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B G Blijenberg

Publications and source records attributed to B G Blijenberg.

At least 19 recordsLinked to original sources
PubMed1999

New developments in the standardization of total prostate-specific antigen.

OBJECTIVE: Analytical evaluation of the calibration of three recently launched assays for the measurement of total prostate-specific antigen, i.e., IMx Total PSA (Abbott), Elecsys PSA (Roche), and IMMULITE 3rd Generation PSA (DPC). DESIGN AND METHODS: For accuracy assessment two reference materials were applied namely, Stanford 90:10 PSA Calibrator and Certified Reference Material 613 Prostate-Specific Antigen. Dilutions of these preparations were analyzed with all assays. In addition, clinical specimens from known prostate cancer or benign prostate hyperplasia patients and samples taken from an ongoing prostate cancer screening study were used for comparison. RESULTS: Application of the Stanford Calibrator revealed results well within 10% of the calculated values for all assays. Regarding the CRM Calibrator only the IMx Total PSA proved to approach the line of identity. The IMMULITE results differed about 40% and the Elecsys about 18% from the calculated values. The comparison with clinical specimens showed statistically different results for the combination IMMULITE-IMx and for IMMULITE-Elecsys. The regression lines for both collections were: y(IMx) = 0.86x(IMMULITE) +0.12 (n = 104, r = 0.970, Sy/x = 0.883 microg/L) and y(Elecsys) = 0.98x(IMMULITE) +0.38 (n = 97, r = 0.976, Sy/x = 0.733 microg/L). In the lower measuring range (PSA <5.0 microg/L) as measured with the screening samples (n = 43), these differences were less pronounced. CONCLUSION: In analytical sense a difference was found for both reference preparations in the assays studied. Clinically, despite improvements in methodology, results for total prostate-specific antigen are still not interchangeable. The possible consequences need to be elaborated.

Calibration↗
PubMed1999

On the standardization of total prostate-specific antigen: an exercise with two reference preparations.

In this study, 112 serum samples were analyzed for total prostate-specific antigen with three well-established assays i.e. Tandem R and Tandem E (both from Hybritech Inc., San Diego, USA) and Prostatus Free/Total from Wallac Oy, Turku, Finland. Thirty-two samples were collected from prostate cancer patients, 32 from patients with benign prostate hyperplasia and 48 from men participating in a screening study for prostate cancer. The aim of the study was to compare the results before and after recalculation with the data obtained with two reference preparations for total prostate-specific antigen: Stanford 90:10 PSA Calibrator and Certified Reference Material 613 Prostate-Specific Antigen. Comparing the actual results revealed almost perfect correlations between Tandem R and Tandem E and between both Tandem assays and Prostatus. We observed statistically significant differences in accuracy between Tandem R and Tandem E: y(Tandem E)= 1.05 x(Tandem R)+0.07 and between Tandem E and Prostatus: y(Prostatus)= 0.94 x(Tandem E)+0.02 In both comparisons prostate-specific antigen values ranged from 0-40 microg/l. Recalculation with both reference preparations did not solve these discrepancies. One exception was the combination Tandem R and Tandem E. The application of either reference preparation solved the differences in accuracy here. In conclusion, even after recalibration, assays for total prostate-specific antigen are still not completely interchangeable.

Humans↗
PubMed1998

Analytical issues on prostate-specific antigen in relation to prostate cancer screening.

OBJECTIVE: Evaluation of the analytical performance of the Hybritech Tandem-E PSA assay as applied to the Rotterdam part of the European Randomized Study of Screening for Prostate Cancer (ERSPC) during 1994-1997. DESIGN AND METHODS: For assessment of test performance imprecision and accuracy contributing to clinical decision making was examined. Pre-analytical variables (specimen handling), long-term reagents stability and calibration check with the Stanford 90:10 PSA Calibrator were studied. RESULTS: Total prostate-specific antigen proved to be a stable marker. Provided correct storage at 4 degrees C, we were not able to find differences between samples analyzed directly after blood withdrawal and those analyzed the following day, with or without centrifugation. Day-to-day precision, we found during 1997 a coefficient of variation of 4.9% for concentration 1.8 micrograms/L and 4.2% for 4.8 micrograms/L (n = 182). The variation among the 21 Tandem-E reagent batches used during 1994-1997 proved to be small. Application of the Stanford 90:10 PSA Calibrator revealed 3% higher values for Tandem-E. CONCLUSION: The overall, long-term picture of Tandem-E PSA is reliable in our hands. Possible differences from the true PSA values, not specific for Tandem-E, need to be elaborated.

