European journal of clinical chemistry and clinical biochemistry : journal of the Forum of European Clinical Chemistry Societies最新文献

Newborns and children may suffer from extremely high ammonia levels in their blood. We evaluated a fast, reliable micromethod, based on the Blood Ammonia Checker II (BAC II) in combination with the dilution with fresh whole blood. Comparison of the proposed method with an enzymatic method revealed a statistically significant correlation. We conclude that the dilution of patient's blood with fresh whole blood extends the measuring range of ammonia on the BAC II analyzer from 286 mumol/l to about 700 mumol/l.

Different results are usually observed when a quantity is measured in different specimens from the same individual obtained over a time span. For an individual, this variation is due to the imprecision of the measurement procedure, that is to say the metrological variability, as well as to the rhythmic and random fluctuations of the quantity value around a virtual homeostatic set point, that is to say the intra-individual biological variability. On the other hand, when studying the intra-individual biological variation of a quantity a mean value, the virtual homeostatic set point, is estimated for each individual participating in the study. The variation among these mean values is due to the inter-individual biological variability.

One hundred sera from intensive care patients, and 93 sera from endocrinological outpatients were used for a comparison between two automated assays for free triiodothyronine (Enzymun Test, and Elecsys 2010, both Boehringer Mannheim, Mannheim, Germany). In outpatients a good correlation between both methods was found (r = 0.932). In contrast, comparability between the two assays was poor in intensive care patients (r = 0.75, after exclusion of two outliers); significantly more values in the hypothyroid range were found with the Elecsys 2010 assay (n = 83, compared with n = 33 with the Enzymun Test; chi 2 test p = 0.001). We conclude that routine measurement of free triiodothyronine which has the theoretical advantage of quantifying the biologically active fraction of thyroid hormones may have methodological limitations in severely ill patients.

In the present study the analytical performances of five new liquid applications on the Roche Cobas Integra were evaluated: urea and high density lipoprotein (HDL) cholesterol in serum and glucose, creatinine and inorganic phosphorus in urine. The analytical evaluation consisted of imprecision, linearity and method comparison performed against either the actual Cobas Integra granulate applications or the corresponding methods on a Hitachi 704, according to the National Committee for Clinical Laboratory Standards protocols. Over 3700 results were obtained within 3 months. Average values of within-run and between-day coefficients of variation (CVs) were 1.15% and 1.48%, respectively, holding to a mean total CV of 2.17%. The linearity was excellent for all the five applications evaluated as the relative non-linearity was always within 1.53%, thus completely fulfilling the 2.5% upper limit. A strict correlation was observed by comparing results of 120 samples with either the corresponding granulate applications on Cobas Integra or the Hitachi reagents. Linear regression analysis of the results yielded correlation coefficients always above 0.987 and the slopes of the Passing & Bablok regression lines did not deviate by more than 7% from unity. No drift was observed over 4 hours of operations. In conclusion, the performance of these new Cobas Integra liquid applications, as demonstrated by the present study, proved them to be highly suitable for routine use in clinical laboratories.

Tissue factor pathway inhibitor, a natural anticoagulant in the extrinsic pathway of blood coagulation, is associated with the endothelial membrane and presumed to be released by heparin. For flow cytometric detection of membrane-bound tissue factor pathway inhibitor we synthesized polyclonal monospecific antibodies directed against each of the three Kunitz-type domains. Antisera were obtained by immunisation of rabbits with synthetic oligopeptides representing the reactive site of each domain. Kunitz-domain delta 1: 26CAFKDDGPCKAIMKR41, domain delta 2: 101EDPGICRGYITR112 and domain delta 3: 192PADRGLCRANENR204. Different cell lines (chondrosarcoma, synovial sarcoma, synovial cells, leukaemic monocytes) and endothelial cells were investigated by flow cytometric analysis using these antibodies. The three tissue factor pathway inhibitor domains were detected on the surface of all cells by the corresponding antisera. Similar results were obtained by immuno-histochemical staining. Since domain delta 3 was recognised by the appropriate antibody, it would seem that this third domain is not the membrane binding site. To investigate the cellular tissue factor pathway inhibitor release, endothelial cells were cultivated with heparin. Protein resynthesis and translocation were inhibited by puromycin and monensin, respectively. After heparin incubation an increased tissue factor pathway inhibitor concentration was determined in the cell culture medium by a chromogenic substrate assay. However, the tissue factor pathway inhibitor density on the cell surface was not influenced by heparin, as shown by flow cytometry using the three tissue factor pathway inhibitor antisera. Our results suggest that functionally active tissue factor pathway inhibitor is not released from the cell surface. Therefore, the effect of heparin appears to be mediated by secretion of tissue factor pathway inhibitor from intracellular stores.

