Plasma midregional proadrenomedullin (MR-proADM) concentrations and their biological determinants in a reference population.

BACKGROUND: Midregional proadrenomedullin (MR-proADM) is emerging as a prognostic biomarker for detecting the failure of multiple organs. Establishment of scientifically robust reference intervals facilitates interpretation of laboratory test results. The objectives of this study were (i) to establish reliable reference intervals for plasma MR-proADM using a commercially available automated fluoroimmunoassay in apparently healthy individuals, and (ii) to identify biological determinants of MR-proADM concentrations. METHODS: A total of 506 questionnaire-identified apparently healthy adults were enrolled in a single-center, cross-sectional study. A final reference group (n=172) was selected after exclusion of obese individuals, those with increased values of laboratory biomarkers indicating asymptomatic myocardial injury or dysfunction, ongoing inflammation, diabetes, dyslipidemia and renal dysfunction and outliers. RESULTS: The 2.5th and 97.5th percentile intervals for MR-proADM values in the reference group (90% confidence interval) were 0.21 (0.19-0.23) and 0.57 (0.55-0.59) nmol/L, respectively. Although older age, higher values of HbA1c, C-reactive protein, B-type natriuretic peptide and body mass index, together with a history of smoking and a decreased estimated glomerular filtration rate were significantly associated with increasing concentrations of MR-proADM in both univariate and multivariate analyses, magnitudes of these relationships were modest and did not substantially influence MR-proADM reference intervals. Sex-dependent difference in MR-proADM reference intervals was not detected [0.19 (0.16-0.22)-0.56 (0.54-0.60) nmol/L in females vs. 0.22 (0.20-0.25)-0.58 (0.57-0.63) nmol/L in males]. CONCLUSIONS: Our study successfully established robust reference intervals for MR-proADM concentrations in plasma. Considering the negligible influence of potential biological determinants on plasma MR-proADM, we recommend the adoption of single reference intervals for adult population as a whole.

Umbilical cord blood serum procalcitonin by Time-Resolved Amplified Cryptate Emission (TRACE) technology: reference values of a potential marker of vertically transmitted neonatal sepsis.

BACKGROUND: Neonatal infection remains a major diagnostic problem because of non-specific clinical signs and symptoms, as well as low sensitivity and specificity of routine laboratory tests. C-reactive protein (CRP), white blood cell count, absolute neutrophil count and immature/total neutrophil ratio are the most widely used tests in the diagnosis of sepsis and provide useful information, but none of these has demonstrated to be reliable in detecting all septic infants. Procalcitonin (PCT) has been suggested as a potentially useful laboratory test performed in umbilical cord blood when perinatal bacterial sepsis is under investigation. METHODS: In this study, the reference interval for umbilical cord blood serum PCT was established for the first time by Time-Resolved Amplified Cryptate Emission (TRACE) technology. RESULTS: The reference interval for PCT in umbilical cord blood serum ranged from 0.04 to 0.43 microg/L in 168 non-infected newborn infants (95% CI 0.02-0.06 and 0.35-0.60 microg/L, respectively). Cord blood serum PCT correctly classified one infected patient out of 90 newborn infants at risk of vertically transmitted sepsis and identified another neonate as a potentially infected patient despite having negative blood cultures. However, cord blood CRP misclassified 21 out of the 90 patients as infected neonates. CONCLUSIONS: Cord blood PCT measured by TRACE is a potentially more useful early marker of neonatal sepsis than cord blood CRP.

International Standards for hepatocyte growth factor/scatter factor: initial assessment of candidate materials and their evaluation by multicentre collaborative study.

Hepatocyte growth factor/scatter factor (HGF/SF) is a potent paracrine growth factor with motogenic, mitogenic and morphogenic activities, and a potential therapeutic role in hepatic and renal disease, as well as diagnostic and prognostic applications. It is synthesised as an inactive, single-chain precursor that is cleaved by serine proteases to give a biologically active, heterodimeric form. To develop World Health Organization (WHO) International Standards (IS) for HGF/SF, candidate preparations of the two forms were assessed in a multicentre study in which they were compared with local standards by bioassay and immunoassay. Among laboratories, there was a wide variation in the estimates of potencies of the candidate standards in terms of in-house reference preparations, but between-assay and within-assay variabilities were low within laboratories. In some assay systems, the precursor and heterodimer showed different responses. Since both molecular forms are widely used in current assay systems, this suggested that a reference preparation was required for each form of the HGF/SF molecule. Accordingly, the Expert Committee on Biological Standardization of WHO established the heterodimeric material (96/564) as the first IS for HGF/SF, human, recombinant, with an assigned unitage of 4000 IU/ampoule and, for the purpose of immunoassay calibration, a nominal HGF/SF content of 4 microg/ampoule. The precursor preparation (96/556) was established as the first IS for HGF/SF (precursor) with an assigned unitage of 2000 IU/ampoule and, for the purpose of immunoassay calibration, a nominal HGF/SF (precursor) content of 4 microg/ampoule. The preparations can be obtained upon written request to the National Institute for Biological Standards and Control (NIBSC, PO Box 1193), by e-mail (standards@nibsc.ac.uk) or ordered at http://www.nibsc.ac.uk.

Sandwich ELISA for proANP 1-98 facilitates investigation of left ventricular dysfunction.

Proatrial natriuretic peptides are proposed to be sensitive and specific markers for various stages of heart deficiency. Here we present a rapid and specific sandwich immunoassay for the measurement of proANP 1-98 in biological fluids like plasma, serum urine. No sample preparation prior to the assay is necessary. Polyclonal antibodies specific for distinct epitopes of proANP 1-98, predicted to be highly immunogenic, were raised in sheep and purified by immunoaffinity chromatography prior to use in the assay. Antigen binding sites of the antibodies were determined by epitope mapping with a set of peptide fragments. The capture antibody, specific for proANP 16-23, is coated directly onto microtiter plates. Recombinant proANP 1-98 is used as a standard. The biotinylated detection antibody, specific for proANP 80-88, is incubated simultaneously with 20microl of sample for 150 min. Signal is generated with a streptavidin-HRPO-conjugate and TMB as substrate. The detection limit of the assay is 50 pmol/l; intraassay CVs are below 5%, interassay CVs are lower than 10%. Dilution curves show good linearity, recovery of synthetic peptide ranged between 85% and 91%. Reference values from healthy volunteers range from 0 to 2000 pmol/l in human plasma. We conclude this assay is a easy to handle, quick and reliable method for routine measurement of proANP 1-98 and the presented manuscript describes the procedure and performance of this ELISA in detail.