Humans↗
PubMed1997

Free and total prostate-specific antigen in a screened population.

OBJECTIVES: To determine whether the ratio of free to total (F/T) prostate-specific antigen (PSA) can differentiate between men with prostate carcinoma or benign conditions in a screened population. SUBJECTS AND METHODS: Total and free serum PSA (measured using Delfia PSA assays, Abbott IMx and Hybritech Tandem E methods) were determined retrospectively in 1726 men aged 55-77 years, in whom 67 prostate carcinomas were detected by screening with a digital rectal examination, transrectal ultrasonography, and total serum PSA level. Predictors for a positive biopsy result were estimated as a function of total PSA, free PSA and the combination of both. RESULTS: There was an excellent correlation between the Delfia ProStatus, the Abbott IMx and the Hybritech Tandem E assays. Compared with the total serum PSA level, the F/T ratio improved the specificity significantly only in those men with a total PSA of > or = 7 ng/mL. Using the information given by the total and free PSA values, a maximum sensitivity of 75% at a specificity of 74% was obtained for the whole PSA range from 4 to 10 ng/mL; the maximum sensitivity was 79% with a specificity of 71%. CONCLUSION: The optimal mathematical combination of free and total serum PSA improves the specificity of total serum PSA level in detecting prostate carcinoma more than the does the F/T PSA ratio.

Aged↗
PubMed1997

The free-to-total serum prostate specific antigen ratio for staging prostate carcinoma.

PURPOSE: We analyzed the relationship between the free-to-total PSA ratio and prostate cancer tumor stage and grade compared to total serum PSA. MATERIALS AND METHODS: In 123 patients clinical and pathological grade and stage were related to total serum PSA and free-to-total PSA ratio. RESULTS: Total serum PSA paralleled clinical staging of prostate cancer. The distributions of total serum PSA and the free-to-total PSA ratio were significantly different between benign and malignant diseases (any stage), and between any T category and nodal disease. For serum PSA significant differences were noted between the distributions of men with locally confined (stages T1 and T2) and locally extended (stage T3) disease, and between all T categories and systemic metastatic disease. This finding was not noted for the free-to-total PSA ratio. CONCLUSIONS: The free-to-total PSA ratio has no additional value in clinical staging of prostate carcinoma compared to serum PSA. The free-to-total PSA ratio may be considered the result of cell differentiation and not an indicator of tumor load.

Humans↗
PubMed1997

Analytical evaluation of the new Prostatus PSA Free/Total assay for prostate-specific antigen as part of a screening study for prostate cancer.

In this communication a limited analytical study is described on the new Prostatus PSA Free/Total assay. The study is considered as a side study of the European Randomized Study of Screening for Prostate Cancer. The between-day imprecision with 8 control samples for free prostate-specific antigen ranged from 10.3% at 0.17 microg/l to 3.7% at a concentration of 35.5 microg/l, while for total prostate-specific antigen we found 7.3% at 0.69 microg/l and 4.3% at 70.7 microg/l. For total prostate-specific antigen we found excellent agreement between the new assay and well-established assays like Abbott IMx and Hybritech Tandem-E, both for prostate cancer and benign prostate hyperplasia specimens. The age-specific reference ranges proved to be well-comparable with the literature data both for free and total prostate-specific antigen.

Adult↗
PubMed1997

The free-to-total prostate specific antigen ratio improves the specificity of prostate specific antigen in screening for prostate cancer in the general population.

PURPOSE: The ratio between free and total prostate specific antigen (PSA) in serum improves the specificity of total serum PSA for the detection of prostate carcinoma in select populations. The value of the free-to-total PSA ratio for a PSA of 4.0 to 10.0 ng./ml. was analyzed in a screening population. MATERIALS AND METHODS: From 4,800 participants 55 to 76 years old 977 biopsies were obtained because of an abnormal digital rectal examination, suspicious transrectal ultrasonography and total serum PSA 4.0 ng./ml. or more. Of 191 patients with prostate carcinoma detected 101 had a serum PSA of 4.0 to 10.0 ng./ml. and 54 of them underwent radical prostatectomy. A free-to-total PSA ratio of 0.20, age specific PSA reference ranges and a PSA density of 0.12 ng./ml./cc were evaluated for the ability to increase the specificity of total serum PSA in predicting positive prostate biopsy results. RESULTS: Receiver operating characteristics curves for the free-to-total PSA ratio showed a significant increase in specificity compared to PSA. Retrospective application of age specific PSA reference ranges, the free-to-total PSA ratio and the PSA density decreased the number of biopsies significantly by up to 40% in our study, with a decrease in cancer detection rate of 12%. When used in combination with digital rectal examination, the pathological stage of undetected carcinomas appeared favorable. CONCLUSIONS: The free-to-total PSA ratio may be used to decrease biopsies in patients with an intermediate PSA of 4.0 to 10.0 ng./ml.

