Gene Carrier Screening

Femina Healthcare 香港婦健 23682333

Gene Carrier Screening ($3000-10000; 175 type of autosomal recessive genes for $6500; 626 genes $7500)

1. Up to 24-60% of pregnant women carried one or more important gene causing serious genetic diseases.

2. If both couple carries a defective gene, 1 in 4 baby will have serious genetic disease.

3. For 175 autosomal recessive genes, we charge $6500 & 274 genes $10000 in single blood test. For 10 most common autosomal recessive conditions in Chinese & Fragile X screening ($3000). 626 genes for $7500.

 

What is genetic carrier screening?

Carrier screening is testing that's done to see whether you or your partner carry a genetic mutation that could cause a serious inherited disorder in your baby. Some of the more common disorders screened for include cystic fibrosis, sickle cell disease, thalassemia, and Tay-Sachs disease, but there are more than 100 others that can be tested for.

Many of these conditions are rare, but one large study found that 24 percent of the patients tested were carriers of at least one mutation. And the average risk of having a child with one of these diseases is higher than that of having a child with Down syndrome or a neural tube defect. What's more, these conditions will not be detected by prenatal tests like CVS and amniocentesis unless you have carrier screening first.

Here's how it works: These disorders are recessive, which means that a baby must inherit a defective gene from each parent to have the disease. If you're a carrier of a defective gene for a recessive disorder, that means you have one normal copy of the gene from one of your parents and one defective copy from the other. (Carriers don't usually have any symptoms of the disease.)

If both you and your partner are carriers of a disorder like cystic fibrosis, sickle cell disease, or Tay-Sachs disease, your child will have a 1 in 4 chance of inheriting one defective gene from each of you and being born with the disease.

How is genetic carrier screening done?

Ideally, you should have the option of being screened before you try to conceive. Your practitioner should offer it to you at your preconception visit. This way, if you find out that you and your partner are both carriers for a condition, you'll have a wider range of options. You can talk to a genetic counselor who will be able to tell you more about the condition and help you sort out your reproductive choices. (More about that below.)

Traditionally, couples have only been offered screening for one or two of the most common mutations if they are determined to be at risk for being a carrier. Risk factors include having a family member with the inherited disorder or who's a known carrier, or being part of an ethnic group at increased risk for the disease.

The problem with this approach is that many people don't belong to distinct ethnic categories. Many people are mixed race, adopted, or simply can't be sure what ethnicity their ancestors were. So there's no good way of determining who's at risk for being a carrier of any particular mutation.

Instead, you can choose to be screened for a wide range of disease mutations – more than 100 instead of just the one or two you may be "at risk" for. This approach is known as expanded carrier screening. If your caregiver doesn't offer you expanded screening, you can ask for it.

If you opt to be screened, you'll be asked to give a blood or saliva sample. If you're found to be a carrier, your partner will be screened as well. Or both partners may be screened at the same time to get the results faster.

You should be given the option of talking with a genetic counselor before the screening and after you get your results. This person can help you understand your results and your options for planning your family.

You might also consider consulting a medical geneticist, a doctor who is specially trained and board certified in genetics. The American College of Medical Genetics and Genomics offers an online tool for finding genetic services.

How much does genetic carrier screening cost?

The cost of carrier screening has declined dramatically in recent years, thanks to advances in technology. Since carrier screening is a recommended part of preconception and prenatal care, it's sometimes covered by insurance. On the other hand, some insurance companies consider the testing optional and don't cover it. Out-of-pocket costs vary, but they're typically not more than a few hundred dollars, even without insurance.

What are our options if we find out we're carriers?

If you find out before you're pregnant, you may decide to try artificial insemination with sperm from a donor who is not a carrier. Another option is to have in vitro fertilization, with special testing of the embryo before it's implanted. (This testing is known as preimplantation genetic diagnosis and many insurance companies are now covering it.) Some couples decide to adopt a child instead or not to have children at all.

Unfortunately, many women are not offered carrier screening until they're pregnant. If you're already pregnant and want carrier screening, it should be done as early as possible in your pregnancy. This will give you time to talk to a genetic counselor about the possibility that your baby has one of these disorders and figure out whether you want to have diagnostic testing like CVS or amniocentesis to find out.

It's important to understand that CVS and amniocentesis won't automatically tell you whether your child has this kind of genetic disorder. You have to have the carrier screening first so you know what mutation you and your partner have and can ask the testing center to look for it.

