Vessella R L, Lange P H, Partin A W, Chan D W, Sokoll L J, Sasse E A, Crawford E D
University of Washington Medical School, Seattle, Washington 98195, USA.
Urology. 2000 Jun;55(6):909-14. doi: 10.1016/s0090-4295(00)00461-1.
The determination of the percentage of free prostate-specific antigen (%fPSA) enhances the specificity of prostate cancer (CaP) detection. This study was undertaken to assess the performance of %fPSA in differentiating benign prostate disease from CaP and to determine the CaP probability estimates using the AxSYM Free PSA and AxSYM Total PSA assays.
In this prospective study, 297 men, 50 years old or older, with a total PSA level between 4 and 10 ng/mL and a nonsuspicious digital rectal examination were enrolled at 10 clinical sites. All subjects underwent at least sextant prostate biopsies to establish the diagnosis. fPSA and total PSA (tPSA) levels were determined using the AxSYM Free PSA and AxSYM Total PSA assays. Percent fPSA values were compared with tPSA values to determine the appropriate cutoffs for prostate biopsy and to calculate the CaP probability estimates.
The strongest predictor of CaP in a logistic regression model was %fPSA (odds ratio 2.29), which contributed significantly more than age or tPSA to the predictive model. In this study population, a %fPSA cutoff of 26.4% would have detected 96% of subjects with CaP (sensitivity) and would have eliminated 27.4% of unnecessary biopsies (specificity). CaP probability estimates ranged from 9% to 69% and increased as the %fPSA value decreased. Men with a %fPSA level of 10% or lower had a 69% probability of CaP, and men with a %fPSA level of greater than 26% had a 9% probability of CaP.
Percent fPSA values can help differentiate CaP from benign prostate disease and reduce unnecessary biopsies in 27% of men 50 years old or older whose digital rectal examination was normal and whose tPSA level was between 4 and 10 ng/mL. A %fPSA result can assist the physician and patient in determining the probability of CaP and assessing the need for prostate biopsy.
测定游离前列腺特异性抗原百分比（%fPSA）可提高前列腺癌（CaP）检测的特异性。本研究旨在评估%fPSA在鉴别良性前列腺疾病与CaP方面的性能，并使用AxSYM游离PSA和AxSYM总PSA检测法确定CaP概率估计值。
在这项前瞻性研究中，10个临床地点招募了297名年龄在50岁及以上、总PSA水平在4至10 ng/mL之间且直肠指检无异常的男性。所有受试者均接受了至少六分区前列腺活检以确立诊断。使用AxSYM游离PSA和AxSYM总PSA检测法测定fPSA和总PSA（tPSA）水平。将%fPSA值与tPSA值进行比较，以确定前列腺活检的合适临界值，并计算CaP概率估计值。
在逻辑回归模型中，CaP的最强预测因子是%fPSA（比值比为2.29），其对预测模型的贡献显著大于年龄或tPSA。在本研究人群中，%fPSA临界值为26.4%时可检测出96%的CaP患者（敏感性），并可减少27.4%的不必要活检（特异性）。CaP概率估计值范围为9%至69%，且随着%fPSA值降低而升高。%fPSA水平为10%或更低的男性患CaP的概率为69%，%fPSA水平大于26%的男性患CaP的概率为9%。
%fPSA值有助于区分CaP与良性前列腺疾病，并减少27%年龄在50岁及以上、直肠指检正常且tPSA水平在4至10 ng/mL之间男性的不必要活检。%fPSA结果可协助医生和患者确定CaP的概率，并评估前列腺活检的必要性。
