene, N1 and N2.