In this study, the QX200™ Droplet Digital™ PCR System (Bio-Rad, Hercules, CA, USA) was used. The ddPCR reaction mixtures contained: 1 × ddPCR™ Supermix for Probes (No dUTP) (Bio-Rad, Pleasanton, CA, USA), 500 nM of each primer, 500 nM of each probe (FAM and HEX), sample and water to a final volume of 22 μL. Droplets were generated using the QX200™ Droplet Generator (DG). A DG8™ cartridge holder and gasket with 70 μL of Droplet Generation Oil/well, 20 μL of PCR reaction mixture were used. From the DG8 cartridge, 40 μL of the generated droplets were transferred to ddPCR™ 96-well-plate. The plate was then heat-sealed using a PX1™ PCR plate sealer and a pierceable foil seal. PCR was performed using a C1000 Touch™ deep-well thermal cycler. The thermocycling protocol was: initial denaturation at 95 °C for 10 min, then 40 cycles of denaturation at 95 °C for 30 sec, annealing at 55 °C for 1 min and extension for 1 min, followed by a final last incubation at 98 °C for 10 min and storage at 4 °C. After amplification,
