What is a PSA test and how is it used?
Editor's note: first of two parts; read part two here .
编者注：两部分中的第一部分；在这里阅读第二部分。
In this two-part series, we'll describe the PSA test - how it's used, and how doctors perform next steps in the event of an abnormal reading.
在这个由两部分组成的系列中，我们将描述 PSA 测试 - 如何使用它，以及医生在读数异常时如何执行后续步骤。
Our first post addresses PSA screening for prostate cancer.
我们的第一篇文章讨论了前列腺癌的 PSA 筛查。
In the second part of our series, we'll describe how doctors use the PSA test to check the status of a cancer that's being watched or treated.
在我们系列的第二部分中，我们将描述医生如何使用 PSA 测试来检查正在观察或治疗的癌症的状态。
All prostate cells make PSA, a protein that helps to dissolve semen so that sperm cells can more easily reach and fertilize an egg.
所有前列腺细胞都会产生 PSA，这是一种有助于溶解精液的蛋白质，使精子细胞能够更容易地到达卵子并使其受精。
Normal and cancerous cells in the prostate each make PSA in similar amounts.
前列腺中的正常细胞和癌细胞各自产生的 PSA 量相似。
But since cancer cells are leakier, they release more of the protein into the bloodstream.
但由于癌细胞更容易渗漏，它们会向血液中释放更多的蛋白质。
PSA screening for prostate cancer came into widespread use during the early 1990s.
前列腺癌 PSA 筛查在 20 世纪 90 年代初得到广泛应用。
But the test is controversial: prostate cancer grows slowly, and the concern is that PSA screening flags too many low-grade tumors that might not be harmful during a man's life.
但该测试存在争议：前列腺癌生长缓慢，人们担心 PSA 筛查会标记出太多低级别肿瘤，而这些肿瘤可能对男性一生无害。
Still, studies do suggest that PSA testing, because it can detect cancers at early and more treatable stages, can be lifesaving in some cases.
尽管如此，研究确实表明，PSA 检测可以在早期和更容易治疗的阶段检测出癌症，因此在某些情况下可以挽救生命。
The US Preventive Services Task Force (USPSTF), an influential volunteer panel of experts in prevention and evidence-based medicine, takes a cautious stance on the matter.
美国预防服务工作组（USPSTF）是一个在预防和循证医学领域颇具影响力的志愿者专家小组，对此事采取谨慎立场。
The USPSTF advises doctors to discuss the pros and cons of PSA screening in men ages 55 to 69, but also cautions against screening men over the age of 70, and gives no recommendation at all for men under 55.
USPSTF 建议医生讨论对 55 至 69 岁男性进行 PSA 筛查的利弊，但也警告不要对 70 岁以上的男性进行筛查，并且对 55 岁以下的男性没有任何建议。
Some expert groups recommend earlier screening for men in higher-risk groups.
一些专家组建议对高危人群进行早期筛查。
Black men, for instance, are about twice as likely to be diagnosed with and die from prostate cancer than white men.
例如，黑人男性被诊断出患有前列腺癌和死于前列腺癌的可能性大约是白人的两倍。
The American Cancer Society (ACS) advises PSA screening for Black men at age 45, or even earlier screening for men with first-degree relatives who developed prostate cancer at young ages, as well as for men who test positive for mutations in certain cancer risk genes, such as BRCA1 and BRCA2.
美国癌症协会 (ACS) 建议黑人男性在 45 岁时进行 PSA 筛查，甚至更早地对有一级亲属在年轻时患上前列腺癌的男性以及某些癌症风险基因（如 BRCA1 和 BRCA2）突变检测呈阳性的男性进行筛查。
Importantly, activities that put pressure on the prostate gland (such as biking and sex) can cause PSA levels in blood to spike, so you should refrain from these activities for two to three days prior to testing.
重要的是，对前列腺施加压力的活动（例如骑自行车和性行为）可能会导致血液中 PSA 水平飙升，因此您应该在测试前两到三天内避免这些活动。
Health conditions affecting the prostate, such as infections, inflammation (prostatitis), or enlargement of the gland that occurs normally in older men (benign prostatic hyperplasia), can also cause PSA levels to spike in ways that are unrelated to cancer.
影响前列腺的健康状况，例如感染、炎症（前列腺炎）或老年男性常见的腺体肿大（良性前列腺增生），也可能导致 PSA 水平以与癌症无关的方式激增。
In general, PSA levels over 4 nanograms per milliliter (ng/mL) in blood are considered abnormal.
一般来说，血液中 PSA 水平超过 4 纳克每毫升 (ng/mL) 就被认为是异常的。
But doctors may also vary PSA cutoffs by age.
但医生也可能会根据年龄改变 PSA 的临界值。
For instance, a PSA of 3.5 ng/mL for a man in his 40s "is definitely abnormal," says Dr. Marc B.
例如，对于 40 多岁的男性来说，PSA 为 3.5 ng/mL“绝对是不正常的”，Marc B.
