有哪些HIV检查？

HIV检测有三种主要类型：抗体检测、组合或第四代检测、核酸检测（NAT）。HIV检测可以通过血液、口腔液体或尿液进行。

大多数HIV检测，包括大多数快速检测和家庭检测，都是抗体检测。抗体是你在暴露于像HIV或细菌等病毒时，免疫系统产生的。HIV抗体检测通过检测血液或口腔液体中的HIV抗体来判断是否感染HIV。通常，使用血液的抗体检测比使用口腔液体的检测能更早发现HIV感染。

通常，从感染HIV到身体产生足够的抗体进行抗体检测，可能需要3到12周（21至84天）。这一阶段称为窗口期。大约97%的人在这个窗口期内会产生可检测的抗体。如果你在窗口期内得到了负结果，建议在可能暴露后的3个月重新检测。

快速抗体筛查测试结果通常在30分钟以内即可得出。比如，OraQuick HIV测试通过口腔拭子采样，可以在20分钟内获得结果。该制造商提供保密的咨询和后续检测的转介。由于口腔液体中的抗体水平低于血液，所以血液检测比口腔液体检测能更早发现感染。这些测试可以在商店或在线购买，适合家庭使用，也适用于一些社区和诊所的检测项目。

Home Access HIV-1测试系统是一个家庭采样套件，用户通过手指采血后将样本邮寄到有执照的实验室，结果最快可以在下一个工作日得到。这种测试是匿名的，制造商提供保密的咨询和治疗转介。

如果你使用任何类型的抗体检测且结果为阳性，你需要进行后续测试以确认结果。如果你的首次测试是家庭快速测试且结果为阳性，你将被送往医疗提供者进行后续测试。如果你在检测实验室进行的首次测试为阳性，实验室将进行后续测试，通常是用相同的血液样本。

组合或第四代检测同时寻找HIV抗体和抗原。抗原是引起免疫系统反应的外来物质，是病毒本身的一部分，并在急性HIV感染阶段（感染后的初期阶段）存在。感染HIV后，即使没有产生抗体，也会出现名为p24的抗原。组合筛查检测现已成为实验室检测的推荐方式，并且在美国变得越来越常见。现在也有可供快速检测的组合测试。

如果你感染了HIV，身体需要2到6周（13到42天）时间才能产生足够的抗体和抗原，进行组合或第四代检测。这也是窗口期的表现。如果在窗口期内得到组合检测的负结果，建议在可能暴露后的3个月重新检测。

核酸检测（NAT）通过血液样本检测HIV。它直接寻找病毒而非抗体。此测试可以给出阳性/阴性结果或病毒在血液中的实际量（称为病毒载量测试）。这种测试非常昂贵，通常不用于常规筛查，除非有高风险暴露或有早期HIV感染症状的人。

核酸检测通常可以在暴露后的7到28天内检测到HIV。通常认为在感染的早期阶段，核酸检测是准确的。但是，最好同时进行抗体检测或组合测试，以帮助医生解读阴性核酸测试的结果。这是因为少数人随着时间推移自然降低血液中的病毒量，可能导致不准确的阴性结果。如果你正在服用暴露前预防（PrEP）或暴露后预防（PEP）药物，可能也会影响核酸检测的准确性。

在做HIV检测时，最好与医生讨论，选择最适合你的HIV检测方式。

检测后，了解检测结果非常重要，这样你可以在确诊为HIV阳性时与医生讨论治疗方案。如果你是HIV阴性，继续采取预防HIV的措施，例如每次性交时正确使用避孕套，并在处于高风险情况下服用预防HIV的药物。

What Are the Types of HIV Tests?

There are three broad types of HIV tests: antibody tests, combination or fourth-generation tests, and nucleic acid tests (NAT). HIV tests may be performed on blood, oral fluid, or urine.

Most HIV tests, including most rapid tests and home tests, are antibody tests. Antibodies are produced by your immune system when you're exposed to viruses like HIV or bacteria. HIV antibody tests look for these antibodies to HIV in your blood or oral fluid. In general, antibody tests using blood can detect HIV slightly sooner after infection than tests done with oral fluid.

It can take 3 to 12 weeks (21 to 84 days) for an HIV-positive person’s body to produce enough antibodies for an antibody test to detect HIV infection. This is called the window period. Approximately 97% of people will develop detectable antibodies during this window period. If you get a negative antibody test result during the window period, you should be re-tested 3 months after your possible exposure to HIV.

With a rapid antibody screening test, results are ready in 30 minutes or less. For example, the OraQuick HIV Test, which involves taking an oral swab, provides fast results in 20 minutes. The manufacturer provides confidential counseling and referrals for follow-up testing sites. Because the level of antibody in oral fluid is lower than in blood, blood tests find infection sooner after exposure than oral fluid tests. These tests are available for purchase in stores and online and may be used at home or in some community and clinic testing programs.

The Home Access HIV-1 Test System is a home collection kit, where you prick your finger to collect a blood sample, mail it to a licensed laboratory, and receive results as early as the next business day. This test is anonymous, and the manufacturer provides confidential counseling and referral for treatment.

If you use any type of antibody test and get a positive result, you will need to take a follow-up test to confirm the result. If your first test is a rapid home test and it’s positive, you will be sent to a healthcare provider for follow-up testing. If your first test is done in a testing lab and it’s positive, the lab will conduct follow-up testing, usually on the same blood sample as the first test.

A combination, or fourth-generation, test looks for both HIV antibodies and antigens. Antigens are foreign substances that trigger your immune system to react. The antigen is part of the virus itself and is present during acute HIV infection (the phase shortly after people are infected but before they develop antibodies to HIV). If you're infected with HIV, an antigen called p24 is produced even before antibodies develop. Combination screening tests are now recommended for lab tests and are becoming more common in the United States. There is also a rapid combination test available.

It can take 2 to 6 weeks (13 to 42 days) for a person’s body to produce enough antigens and antibodies for a combination or fourth-generation test to detect HIV. This is the window period. If you get a negative combination test result during the window period, you should be retested 3 months after your possible exposure.

A nucleic acid test (NAT) looks for HIV in the blood. It directly looks for the virus, not the antibodies to the virus. This test can give either a positive/negative result or the actual amount of virus in the blood (known as a viral load test). This test is very expensive and not routinely used for screening unless there’s been a high-risk exposure or early symptoms of HIV infection.

It can take 7 to 28 days for a NAT to detect HIV. NAT is usually considered accurate during the early stages of infection. However, it's best to get an antibody or combination test at the same time to help the doctor interpret the negative NAT. This is because some people naturally reduce the amount of virus in their blood over time, which can lead to an inaccurate negative NAT result. Taking pre-exposure prophylaxis (PrEP) or post-exposure prophylaxis (PEP) may also reduce the accuracy of NAT if you have HIV.

Talk to your healthcare provider to see which type of HIV test is right for you.

After you get tested, it’s important to find out your result so you can discuss treatment options with your doctor if you're HIV-positive. If you're HIV-negative, continue taking preventive actions, like using condoms the right way every time you have sex and taking medicines to prevent HIV if you're at high risk.