目的：探讨现阶段新型冠状病毒（新冠）肺炎患者核酸检测中的相关问题和解决方案,为临床实验室提供参考。方法：选取2022年4月1日至4月10日入院的462例新冠肺炎患者,对其核酸检测基础循环阈值（cycle threshold,Ct值）和时间变化规律进行分析;分析3月20日至3月31日和4月1日至4月10日2个时间段内,因样本采集原因导致的核酸检测结果假阴性的情况。选取213份临床核酸检测样本,采用试剂A和试剂B进行平行检测,比较两者间的差异。根据相关文件,制定可疑样本的复检标准作业程序（standard operation procedure,SOP）文件;制备弱阳性质控品,参考定量试验的质控方法,每天分5批次检测,共4 d,获得20组数据,以此为初始数据制作质控图。结果：462例新冠肺炎患者的ORF1ab和N基因基础Ct值中位数分别为24.50（20.58~32.10）和23.38（19.43~31.24）,184例Ct值<30的患者,其Ct值升至30以上所需的中位时间为6（4~8） d。北部院区转型前期和转型后期,采样不合格率分别为12.4%和2.4%,差异具有统计学意义（P<0.01）。2种试剂在新冠核酸检测Ct值<30的样本中一致性较好,但检测Ct值在30~40的样本时,两者一致性降低。自制弱阳性质控品20次检测ORF1ab和N基因Ct值分别为35.17±0.55和35.23±0.88,能较好地监控临床上较为关注的Ct值在35左右的样本检测情况。结论：对于入院基础Ct值<30的新冠肺炎患者,其核酸检测频次可设定为3~4 d进行1次。2种常用新冠核酸检测试剂,在检测Ct值≤30的样本时一致性较好,但检测Ct值在30~40的样本时,两者结果差异明显。建立适用于定点医院实验室的样本复检规范和流程,同时应加强对Ct值处于35左右样品检测的质量监控,以保证实验室新冠核酸检测结果的一致性。

Objective: To explore the related problems and solutions in nucleic acid detection of COVID-19 patients at the present stage, and to provide reference for clinical laboratories. Methods: A total of 462 patients admitted from April 1 to April 10 were selected and their basic Ct values and time changes were analyzed. The false-negative test results caused by sample collection from March 20 to March 31 and from April 1 to April 10 were statistically analyzed, respectively. A total of 213 clinical samples were selected for parallel detection using reagents A and B to compare the differences between them. According to relevant documents, make the reinspection standard operation procedure (SOP) document of suspicious samples. According to the quality control method of quantitative test, weak-positive control was prepared and tested 5 batches every day for 4 days, and 20 groups of data were obtained and used as the initial data to make quality control charts. Results: The median Ct values of ORF1ab and N gene in 462 patients were 24.50 (20.58-32.10) and 23.38 (19.43-31.24), respectively. In 184 patients with Ct value less than 30, the median time for Ct value to rise above 30 was 6 days (4-8 days). The sampling unqualified rates were 12.4% and 2.4% in the early and late stages, respectively, and the difference was statistically significant (P<0.01). The consistency of the two reagents was good in the detection of samples with Ct values less than 30, but decreased in the detection of samples with Ct values between 30 and 40. The Ct values of ORF1ab and N gene in weak-positive control were 35.17±0.55 and 35.23±0.88, respectively, which can better monitor the detection of clinically concerned samples with Ct values within the range of 35. Conclusions: For COVID-19 patients with basic Ct value less than 30, the frequency of nucleic acid test can be set to once every 3 or 4 days. The difference between the two regents in detection of the smple with Ct value less than 30 is minor, but for the sample with Ct value 30-40, the difference is apparently large. Laboratories should establish the standards and procedures for sample re-test, and the quality monitoring at the level of Ct value 35 should be strengthened to ensure the consistency of COVID-19 nucleic acid test results.