Aged↗
PubMed1997

Validation of a natural urinary stone data based infrared library searching system with artificial survey samples.

In this study we evaluated a Fourier transform IR spectrometer (Bio-Rad, USA) equipped with a search system for the analysis of urinary stones. We constructed a database of the stone library with the help of results found with X-ray diffraction analysis. In total, we included 223 stone results (213 natural and 10 spurious stones) consisting of single and composite nature. Regarding the latter we used many comparable and many diverging combinations. Applying 60 artificial referee samples that were used in the urinary stone surveys as organized by the German Society for Clinical Chemistry, we found the instrument hit quality index alone, as a measure of best spectral match not entirely sufficient in relation to acceptable performance. This was also caused by the absence of some rare components. Of those 60 survey samples, 17 did not meet the guidelines of the survey organization. These guidelines are: qualitatively correct and quantitatively within tolerance limits +/-20%. Though a number of these samples seemed irrelevant in a clinical setting, they nevertheless represent a challenge for better performance. In the second round, therefore, we included new entries and human expertise as well, which resulted in an upgrading of the score. We only missed, finally, 4 combinations, mainly related to the purine molecule, i.e. uric acid, sodium urate and ammonium urate. In conclusion, based on extension of the library, we consider the search system as acceptable. Despite that, human interpretation proved to be necessary.

Clinical Laboratory Information Systems↗
PubMed1996

European randomized study of screening for prostate cancer--the Rotterdam pilot studies.

Five randomized pilot studies of screening for prostate cancer (PC) have been conducted in the area of Rotterdam from 1991 to 1994. The purpose of these studies was to establish the feasibility of a randomized screening protocol with PC mortality as the major end point in The Netherlands and at a European level. All procedures related to recruitment of participants, to application of the screening tests and to data collection were evaluated. Men (7,200) aged 55-74 years were invited through the Rotterdam Population Registry. The recruitment rate over the 5 pilot studies averaged 38.2% (2,747 men). Recruitment procedures proved to be relevant for establishing higher participation rates (invitation and consent by mail). The screening tests were well accepted and tolerated. The general population-based character of the sample was confirmed by studying symptoms of prostatic disease in participants and in men who refused participation. Data based on one PSA serum determination, rectal examination and transrectal ultrasonography are presented; 204/1,403 men (14.5%) had a positive screening result by either test combination and underwent biopsy. Forty-nine cancers were found in 1,403 men (3.5%); 65% of prostate cancers (17/26) identified in men who eventually underwent radical prostatectomy proved to be locally confined. From the pilot studies, we conclude that a large contribution to a European Randomized Study of Screening for Prostate Cancer (ERSPC) can be made by recruiting about 40,000 men in the area of Rotterdam. The preliminary data suggest that after confirmation of the present data during the first years in the European study, DRE and TRUS can be withheld depending on the PSA result in a large proportion of the screening population.

Age Factors↗
PubMed1996

Some analytical considerations on the measurement of prostate-specific antigen.

In this study, various analytical aspects of the determination of serum prostate-specific antigen are described as applied to the Abbott IMx PSA and the Hybritech Tandem-E PSA assays. We used mainly specimens from a prostate cancer screening study in progress. A very good comparability between the assays proved to exist in our hands. The long-run variation (16 months) was also rated as acceptable, both for the IMx and the Tandem-E method. The method of choice, Tandem-E, showed good reagent stability over this period. We found, however, a difference in accuracy (Tandem-E +/- 8% higher values) that could not be explained by comparison with Tandem-R.

Humans↗
PubMed1996

The transferability of a candidate reference method for determination of creatinine in serum.

We developed a candidate reference method for the determination of creatinine in serum. For the acceptance of a reference method it is important that it be rigorously validated against a definitive method and that the method can be transferred from one laboratory to another. This study focussed on the transferability and consisted of two parts: introduction and familiarization with the method in four clinical chemistry laboratories in the Netherlands, followed by independent measurements of Standard Reference Material 909a2 and several commercial quality control materials provided with reference method values according to the protocol of the German Quality Assessment Organisation. The criterion for judging transferability was the mean total error (%) of the five sera used in the accuracy experiment. For creatinine we used a total error of < 2.2%. For Standard Reference Material 909a2 all four laboratories were able to comply with this demand, while only two laboratories met this requirement for the other four sera. The results for the Standard Reference Material 909a2 from the collaborating laboratories demonstrate that this candidate reference method can be successfully transferred without loss of precision and accuracy.