Garnick, the Gorman Brothers Professor of Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center, and editor in chief of the Harvard Medical School Guide to Prostate Diseases .
加尼克是哈佛医学院和贝斯以色列女执事医疗中心的戈尔曼兄弟医学教授，也是哈佛医学院前列腺疾病指南的主编。
However, a PSA of 5.5 ng/mL among men in their 60s, Dr. Garnick adds, may not be.
然而，Garnick 博士补充说，60 多岁男性的 PSA 值可能不是 5.5 ng/mL。
It's best to think of PSA values as being on a continuum, with higher levels associated with having prostate cancer.
最好将 PSA 值视为连续体，较高的水平与患有前列腺癌相关。
PSA testing can sometimes miss a cancer diagnosis altogether.
PSA 检测有时会完全漏掉癌症诊断。
One study found that up to 15% of men with PSA levels under 4 ng/mL actually did have prostate cancer, and a sizeable fraction of these tumors were clinically significant.
一项研究发现，PSA 水平低于 4 ng/mL 的男性中，高达 15% 的人实际上患有前列腺癌，并且这些肿瘤中有相当大一部分具有临床意义。
It's also possible for high-grade cancer to be present without causing a large increase in PSA.
也有可能存在高级别癌症，但不会导致 PSA 大幅增加。
That's because high-grade cancer cells can lose their ability to actually make the protein.
这是因为高级癌细胞可能会失去实际制造蛋白质的能力。
It used to be that elevated PSA readings were followed routinely by a prostate biopsy, and then treatment if cancer was detected.
过去，PSA 读数升高后，通常会进行前列腺活检，如果检测到癌症则进行治疗。
Today the paradigm is shifting.
如今，范式正在发生转变。
An abnormal result is now likely to be followed by a magnetic resonance imaging (MRI) scan, which can identify areas of the prostate gland that look suspicious for cancer.
现在，如果出现异常结果，可能会进行磁共振成像 (MRI) 扫描，该扫描可以识别出可疑癌症的前列腺区域。
In Europe and some hospitals in the US, men with abnormal PSA readings might avoid an initial biopsy altogether if the MRI results are negative.
在欧洲和美国的一些医院，如果 MRI 结果呈阴性，PSA 读数异常的男性可能会完全避免进行初次活检。
However, many physicians will still opt for an initial biopsy in such cases, followed by periodic PSA tests and MRI scans to determine if further biopsies are needed.
然而，在这种情况下，许多医生仍然会选择进行初步活检，然后定期进行 PSA 测试和 MRI 扫描，以确定是否需要进一步活检。
If the initial biopsy and MRI results are positive, then doctors will perform a targeted biopsy focused on areas where the MRI showed evidence of cancer.
如果最初的活检和 MRI 结果呈阳性，那么医生将针对 MRI 显示癌症证据的区域进行有针对性的活检。
If a cancer diagnosis is confirmed, then next steps will be initiated.
如果癌症诊断得到证实，则将启动后续步骤。
Today, many low-grade cancers are watched with active surveillance, and treated only if follow-up biopsies and MRI scans show worsening of the disease.
如今，许多低级别癌症都受到积极监测，只有在后续活检和核磁共振扫描显示疾病恶化时才进行治疗。
Higher-grade cancers will be treated immediately.
高级癌症将立即得到治疗。
"The goal of this risk-adapted approach to screening," Dr. Garnick says, is to "identify clinically significant cancers that actually do need treatment while decreasing diagnoses of clinically insignificant cancers that do not."
加尼克博士说：“这种适应风险的筛查方法的目标是识别实际上确实需要治疗的临床显着癌症，同时减少不需要治疗的临床不显着癌症的诊断。”
Rather than subject everyone with an elevated PSA reading to a biopsy, some doctors perform additional tests that involve more detailed interpretations of PSA levels.
一些医生不会对所有 PSA 读数升高的人进行活检，而是进行额外的测试，对 PSA 水平进行更详细的解释。
In the next part of our series, we'll address how PSA is used as a test for monitoring and managing patients with prostate cancer.
在我们系列的下一部分中，我们将讨论如何使用 PSA 作为监测和管理前列腺癌患者的测试。
C.W.
C.W.
Schmidt , Editor, Harvard Medical School Annual Report on Prostate Diseases
施密特，哈佛医学院前列腺疾病年度报告编辑
Marc B.
马克·B.
Garnick, MD , Editor in Chief, Harvard Medical School Annual Report on Prostate Diseases; Editorial Advisory Board Member, Harvard Health Publishing
Garnick，医学博士，哈佛医学院前列腺疾病年度报告主编；哈佛健康出版社编辑顾问委员会成员
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作为为读者提供的一项服务，哈佛健康出版社提供对我们存档内容库的访问。
Please note the date of last review or update on all articles.
请注意所有文章的最后审查或更新日期。
No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.
本网站上的任何内容，无论日期如何，都不应替代您的医生或其他合格临床医生的直接医疗建议。
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