| 1. |
- Jacobsen, Steven J., et al.
(författare)
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Comparability of the tandem-R andIMx assays for the measurement of serum prostate-specific antigen
- 1994
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Ingår i: Urology. - 0090-4295. ; 44:4, s. 512-518
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Tidskriftsartikel (refereegranskat)abstract
- Objectives.: To assess the comparability of the Tandem-R and IMx serumprostate-specific antigen (PSA) assays across levels of the ratio of free-to-total serum PSA found in a community-based population of healthy men. Methods.: Banked serum samples from the baseline component of the Olmsted CountyStudy of Urinary Symptoms and Health Status Among Men were thawed and analyzed using the Tandem-R and IMx PSA assays. Serum levels also were determined for the free, noncomplexed form of PSA, PSA complexed to alpha-1 antichymotrypsin, and total PSA with a research-based immunofluorometric assay. Results.: The results of the Tandem-R and IMx assays were strongly correlated at alllevels of the ratio of free-to-total serum PSA. The Spearman correlation coefficients ranged from 0.87 to 0.98 (all p < 0.001). The relationship between the Tandem-R and IMx assays, however, differed at low levels of free-to-total serum PSA compared with high levels. In the lowest 10th percentile of the ratio of free-to-total serum PSA (0.04 to 0.18), the IMx assay read lower than the Tandem-R (slope ± standard error = 0.92±0.04, intercept ± standard error = 0.21 ± 0.14); whereas in the upper 10th percentile of free-to-total ratio (0.46 to 0.65) the IMx assay yielded values higher than the Tandem-R assay (slope = 1.21 ± 0.07, intercept = 0.14 ± 0.05). In the middle 90%, the slope did not statistically differ from 1.0. Conclusions.: For the majority of men, results of the Tandem-R and IMx PSA assays were virtually identical. The small differences found would not be of clinical significance for most men but should be considered when comparing results of different assays in sequential determinations for a specific man.
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| 2. |
- Jacobsen, Steven J., et al.
(författare)
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Stability of serum prostate-specific antigen determination across laboratory, assay, and storage time
- 1995
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Ingår i: Urology. - 0090-4295. ; 45:3, s. 447-453
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: To understand the comparability of serum prostate-specific antigen (PSA) determinations across assays and storage time. Methods: Serum PSA levels were determined for men aged 40 to 79 years from the clinical subset of the Olmsted County Study of Urinary Symptoms and Health Status Among Men on fresh samples and after a median of 32 months on banked samples, frozen at -70 °C. Baseline serum PSA levels were determined by Tandem-R PSA assay. Follow-up levels on the banked samples were determined by the IMx PSA assay and a repeat Tandem-R PSA assay in a different laboratory and by an immunofluorometric PSA assay at another site. Results: The median serum PSA level determined by Tandem-R assay at baseline was 1.0 ng/mL (25th percentile, 0.6; 75th percentile, 1.7). The distributions of determination made by follow-up Tandem-R, IMx, and immunofluorometric analyses were essentially identical. Overall, the assays were highly correlated. The correlations between the baseline serum PSA determination and repeated Tandem-R, IMx, and immunofluorometric determinations were 0.96, 0.96, and 0.97, respectively (all P < 0.001). The median duration of frozen storage was 32 months (range, 26 to 39 months), and the correlations between baseline and follow-up determinations did not change when stratified by duration of storage. Conclusions: These data provide important reassurance about the use of serum PSA determinations obtained by different assays, in different laboratories, and in properly tored samples across time.
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| 3. |
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| 4. |
- Oesterling, Joseph E., et al.
(författare)
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Free, Complexed and Total Serum Prostate Specific Antigen : The Establishment of Appropriate Reference Ranges for their Concentrations and Ratios
- 1995
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Ingår i: The Journal of urology. - 0022-5347. ; 154:3, s. 1090-1095
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Prostate specific antigen (PSA) exists in the serum in several molecular forms that can be measured by immunodetectable assays: free PSA, PSA complexed to alpha 1-antichymotrypsin (complexed PSA) and total PSA, which represents the sum of the free and complexed forms. We determined the normal distribution of values and established the appropriate reference ranges for these 3 molecular forms of PSA and their ratios (free-to-total, complexed-to-total and free-to-complexed PSA). Knowing the amount and ratio of these molecular forms appears to be useful in enhancing the ability of PSA to distinguish potentially curable prostate cancer from benign prostatic hyperplasia and in decreasing the number of unnecessary prostate biopsies. Materials and Methods: A total of 422 healthy men 40 to 79 years old was randomly chosen from the male population of Olmsted County Minnesota and underwent a detailed clinical examination that included digital rectal examination, serum PSA determination and transrectal ultrasound to exclude the presence of prostate cancer. Using newly developed, monoclonal-monoclonal immunofluorometric assays for each molecular form, the free, complexed and total PSA, and the ratios of these 3 forms were determined for each study participant. Results: All 3 molecular forms correlated directly with patient age (r = 0.45, r = 0.43 and r = 0.45, respectively). Using the 95th percentile, the recommended age-specific reference ranges for the free, complexed and total PSA forms, respectively, are 0.5, 1.0 and 2.0 ng./ml. for men 40 to 49 years old; 0.7, 1.5 and 3.0 ng./ml. for men 50 to 59 years old; 1.0, 2.0 and 4.0 ng./ml. for men 60 to 69 years old, and 1.2, 3.0 and 5.5 ng./ml. for men 70 to 79 years old. With regard to each of the ratios (free-to-total, complexed-to-total and free-to-complexed PSA) none correlated with patient age. As a result, the appropriate upper limit of normal (95th percentile) for all 3 ratios is constant for men of all ages. These reference ranges are greater than 0.15 for free-to-total PSA ratio, less than 0.70 for complexed-to-total PSA ratio and greater than 0.25 for free-to-complexed PSA ratio. The free-to-total PSA ratio will have its greatest value for men with a serum PSA value between 2 and 10 ng./ml. Conclusions: The establishment of appropriate reference ranges for free, complexed and total PSA as well as the ratios will allow the practicing urologist to incorporate these new parameters into the diagnostic evaluation of men at risk for early, potentially curable prostate cancer.
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| 5. |
- 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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