Brigitte Brux

Bone resorption parameters [carboxy-terminal telopeptide of type-I collagen (ICTP), amino-terminal collagen type-I telopeptide (NTx), and deoxypyridinoline (Dpd)] in MGUS and multiple myeloma.

Abstract: Skeletal morbidity is a major problem in multiple myeloma. Histomorphometric studies have demonstrated that increased bone resorption can be present even in the absence of radiographic abnormalities. To overcome diagnostic problems in estimating the activity of bone resorption, new laboratory parameters that reflect bone metabolism accurately are urgently needed. We analyzed three parameters of osteoclastic bone destruction, i.e. deoxypyridinoline (Dpd) and amino‐terminal collagen type‐I telopeptide (NTx) in urine and carboxy‐terminal telopeptide of type‐I collagen (ICTP) in serum, of 75 patients with multiple myeloma (n = 57) or monoclonal gammopathy of undetermined significance (MGUS, n = 18) by ELISA/RIA techniques. Serum ICTP and urinary Dpd levels increased parallel to the stage of the disease and differed significantly (P < 0.001 for ICTP and P = 0.03 for Dpd) between MGUS, myeloma stage I, and myeloma in stages II and III according to Salmon and Durie. ICTP and Dpd were significantly elevated in patients with multiple myeloma in stage I compared to individuals with MGUS, while no significant difference was found for NTx. In this first study comparing the prognostic relevance of ICTP, NTx, and Dpd in multiple myeloma patients, ICTP was found to be a prognostic factor for overall survival in the Kaplan–Meier analysis (log‐rank test: P < 0.03). Urinary NTx showed borderline significance (P = 0.05), and Dpd had no prognostic value in the survival analysis. Our data show that serum ICTP and urinary Dpd levels increase in parallel to advanced disease stages, and gives the first report on a significant difference in the bone resorption parameters ICTP and Dpd between individuals with MGUS and patients with myeloma in stage I. Among the bone resorption parameters studied serum ICTP was found to be the best prognostic factor for survival in multiple myeloma.

An artificial neural network considerably improves the diagnostic power of percent free prostate‐specific antigen in prostate cancer diagnosis: Results of a 5‐year investigation

Our study was performed to evaluate the diagnostic usefulness of %fPSA alone and combined with an ANN at different PSA concentration ranges, including the low range 2–4 ng/ml, to improve the risk assessment of prostate cancer. A total of 928 men with prostate cancer and BPH without any pretreatment of the prostate in the PSA range 2–20 ng/ml were enrolled in the study between 1996 and 2001. An ANN with input data of PSA, %fPSA, patients age, prostate volume and DRE status was developed to calculate the individuals risk before performing a prostate biopsy within the different PSA ranges 2–4, 4.1–10 and 10.1–20 ng/ml. ROC analysis and cut‐off calculations were used to estimate the diagnostic improvement of %fPSA and ANN in comparison to PSA. At the 90% sensitivity level, %fPSA and ANN performed better than PSA in all ranges, enhancing the specificity by 15–28% and 32–44%, respectively. For the low PSA range 2–4 ng/mL, we recommend a first‐time biopsy at an ANN specificity level of 90%. For PSA 4–10 ng/mL, we recommend a first‐time biopsy based on the ANN at the 90% sensitivity level. Use of an ANN enhances the %fPSA performance to further reduce the number of unnecessary biopsies within the PSA range 2–10 ng/ml.

Determination of alpha1-antichymotrypsin-PSA complex in serum does not improve the differentiation between benign prostatic hyperplasia and prostate cancer compared with total PSA and percent free PSA.