We have established reference intervals for healthy adults of serum thyrotropin, free thyroxine and free triiodothyronine using the AutoDELFIA (Wallac, Finland) automatic measuring device. The determination of reference intervals in a proper manner is costly, and many laboratories adopt reference ranges from the literature rather than determining them alone. This is the first report on reference values in thyroidology where this automatic system based on time-resolved fluorescence has been used. The reference intervals for thyrotropin, free thyroxine and free triiodothyronine were 0.6-4.3 mIU/l, 9.6-17.1 pmol/l and 4.3-7.5 pmol/l, respectively.

An animal (rat) model of gingival injury ("impaction") induced a gingival inflammatory reaction, which was characterized by a breakdown of gingival collagen and the elastic network, as well as a significant increase of gingival elastase. The present study was conducted to investigate whether ceramides, sphingolipids composed of sphingosine N-acyl-linked to fatty acids, a chemical structure with antielastase properties, could counteract the development of such an inflammatory process. The ceramides used in these experimental series were extracted from wheat and characterized. The main fatty acids were 16:0, 18:1, 18:2, and the sphingoid moiety was phytosphingosine. Inhibition of elastase by ceramides was demonstrated in vitro and the concentration necessary to inhibit 50% of elastase activity was 41 mg/l using the synthetic substrate methoxysuccinyl-alanine-alanine-proline-valine-p-nitroanilide (MeOSuc-AlaAlaProValpNA). However, this anti-elastase activity was not observed in vivo in our animal model of gingival inflammation. A glycosaminoglycan (Heparin), recognized as a potent inhibitor of elastase, was entrapped in ceramides. A local treatment of impacted gingivae by encapsulated heparin led to a dose-related decrease of the elastase level in gingival extracts. Encapsulation in ceramides potentiated the effect exerted by heparin alone. This inhibitory effect of encapsulated heparin on elastase suggested a vector effect of these amphipathic molecules.

Objective: The aim of the study was to evaluate the influence of human anti-mouse antibodies on the measurement of thyrotropin.

Investigations: Samples from 11 patients with measureable human anti-mouse antibody titres (19 micrograms/l-3880 micrograms/l) after radioimmuno-scintigraphy were analysed with 6 different thyrotropin immuno-radiometric assay kits (IRMA). Each sample was analysed in the routine way (sample influenced by human anti-mouse antibodies), as well as after incubation with murine immunoglobulin to precipitate human anti-mouse antibodies (samples not influenced by human anti-mouse antibodies).

Results: Two kits showed clear deviations of measured thyrotropin levels when the human anti-mouse antibody titres were higher than 1350 micrograms/l. A third kit was influenced to a lesser extent by human anti-mouse antibodies. Three of the 6 investigated thyrotropin IRMA kits produced thyrotropin values that were unaffected by the presence of elevated human anti-mouse antibodies. In comparison with former studies after immunotherapy, the thyrotropin deviations were marginal. However, differences were found between the commercially available thyrotropin assays. According to the results of this study only three out of the six investigated kits were unaffected by human anti-mouse antibodies.

Conclusion: Since thyrotropin is one of the key quantities for the endocrinologist dealing with the thyroid gland, every laboratory should ensure high quality thyrotropin assays by critically analysing their method for human anti-mouse antibody.

A highly sensitive and simplified method for the luminometric determination of plasma metabolites has been developed. Furthermore, the technique has been automated for the Dynatech ML2250 Microtiter Plate Luminometer and can be applied to the measurement of any plasma metabolite which may be coupled to a reaction involving the reduction of NAD+. Assays are described for lactose/galactose, beta-hydroxybutyrate and D-lactate, and have been validated with plasma samples. The assays require 1-2 microliters of plasma, and are capable of detecting concentrations below 5 mumol/l. Since luminometry is based on the kinetics of the luciferase/oxidoreductase enzyme system, components of complex biological samples may interfere with the rate of the reaction; necessitating the use of internal standards for individual samples. However, the need for internal standards to account for sample to sample variation in the luminescent response, has been eliminated with the present technique.