Figure 2. Relationships of time from symptom onset to testing and cycle threshold values to results for rapid antigen detection tests and PCR for diagnosis of severe acute respiratory syndrome coronavirus 2, the Netherlands. A) Cycle thresholds of positive samples in relation to days since symptom onset, Ag RDT positivity, and culture outcomes of participation with known disease onset date (n = 140). B) PCR-positive samples by cycle threshold (n = 186) in relation to Ag RDT and culture test results. Ag RDT, antigen rapid detection test; Ct, cycle threshold; E gene, envelope gene; NA, not available; RT-PCR, reverse transcription PCR.