Okamura Kikuo, Takaba Hidenori, Kamihira Osamu, Kinukawa Tsuneo, Ono Yoshinari, Ohshima Shinichi, Nagasaka Tetsuro
Depatment of Urology, National Center for Geriatrics and Gerontology, Obu, Japan.
Int J Urol. 2005 Apr;12(4):346-52. doi: 10.1111/j.1442-2042.2005.01056.x.
To investigate whether using a new concept of relative probability for prostate cancer (RPpca) can increase sensitivity and specificity in detecting prostate cancer.
For 217 patients with total prostate-specific antigen (PSA) level of 4-20 ng/mL, prostate volume and free to total PSA (F/T) ratio were measured. From the fitted curves between positive predictive values for prostate cancer and age, prostate volume, total PSA or the F/T ratio, each function predicting prostate cancer was determined. RPpca defined by the combined functions of age, prostate volume, total PSA and F/T ratio was calculated for each individual patient. The probability of prostate cancer was also calculated, using logistic regression analysis (LRPpca). Receiver-operating characteristic analysis was performed to elucidate the areas under the curve (AUC), sensitivities and specificities and cutoff values of the conventional and new parameters. Finally, we investigated the applicability of the above parameters in the other patient group using a different PSA assay kit (AxSYM).
Although RPpca had the largest AUC in the total PSA range of 4-20 ng/mL, it did not reach statistical significance between RPpca and F/T ratio or LRPpca. The cutoff values of F/T ratio, LRPpca and RPpca were determined as 0.15, 0.12 and 0.20, respectively. Using these cutoff values in AxSYM data, RPpca had the highest sensitivity (91%) and specificity (57%).
RPpca can provide more precise information to avoid unnecessary biopsy than LRPpca or F/T ratio. RPpca could be valuable to decide whether to perform prostate biopsy when using various PSA kits.
研究使用前列腺癌相对概率（RPpca）这一新概念是否能提高前列腺癌检测的敏感性和特异性。
对217例总前列腺特异性抗原（PSA）水平为4 - 20 ng/mL的患者测量前列腺体积及游离PSA与总PSA（F/T）比值。根据前列腺癌阳性预测值与年龄、前列腺体积、总PSA或F/T比值之间的拟合曲线，确定每个预测前列腺癌的函数。计算每位患者由年龄、前列腺体积、总PSA和F/T比值的联合函数定义的RPpca。还使用逻辑回归分析（LRPpca）计算前列腺癌的概率。进行受试者操作特征分析以阐明传统参数和新参数的曲线下面积（AUC）、敏感性、特异性及临界值。最后，我们使用不同的PSA检测试剂盒（AxSYM）研究上述参数在另一患者组中的适用性。
尽管在总PSA范围为4 - 20 ng/mL时RPpca的AUC最大，但RPpca与F/T比值或LRPpca之间未达到统计学显著性。F/T比值、LRPpca和RPpca的临界值分别确定为0.15、0.12和0.20。在AxSYM数据中使用这些临界值时，RPpca具有最高的敏感性（91%）和特异性（57%）。
与LRPpca或F/T比值相比，RPpca可为避免不必要的活检提供更精确的信息。在使用各种PSA试剂盒时，RPpca对于决定是否进行前列腺活检可能具有重要价值。
