基因檢測結果呈陰性？這可能是“虛假的安慰”
隨着醫療技術的發展，越來越多的公司開展了基因檢測項目，通過分析受試者提供的生物學樣本，檢測其基因變異，分析未來患上某種疾病的機率。但最新研究指出，即使檢測結果呈陰性，人們也不能完全放鬆警惕，因爲這可能是“虛假的安慰”。
Consumer genetic tests could be giving false reassurance to those at heightened risk of cancers, according to findings presented at an international conference last week.
上週一次國際會議上公佈的研究結果顯示，消費者基因測試可能會給那些癌症風險更高的人帶來虛假的安慰。
The study, by clinical genetic testing company Invitae, revealed that tests for breast and bowel cancer risk by direct-to-consumer companies such as 23andMe give negative results to the vast majority of those carrying DNA mutations in the genes under investigation.
這項由臨牀基因檢測公司Invitae開展的研究顯示，23andMe等直接面向消費者的公司對乳腺癌和腸癌風險的檢測顯示，絕大多數攜帶受測基因DNA突變的人檢測結果都是陰性的。
“These tests should not be taken at face value at all, whether they are positive or negative,” said Edward Esplin from Invitae ahead of the annual meeting of the American Society of Human Genetics in Houston, Texas.
在美國人類遺傳學學會於德克薩斯州休斯頓召開年度會議之前，來自Invitae的愛德華·埃斯普林說：“這些檢測不應該只看表面價值，無論檢測結果是陽性還是陰性。”
face value：表面價值
“The data really underscores that there needs to be increased awareness that results from this type of screening may not be wrong but they’re woefully incomplete.”
“研究數據強調的是，人們需要認識到，這種檢測的結果可能不會是錯誤的，但遺憾的是，它們是不完整的。”
woefully [ˈwəʊfəli]：adv.悲傷地；不幸地
The research also showed that those from Asian and African-American backgrounds were more likely to carry mutations that were not designed to be detected by the consumer tests.
這項研究還表明，有亞裔和非洲裔血統的美國人更有可能攜帶突變基因，而消費者測試無法檢測到這些突變基因。
The research focused on DNA-based tests relating to breast, ovarian and bowel cancer that were recently approved by the US Food and Drug Administration.
這項研究的重點是美國食品和藥物管理局（FDA）最近批准的與乳腺癌、卵巢癌和腸癌相關的DNA檢測。
The tests operate by a subject sending a DNA swab in the post for analysis and then receiving results with information about how their genetics could influence their health.
測試是這樣進行的：受試者寄送DNA樣本用於分析，然後收到有關基因對健康影響的檢測結果。
In the case of breast and ovarian cancer, the FDA has approved a screening test for three specific mutations on the BRCA1 and BRCA2 genes, which are most common in people of Ashkenazi Jewish heritage. However, these mutations are rare in people from other backgrounds.
就乳腺癌和卵巢癌而言，FDA已經批准了一項針對BRCA1和BRCA2基因三種特定突變的篩查測試，這兩種突變在德系猶太人中最爲常見。然而，這些突變在其他血統的人身上很少見。
Ashkenazi[ˌæʃkəˈnɑːzi]：n.德系猶太人
Similarly, for bowel cancer, 23andMe offers FDA-authorised tests for two mutations, which are most common among individuals of northern European ancestry. The company explains the limitations of these tests to consumers and on its website.
類似地，對於腸癌，23andMe公司提供FDA授權的兩種基因突變檢測，這在北歐血統的人中最爲常見。該公司在其網站上向消費者解釋了這些測試的侷限性。
Esplin said that despite this, consumers could be wrongly reassured by a negative result.
埃斯普林表示，儘管如此，消費者仍可能被陰性結果錯誤地打消疑慮。
The study analysed the DNA of 270,806 patients who had been referred by healthcare providers for testing of the MUTYH gene, and 119,328 who had been referred for BRCA1/2 genetic testing.
