瘤体微卫星不稳定性（MSI）分析用于指导林奇综合征检测、治疗选择和预后评估。MSI的状态主要通过聚合酶链反应与毛细管电泳相结合进行检测。然而，存在着不同检测位点的各种检测方法，获得的结果可能会有所差异。本研究旨在评估不同检测方法之间的一致性和不同实验室之间的性能。外部质量评估（EQA）于2021年和2022年进行了MSI检测。每个样本组包含五个样本，包括微卫星稳定和MSI肿瘤组织。样本组被随机编码，并比较和评分返回的结果。经完全验证的样本组与市售检测方法具有良好的适用性。2021年有8个假阴性结果，2022年有5个错误结果（两个假阳性和三个假阴性）。参与实验室中，2021年有20个（74.07%）获得完全正确的结果；2022年有38个（92.68%）获得最佳评分。中国的MSI分子检测在为期2年的EQA研究中表现出改善。参与EQA计划是评估实验室性能和提高能力的一种有效方式。

Microsatellite instability (MSI) analysis of tumors informs Lynch syndrome testing, therapeutic choice, and prognosis. The status of MSI is mainly detected by polymerase chain reaction coupled with capillary electrophoresis. However, there are various assays with different detection loci and the obtained results may vary. The objective of this study was to evaluate the concordance among different assays and the performance among different laboratories.External quality assessment (EQA) for the detection of MSI was performed in 2021 and 2022. Each sample panel consisted of five samples, including microsatellite-stable and MSI tumor tissues. The sample panels were coded at random, and the returned results were compared and scored.The fully validated sample panels showed good applicability with commercially available assays. There were eight false-negative results in 2021 and five false results (two false-positives and three false-negatives) in 2022. Among the participating laboratories, in 2021, 20 (74.07%) provided completely correct results; in 2022, 38 (92.68%) obtained an optimal score.The molecular detection of MSI in China exhibited an improvement in a 2-year EQA study. Participation in EQA program is an efficient way of assessing the performance of laboratories and improving their ability.