Early screening may have other advantages. For some diseases, knowing your baby is affected before birth makes it more likely that your child can be helped by early treatment. It allows you to line up the right medical specialists, who can be on hand to start treating your child after delivery.

Below is more information on some of the more common genetic conditions that carrier screening tests for.

Cystic fibrosis screening

Cystic fibrosis (CF) is a life-threatening genetic disease. People with CF are prone to breathing difficulties (including lung infections and severe lung damage), digestive problems, and other complications.

People at high risk include Caucasians and people who have a relative who has CF or who is known to be a carrier. One in 29 Caucasians carries an abnormal cystic fibrosis gene, compared to 1 in 46 Hispanic Americans, 1 in 61 African Americans, and 1 in 90 Asian Americans.

Because CF is one of the most common genetic disorders, the American College of Obstetricians and Gynecologists (ACOG) recommends that all women be offered genetic testing for some CF mutations as part of routine prenatal planning. If you carry the trait, your partner will be offered screening as well.

Among Caucasians, the chance that both parents are carriers is 1 in 841. If you and your partner are both carriers, the odds are 1 in 4 that your baby will have CF.

No screening test is 100 percent accurate, but if both you and your partner are negative for the CF mutation, your chance of having a baby with the condition is less than half of one percent.

Sickle cell screening

Sickle cell disease is a debilitating red blood cell disorder.

High-risk groups include people of African, Caribbean, South or Central American, Mediterranean, Indian, or Arabian descent. According to the National Institutes of Health, 1 in 13 African Americans carries the gene for this disorder.

If you're a carrier, your partner will be offered testing as well. If you and your partner are both carriers (or your partner is a carrier of a related blood disorder), your baby's chance of having sickle cell disease is 1 in 4.

Thalassemia screening

Thalassemia encompasses a varied group of inherited blood disorders, including some that are relatively mild and others that may cause severe anemia and other serious problems. More than 2 million people in the United States carry the genetic trait for it.

High-risk groups include people of Southeast Asian, Chinese, Indian, African, Middle Eastern, Italian, Greek, and Mediterranean ancestry, as well as anyone with a family history of the disease or a family member who is a known carrier.

People who have the thalassemia trait may have a mild form of anemia. If your initial blood count shows that your red blood cells are small but your iron status is normal, further testing will be done to check for the thalassemia trait.

If you're a carrier, your partner should be offered testing as well. If you're both carriers (or your partner is a carrier for another red blood cell disorder like sickle cell disease), your baby is at high risk for the disease.

Tay-Sachs screening

Tay-Sachs is a fatal disease of the central nervous system. About 1 in 250 people in the United States carries the genetic trait for it.

Among Central or Eastern European (Ashkenazi) Jews, French Canadians, and Cajuns, the carrier rate is about 1 in 27. Among Irish Americans, it's 1 in 50. You're considered high risk if you belong to any of these groups or have a family history of the disease.

(Ashkenazi Jews are also at risk for carrying the genes that cause two other severe nervous system disorders – familial dysautonomia and Canavan disease – and over three dozen other diseases as well.)

If you and your partner both carry the gene for Tay-Sachs, your baby has a 1 in 4 chance of having the disease.

香港婦健 23682333

遺傳病隱性基因篩選

$3000或以上

1. 隱性遺傳性疾病比唐氏綜合征更常見

2. 高達25-60%的孕婦具有至少一個或多個缺陷基因

3. 那些有異常基因的人有50%傳給她的孩子

4. 如果兩個夫妻有相似的缺陷基因,將有1/4的風險嚴重影響他們的孩子

5. 篩選包括地中海貧血(終身輸血依賴),脆性X(引起智力遲鈍),肌營養不良(影響行走能力),許多其他嚴重疾病。超過50%的香港孕婦隱性基因攜帶者

6. 如果兩個夫婦都是攜帶者,則有1/4的受影響嬰兒的風險

7. 我們提供 10個基因篩選 (只需$3000); 129個基因篩選 (只需$6000); 175個基因篩選 (只需$6500); 626個基因篩選,只需$7500港元

