Tumor type M2 pyruvate kinase expression in metastatic renal cell carcinoma.

The M2 isoenzyme of pyruvate kinase (M2-PK) is specifically expressed in tumor cells (TuM2-PK) and has been detected in the peripheral blood of patients with renal cell carcinoma (RCC). TuM2-PK is not useful as a biological marker in localized RCC. We analysed TuM2-PK in 68 patients with metastatic RCC after initial surgery and prior to or during chemoimmunotherapy of metastases. In 50 patients, the levels of TuM2-PK were measured during chemoimmunotherapy with interleukin-2, interferon-alpha2a and 5-fluorouracil for up to 8 months and were correlated to response as assessed by radiological imaging techniques. TuM2-PK was quantified with a commercially available enzyme linked immunosorbent assay kit using a cut off of 15 kU/l. In 48 of 68 patients (71%), TuM2-PK was elevated above the cut-off. TuM2-PK was significantly higher in G3 tumors than in G2 tumors. In 34 of 50 patients (68%) undergoing chemoimmunotherapy, a positive correlation between TuM2-PK values and response to treatment was observed. Based on these data, we would not recommend the routine clinical use of TuM2-PK in metastatic RCC at this point.

Molecular forms of prostate-specific antigen in serum with concentrations of total prostate-specific antigen <4 microg/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 microg/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 microg/l, total PSA (tPSA), alpha(1)-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.

A multicenter clinical trial on the use of alpha1-antichymotrypsin-prostate-specific antigen in prostate cancer diagnosis.

BACKGROUND: The aim was to evaluate the clinical performance of alpha(1)-antichymotrypsin prostate-specific antigen (PSA-ACT) for early diagnosis of prostate cancer (PCa) in a multicenter trial. METHODS: Three hundred sixty-seven white men with PCa and 290 with benign prostatic hyperplasia (BPH) with tPSA concentrations between 2 and 20 microg/L were analyzed. The Elecsys system 2010 (Roche Diagnostics, Germany) was used for determination of total PSA (tPSA) and free PSA (fPSA). The PSA-ACT test was a prototype assay used on the ES system (Roche Diagnostics). RESULTS: The median concentrations of tPSA (PCa: 8.43 microg/L vs. BPH: 6.60 microg/L) and PSA-ACT (8.30 microg/L vs. 6.46 microg/L) were significantly different, respectively. The median ratios of fPSA/tPSA (PCa: 12% vs. BPH: 16%) and PSA-ACT/tPSA (98% vs. 95%) were significantly different. Receiver operating characteristics (ROC) analysis for discrimination between PCa and BPH (tPSA between 2 and 20 microg/L) was performed with 252 matched pairs and showed that the area under the curve (AUC) of the ratio fPSA/tPSA (0.66) was significantly different from tPSA (0.50) and PSA-ACT (0.52). PSA-ACT alone or the ratio PSA-ACT/tPSA (0.56) were not significantly different from tPSA. For tPSA between 4 and 10 microg/L (n = 145 pairs), the AUC of the ratio fPSA/tPSA (0.65) was significantly higher than tPSA (0.50) and PSA-ACT (0.54). Significant differences between tPSA and PSA-ACT or PSA-ACT/tPSA (0.56) were not found. CONCLUSIONS: The determination of PSA-ACT as well as the PSA-ACT/tPSA ratio did not improve the diagnostic impact in patients undergoing evaluation for PCa compared to fPSA/tPSA ratio.

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

BACKGROUND: 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). METHODS: Using a standard software (GraphROC for Windows), ROC analyses were performed and the areas under the curves were calculated for four hypothetical pairs of groups. Every group included 40 patients with prostate cancer and with BPH showing different tPSA concentrations (range of 2-10 microg, but similar free-to-total PSA ratios (fPSA%). RESULTS: The area under the fPSA% ROC curve showed the highest value, whereas the areas under the tPSA ROC curves were dependent on the distributions of tPSA concentrations in the patients. The ability of fPSA% to improve the differential diagnosis between prostate cancer and BPH in comparison to tPSA was not furthermore evident, if the prostate cancer group included more patients with higher tPSA concentrations than the BPH group. CONCLUSIONS: When the diagnostic performance of tPSA and its derivatives like molecular forms in patients with prostate cancer and BPH should be compared by ROC analysis, a matching procedure is recommended prior to ROC analysis to compensate the effect of possible unequal tPSA distributions in both groups. Each BPH (or PCa) patient should be matched with a PCa (or BPH) patient with nearest tPSA concentration so that an optimum of overlapping tPSA concentrations in both groups can be achieved.

