Differences in Ct Values in qPCR Tests for the Diagnosis of Mpox: Results of a Cross-Sectional Study

There is little evidence regarding whether Ct values are influenced by age, type of care, and the timing from the date of symptom onset to obtaining samples. The aim of this study was to determine the differences in the qPCR Ct values for mpox by age, type of care, and sampling opportunity. This descriptive, retrospective study analyzed the qPCR Ct values for mpox. The odds of a low Ct value were assessed by age group, type of care, sampling opportunity, and type of exudate. To determine the odds of a low Ct value, a multivariate bivariate analysis of the variables was performed, and a logistic regression model was developed. A total of 520 positive mpox tests were identified; the general median Ct value was 23.67. There was a difference in Ct values between inpatients and outpatients. Pharyngeal exudate samples had the highest Ct value (34.24), and pustule and scab exudate samples had the lowest values. Samples with a low Ct value (OR = 2.45, 95% CI: 1.13-5.29) were associated with hospital care. Low Ct values were more likely for samples from individuals being cared for in a hospital setting and with pustule skin lesions.