Fig. 4.

Limit of detection and specificity of DPO-based real-time PCR assay for TGEV, PEDV, PoRV, and PDCoV. (A) Limit of detection. 10-fold serially diluted PEDV-, TGEV-, PoRV-, or PDCoV-positive feces sample was used to evaluate the LOD of DPO-based real-time RT-PCR assay in clinical specimens, followed by calculation of the copy number of viral nucleic acids with standard curve equation established in this study. a: Amplification plot with 1–8: 10¹, 10², 10³, 10⁴, 10⁵, 10⁶, 10⁷, and 10⁸ dilution of feces sample; b: Melt curve. (B) Specificity result. a: Amplification plot; b: Melt curve. 1: target viruses; 2–12: other viruses and negative control.