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 microg/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 microg/l were enrolled. The median concentrations of tPSA (Bayer: PCa 7.36 microg/l, BPH 4.03 microg/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 microg/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.

Elimination of serum complexed prostate-specific antigen after radical retropubic prostatectomy.

Total prostate-specific antigen (PSA) and complexed PSA were determined in venous blood from 12 patients with prostate cancer before and after radical prostatectomy by using Immuno 1 PSA assays. The elimination kinetics of complexed PSA were compared with that of total PSA. Nearly constant concentrations of complexed PSA were found during the first six hours after surgery, in contrast to the rapid elimination of free PSA and the significant decrease of total PSA. From day one to ten there was a continuous and nearly identical decrease of complexed PSA compared to total PSA. Our findings suggest that the initial rapid decrease of free PSA immediately after operation could be caused by formation of new PSA-complex.

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.

Molecular forms of prostate-specific antigen in malignant and benign prostatic tissue: biochemical and diagnostic implications.

BACKGROUND: Patients with prostate cancer (PCa) show a lower ratio of free prostate-specific antigen (fPSA) to total PSA (tPSA) in serum than patients with benign prostatic hyperplasia (BPH). The patterns of the intracellular PSA isoforms in malignant and benign prostatic tissue have been studied as potential molecular reasons for this phenomenon. METHODS: Prostatic tissue samples were obtained after cystoprostatectomy from patients with bladder cancer (n = 10), from BPH patients (transurethral resection of the prostate, n = 10; adenomectomy, n = 10), and from the cancerous and noncancerous parts of the same prostates removed surgically by prostatectomy because of PCa (n = 20). PSA pattern was characterized by gel filtration, immunoblotting, and immunoassays for tPSA, fPSA, alpha(1)-antichymotrypsin-PSA (ACT-PSA), and complexed PSA (Bayer Immuno 1 assay). Comparisons were made with the PSA concentrations in serum. RESULTS: The major portion of tPSA in all tissue samples was fPSA; complexed PSA forms were <2%. Samples from cystoprostatectomy patients had the lowest and those from adenomectomy patients the highest values of tPSA and fPSA. PSA concentrations were lower in cancerous than in the noncancerous parts of the prostate. No significant correlations were found between tumor stage or grade and the amounts of tPSA, fPSA, and ACT-PSA in tissue. Tissue PSA values were not correlated with the serum PSA concentrations nor with the ratios fPSA/tPSA and ACT-PSA/tPSA in sera. CONCLUSIONS: The amounts of tPSA and the PSA isoforms in prostatic tissue explain neither the concentrations of tPSA and PSA isoforms in serum nor the behavior of the ratio fPSA/tPSA in patients with BPH and PCa.

Ratio of free or complexed prostate-specific antigen (PSA) to total PSA: which ratio improves differentiation between benign prostatic hyperplasia and prostate cancer?

BACKGROUND: The aim of this study was to compare the diagnostic utility of a new assay that measures all forms of prostate-specific antigen complexed (cPSA) to serum proteins except alpha(2)-macroglobulin with the assay of free PSA (fPSA) and the corresponding ratios to total PSA (tPSA) to improve the differentiation between benign prostatic hyperplasia (BPH) and prostate cancer (PCa). METHODS: Serum samples were collected from 91 men without prostate disease and with normal digital rectal examination (controls), 144 untreated patients with PCa, and 89 patients with BPH. tPSA and cPSA were measured using the Bayer Immuno 1 system; fPSA and the additional tPSA were measured with the Roche Elecsys system. RESULTS: The median cPSA/tPSA, fPSA/tPSA, and fPSA/cPSA ratios were significantly different between patients with BPH and PCa (78.7% vs 90.7%, 25.5% vs 12.1%, and 36.8% vs 14.3%, respectively; P <0.001). No correlations of cPSA and its ratios to tumor stage and grade were found. ROC analysis showed that cPSA was not different from tPSA (areas under the curve, 0.632 vs 0.568), whereas the cPSA/tPSA ratio was similar to the fPSA/tPSA ratio in increasing discrimination between BPH and PCa patients with tPSA concentrations in the tPSA gray zone between 2 and 10 microg/L (areas under the curve, 0.851 vs 0.838). CONCLUSIONS: Compared with tPSA, the fPSA/tPSA and cPSA/tPSA ratios both improve the differentiation between BPH and PCa comparably and are similarly effective in reducing the rate of unnecessary biopsies, whereas cPSA alone does not have any effect.

