Limit of Detection (LoD) Determination
The four OaPV genes were detected using ddPCR standard curves of the positive controls used in the serial dilutions. A calibration curve of the positive sample dilutions (log10) was plotted against the number of PCR cycles. The linear range was determined by diluting the positive controls from 105 to 10−1 copies/μL, detecting each dilution thrice, taking the average value, and correlating the result with the theoretical value. The lower detection limit obtained by ddPCR, with values <1 copies/μL, indicated high sensitivity.