Evaluation of capabilities of Chinese provincial veterinary laboratories in detection of African swine fever virus: a proficiency testing program

Introduction Effective surveillance is essential for controlling African swine fever (ASF). Proficiency testing program (PTP) enhances the capability of veterinary laboratory in ASF surveillance and diagnosis. Methods To evaluate and compare the capabilities of official provincial veterinary laboratories in China for detection of African swine fever virus (ASFV), a PTP based on inter-laboratory comparisons (ILCs) was implemented during 2020 and 2021. A six-item test panel was developed for the PTP using certified reference material (CRM), consisting of one negative control and five ASFV nucleic acid-positive samples at varying dilutions. A quantitative polymerase chain reaction (qPCR) was employed to detect the six coding samples. The qualitative evaluation of each participant was based on the consistency of the obtained results with the reference results. A Z-score evaluation system was utilized for quantitative assessment, which was further validated using a Youden plot and principal component analysis (PCA). Subsequently, the equipment, reagents and consumables used by the participants for testing were subjected to statistical evaluation. Results Our results indicated that all laboratories (100%, 37/37) exhibited 100% consistency as expected. In the quantitative assessment, 89.19% (33/37) and 94.6% (35/37) of participants were qualified in the evaluations conducted in 2020 and 2021, respectively. Among the four participants who reported unsatisfactory results in 2020, one failed to detect two diluted weak positive samples, while the other three failed to detect strong positive samples. In 2021, two participants failed at both concentrations. There was no statistically significant difference in the method of nucleic acid extraction, reagents and consumables used in the PTP. Discussion This study reports for the first time the systematic evaluation of the capacity of Chinese official veterinary laboratories in quantitative nucleic acid detection of ASFV via a two-year PTP, with qualitative detection serving as a basic competency verification. The results provide a reference for enhancing the capability of prevention and control of ASF in China.