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

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 alpha1-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 degrees C, at room temperature or at 4 degrees 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 degrees C when the analysis is performed within 8 h after blood collection, or they should be stored at -80 degrees C if the analysis is not feasible during that period.

Ratio of alpha 1-antichymotrypsin--prostate specific antigen to total prostate specific antigen in prostate cancer diagnosis.

OBJECTIVE: To evaluate the analytical performance and diagnostic utility of prostate specific antigen (PSA) bound to alpha 1-antichymotrypsin (ACT) in serum to improve the differentiation between benign prostatic hyperplasia (BPH) and prostate cancer (PCa). METHODS: A total of 351 white men 21 to 88 years old were analysed. Serum concentration of tPSA, free PSA (fPSA) and ACT-PSA were measured in 163 untreated PCa patients (median age 66 years), 94 patients with histologically or clinically confirmed BPH (median age 65 years) and 94 men without prostate disease considered as controls (median age 54 years). The Elecsys system 2010 (Roche Diagnostics, Germany) was used for the determinations of tPSA and fPSA. The ACT-PSA assay is a new developed prototype on the ES system (Roche Diagnostics, Germany). RESULTS: The ACT-PSA assay showed reliable data of analytical performance in comparison to established assays for tPSA and fPSA. The median concentrations of tPSA (PCa: 9.22 micrograms/L, BPH: 2.28 micrograms/L, controls: 0.99 microgram/L) and ACT-PSA (7.99 micrograms/L vs. 1.63 micrograms/L vs. 0.58 microgram/L) were significantly different, respectively. The median ratios of fPSA/tPSA (PCa: 12.3%, BPH: 25.4%), ACT-PSA/tPSA (90.5% vs. 66.6%) and fPSA/ACT-PSA (14.0% vs. 38.6%) were significantly different between PCa and BPH patients. Significant differences of ratios between BPH and controls were not observed. Receiver operating characteristics analysis (tPSA up to 20 micrograms/L) for discrimination between PCa and BPH showed that the ratios fPSA/tPSA (area under the curve: 0.861) and fPSA/ACT-PSA (0.847) were significantly different from tPSA (0.663), but ACT-PSA (0.733) alone and also the ratio of ACT-PSA/tPSA (0.780) were not significantly different from tPSA (0.663). CONCLUSION: The ratio fPSA/tPSA showed the best discrimination between BPH and PCa. The single or additional determination of ACT-PSA to tPSA does not improve the differentiation between the two groups of patients.

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.

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.

K-ras mutations in stools and tissue samples from patients with malignant and nonmalignant pancreatic diseases.

Mutant-enriched PCR and reverse dot blot hybridization in microplates were applied for examining K-ras status in stools and tissue samples from patients with pancreatic tumors and chronic pancreatitis. In tissue samples, K-ras mutations were found in 32 of 35 cases of ductal adenocarcinoma, in 5 of 7 periampullary cancers, in 1 cystadenocarcinoma, and in 3 of 5 patients with chronic pancreatitis. In stools, mutated K-ras was seen in 10 of 25 cases of ductal adenocarcinoma, in 1 case of cystadenocarcinoma, and in 2 of 6 cases of chronic pancreatitis. These data indicate that the K-ras status of stool samples may help identify pancreatic carcinoma and persons at risk for cancer development; however, it does not allow discrimination of malignant from nonmalignant diseases.

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.

A multicentre evaluation of the CA 15-3 assay, CA 19-9 assay and CA 125 II assay on the Bayer Immuno 1 System.

The analytical performance of the tumour markers CA 15-3 assay, CA 19-9 assay and Ca 125 II assay on the Bayer Immuno I System was studied according to a revised version of the ECCLS guidelines (Haeckel R. In: Evaluation methods in laboratory medicine, Weinheim, VCH Verlag 1993:47-69) in a multicentre evaluation involving five laboratories. Determination of the 3 analytes generated more than 6000 data. On the Bayer Immuno I System, the imprecisions of the CA 15-3 assay, CA 19-9 assay and CA 125 II assay were better than those found for comparison methods. The median recovery over all five laboratories of system assigned values in control sera was within the 1-s range for the three tumour marker assays. No deviation of linearity could be detected experimentally for all assays. Results for patients' samples showed acceptable agreement between the Bayer Immuno 1 system and several different comparison methods in most cases. One exception was the CA 15-3 assay in comparison with the MCA assay from Roche Diagnostic Systems, where the large difference in values is due to the use of different antibodies and calibrators in the two assays. No carry-over effects could be detected. The selective Bayer Immuno 1 system is fully automated; its practicability was rated as high.