Catalona W J, Partin A W, Slawin K M, Brawer M K, Flanigan R C, Patel A, Richie J P, deKernion J B, Walsh P C, Scardino P T, Lange P H, Subong E N, Parson R E, Gasior G H, Loveland K G, Southwick P C
Division of Urologic Surgery, Washington University School of Medicine, St Louis, MO 63110, USA.
JAMA. 1998 May 20;279(19):1542-7. doi: 10.1001/jama.279.19.1542.
The percentage of free prostate-specific antigen (PSA) in serum has been shown to enhance the specificity of PSA testing for prostate cancer detection, but earlier studies provided only preliminary cutoffs for clinical use.
To develop risk assessment guidelines and a cutoff value for defining abnormal percentage of free PSA in a population of men to whom the test would be applied.
Prospective blinded study using the Tandem PSA and free PSA assays (Hybritech Inc, San Diego, Calif).
Seven nationwide university medical centers.
A total of 773 men (379 with prostate cancer, 394 with benign prostatic disease) 50 to 75 years of age with a palpably benign prostate gland, PSA level of 4.0 to 10.0 ng/mL, and histologically confirmed diagnosis.
A percentage of free PSA cutoff that maintained 95% sensitivity for prostate cancer detection, and probability of cancer for individual patients.
The percentage of free PSA may be used in 2 ways: as a single cut-off (ie, perform a biopsy for all patients at or below a cutoff of 25% free PSA) or as an individual patient risk assessment (ie, base biopsy decisions on each patient's risk of cancer). The 25% free PSA cutoff detected 95% of cancers while avoiding 20% of unnecessary biopsies. The cancers associated with greater than 25% free PSA were more prevalent in older patients, and generally were less threatening in terms of tumor grade and volume. For individual patients, a lower percentage of free PSA was associated with a higher risk of cancer (range, 8%-56%). In the multivariate model used, the percentage of free PSA was an independent predictor of prostate cancer (odds ratio [OR], 3.2; 95% confidence interval [CI], 2.5-4.1; P < .001) and contributed significantly more than age (OR, 1.2; 95% CI, 0.92-1.55) or total PSA level (OR, 1.0; 95% CI, 0.92-1.11) in this cohort of subjects with total PSA values between 4.0 and 10.0 ng/mL.
Use of the percentage of free PSA can reduce unnecessary biopsies in patients undergoing evaluation for prostate cancer, with a minimal loss in sensitivity in detecting cancer. A cutoff of 25% or less free PSA is recommended for patients with PSA values between 4.0 and 10.0 ng/mL and a palpably benign gland, regardless of patient age or prostate size. To our knowledge, this study is the largest series to date evaluating the percentage of free PSA in a population representative of patients in whom the test would be used in clinical practice.
血清中游离前列腺特异性抗原（PSA）的百分比已被证明可提高PSA检测在前列腺癌检测中的特异性，但早期研究仅提供了临床应用的初步临界值。
制定风险评估指南和临界值，以定义将应用该检测的男性人群中游离PSA的异常百分比。
使用串联PSA和游离PSA检测法（Hybritech公司，加利福尼亚州圣地亚哥）进行前瞻性盲法研究。
七个全国性大学医学中心。
共有773名50至75岁的男性（379例前列腺癌患者，394例良性前列腺疾病患者），前列腺触诊为良性，PSA水平为4.0至10.0 ng/mL，且经组织学确诊。
维持前列腺癌检测95%敏感性的游离PSA临界百分比，以及个体患者的癌症概率。
游离PSA百分比可通过两种方式使用：作为单一临界值（即对游离PSA临界值为25%或更低的所有患者进行活检）或作为个体患者风险评估（即根据每位患者的癌症风险做出活检决定）。25%的游离PSA临界值可检测出95%的癌症，同时避免20%的不必要活检。游离PSA大于25%的癌症在老年患者中更常见，且一般在肿瘤分级和体积方面威胁性较小。对于个体患者，游离PSA百分比越低，癌症风险越高（范围为8%-56%）。在使用的多变量模型中，游离PSA百分比是前列腺癌的独立预测因子（优势比[OR]为3.2；95%置信区间[CI]为2.5-4.1；P <.001），在该总PSA值介于4.0至10.0 ng/mL的受试者队列中，其贡献显著大于年龄（OR为1.2；95% CI为0.92-1.55）或总PSA水平（OR为1.0；95% CI为0.92-1.11）。
使用游离PSA百分比可减少接受前列腺癌评估患者的不必要活检，在检测癌症时敏感性损失最小。对于PSA值介于4.0至10.0 ng/mL且前列腺触诊为良性的患者，无论患者年龄或前列腺大小，建议游离PSA临界值为25%或更低。据我们所知，本研究是迄今为止评估游离PSA百分比的最大系列研究，该研究人群代表了临床实践中使用该检测的患者。
