尺度平均對等性檢定於基因改造產品統計評估之研究

Abstract

根據歐盟委員會 (European Commission)，植物或動物經由人工進行基因轉植之後，使其擁有新的特性或性質者，稱為基因改造生物 (genetically modified organisms, GMOs)。然而，隨著基改作物的發展，基改作物的安全性評估成為一大重要議題。基改作物的成分、基因型、外表型皆需要接受評估與鑑定。 歐盟食品安全管理局 (European Food Safety Authority, EFSA) 提出了針對基因改造作物安全性的統計考量評估方法。基改作物團隊 (GMO Panel) 建議同時利用差異性檢定 (proof of difference) 以及對等性檢定 (proof of equivalence) 來進行評估，並建立其信賴區間 (confidence interval)與對等性限度 (equivalence limit) 。 歐盟食品安全管理局 (European Food Safety Authority, EFSA) 對於安全性評估之科學統計考量建議，基改作物與其傳統作物之平均差異值應落於商業品種之自然變異中。因此，我們提出一項新的標準，亦即利用基改作物與其相對應之傳統作物的平均平方差異，與商業品種變異的比例，來進行基改作物安全性之對等性評估。 在混和效應的模式 (mixed-effects model) 之下，我們採用大樣本修正法 (Modified Large-Sample Method, MLS) 建立線性化指標的95% 信賴上限，作為基改作物與其相對應傳統作物的安全性對等性評估之檢定程序。最後利用模擬資料，以經驗型Ⅰ錯誤率和經驗檢定力來評估此一檢定程序。並以一個例子介紹本方法之應用。

According to the European Commission, genetically modified organisms (GMOs) are organisms, such as plants and animals, whose genetic characteristics are being modified artificially in order to give them a new property. However, with the development of genetically modified organisms, the assessment of GMOs for safety is an important issue. The components, genotype and phenotype of GM plants should be identified and evaluated. The Panel on GMOs of the European Food Safety Authority (EFSA) issued a guideline of scientific opinion on the statistical considerations for safety evaluation of GMOs in 2010. The GMO Panel of the EFSA indicated that both the proof of difference and the proof of equivalence are required for evaluation of the safety of GMOs. The EFSA’s scientific opinion on statistical considerations for the safety evaluation suggests that the difference in average between the GM crop and its conventional counterpart lie within the natural variability which can be estimated from the commercial varieties. Therefore, we propose a new criterion for assessment of equivalence of the safety profile between the GM crop and conventional crop which is the scaled square mean difference between the GM crop and its conventional crop with the variance of commercial crops as the scaled factor. Under the mixed-effects model, we applied the modified large-sample (MLS) method to derive the 95% upper confidence limit of the linearized criterion as the testing procedure for evaluation of equivalence in the safety profile between the GMO and its conventional crop. A simulation was conducted to investigate the performance, in terms of size and power, for the proposed procedure. A numerical example illustrates the applications of the proposed method.