CT values
Clinical SARS-CoV-2 testing was completed on five different platforms depending on patient encounter classification and turn-around-time requirements. Therefore, to standardize results and enable further characterization of SARS-CoV-2 CT values, we identified a subgroup of 7 children who had multiple respiratory samples available for repeat testing. Demographic and clinical information regarding this subgroup is summarized in Table 3.
Using the CDC assay for repeat testing, we evaluated SARS-CoV-2 CT values for a total of 20 specimens from these 7 individuals over time, presuming CT value as a surrogate for viral load. Five of 7 (71%) children had initial CTvalues <30, indicating a moderate to high viral load, and of these, 4 (57%) children had repeat testing 21 to 30 days later with CT values <30, suggesting persistence of moderate to high viral loads (Figure 3). Two of 7 (29%) patients had a single negative test followed by a positive test. By 40 days after initial positive testing, 6 of 7 (86%) children had negative tests (indicated as CT of 40) or CT values >35. The exception was one patient who remained positive until day 85. One patient (Patient 4) had a positive result on a specimen when tested clinically but a negative result when re-tested on the CDC assay. This is most likely indicative of a low viral load in the specimen, since the assay used for clinical testing and the CDC assay have similar, but not identical, limits of detection.