前列腺特异性抗原

检测血液中前列腺特异性抗原（PSA）的总量。PSA已经成为筛查和监测前列腺癌的一个肿瘤标志物，它是一个很好的指标，但并不完美。PSA浓度的升高与前列腺癌相关，但也可见于前列腺炎和前列腺良性增生（benign prostatic hyperplasia ，BPH）。PSA的轻度或中度升高可见于非洲裔美国人中，而且随着年龄的增长，PSA浓度逐渐升高。

PSA是主要由前列腺细胞产生的蛋白。前列腺是一个包饶在男性尿道外的小腺体，产生的液体是精液的组成成分。大部分前列腺产生的PSA会分泌到前列腺液中，但是也有少量会分泌到血液中。PSA在血中有两种存在形式：游离的（未结合）和结合的（与蛋白结合）。最常见的PSA检测是检测总的PSA，即是检测游离PSA与结合PSA的总和。当医生申请“PSA检测”时，即检测总PSA。

游离与结合的PSA也可以分别检测，它们能更好的区分恶性和非恶性的PSA升高。通常前列腺癌患者体内两种PSA形式的比例会发生改变--游离PSA浓度降低和结合PSA浓度增加。

PSA不能用于诊断前列腺癌，诊断前列腺癌的金标准仍是前列腺活检，采集少量前列腺组织样本在显微镜下鉴别异常细胞。联合总PSA检测和直肠指检（DRE）可以帮助确定是否有必要进行前列腺活检。PSA检测的目的是减少不必要的活检以及发现还局限于前列腺内的癌症。因为前列腺癌随男性年龄的增长而发病率升高，前列腺癌细胞生长非常缓慢，PSA　筛查具有非常重要的临床意义。医生必须尽力检出前列腺癌并能区分那些缓慢增长的和具有侵袭性、扩散性（扩散到身体的部位）的前列腺癌。过度诊断和过度治疗都是医生目前需要解决的问题。在某些情况下，治疗可能会引起严重的副作用，也许比癌症本身更糟糕，比如出现阳痿和早泄。PSA检测和DRE能发现大部分前列腺癌，但是一般不能预测患者疾病的进程。

手臂处静脉穿刺采血获得血液标本。

样本需在临床医生进行直肠指检（DRE）前和前列腺活检前（或几周以后）采集。

疾病: 前列腺癌, 良性前列腺肥大(BPH)
筛查: 前列腺癌- 成年人(30-49), 前列腺癌- 成年人50及以上

National Cancer Institute: What You Need to Know about Prostate Cancer
National Cancer Institute: Fact Sheet, Prostate-Specific Antigen (PSA) Test
American Cancer Society: Detailed Guide, Prostate Cancer.
American Cancer Society: Prostate Cancer
Centers for Disease Control and Prevention: Prostate Cancer
Prostate Cancer Research Institute

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