OBJECTIVES To evaluate the analytical performance and diagnostic utility of alpha1-antichymotrypsin (ACT)-prostate-specific antigen (PSA) complex in serum to improve the differentiation between benign prostatic hyperplasia (BPH) and prostate cancer (PCa). METHODS Serum concentrations of total PSA (tPSA), free PSA (fPSA), and ACT-PSA were measured in 112 untreated patients with PCa (median age 65 years), 34 patients with BPH (median age 66 years) with histologic confirmation, and 33 men without prostate disease and with a normal digital rectal examination considered as controls (median age 54 years). Sera were frozen at -80 degrees C within 2 hours after collection and then analyzed during a 12-week period. Determinations were made with the Enzymun-Test for tPSA and fPSA and with a prototype assay for ACT-PSA on the ES system (Roche Diagnostics, Boehringer Mannheim). RESULTS The new ACT-PSA assay showed reliable data of analytical performance. The lower detection limit amounted to 0.068 microg/L. The assay was linear to 50 microg/L. Spiking experiments showed a mean recovery rate of 98.2%. No interferences of the assay were observed in patients with acute inflammation and highly increased ACT concentrations. The values of intra- and interassay imprecision ranged from 1.51% to 3.48% and 2.1% to 6.3%, respectively. The median value of ACT-PSA concentrations were significantly different (P <0.001) between controls and patients with BPH and PCa (0.40, 3.86, 5.26 microg/L, respectively). The median fPSA/tPSA and fPSA/ACT-PSA ratios were significantly different between BPH and PCa (24.3% versus 12.2%, P <0.001 and 32.9% versus 15.0%, P <0.001, respectively), but no difference of the ACT-PSA/tPSA ratio was observed (78.2% versus 78.7%, P = 0.696). Receiver operating characteristics of ACT-PSA (area under the curve = 0.630) and all the derivative ratios of fPSA/ACT-PSA (area = 0.737) and ACT-PSA/tPSA (area = 0.528) were not different from that of tPSA (area = 0.619), but showed a lower discrimination power between BPH and PCa than the fPSA/tPSA ratio (area = 0.790). CONCLUSIONS Using this prototype assay to quantify ACT-PSA in serum, we have demonstrated that ACT-PSA and the calculated derivatives are not superior in the differentiation between BPH and PCa compared with tPSA and the ratio of fPSA to tPSA.

Different stability of free and complexed prostate-specific antigen in serum in relation to specimen handling and storage conditions

Abstract The effect of sample collection, storage conditions (time and temperature), and freeze-thaw cycles on the stability of free prostate-specific antigen (fPSA), PSA complexed with α1-antichymotrypsin (ACT-PSA), and total PSA (tPSA) in serum was studied. The analytes were quantified using immunoassays for tPSA and fPSA on the Elecsys system 2010 and a research assay for ACT-PSA on the ES system (Roche Diagnostics). The stability of the analytes was calculated as percentages of the values measured in samples 1 h after blood collection. When the samples were stored at 37 °C, at room temperature or at 4 °C, the stability of ACT-PSA was less impaired than that of fPSA. To avoid erroneous results in the determination of PSA isoforms and their corresponding ratios, serum samples should be preserved at 4 °C when the analysis is performed within 8 h after blood collection, or they should be stored at −80 °C if the analysis is not feasible during that period.

Molecular forms of prostate-specific antigen in serum with concentrations of total prostate-specific antigen <4 μg/L : Are they useful tools for early detection and screening of prostate cancer?

Molecular forms of prostate‐specific antigen (PSA) improve the differentiation between benign prostatic hyperplasia (BPH) and prostate cancer (PCa) in men with total PSA concentrations between 4 and 10 μg/l. To evaluate the diagnostic utility of free PSA (fPSA) and complexed PSA forms for identification of men with PCa in the low PSA range of <4 μg/l, total PSA (tPSA), α1‐antichymotrypsin complexed PSA (PSA‐ACT) and fPSA (Roche Elecsys [ES] system) as well as tPSA and complexed PSA (cPSA) (Bayer Immuno 1 system) were measured in archival serum samples from 31 untreated patients with PCa, 66 patients with BPH, and 90 men without prostatic disease. The median ratios of fPSA/tPSA, PSA‐ACT/tPSA and cPSA/tPSA were significantly different between patients with BPH and PCa (27.2 vs. 19.4%, 64 vs. 88%, 77.2 vs. 88.2%, p < 0.05). No associations between PSA forms and tumor stage and grade were found. Analysis of the receiver operating characteristic curves showed that these ratios could discriminate better between BPH and PCa patients than determination of the analytes tPSA, fPSA, cPSA and PSA‐ACT alone. The use of one of the ratios would have eliminated roughly half of the unnecessary biopsies in this study. The ratios should be considered as potential tools to increase the selectivity of PCa detection at low PSA concentration. The ratios fPSA/tPSA and cPSA/tPSA can be determined using commercially available assays so that one of these ratios could be preferred instead of PSA‐ACT determination. The ratios could be useful in assessing the risk of PCa in the individual and therefore in deciding on prostate biopsy for final diagnosis.