Chromatography, High Pressure Liquid↗
PubMed1995

Disease monitoring by the tumour markers cyfra 21.1 and TPA in patients with non-small cell lung cancer.

We evaluated the use of two tumour markers Cyfra 21.1 and tissue polypeptide antigen (TPA) for disease monitoring. Assessment of response to WHO criteria was compared to response assessment according to changes in the tumour marker levels. The criteria defined for marker response were a 65% decrease for a partial response and a 40% increase for progressive disease. When response evaluations with a positive lead time were included, 72% of 115 evaluations for Cyfra 21.1 and 59% of 107 evaluations for TPA yielded the same result. Most discordant evaluations were caused by those evaluations whereby the patient achieved a partial response according to the WHO criteria and had normalisation of the marker. Less cases with a positive lead time, more negative lead times, and more patients with progressive disease without an increase of the marker were seen with TPA compared to Cyfra 21.1. In conclusion, Cyfra 21.1 follows the changes in the tumour load better than TPA. Rising levels of both markers nearly always indicate disease progression, and such knowledge easily obtained may prevent the continuation of ineffective treatment.

Adult↗
PubMed1995

The value of screening tests in the detection of prostate cancer. Part I: Results of a retrospective evaluation of 1726 men.

OBJECTIVES: The ratio between free and total prostate-specific antigen (PSA) in serum (F/T ratio) was shown to improve the differentiation between prostate carcinoma and benign conditions in selected series of patients. In this study the F/T ratio was analyzed for its ability to improve the specificity of total serum PSA, digital rectal examination (DRE), and transrectal ultrasonography (TRUS) for the detection of prostate cancer in an unselected screening population of men identified in the Rotterdam population. METHODS: In 1726 men between 55 and 76 years old, 67 prostate carcinomas were detected by DRE, TRUS, and total serum PSA (Abbott IMx, Hybritech Tandem E). The DELFIA ProStatus PSA EQM and ProStatus PSA Free/Total assays (Wallac) were applied in retrospect to determine total and free serum PSA. Age, total prostate and inner zone volumes were taken into consideration. RESULTS: Sixty-seven carcinomas were detected, two by TRUS and three by DRE alone. Total serum PSA was the most important single predictor of prostate cancer, followed by DRE. The F/T ratio increased the specificity of total serum PSA in the PSA range between 4.0 and 10.0 ng/mL. However, this improved specificity was not significant, nor for gland volumes restricted to 50 mL or less. CONCLUSIONS: The combination of total serum PSA and DRE remains the standard for detection of prostate carcinoma in a screening population. Their specificity may be improved minimally by the F/T ratio, but not significantly in a sample of 1726 screened men. The threshold of the F/T ratio, and the optimal PSA range for its application, remains to be assessed prospectively.

Aged↗
PubMed1995

The value of screening tests in the detection of prostate cancer. Part II: Retrospective analysis of free/total prostate-specific analysis ratio, age-specific reference ranges, and PSA density.

OBJECTIVES: The ratio between free and total prostate-specific antigen (PSA) in serum (F/T ratio) was shown to improve the specificity of total serum PSA for the detection of prostate carcinoma in selected populations. In this study, the value of the F/T ratio for screening of prostate cancer was compared with that of age-specific reference ranges for PSA and PSA density (PSAD) by a simulation experiment. METHODS: In 1726 men between 55 and 76 years old, 67 prostate carcinomas were detected by application of digital rectal examination (DRE), transrectal ultrasonography (TRUS), and total serum PSA. A serum PSA of 4.0 ng/mL or more, an abnormal DRE, or an abnormal TRUS were the indications to perform 308 biopsies. A simulation was performed in which an F/T ratio of 0.20 (ProStatus PSA Free/Total), age-specific PSA reference ranges, and a PSAD of 0.12 ng/mL/cc were used to study their capability to increase the specificity of total serum PSA in predicting prostate biopsy results. RESULTS: Using age-specific PSA reference ranges and DRE as indicators for biopsy, a reduction of 37% (113) of biopsies would have been obtained with a loss of detected cancers of 12% (11). For the use of PSAD and DRE, these numbers were 28% (96) and 11% (7), respectively. Application of a serum PSA of 4.0 ng/mL or more and an F/T ratio of 0.20 or less and an abnormal DRE as indicators for biopsy would reduce the number of biopsies by 37% (112) and the number of detected cancers by 11% (7). The biopsy to prostate cancer ratio of these simulations varied between 3.3 and 3.6. Minimal loss of cancer detection of 3% (2) with a reduction in the number of biopsies of 17% (53) is obtained when TRUS is omitted from the screening protocol. Selecting men by a total serum PSA value of 2.0 ng/mL for further diagnostic workup by TRUS and DRE would have reduced the number of biopsies by 30% (102), and the number of cancers detected by 6% (4). CONCLUSIONS: The most cost-effective protocol for screening prostate carcinoma appears to be prescreening by total serum PSA. The F/T ratio might be used to detect carcinomas in the PSA range below 4.0 ng/mL, but the best threshold remains to be assessed.