遺傳輔導及遺傳篩選 什麼是遺傳輔導 ? 遺傳輔導是透過對話,讓有可能出現遺傳異常問題的個人或家 庭,從中得到有關的資料及支援。輔導員會先向他們解釋複雜 的醫學及遺傳資料,及出現遺傳異常問題的概率及其後果,和 一些預防的途徑;同時幫助他們綜合資料,對遺傳測試、健康 護理 ,及是否生育作出個人的抉擇。在這些家庭明白其遺傳隱 患後,輔導員亦會因應他們在情緒上、心理上、社群上及經濟 上出現的問題作出支援。 誰提供遺傳輔導 ? 遺傳輔導通常由受過遺傳醫學及具有輔導技 巧的專業護理人士擔任。他們具備豐富的經 驗,能協助某些家庭認識先天缺陷的原因, 及其遺傳機制,亦提供一些可行的選擇,讓 父母對懷孕及其他問題作出明智的抉擇。 在遺傳輔導時,會進行些什麼 ? 1. 遺傳輔導員首先會了解個案中的人士尋求服務的原因,及了 解他們希望得知的資料。 2. 接著蒐集個案中各家族成員的遺傳背景,編製譜系。譜系有 助診斷某一遺傳異常、某人出現某種遺傳異常的機會,及其 孩子患上遺傳異常的可能性。 3. 除此之外,遺傳輔導員亦會提供遺傳疾病的一般資料,及解 釋其在家族中出現的機會。4. 譜系編製完畢及確認後,或會進行一些醫學測試,包括專門 的遺傳測試,例如核型圖(研究染色體)或 DNA 分析(測定基 因突變)、或普通測試,例如 X 光、超聲波掃描、尿液分析、 皮膚活組織檢驗或體格檢查。 5. 遺傳輔導員會協助統籌各類測試及提供支援性輔導,有需要 時更會轉介至其他社區服務。 6. 完成各項醫學測試及蒐集有關資料後,遺傳輔導員便可作出 診斷及知道某人是否沒有患上或沒有機 會患上某類遺傳疾 病 。 哪類人士需要遺傳輔導 ? 1. 已有一名孩子受到遺傳病的影響,及計劃再次懷孕或希望對 這種遺傳病知多一點的父母。 2. 已患有某一種遺傳病,及關心家族其他成員情況的人士。 3. 近親中患有某一種遺傳病,對自己及孩子情況憂心的人士。 什麼是遺傳篩選 ? 從遺傳篩選中,能夠找出孩子通過父母遺傳,可能得到的疾病 或先天缺陷。遺傳篩選包括核型圖或 DNA 分析,用以決定某人 是否有或可能有某種遺傳病的情況。沒有單一種的測試可判斷 某一對夫婦的孩子是否有機會患上任何一種遺傳疾病。此外, 遺傳篩選亦不能測知一些非遺傳原 因導致的先天缺陷 (例如暴 露於環境及毒素下,或偶然發生 )。

有哪些 測試種類 ? · 帶病基因者的檢定 — 家族成員中曾出現某些隱性遺傳疾病, 而又考慮生育孩子的夫婦,可進行這種測試,例如囊性纖維 變性及鐮狀細胞性貧血。 · 產前測試 — 胎兒的遺傳測試。若胎兒有潛在的遺傳異常危 機,例如唐氏綜合症,便可進行此類測試,下列是數種不同 的產前測試。 1. 母體血液測試 — 在懷孕期十五至十九週進行,測定甲胎 蛋白的水平。 2. 超聲波掃描 — 在懷孕期十五週後進行,檢驗胎兒的腦 部、心臟、脊髓、足、手或其他器官,是否出現先天缺 陷 。 3. 羊膜穿刺術 — 在懷孕期十二至二十週時檢驗羊水,測定 染色體有否異常,及其他物質例如甲胎蛋白。 4. 絨膜絨毛取樣 — 在懷孕期八至十二週時,從胎盤抽取一 些組織樣本,檢定染色體是否異常。 5. 臍帶血取樣 — 在懷孕期二十週後進行,從臍帶臍靜脈中 抽取血液樣本以作測試。 · 初生嬰兒篩選 — 從初生嬰兒中抽取血液或組織樣本,測試有 否遺傳病,從而及早進行治療,避免出現嚴重的健康問題或 夭折。

誰應進行遺傳篩選 ? · 孕婦在分娩時年齡超過 35 歲 。 · 已有一名孩子患上遺傳病或先天缺陷的夫婦。 · 已有數次流產經驗的婦女。 · 已發現一種不正常的現象,例如血清甲胎蛋白水平不正常、 圍繞胎兒的羊水太多或太少。 · 家族中有遺傳病史,例如地中海貧血症、G6PD 缺乏症、囊 性纖維變性、唐氏綜合症、血友病、鐮狀細胞性貧血。 · 一些種族或族裔有關的疾病,例如鐮狀細胞性貧血 (每十個非 洲裔美國人中有一個是攜帶者)和地中海貧血症(地中海沿岸 居民或亞裔人士有較多機會患上 )。