| 1. |
- Björk, Thomas, et al.
(författare)
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Comparison of analysis of the different prostate-specific antigen forms in serum for detection of clinically localized prostate cancer
- 1996
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Ingår i: Urology. - 1527-9995. ; 48:6, s. 882-888
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To compare different forms and ratios of serum prostate-specific antigen (PSA) to determine which form or ratio provides optimal diagnostic specificity and sensitivity in distinguishing between benign prostatic hyperplasia (BPH) and clinically localized prostate cancer. METHODS: Serum samples were obtained from 47 patients with BPH and 39 with clinically localized prostate cancer. Patients with BPH underwent either transurethral resection of the prostate or transurethral microwave thermotherapy. Patients with prostate cancer, all of whom had no metastases on radionucleotide bone scans and no pelvic lymph node involvement, underwent either radical external beam radiation therapy or radical retropubic prostatectomy. All patients had pretreatment serum PSA levels between 1 and 20 ng/mL. The different forms of serum PSA (free PSA [PSA-F], PSA complexed to alpha 1-antichymotrypsin [PSA-ACT], and total PSA [PSA-T]) were measured using different monoclonal antibodies against PSA and ACT and immunofluorometric assay techniques. Furthermore, three ratios (PSA-F/PSA-T, PSA-ACT/PSA-T, and PSA-F/PSA-ACT) were calculated. RESULTS: By receiver operating characteristic curve analysis, the performance of the different forms and ratios were compared. The PSA-F/PSA-T ratio had the greatest area under the curve (AUC, 0.776), significantly larger than that for PSA-T (0.612; P = 0.024). For PSA-ACT/PSA-T, the AUC was 0.695 (P = 0.283 versus PSA-T) and 0.773 for PSA-F/PSA-ACT (P = 0.051 versus PSA-T). At a cutoff level < 0.17, PSA-F/PSA-T had a sensitivity of 79%, a specificity of 66%, and a positive predictive value of 66% compared with 74%, 38%, and 50%, respectively, for PSA-T at a cutoff level > 4.0 ng/mL. CONCLUSIONS: The PSA-F/PSA-T ratio gives the best diagnostic performance compared with that for other forms and ratios of PSA and will reduce the number of prostatic biopsies in patients with BPH.
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| 2. |
- Lilja, Hans, et al.
(författare)
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Successful separation between benign prostatic hyperplasia and prostate cancer by measurement of free and complexed PSA
- 1996
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Ingår i: Diagnosis and Treatment of Genitourinary Malignancies. - Boston, MA : Springer US. - 0927-3042. - 9781461379133 - 9781461563433 ; 88, s. 93-101
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Bokkapitel (refereegranskat)abstract
- Prostate-specific antigen (PSA) is a serine protease belonging to the human glandular kallikrein gene family [1–3]. The expression of PSA is mainly androgen dependent, and the detection of very high expression levels is restricted to the prostate tissue, but extraprostatic production at much lower levels has been demonstrated in several other tissues such as normal and malignant breast epithelium, endometrium, and bulbourethral glands [4–10]. PSA is synthesized by the columnar epithelium in the glandular ducts and acini of the prostate, but not by any other cells in prostate tissue. It is secreted at high concentrations (0.2-5mg/mL) into seminal fluid [4–6,11]. PSA is synthesized as an inactive precursor [2,3,12]. Like other glandular kallikreins, the PSA-precursor is processed stepwise by release of a leader peptide followed by liberation of an activation peptide that results in conversion of the zymogen into enzymatically active PSA [12]. This process may occur in parallel with the secretory release from the prostate epithelium and most probably occurs prior to the ejaculatory mixing of secretions from the prostate, seminal vesicles, and epididymis, since PSA is active in ejaculates collected from subjects with defective seminal vesicles and deferent ducts [1]. The protease(s) responsible for processing of the PSA precursor have not been identified. The mature 237-amino-acid form of PSA is a single-chain serine protease with extensive structural similarity to the glandular kallikreins [1,12–14]. However, the substrate specificity is uniquely different from that of the trypsin-like glandular kallikreins and resembles that of chymotrypsin, since PSA catalyzes the hydrolysis of peptide bonds’ carboxy-terminal to residues of tyrosine and leucine [15–17]. Synthetic peptide substrates for chymotrypsin can be used to measure PSA activity, but they are hydrolyzed much less efficiently by PSA than by chymotrypsin and are therefore both nonspecific and insensitive in detecting PSA activity [16].
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| 3. |
- Piironen, Timo, et al.
(författare)
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In vitro stability of free prostate-specific antigen (PSA) and prostate- specific antigen (PSA) complexed to α1-antichymotrypsin in blood samples
- 1996
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Ingår i: Urology. - 0090-4295. ; 48:6 SUPPL., s. 81-87
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. To study the in vitro stability of free and complexed forms of prostate specific antigen (PSA) in blood samples in order to establish guidelines for specimen handling, in particular for the clinical utility of the analysis of percentage free PSA. Methods. Blood samples were collected and processed to generate serum, heparin plasma, and EDTA plasma. Three different two-site immunoassays were used to measure the concentrations of total PSA (PSA-T), free form of PSA (PSA-F), and PSA-α1-antichymotrypsin complex (PSA-ACT) in order to determine the effect of repeated freezing and thawing, delayed separation of serum from blood cells, and stability during storage at 4°C and 30°C. Results. Five cycles of freezing and thawing introduced no statistically significant changes in the measured concentrations of PSA-T, PSA-F, or PSA-ACT. The effect of storing blood samples at room temperature for 1-6 h before separation of serum revealed a statistically significant decrease only for PSA-F after 5.5 h of storage (mean decrease 3.5%). PSA-T and PSA-ACT showed good stability in both serum and plasma samples, whereas PSA-F, after 1 week of storage at 4°C, decreased on average by 28.8%, 7.8%, and 5.6%, respectively, in serum, heparin plasma, and EDTA plasma. The decreases of PSA-F at 4°C were statistically significant (P < 0.05) relative to the controls (samples stored at -20°C) after storage for 23 h in serum, 86 h in heparin plasma, and 71 h in EDTA plasma. When the same samples were stored at 30°C for 24 h, only the mean decrease of PSA-F (4.8%) in serum was statistically significant. Conclusions. PSA-F in blood samples is less stable than PSA-ACT. It is not advisable to store samples on the clot, especially if time and temperature cannot be controlled. Serum samples should be stored frozen if not analyzed during the same day. After thawing, samples can be stored up to 23 h at 4°C prior to analysis. The use of plasma samples improves the stability of free PSA.
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