Assessing the comparability of cycle threshold values derived from five
external quality assessment rounds for omicron nucleic test in Beijing,
Backgroud: A variety of open-system Real-time PCR (RT-PCR) assays for
several acute respiratory syndrome coronavirus 2 are currently in use.
The impact of omicron on the laboratories’ testing capacity is unknown.
This study aimed to ensure the quality of omicron testing and to assess
the comparability of cycle threshold (Ct) values derived from RT-PCR.
Methods: Five external quality assessment (EQA) rounds using the omicron
virus-like-particles were organized between February 2022 and June 2022
in Beijing, China. Results: A total of 1401 qualitative EQA reports have
been collected. The overall positive percentage agreement was 99.72%,
the negative percentage agreement was 99.75%, and the percent agreement
was 99.73%. This study observed a significant variance in Ct values
derived from different test systems. While interlaboratory using the
same test system yielded comparable Ct values. Conclusion: There was
strong concordance among laboratories performing qualitative omicron
testing. However, caution is needed when comparing Ct values derived
from the different test systems.