Use of copeptin and high-sensitive cardiac troponin T for diagnosis and prognosis in patients with diabetes mellitus and suspected acute myocardial infarction.

BACKGROUND: Diabetes is a major risk factor for acute myocardial infarction (AMI). Assessment of diabetic patients is challenging due to an often atypical presentation of symptoms. We aimed to evaluate the two novel biomarkers copeptin and high-sensitive cardiac troponin (hs-TnT) for the improvement of early diagnosis and risk-stratification in patients with diabetes and suspected AMI. METHODS: In this prospective international multicenter study we evaluated 379 patients with diabetes in a cohort of 1991 patients presenting with symptoms suggestive of AMI. The measurement of biomarkers was performed at presentation. RESULTS: Among the 379 diabetic patients, 32.7% had AMI, and in the 1621 patients without diabetes, 18.8% had AMI. The additional use of copeptin improved the diagnostic accuracy provided by conventional troponin alone (AUC 0.86 vs. 0.79, p=0.004). During a median follow-up of 814 days, 49 (13.1%) diabetic patients died. Cumulative 2-year survival rate for patients with copeptin levels below 9 pmol/l was 96.6% compared to 82.8% in patients above that level (p<0.001). The same was observed for hs-TnT with a cutoff level of 14 ng/l (97.7% vs. 82.0%, p<0.001) respective of cTnT with a cutoff level of 10 ng/l (93.5% vs. 75.6%, p<0.001). In multivariate Cox analysis, copeptin, hs-TnT and cTnT were strong and independent predictors of 24-month-mortality. Using the dual marker strategy (copeptin and troponin) identified two groups of high-risk patients where 22.5% of the group with hs-cTnT and copeptin above the cutoff and 28.6% with cTnT and copeptin above the cutoff died. CONCLUSION: In diabetic patients, copeptin only slightly improves the early diagnosis of AMI provided by hs-cTnT. However, both markers (copeptin and troponin) predict long-term mortality accurately and independently of each other.

Homogeneous immunoassays using rare earth cryptates and time resolved fluorescence: principles and specific advantages for tumor markers.

We have developed a new type of long lived fluorescent tracer, the rare earth cryptates formed by the inclusion of a Eu3+ ion into the intra molecular cavity of a macrobicyclic ligand containing bipyridine units. This tracer is used in a new homogeneous assay format based on spectral and temporal selectivity as well as on an amplification of the cryptate fluorescence. As a consequence of these features, the measurement of the specific signal is totally shielded from media interaction and corrected in real time for sample to sample optical variation. We show the example of a PSA assay where an analytical sensitivity of 0.03 ng/ml is obtained and an AFP assay where measurements in the first minutes of the incubation allow a rapid estimation of the AFP concentration and therefore an immediate dilution of the samples if required. These results illustrate the performance of this new homogeneous method and point out the specific advantages it allows in terms of sensitivity, precision and flexibility. It is therefore particularly well adapted for the assay of analytes like tumor markers where both sensitivity and wide dynamic range are needed.

A descriptive model for the kinetics of a homogeneous fluorometric immunoassay.

A descriptive mathematical model was chosen to fit the antigen-antibody association kinetics of a new homogeneous immunometric assay for prolactin, involving time-resolved fluorescence detection (TRACE technology, Time Resolved Amplified Cryptate Emission). We paid special attention to the methodology and criteria applied, to yield a convenient and statistically valid model, designed to allow potential exploitation of kinetic information in the data processing of the assay. We compared specific parameterizations of an hyperbolic model, the Gompertz, and the monomolecular models on the basis of morphological considerations, a statistical analysis of fit, and an assessment of the parameters estimation quality, over a wide range of antigen concentrations. The monomolecular model gave the best fit, and the most precise and stable estimation of its parameters. The study of parameter properties confirmed this choice.

Intertissular variations in osteonectin: a monoclonal antibody directed to bone osteonectin shows reduced affinity for platelet osteonectin.

Osteonectin, a major noncollagenous protein of bone, is also synthesized and secreted by various non-mineralized tissues and by platelets. To establish whether there are structural specificities of osteonectin according to its tissular origin, we raised 12 monoclonal antibodies against bovine bone osteonectin and screened them for their ability to recognize bone and platelet osteonectin. When hybridoma culture media were radioimmunoassayed all MAbs showed the same titer for [125I]human platelet osteonectin and for [125I]bovine bone osteonectin, except MAb 2, which poorly bound platelet osteonectin. Immunoprecipitation and immunoblotting experiments were performed on human bone protein extracts and on material secreted by human platelets upon thrombin stimulation; in these experiments MAb 2 recognized human bone osteonectin and only faintly human platelet osteonectin. A "sandwich" immunoradiometric assay was devised in which osteonectin bound to a solid phase by a first MAb was recognized by a 125I-labeled second MAb. In this assay MAb 2, used as a tracer, showed a 100-fold lower affinity for purified human platelet osteonectin than for purified human bone osteonectin. These results suggest the existence of structural variations in osteonectin obtained from bone and platelets. Whether these variations result from differences in sequence, post-translational processing, or postsecretional fate remains to be established.

Monoclonal antibody mapping of the antigenic surface of human thyrotropin and its subunits.

Although the amino acid sequence of the alpha- and beta-subunits of glycoprotein hormones in various species has been deciphered, data on their tertiary structure are not abundant. This impedes correlation between structure and function. The availability of monoclonal antibodies to human TSH (hTSH) offers the opportunity to enumerate the antigenic determinants present on the surface of hTSH and its subunits and to examine their spatial relationships. Twenty-eight monoclonal antibodies to hTSH were obtained from several fusions, and screens carried out separately in the laboratories involved in this study. Affinities for hTSH ranged from 10(8)-10(11) M-1. Cross-reactivity with bovine TSH (bTSH), human gonadotropins (hLH, hFSH, and hCG), and the alpha- and beta-subunits of hTSH distinguished 10 groups of monoclonal antibodies (mAb) according to their main cross-reactions: 1) hTSH alpha, hLH, hFSH, and hCG; 2) hTSH alpha, bTSH, hLH, hFSH, and hCG; 3) hFSH; 4) bTSH and hFSH; 5) bTSH, hLH, and hFSH; 6) bTSH, hLH, hFSH, and hCG; 7) hTSH beta; 8) hTSH beta and bTSH; 9) hTSH beta and hFSH; and 10) hTSH beta, hLH, hFSH, and hCG. mAb were incorporated into 2-site binding assays to probe hTSH by a 28 X 28 matrix, the free alpha-subunit by a 4 X 4 matrix, and the free beta-subunit by a 18 X 18 matrix. Regarding intact hTSH, 12 different clusters of mAb were distinguished and interpreted as reflecting 12 distinct antigenic regions on the surface of the hTSH molecule. Two of them were localized on the alpha-subunit, and 6 on the beta-subunit; 4 were only expressed by the holo-hormone and, thus were designated conformational antigenic regions (alpha beta). Surface mapping of the free alpha- and beta-subunits was virtually identical to that observed with the holo-hormone. Modification of the operative conditions of mAb reacting only with holo-hTSH shows that they recognize the alpha-subunit, but not the beta-subunit of hTSH. These results indicate that 1) hTSH beta presents epitopes that are evolutionary conserved; 2) hTSH alpha presents several epitopes that are species specific and 2 that are not hormone specific; 3) dissociation of hTSH does not modify the antigenic surface expressed by both subunits when they are associated; and 4) some of the conformational determinants expressed only by holo-hTSH are more likely derived from the alpha-subunit than from the beta-subunit.