Hsieh Min-Shu, Hung Tze-Chun, Huang Hsien-Neng, Lu Chao-Wen, Hu Hsiang-Wei, Lai Jin-Yao, Lee Wen-Yao, Chen Jin-Shing
Department of Pathology, National Taiwan University Hospital, Taipei 10845, Taiwan.
Department of Pathology, National Taiwan University Cancer Center, Taipei 10672, Taiwan.
Diagnostics (Basel). 2025 Apr 8;15(8):948. doi: 10.3390/diagnostics15080948.
The cobas EGFR test v2, used for detecting EGFR mutations, can yield invalid results due to internal control (IC) issues, such as "IC not detected", "IC out of range: high Ct value", or "IC out of range: low Ct value". This study aimed to examine the incidence of invalid cobas results and explored the mechanism behind low IC Ct values. We retrospectively reviewed invalid cases, linking undetectable or high IC Ct values to inadequate DNA from small biopsies, as determined by conducting a pathological review. Cases with low IC Ct values were further tested, with the hypothesis of EGFR amplification confirmed using Sanger sequencing, the Idylla assay, next-generation sequencing (NGS), and fluorescence in situ hybridization (FISH). Among 4148 cases, the incidence of invalid results was 0.99% (41/4148). In four cases with low IC Ct values, EGFR amplification was confirmed using alternative methods with successful cobas testing on diluted DNA. These findings suggest that EGFR amplification, rather than specimen inadequacy, is the cause of low IC Ct results, making rebiopsy unnecessary. Alternative assays or diluted DNA allow for successful EGFR testing.
用于检测表皮生长因子受体（EGFR）突变的cobas EGFR检测v2可能会因内部控制（IC）问题产生无效结果，如“未检测到IC”、“IC超出范围：高Ct值”或“IC超出范围：低Ct值”。本研究旨在检查cobas检测无效结果的发生率，并探究低IC Ct值背后的机制。我们回顾性分析了无效病例，通过病理检查确定，未检测到或高IC Ct值与小活检样本DNA不足有关。对低IC Ct值的病例进行了进一步检测，通过桑格测序、Idylla检测、二代测序（NGS）和荧光原位杂交（FISH）证实了EGFR扩增的假设。在4148例病例中，无效结果的发生率为0.99%（41/4148）。在4例低IC Ct值病例中，使用替代方法证实了EGFR扩增，稀释后的DNA进行cobas检测成功。这些发现表明，EGFR扩增而非样本不足是低IC Ct结果的原因，无需再次活检。替代检测方法或稀释后的DNA可实现EGFR检测成功。
