诊断为慢性乙型肝炎？您的HBV DNA测试告诉您什么？

StephenW

Diagnosed With Chronic Hepatitis B? What Does Your HBV DNA Test Tell You?
February 15, 2016 hepbtalk       
Image courtesy of Praisaeng, at FreeDigitalPhotos.net.
Image courtesy of Praisaeng, at FreeDigitalPhotos.net.

If you have been diagnosed with chronic hepatitis B, your doctor has probably run several blood tests that show if the infection is harming your liver and identify what stage of infection you are in.  Doctors consider all of these results when deciding if you need treatment and how often you should be monitored.

In this blog, we’ll examine how one of the tests — the HBV DNA or viral load test –can give you a snapshot into your hepatitis B infection and your health. The HBV DNA test  is performed on a blood sample using a Polymerase Chain Reaction (PCR) technique that rapidly generates HBV DNA fragments so they can be measured. Today, viral load is usually measured using international units per milliliter (IU/mL). However, in the past it was measured in copies per milliliter (copies/mL), and in some regions and labs, it is still used.

If you ever need to convert copies into international units, there are about 5.6 copies in one international unit, so 5,000 copies/mL equals about 893 IU/mL. Remember to keep copies of your lab information on file so you can track your status. An Excel spreadsheet works great.

The sensitivity of HBV DNA tests may vary with each lab so it’s a good idea to always use the same lab for your test. Labs usually measure down to about 300 IU/mL. Below that threshold, the viral load is considered “undetectable” – something all of us with chronic hepatitis B wants to hear.

How HBV DNA results are presented mathematically on your lab report can be confusing. Because the amount of virus in the blood may be very high – in the millions or billions – the result may be displayed as an exponent or a log, rather than a whole number. If this is confusing to you, please take a look at this explanation on the math.

What does viral load say about what stage of hepatitis B you are in? Your viral load also varies over time, depending on your age and “stage” of infection.

Children and adults in the “immune tolerant” stage can have viral loads in the millions or even billions. It sounds scary, but it’s not unusual. Your viral load can remain very high for decades until your immune system begins attacking the infection. Most children and young adults who test positive for the hepatitis B “e” antigen (HBeAg) generally have high viral loads, generally doctors don’t treat patients in this stage. Once their immune systems get rid of HBeAg and generate “e” antibodies (HBeAb), their viral loads begin to decline.

Adults with undetectable or low viral loads and no signs of liver damage are in an “inactive” stage. Adults with normal ALT (SGPT) levels, which usually indicate no current  liver damage, and undetectable or viral loads less than 2,000 IU/mL generally do not require treatment. However, it is important to confirm with your doctor that there is no evidence of advanced liver disease.

People in the “active” stage with elevated viral loads and signs of liver damage need treatment. Many people in their 40s, 50s or 60s, develop HBeAg-negative hepatitis B, though this may occur in younger individuals as well. Though individuals may have lost HBeAg, the virus has mutated over time and is able to keep replicating, putting these patients at risk of liver damage. Doctors recommend antiviral treatment if these patients’ viral load exceeds 2,000 IU/ML and their ALT levels are elevated.

Why is it important to measure HBV DNA during treatment? When daily antiviral pills (either tenofovir or entecavir) are prescribed, doctors measure your HBV DNA to see if the drug is working to reduce your viral load. Antivirals work by meddling with the viral DNA so the virus cannot reproduce effectively. Doctors measure your viral load to make sure the antiviral is working.

Why is measuring viral load important if you’re pregnant? Today, all pregnant women are screened for hepatitis B, and experts also want their viral loads to be measured. When pregnant women have high viral loads—exceeding 200,000 IU/mL—medical guidelines recommend antiviral therapy during their third trimester of pregnancy to reduce their risk of infecting their newborns. Babies born to HBV-infected women can become infected even if they are immunized at birth and treated with HBIG (hepatitis B antibodies) if their mothers have high viral loads.

It is important to remember that a viral load test provides you with important information, but it must be considered in relation to your other HBV and liver function tests results to determine if treatment is needed at all, or if you are responding favorably to current treatment. Although an undetectable or low viral load is good news, it does not necessarily guarantee that you have not, or will not experience liver damage. Hepatitis B is a tricky virus. Talk to your liver specialist about all of your test results.

