Veltri R W, Miller M C
UroSciences Group, UroCor, Inc., Oklahoma City, Oklahoma 73104, USA.
Urology. 1999 Apr;53(4):736-45. doi: 10.1016/s0090-4295(98)00617-7.
To evaluate the ability of free PSA (fPSA), total PSA (tPSA), and the free/total PSA (f/t PSA) ratio to differentiate between benign prostate disease (benign prostatic hyperplasia [BPH] and no evidence of malignancy [NEM]) and prostate cancer (CaP) using two different testing populations, and to compare predictive probabilities for the two test populations.
One test population consisted of sera from 531 men with clinically well-defined and biopsy-confirmed BPH (n = 255) or CaP (n = 276), with tPSA values ranging from 2 to 20 ng/mL. All of these serum samples were retrospective and obtained from patients evaluated in academic settings before any treatment. A second test population consisted of a prospective analysis of sera obtained from 4870 men, collected by urologists throughout the United States and processed at a single pathology laboratory. All these patients had a systematic biopsy evaluated and diagnosed at the same pathology laboratory, with the diagnosis categorized as either NEM (n = 2961) or CaP (n = 1909). No additional information on concurrent disease or pre- or current treatment status was known for this test population. For both populations, two tPSA reflex range groups, 2 to 10 and 2 to 20 ng/mL, were evaluated.
Both test populations benefited from the application of either fPSA alone or the f/t PSA ratio to differentiate benign from malignant disease (t test P value less than 0.001). The receiver operating characteristic (ROC) curve for the f/t PSA ratio had an area under the curve (AUC) of 72% for n = 531 versus 63% for n = 4870, irrespective of the tPSA reflex range. Average fPSA values demonstrated a linear correlation to a range of tPSA concentrations for both test populations. Predictive probabilities (adjusted for established cancer prevalence rates in the academic population [n = 531]) calculated using f/t PSA ratios also demonstrated their value in contrasting the performance characteristics in the two test populations.
The fPSA and f/t PSA ratio improved the differentiation of benign disease and CaP in two different patient samples. The f/t PSA ratio demonstrated an increased sensitivity and specificity when applied to differentiate clinically well-defined BPH and CaP (n = 531). The differences in the results between the two test samples are probably attributable to the variability of the patient's disease and treatment status in the larger, less refined, community-based population. The use of predictive probabilities provides the opportunity to provide patient-specific cancer probabilities instead of using population-based specific single cutoffs.
使用两个不同的测试人群，评估游离前列腺特异性抗原（fPSA）、总前列腺特异性抗原（tPSA）以及游离/总前列腺特异性抗原（f/t PSA）比值区分良性前列腺疾病（良性前列腺增生[BPH]和无恶性证据[NEM]）与前列腺癌（CaP）的能力，并比较两个测试人群的预测概率。
一个测试人群由531名男性的血清组成，这些男性临床诊断明确且经活检证实为BPH（n = 255）或CaP（n = 276），tPSA值范围为2至20 ng/mL。所有这些血清样本均为回顾性样本，取自学术环境中未经任何治疗的患者。第二个测试人群由对4870名男性血清的前瞻性分析组成，这些血清由美国各地的泌尿科医生收集，并在单一病理实验室进行处理。所有这些患者均在同一病理实验室进行了系统活检并确诊，诊断分为NEM（n = 2961）或CaP（n = 1909）。对于这个测试人群，不知道关于并发疾病或既往及当前治疗状态的其他信息。对于这两个人群，评估了两个tPSA反应范围组，即2至10 ng/mL和2至20 ng/mL。
两个测试人群通过单独应用fPSA或f/t PSA比值来区分良性与恶性疾病均有益（t检验P值小于0.001）。无论tPSA反应范围如何，f/t PSA比值的受试者工作特征（ROC）曲线在n = 531时曲线下面积（AUC）为72%，在n = 4870时为63%。对于两个测试人群，平均fPSA值与一系列tPSA浓度呈线性相关。使用f/t PSA比值计算的预测概率（根据学术人群[n = 531]中既定的癌症患病率进行调整）也证明了其在对比两个测试人群性能特征方面的价值。
fPSA和f/t PSA比值在两个不同的患者样本中改善了良性疾病与CaP的区分。当应用于区分临床诊断明确的BPH和CaP（n = 531）时，f/t PSA比值显示出更高的敏感性和特异性。两个测试样本结果的差异可能归因于在规模更大、精细化程度较低的社区人群中患者疾病和治疗状态的变异性。使用预测概率提供了机会来提供针对患者的癌症概率，而不是使用基于人群的特定单一临界值。