Comparison of the clinical validity of free prostate-specific antigen, alpha-1 antichymotrypsin-bound prostate-specific antigen and complexed prostate-specific antigen in prostate cancer diagnosis.

Objective: To evaluate the diagnostic utility of free prostate specific antigen (fPSA), alpha–1– antichymotrypsin–bound PSA (PSA–ACT), complexed PSA (cPSA), and including their associated ratios to total PSA (tPSA) in serum for discrimination between prostate cancer (PCa) and benign prostatic hyperplasia (BPH). Methods: A total of 166 white men (age: 65–88 years) with a tPSA between 2 and 20 µg/l were retrospectively analysed. Serum concentrations of tPSA, fPSA, PSA–ACT and cPSA were measured in 118 untreated PCa patients and 48 patients with BPH. The tPSA and cPSA concentrations were measured with the Bayer Immuno 1 system (Bayer Diagnostics, Tarrytown, USA). The Elecsys system 2010 (Roche Diagnostics, Mannheim, Germany) was used for determination of tPSA and fPSA. The PSA–ACT assay is a newly, developed prototype assay on the ES system (Roche Diagnostics, Mannheim, Germany). Results: For statistical analysis only patients with tPSA between 2 and 20 µg/l were enrolled. The median concentrations of tPSA (Bayer: PCa 7.36 µg/l, BPH 4.03 µg/l; Roche: PCa 7.75, BPH 4.13), PSA–ACT (PCa 6.98, BPH 3.18) and cPSA (PCa 6.46, BPH 3.20) were significantly different. The median ratios of fPSA/tPSA (PCa 12.8 vs. BPH 22.4%), PSA–ACT/tPSA (PCa 89.8 vs. BPH 76.1%) and cPSA/tPSA (PCa 90.5 vs. BPH 81.7%) were significantly different between PCa and BPH patients. Using the areas under the curves, receiver operating characteristics analysis (tPSA: 2–20 µg/l) for discrimination between PCa and BPH showed that the ratios fPSA/tPSA (area under the curve: 0.77), PSA–ACT/tPSA (0.72) and cPSA/tPSA (0.78) were significantly different from tPSA (Bayer: 0.53; Roche: 0.55). PSA–ACT (0.64) and cPSA (0.59) alone were not significantly different from tPSA. The calculated ratios fPSA/tPSA, PSA–ACT/tPSA and cPSA/tPSA were not significantly different. Conclusion: The determination of PSA–ACT or cPSA and the associated ratios do not improve the diagnostic impact to discriminate between PCa and BPH compared to fPSA/tPSA ratio. The ratios PSA–ACT/tPSA or cPSA/tPSA can be considered to be alternative tools of fPSA/tPSA.

ACT-PSA and complexed PSA elimination kinetics in serum after radical retropubic prostatectomy: proof of new complex forming of PSA after release into circulation

