Value of Free Prostate-Specific Antigen (Hybritech Tandem-R) in Symptomatic Patients Consulting the Urologist

Abstract

Introduction: Prostate-specific antigen (PSA) is a widely used tumor marker in the detection and follow-up of adenocarcinoma of the prostate. Selection of candidates for prostate biopsies is hampered by the lack of specificity resulting in a large number of unnecessary biopsies. The intention of our study was to compare the percent free PSA (f-PSA; Hybritech Tandem-R) with total PSA and age-specific PSA reference values to evaluate the clinical benefit in detecting patients with prostate cancer (PC) in a selected group of patients consulting the urologist. The question was whether cutoff points are influenced by this selection of patients. Methods: A total of 188 patients, 114 with benign prostate hyperplasia (BPH) and 74 with PC were selected. It is a selected group of patients consulting the urologist. Diagnosis was confirmed in the BPH and PC groups by either ultrasound-guided biopsy or transurethral resection of the prostate or suprapubic adenomectomy or cystoprostatectomy. Total PSA (t-PSA) and f-PSA of all patients were measured before any manipulation by Tandem-R assay for f-PSA and Tandem-E assay for t-PSA (Hybritech). Mean values of age, prostate volume, t-PSA, f-PSA, percent f-PSA were compared in patients with BPH and PC by Mann-Whitney U test. The sensitivity and specificity of t-PSA and age-specific PSA were compared to the sensitivities and specificities of different cutoff points of percent f-PSA. Results: The mean value of t-PSA, f-PSA and percent f-PSA in patients with BPH (n = 114) and PC (n = 74) were statistically significantly different. At PSA levels between 4 and 10 ng/ml 19% of negative biopsies could be avoided by the use of percent f-PSA (cutoff point 25%). There was no additional benefit of age-specific PSA. At a PSA of <4 ng/ml 6 of 7 PCs could be diagnosed by percent f-PSA (cutoff point 25%), whereas only 1 patient would be diagnosed by age-specific PSA. Conclusion: Percent f-PSA seems to decrease the biopsy rate at PSA levels from 4 to 10 ng/ml without missing a relevant number of cancers and to increase the detection rate at PSA <4 ng/ml. Our data indicate that it might be necessary to choose high cutoff points (25%; Tandem-E and R assay, Hybritech) in a selected study population consulting the urologist with large glands and a high prevalence of disease. However, this situation is not comparable to testing of screening populations. No benefit of age-specific PSA could be observed in this study.

Screening for prostate cancer in a city in Japan: age-specific prostate-specific antigen cutoff thresholds

“…2 shows the screening accuracy summary of our study and that of 14 other studies reported by Merriel et al [25] with a PSA of 4 ng/mL or higher as a cutoff. The sensitivity in this study was comparable to those of past reports, [11][12][13][14][15][16][17][18][19][20][21][22][23][24] but the speci city was higher. Figure 2 shows the ROC curves for identifying the optimal cutoff for PSA for predicting prostate cancer in each age group.…”

PSA y hK2 en el diagnóstico de cáncer de próstata

“…Sin embargo, y como podemos apreciar en la tabla 1, existe una gran variabilidad en los puntos de corte de PSA para cada grupo de edad. Además, el aumento de la especificidad que proporciona el PSA-edad en los sujetos mayores de 60 años conlleva una pérdida en el diagnóstico de un 20-30% de CaP 35,36 .…”

Pilot Study: A Non-Invasive Urine Test for Potential Prostate Abnormalities

“…The principal drawback of the PSA test is its imperfect specificity, owing to the fact that common conditions, such as benign prostate hyperplasia (BPH) and prostatitis, can cause borderline or even markedly abnormal test results [3,4]. These results can lead to expensive diagnostic evaluation and unwarranted patient anxiety.…”