Method comparison for CA 15-3, CA 19-9, and CA 125 determination using the new LOCI technique of Dimension Vista 1500 and Immulite 2000 XPI.

We performed method comparison for the tumor markers CA 15-3, CA 19-9, and CA 125 measured by luminescent oxygen channeling immunoassay technology on the Dimension Vista 1500 and by classic luminescence technology on the Immulite 2000 XPI. Within-day and total imprecision were determined according to Clinical and Laboratory Standards Institute (CLSI) guidelines using three serum pools at different clinically relevant levels. In addition, parallel measurements on both systems were performed in a total of 738 routine serum samples (133 CA 15-3, 395 CA 19-9, and 210 CA 125). Total imprecision of serum pools for CA 15-3 ranged between 4.6% and 5.9%, for CA 19-9 between 4.4% and 7.8%, and for CA 125 between 3.3% and 4.3%. Marker values determined within the measurement range of both systems correlated well with each other (R = 0.88 for CA 15-3, R = 0.93 for CA 19-9, and R = 0.96 for CA 125). Slopes between the Vista and the Immulite method were 0.96 for CA 125, 0.72 for CA 15-3, and 0.87 for CA 19-9, indicating lower values for CA 15-3 and CA 19-9 when measured by the Vista method. This was particularly obvious for CA 19-9 levels in the lower measuring range of <100 U/mL (R = 0.85; slope 0.73).

Method comparison for determination of the tumor markers AFP, CEA, PSA and free PSA between Immulite 2000 XPI and Dimension Vista 1500.

BACKGROUND: For the Luminescent Oxygen Channeling Immunoassay (LOCI) technology as established for Dimension Vista 1500, assays have been developed for the serum tumor markers AFP, CEA, PSA and free PSA. We performed a method analysis for these parameters using the Immulite 2000 XPI. METHODS: Determination of within-day and total imprecision of the methods was carried out according to CLSI guidelines with three serum pools. In addition, parallel measurements were performed with both systems in 1,871 routine serum samples and correlations were calculated. RESULTS: Calculated total imprecision of the three serum pools for AFP was 3.8 - 4.3%, for CEA 3.3 - 4.3%, for tPSA 3.6 - 4.0% and for fPSA it was 3.5 - 8.2%. Correlations of these markers across the entire value range were very good with the following correlation coefficients: 0.997 for AFP, 0.996 for CEA, 0.971 for tPSA and 0.988 for fPSA. While values for AFP and tPSA from both methods were comparable (slopes 1.02 and 1.01), lower values were measured for CEA and fPSA with the Dimension Vista (slopes 0.83 and 0.91). For AFP, a sample cluster with considerably higher values than with Dimension Vista was observed in the lower measurement range (< 20 ng/mL). CONCLUSIONS: The assays for AFP, CEA, tPSA and fPSA, as developed with the LOCI technology for the Dimension Vista, show good comparability with results obtained from the Immulite 2000 XPI. However, lower measurement ranges for CEA and fPSA as well as individual divergences, especially with AFP, must be taken into consideration in the event of method changeover.

N-terminal pro-B-type natriuretic peptide in the circulation of fetuses with cardiac malformations.

Cardiac malformations with impact on loading patterns have the potential to progress to irreversible loss of ventricular function during human fetal life. N-terminal pro-B-type natriuretic peptide (nt-proBNP) is a marker of cardiac dysfunction and involved in cardiac remodeling and fibrosis. We evaluated nt-proBNP levels in the circulation of human fetuses with cardiac defects. A total of 45 cases and 75 controls during the second half of gestation were recruited. Nt-proBNP concentrations were determined in venous specimens obtained by fetal blood sampling. Results were correlated to echocardiography and Doppler studies. Mean gestational age was 26.9 weeks (range 21.0-33.4 weeks). Levels of circulating nt-proBNP were elevated in fetuses with cardiac defects (mean 6,896 ng/L (range 595-42,479 ng/L) vs. 1,867 ng/L (73-3,751 ng/L), p < 0.001). In the presence of abnormal Doppler indices a further increase was detected (mean 11,287 ng/L (range 1,403-42,479 ng/L) vs. 4,659 ng/L (595-30,848 ng/L), p = 0.021). No difference was found in fetuses with co-existing growth restriction. Malformations were classified according to their hemodynamic effect. Compared to shunt defects nt-proBNP concentrations were significantly higher in left or right ventricular outflow tract obstruction with intact ventricular septum (mean 15,639 ng/L (range 2,301-42,479 ng/L) vs. 3,891 ng/L (595-13,752 ng/L), p = 0.013), and corresponded to the degree of ventricular dysfunction. In the circulation of human fetuses with cardiac defects levels of circulating nt-proBNP are elevated. Concentrations correlate with the type of myocardial wall stress. This finding supports a role for nt-proBNP as early indicator of intrauterine cardiovascular dysfunction and cardiac remodeling.

Reference values for N-terminal pro-B-type natriuretic peptide in fetal circulation between 20 and 34 weeks of gestation.

OBJECTIVE: We aimed to investigate the range of fetal NT-proBNP values in normal pregnancy between 20 and 34 weeks of gestation. METHOD: NT-proBNP was measured in 56 fetal blood samples. RESULTS: Mean (+ or - 2 SD) NT-proBNP concentration was 1998 (242-3754) ng/L; a significant decline occurred with advancing gestational age (p=0.012). CONCLUSIONS: Gestational age has to be taken in to consideration in the assessment of NT-proBNP. Our data may be used as reference values in fetal and neonatal medicine.

Rapid profiling of peptide stability in proteolytic environments.

The notorious degradation susceptibility of peptides is a major obstacle to their use as medicinal drugs. Assays with which the stability of peptides in complex proteolytic environments can be determined are thus indispensable for peptide drug development. Herein, we describe a new peptide proteolysis assay that meets that demand. It unites the high-throughput capacity of heterogeneous with the well-defined kinetic characteristics of homogeneous assay formats and operates on the cleavage-caused loss of a detection handle. We have confirmed the assay's accuracy with well-defined model interactions and proved its high versatility and robustness with a representative application where we determined the half-lives of 375 different peptides in a crude intestinal protease preparation. With this reliable, reproducible, and efficient assay the enzyme kinetics of any peptide-protease interaction is accessible even for complex protease solutions.