StephenW

诊断为慢性乙型肝炎？您的HBV DNA测试告诉您什么？
2016年2月15日hepbtalk
图片由Praisaeng提供，位于FreeDigitalPhotos.net。
图片由Praisaeng提供，位于FreeDigitalPhotos.net。

如果您被诊断患有慢性乙型肝炎，您的医生可能会进行多次血液检查，以显示感染是否会伤害您的肝脏，并确定您所处的感染阶段。医生会在决定您是否需要治疗时考虑所有这些结果。你应该多久监视一次。

在这篇博客中，我们将研究其中一项测试 -  HBV DNA或病毒载量测试 - 可以为您提供有关您的乙型肝炎感染和您的健康的快照。使用聚合酶链式反应（PCR）技术对血液样品进行HBV DNA测试，该技术可快速产生HBV DNA片段，从而可以测量它们。今天，病毒载量通常使用每毫升国际单位（IU / mL）来测量。然而，在过去，它以每毫升副本（拷贝/ mL）进行测量，并且在一些地区和实验室中，仍然使用它。

如果您需要将副本转换为国际单位，则在一个国际单位中大约有5.6份副本，因此5,000份/ mL等于大约893 IU / mL。请记住将实验室信息的副本存档，以便跟踪您的状态。 Excel电子表格效果很好。

HBV DNA测试的灵敏度可能因每个实验室而异，因此最好始终使用相同的实验室进行测试。实验室通常测量低至约300 IU / mL。低于该阈值，病毒载量被认为是“不可检测的” - 我们所有患有慢性乙型肝炎的人都希望听到。

如何在您的实验室报告中以数学方式呈现HBV DNA结果可能会令人困惑。因为血液中的病毒量可能非常高 - 数百万或数十亿 - 结果可能显示为指数或日志，而不是整数。如果这让您感到困惑，请查看数学上的这个解释。

病毒载量对你患乙型肝炎的哪个阶段有什么影响？您的病毒载量也会随着时间的推移而变化，具体取决于您的年龄和感染的“阶段”。

处于“免疫耐受”阶段的儿童和成人可能有数百万甚至数十亿的病毒载量。这听起来很吓人，但这并不罕见。几十年后，您的病毒载量可能会非常高，直到您的免疫系统开始攻击感染。大多数乙型肝炎“e”抗原（HBeAg）检测呈阳性的儿童和年轻人通常具有高病毒载量，通常医生不会在此阶段治疗患者。一旦他们的免疫系统摆脱HBeAg并产生“e”抗体（HBeAb），他们的病毒载量开始下降。

具有不可检测或低病毒载量且无肝损伤迹象的成人处于“无活动”阶段。具有正常ALT（SGPT）水平的成人，通常表明目前没有肝脏损伤，以及低于2,000 IU / mL的不可检测或病毒载量通常不需要治疗。但是，重要的是要与您的医生确认没有晚期肝病的证据。

处于“活跃”阶段且病毒载量升高和肝脏损害迹象的人需要治疗。许多40多岁，50多岁或60多岁的人患有HBeAg阴性的乙型肝炎，尽管这可能发生在年轻人身上。虽然个体可能已经失去了HBeAg，但该病毒随着时间的推移已经发生突变并且能够继续复制，使这些患者面临肝损伤的风险。如果这些患者的病毒载量超过2,000 IU / ML并且其ALT水平升高，医生建议进行抗病毒治疗。

为什么在治疗期间测量HBV DNA很重要？当每日服用抗病毒药物（替诺福韦或恩替卡韦）时，医生会测量您的HBV DNA，看看该药物是否有效降低您的病毒载量。抗病毒药物通过干预病毒DNA起作用，因此病毒无法有效繁殖。医生测量你的病毒载量，以确保抗病毒药物正常工作。

如果您怀孕，为什么测量病毒载量很重要？今天，所有孕妇都接受乙型肝炎筛查，专家们也希望测量他们的病毒载量。当孕妇的病毒载量高达200,000 IU / mL时，医疗指南建议在怀孕的第三个三个月进行抗病毒治疗，以降低感染新生儿的风险。 HBV感染妇女所生的婴儿即使在出生时接种疫苗并且如果其母亲病毒载量高，也会接受HBIG（乙型肝炎抗体）治疗，即可感染。重要的是要记住，病毒载量测试为您提供重要信息，但必须考虑与您的其他HBV和肝功能测试结果相关，以确定是否需要治疗，或者您是否对当前治疗有积极响应。虽然无法检测到或低病毒载量是好消息，但并不一定能保证您没有或不会经历肝损伤。乙型肝炎是一种棘手的病毒。与您的肝脏专家讨论您的所有问题