Age Factors↗
PubMed1995

Creatinine and surveys: an assessment.

We analysed the results of surveys on creatinine held in The Netherlands during the years 1992, 1993 and 1994. Assay results of 113 samples were reviewed: 88 human sera and 25 samples of animal origin. The results of 5 creatinine assays, 4 based on the Jaffé reaction and 1 enzymatic procedure, are discussed. The enzymatic assay showed by far the best performance, while some of the Jaffé methods differed considerably. All results were evaluated by reference to a HPLC-based selected method for creatinine. Our study shows the need for caution when applying survey performance criteria for creatinine.

Animals↗
PubMed1995

Prostate-specific antigen: its clinical use and application in screening for prostate cancer.

Prostate cancer in most European countries is the second most frequent cancer in males and the second most frequent cause of cancer death. Prostate specific antigen (PSA) is an important tumour marker, which relates to many aspects of this disease. It has been shown that PSA is helpful in the early diagnosis of prostate cancer and in this respect is superior to other available tests like rectal examination and transrectal ultrasonography. PSA is also helpful in staging of locally confined disease. It can be used to identify or exclude local extension of disease, if combined with T category and grade of differentiation determined on biopsy. The same parameters also give an indication of the presence of lymph node metastases, which may prevent unnecessary and invasive staging procedures in certain groups of patients with favourable prognostic factors and a low PSA value. PSA is less suitable as a marker for metastatic disease. Progression of untreated prostate cancer in various stages can be monitored by PSA. The true value of the marker in this respect is still underexplored. It may be possible that PSA will be shown to differentiate effectively between aggressive and non-progressive disease. In this respect, it could become an essential tool to identify those patients that may not require treatment at all. PSA is also a useful marker for therapy response. An elevation of PSA after radical prostatectomy indicates local or metastatic progression, which will occur within 1-2 years. PSA is an androgen dependent enzyme and decreases under endocrine treatment. It is unexplained why in spite of its endocrine dependent character, PSA rises with endocrine independent progression of prostate cancer.

Humans↗
PubMed1995

The analytical and clinical performance of the new Boehringer Mannheim Enzymun-Test PSA assay for prostate-specific antigen.

A combined evaluation effort of the Boehringer Mannheim Research and Development and Evaluation Departments and the University Hospital Rotterdam is described regarding the new, fully automated Enzymun-Test PSA assay for prostate-specific antigen. The study consisted of an analytical and a clinical part. At both sites, the vast majority of intra-assay coefficients of variation ranged from 2 to 3% above prostate-specific antigen = 1 microgram/l. Below that concentration higher coefficients of variation were measured. Comparable results were obtained for the interassay imprecision. The analytical sensitivity (lower limit of detection) was found to be 0.02 microgram/l at both sites. Regarding the linearity of the assay no systematic drift to either elevated or lower values which increasing dilution was found. Deviations remained well in the range between 100 +/- 10%. The correlation with the Abbot IMx PSA assay as performed with a large set of clinical specimens revealed: y (= Enzymun) = 1.16x (= IMx) + 0.0; r = 0.985; n = 245. In this comparison study small differences between benign prostatic hyperplasia patients and prostate cancer patients were detected, perhaps partly based on the differences in recognition patterns of various molecular prostate-specific antigen forms in both assays. A follow-up after radical prostatectomy with 17 patients (50 serum samples) also showed a good comparability between the Enzymun-Test and the IMx assay. The limited check of the reference range resulted in data comparable to what can be found in the literature: out of 100 samples originating from healthy males, aged 20-60 years, 99 had prostate-specific antigen values lower than 4 micrograms/l. Based on our findings it can be concluded that the new Enzymun-Test PSA assay meets the current state-of-the-art criteria in prostate-specific antigen methodology.

Adult↗