Herschman J D, Smith D S, Catalona W J
Department of Surgery, Washington University School of Medicine, St. Louis, Missouri, USA.
Urology. 1997 Aug;50(2):239-43. doi: 10.1016/S0090-4295(97)00209-4.
Measurement of total serum prostate-specific antigen (PSA) is widely used as an aid to early detection of prostate cancer. Measurement of the ratio of free to total PSA may increase the specificity of PSA testing. To improve specificity further, other factors that may cause transient increases in PSA, such as ejaculation, have been identified. We prospectively studied the effect of ejaculation on total and free PSA levels and examined whether changes induced by ejaculation would affect recommendations for performing prostatic biopsy.
We measured the baseline total and free serum PSA levels and obtained measurements 1.6, and 24 hours after ejaculation in 20 volunteers (mean age 59 years). All men had baseline PSA levels less than 4.0 ng/mL. We used repeated-measures analysis of variance to test for changes in total, free, and percent free PSA after ejaculation. We also calculated the proportion of men with PSA levels greater than the expected biologic variability at each timepoint.
The mean total, free, and percent free serum PSA increased 1 hour after ejaculation. Mean total PSA levels remained significantly increased 6 and 24 hours after ejaculation. Mean free PSA decreased to baseline levels by 6 hours after ejaculation, and percent free PSA returned to baseline by 6 hours after ejaculation and then decreased below baseline by 24 hours. When normal biologic variation was accounted for, 40% of men, at 24 hours after ejaculation, had total PSA levels above the baseline level. Similarly, 24 hours after ejaculation, the percent free PSA remained above baseline level in 10% and below baseline level in 35% of the men.
Both total and free PSA increase immediately after ejaculation, with differing rates of return to baseline levels. PSA testing within 24 hours after ejaculation may lead to an erroneous interpretation of the results of both total and percent free PSA measurements in a small proportion of men.
血清总前列腺特异性抗原（PSA）检测被广泛用于辅助前列腺癌的早期诊断。游离PSA与总PSA比值的检测可能会提高PSA检测的特异性。为进一步提高特异性，已确定了其他可能导致PSA短暂升高的因素，如射精。我们前瞻性地研究了射精对总PSA和游离PSA水平的影响，并探讨射精引起的变化是否会影响前列腺活检的建议。
我们测量了20名志愿者（平均年龄59岁）射精前的血清总PSA和游离PSA基线水平，并在射精后1.6小时和24小时进行测量。所有男性的基线PSA水平均低于4.0 ng/mL。我们使用重复测量方差分析来检测射精后总PSA、游离PSA和游离PSA百分比的变化。我们还计算了每个时间点PSA水平高于预期生物学变异的男性比例。
射精后1小时，血清总PSA、游离PSA和游离PSA百分比的平均值均升高。射精后6小时和24小时，总PSA平均水平仍显著升高。射精后6小时，游离PSA平均水平降至基线水平，游离PSA百分比在射精后6小时恢复至基线水平，然后在24小时降至基线水平以下。考虑到正常生物学变异，射精后24小时，40%的男性总PSA水平高于基线水平。同样，射精后24小时，10%的男性游离PSA百分比仍高于基线水平，35%的男性低于基线水平。
射精后总PSA和游离PSA均立即升高，但恢复至基线水平的速率不同。射精后24小时内进行PSA检测可能会导致一小部分男性的总PSA和游离PSA百分比测量结果出现错误解读。
