[National external quality assessment for molecular detection of severe acute respiratory syndrome coronavirus 2 Delta variant].

Objective: To clarify the impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant on the performance of existing molecular diagnostic assays, and investigate the detection ability of clinical laboratories across China. Methods: The first nationwide external quality assessment (EQA) for molecular detection of Delta variant was carried out based on the non-infectious phage virus-like particles samples, which were prepared by genetic engineering methods and distributed to 8 488 laboratories nationwide. The EQA panel was composed of three Delta variant samples (7.5×102, 1.5×103 and 6.0×103 copies/ml), one non-variant weak positive sample and one negative sample. The percentage of agreement (PA) of Delta variant samples with different concentration, the PA of Delta variant and non-variant samples with 7.5×102 copies/ml, the PA of assays used by more than 100 laboratories for Delta variant samples with different concentration and the PA of Delta variant and non-variant samples with 7.5×102 copies/ml were calculated and analyzed. Results: The data from 8 127 laboratories were available for evaluation. The testing capability of 98.77% (8 027/8 127) of the participating laboratories was found to be competent in reporting correct results for all samples. The overall percentage of agreement (OPA), negative percentage of agreement (NPA) and positive percentage of agreement (PPA) of the samples were 99.64% (40 490/40 635), 99.73% (8 105/8 127), 99.62% (32 385/32 508), respectively. With the decrease of the concentration of the samples, the PPA of Delta variant samples decreased. The PPAs were 99.41% and 99.51% for Delta variant and non-variant samples with 7.5×102 copies/ml, respectively, with no statistical difference (P=0.392). The OPA, NPA and PPA of the assays used by more than 100 laboratories were all greater than 98%, and no statistical difference of the PPAs was identified between Delta variant and non-variant samples with 7.5×102 copies/ml (P>0.05). Conclusions: Delta variant fails to impair the performance of current molecular diagnostic assays in China. The clinical laboratories have the same detection capabilities for Delta variant and non-variant samples. However, in certain laboratories, further improvement is required to ensure the accurate detection of weak positive samples.目的： 明确我国现有核酸检测试剂对新型冠状病毒德尔塔变异株的适用性，了解全国临床实验室对德尔塔变异株的检测能力。 方法： 采用基因工程方法制备无生物传染危险性的噬菌体病毒样颗粒模拟样本，发放到全国8 488家实验室，开展全国新型冠状病毒德尔塔变异株核酸检测室间质量评价。样本盘包括3支不同浓度的德尔塔变异株样本（7.5×102、1.5×103、6.0×103 拷贝/ml）、1支非变异株弱阳性样本（7.5×102 拷贝/ml）和1支阴性样本。计算实验室检测不同浓度德尔塔变异株样本的符合率、同等浓度水平的德尔塔变异株和非变异株样本的符合率，以及使用实验室数≥100家的各检测试剂对不同浓度德尔塔变异株样本的检测符合率、同等浓度水平的德尔塔变异株和非变异株样本的检测符合率。 结果： 本次室间质量评价共计收到8 127份回报结果，成绩合格的实验室占98.77%（8 027/8 127）。样本的总符合率为99.64%（40 490/40 635），阴性符合率为99.73%（8 105/8 127），阳性符合率为99.62%（32 385/32 508）。德尔塔变异株阳性样本符合率随浓度减少相应降低。同浓度（7.5×102 拷贝/ml）水平的德尔塔变异株和非变异株样本符合率分别为99.41%（8 079/8 127）、99.51%（8 087/8 127），差异无统计学意义（P=0.392）。使用实验室数≥100家的各检测试剂的样本总符合率、阴性符合率和阳性符合率均>98%，对7.5×102 拷贝/ml的德尔塔变异株和非变异株样本检测的符合率差异均无统计学意义（均P>0.05）。 结论： 德尔塔变异株未影响我国现有核酸检测试剂的适用性。临床实验室对德尔塔变异株和非变异株具有同等检测能力，但少部分实验室对弱阳性样本的检测能力需进一步提高。.