這項研究分析了270806名被醫療機構推薦進行MUTYH基因檢測患者的DNA，以及119328名被推薦進行BRCA1/2基因檢測患者的DNA。
It showed that for both tests, the majority of those carrying mutations would not be spotted, which Invitae describes as a “clinical false-negative result”.
結果顯示，在這兩種檢測中，大多數攜帶突變的人都沒有被發現，Invitae將其描述爲“臨牀假陰性結果”。
For MUYTH, 40% of individuals with mutations in both copies of their MUTYH genes – consistent with an almost 100% lifetime risk of bowel cancer – had different mutations to those screened for in the FDA-approved test. This figure rose to 100% for those from Asian backgrounds and 75% for African-Americans.
對於MUYTH基因，在攜帶有兩種MUTYH基因拷貝突變的人中，有40%的人的突變與FDA授權檢測到的突變不同。這個數字在亞裔美國人中上升到100%，在非洲裔美國人中上升到75%。攜帶有這兩種基因突變的人一生中罹患腸癌的風險幾乎是100%。
For BRCA genes, 94% of non-Ashkenazi Jewish individuals and 19% of those of Ashkenazi heritage had a mutation that would be missed. Again, the figures were highest for those of Asian (98%) and African-American (99%) ancestry.
對於BRCA基因，94%的非德系猶太人和19%的德系猶太人攜帶有可能被遺漏的基因突變。同樣，亞裔（98%）和非裔（99%）的比例最高。
“A clinical false-negative result can be incorrectly reassuring, excluding a patient from receiving the preventive care they need based on their risk,” he added. “It could be the difference between preventing cancer and developing cancer.”
他補充說：“臨牀假陰性的結果可能是誤導性的安慰，使人們不再接受需要基於風險而進行的預防性治療。人們可能會患上原本可以預防的癌症。”
In response to the findings, 23andMe said in a statement: “The claims made by a competitor that we are returning ‘clinical false negatives’ is incorrect and a false characterisation of 23andMe’s test. Our test is extremely accurate. As part of the FDA authorisation process we’ve demonstrated over 99% accuracy for the variants we test for in our health product.”
針對這些發現，23andMe在一份聲明中表示：“競爭對手聲稱我們正將‘臨牀假陰性結果’退回是假消息，其對本公司測試的特徵描述也是錯誤的。我們的測試非常準確。作爲FDA授權檢測過程的一部分，我們已經證明，我們的健康產品基因變異測試準確性超過99%。”
The company said it makes clear to customers that it tests only for certain genetic variants and that customers should not forgo any recommended testing based on 23andMe results. “23andMe is not a diagnostic test,” the company said. “If an individual has a family history of cancer or other indications for clinical testing we always recommend consulting a healthcare provider first.”
該公司表示，已向客戶明確表示，只檢測某些基因變異，客戶不應放棄任何基於23andMe結果的推薦檢測。該公司表示：“這不是診斷測試。如果一個人有癌症家族史或其他臨牀檢測的適應症，我們一直建議首先諮詢醫療機構。”
forgo[fɔːˈɡəʊ]：vi.放棄；停止
diagnostic[ˌdaɪəɡˈnɒstɪk]：adj.診斷的
Prof Anneke Lucassen, a clinical geneticist at the University of Southampton, said that, in her experience, non-specialists would be likely to wrongly interpret negative results as an “all-clear”.
南安普頓大學臨牀遺傳學家安妮克•盧卡森教授表示，根據她的經驗，非專業人士很可能會錯誤地將陰性結果解讀爲“沒有風險”。
“I do think the ‘false-negative’ rate is an issue, not necessarily through the companies’ fault but through low general awareness,” she said. “Most people who come to clinic ask: ‘Have I got the gene for breast cancer?’ and imagine it’s a single test, not that the test involves looking through around 20,000 letters of the genetic code to see if any one of them might be different.”
她說：“我確實認爲假陰性率是個問題，這不一定是由於公司的失誤，而是由於人們的普遍意識不強。大多數來診所的人會問：‘我有乳腺癌的基因嗎？’想象一下，這是一個單一的測試，而不是通過檢查大約兩萬個基因序列編碼來判斷哪些有所不同。”