OBJECTIVES To study the elimination kinetics of alpha(1)-antichymotrypsin (ACT)-prostate-specific antigen (PSA) and complexed PSA (cPSA) in comparison to the biexponential decrease of total PSA and free PSA after radical prostatectomy. METHODS Serum total PSA, free PSA, ACT-PSA, and cPSA values and the corresponding ratios were determined in venous blood from 12 patients with prostate cancer. The samples were taken before surgery, immediately after surgery, 1, 2, 3, 4, 5, and 6 hours after surgery, and then once daily for the next 10 days. Total PSA and cPSA were analyzed by using Immuno 1 PSA assays (Bayer Corporation); free PSA was measured using the AxSym test kit (Abbott Diagnostics). For ACT-PSA, the ES analyzer system was used (Roche Diagnostics). Statistical calculations were performed with the analysis of variance and Wilcoxon tests. RESULTS During the first 6 hours after radical retropubic prostatectomy, we found nearly constant levels of ACT-PSA and cPSA, in contrast to the rapid elimination of free PSA and significant decrease in total PSA. From days 1 to 10, a continuous and nearly identical decrease of ACT-PSA and cPSA occurred compared with total PSA; free PSA was eliminated more rapidly. CONCLUSIONS In addition to the opinion that the first PSA decrease might be an effect of the operation itself or caused by renal elimination alone, our findings indicate that the initial rapid decrease of free PSA immediately after surgery could be caused by new complex forming of PSA with ACT and other serum protease inhibitors.

Rapid detection of elevated prostate-specific antigen levels in blood : Performance of various membrane strip tests compared

OBJECTIVES To compare the ability of four commercially available membrane strip tests to detect increased (4 microg/L or more) concentrations of prostate-specific antigen (PSA) in blood. METHODS Serum samples with PSA concentrations less than 4 microg/L (n = 67) and from greater than 4 microg/L to 20 microg/L (n = 32) were independently examined by two observers using the PSA membrane strip tests from Chembio, Medpro, Seratec, and Syntron. The positive and negative results of each membrane strip test were classified as either true positive or negative and false negative or positive by comparing them with the quantitative PSA assay of Immulite DPC using the conventional threshold value of 4 microg/L. RESULTS The interobserver variations of the tests were between 93% and 97%. The color stability of the Seratec and Chembio tests did not show significant differences between test results read within 10 to 20 minutes of the reaction time; however, the results of the other two tests were especially affected by variations in the reading time. The sensitivity and specificity of the tests in relation to the threshold of 4 microg/L were 67% to 93% and 87% to 97%, respectively. CONCLUSIONS The Syntron test and, within certain limitations, the Seratec test fulfill the concept of a rapid and convenient PSA determination to detect PSA concentrations greater than 4 microg/L. Methodologic optimization of the tests by a grading of the PSA measuring ranges (eg, between 0 and 2, 3 and 4, 4 and 6, and 7 and 10 microg/L) should be taken into account for future development.

Receiver-operating characteristic as a tool for evaluating the diagnostic performance of prostate-specific antigen and its molecular forms—What has to be considered?

Receiver‐operating characteristic (ROC) analysis is often applied as evaluation tool to compare the diagnostic validity of laboratory tests. The aim of this study was to draw attention to preconditions which should be taken into account when ROC analysis is used to assess the diagnostic performance of total prostate‐specific antigen (tPSA) and its molecular forms in differential diagnosis between prostate cancer and benign prostatic hyperplasia (BPH).

Elimination of Serum Free and Total Prostate-Specific Antigen after Radical Retropubic Prostatectomy

Elimination kinetics of serum total and free prostate-specific antigen were studied for a ten days course after radical retropubic prostatectomy on 11 patients suffering from organ confined prostate cancer. Samples were taken before operation, immediately after finishing the operation and 1, 2, 3, 4, 5, 6 h after prostatectomy and then once a day for the following ten days. The measurements were performed with AxSym assays from Abbott Laboratories. The elimination of both total and free prostate-specific antigen followed a biphasic kinetics. In the fast phase, the average of the individual elimination half-lives of total and free prostate-specific antigen amounted to 6.3 h (SD = 6.1 h; range: 0.55 to 37.1 h) and 0.57 h (SD = 0.18 h; range: 0.22 to 0.89 h), respectively. In the slow phase, total prostate-specific antigen disappeared with an average half-life of 85.6 h (SD = 11 h; range: 47.2 to 261.7 h) and free prostate-specific antigen with an average half-life of 14.4 h (SD = 10.4 h; range: 2.4 to 30.3 h). These results might be significant for the use of free and total prostate-specific antigen and its ratio as a diagnostic and prognostic tool.