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

In this study we have analysed the influence of temperature and time of storage and of repeated freezing on procalcitonin plasma concentrations ex vivo. We have also analysed the difference of procalcitonin concentrations in arterial or venous blood samples and the influence of different anticoagulation techniques on procalcitonin concentrations (serum, EDTA-, lithium-heparin- or citrate plasma). At room temperature (25 degrees C) a loss of procalcitonin plasma concentrations of 6.4% +/- 2.6% (mean, 2 standard error of the mean) after 3 hours (4.6% +/- 5.2% at 4 degrees C) and 12.3% +/- 3.1% after 24 hours occurred (6.3% +/- 5.0% at 4 degrees C, n = 17 each). Comparing the procalcitonin concentrations of blood samples with different anticoagulants (n = 24 each), there was only a significant difference between procalcitonin concentrations in heparinized plasma and serum (+ 7.6%, difference of the mean). There was no significant influence of the blood sampling technique (arterial or venous line) and of repeated freezing/thawing cycles (up to 3 times) on the procalcitonin concentrations measured. Although the difference of sampling and storage of the blood on procalcitonin concentrations is not significant, multiple factors may act synergistically on the result of procalcitonin measurement. To keep variations of ex vivo conditions as minimal as possible, a standardized technique of anticoagulation, time and temperature of storage is recommended, e.g. the use of EDTA-plasma and storage at room temperature, when samples are measured within 4 hours after blood drawing.

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.

The aim of this article is to describe guidelines for rational use of lactate dehydrogenase and its isoenzymes, in the diagnostic processes and during follow-up, based on a systematic review of relevant literature. Sources of data for this study were English-language scientific publications, obtained from the database of the National Library of Medicine (Medline), concerning the clinical application (diagnosis, monitoring or treatment of disease) of lactate dehydrogenase and lactate dehydrogenase isoenzyme measurements in serum in the following main clinical fields: cardiology, hepatology, haematology and oncology. For acceptance in the present review, studies had to include: a proper definition of the tested patient population, diagnostic criteria, sampling time, sampling frequency, and test characteristics. Estimation of the relation between lactate dehydrogenase or lactate dehydrogenase isoenzymes and specific diseases expressed as sensitivity, specificity, survival or remission rate were extracted. The application of serum lactate dehydrogenase is relevant in the diagnosis of myocardial infarction (late detection), haemolytic anaemia, ovarian dysgerminoma and testicular germ cell tumor. For monitoring the progress of a disease lactate dehydrogenase is relevant in establishing the survival duration and rate in Hodgkin's disease and non-Hodgkin's lymphoma, and in the follow-up of ovarian dysgerminoma. Rational use of lactate dehydrogenase can be achieved when requests for its determination are limited to the above mentioned conditions. No rationale could be found for measuring lactate dehydrogenase isoenzymes.

A commercial ferritin kit (Abbott AxSYM Ferritin) was calibrated using the WHO Human Liver Ferritin International Standard 80/602. The reconstituted WHO freeze-dried standard was diluted to obtain six concentration levels ranging from 10-840 micrograms/l. In the analysis of the data, logarithmic transformation of the results was performed in order to stabilize the variance. The AxSYM kit yielded slightly higher values than the WHO Ferritin Standard (p < 0.05). The relation between the AxSYM kit and the WHO Ferritin Standard (untransformed values) was described by a proportionality: FerritinAxSYM = 1.057 x FerritinWHO. WHO Ferritin Standard values of 12 and 15 micrograms/l (used as cut-off values for absent or small body iron reserves) yielded calculated AxSYM values of 12.7 and 15.9 micrograms/l. A WHO Ferritin Standard value of 30 micrograms/l (used threshold value for the presence of stainable bone marrow haemosiderin iron) yielded a calculated AxSYM value of 31.7 micrograms/l.

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.

We compared seven thyrotropin luminescent immunometric assay kits in two centres, by use of panel sera from 438 patients: controls (n = 203) and different groups of subjects: hyperthyroidism (n = 42), hypothyroidism (n = 46), non-thyroidal illness (n = 102), geriatrics (n = 24) and selected patients previously treated for thyroid cancer and maintained on suppressive doses of L-thyroxine (n = 17), anti-thyrotropin antibody (n = 4). We did not observe any significant differences in analytical tests among the seven methods on the Probioqual control sera, Anemia control serum and human serum pools. The linearity of serial dilutions was found with all kits. Some variations were noticed at extreme dilutions. The within-assay precision was acceptable in all cases. The functional sensitivity limits were estimated from 20% compound precision profile: they ranged from 0.011 to 0.030 mU/l. In the clinical study, the seven assay demonstrated high diagnostic performance. Some interference by heterophilic antibodies were observed.

Apolipoprotein E is one of the apolipoproteins involved in cholesterol metabolism. Three major isoforms are present in men: E2, E3, E4 corresponding to the products of three alleles. They have different affinities for receptors and the epsilon 4 allele is a risk factor for cardiovascular diseases and more recently for Alzheimer's disease. We describe here the production, by heterologous expression in Escherichia coli, of the three apolipoprotein E isoforms for use in both research and clinical laboratories. By Surface Plasmon Resonance, the purified recombinant apolipoprotein E isoforms were able to recognize three monoclonal anti-human apolipoprotein E antibodies with affinity constants close to those of purified human apolipoprotein E. For receptor binding studies, the recombinant apolipoprotein E isoforms were associated with VLDL isolated from apolipoprotein E knockout mice. Although the association of the recombinant apolipoproteins E with the mouse VLDL was less efficient than that of human plasma apolipoprotein E3, the recombinant apolipoprotein E3 and apolipoprotein E4 complexes competed efficiently with 125I-labelled LDL for binding to the LDL receptor in J774 macrophages, whereas the recombinant apolipoprotein E2-VLDL complexes did not. These results suggest that the recombinant apolipoprotein E isoforms have biological properties similar to the human apolipoprotein E isoforms.

It has been shown that benzethonium chloride produces linear mixed-type inhibition of choline esterase and acetylcholine esterase. These enzymes also show-reagent-carry-over inhibition if the enzyme activities are measured in plastic cuvettes in which previously protein has been determined by the alkaline benzethonium chloride method. Choline esterase is about 10-fold more sensitive to benzethonium chloride than acetylcholine esterase. With acetylthiocholine as substrate Michaelis-Menten constants for choline esterase and acetylcholine esterase are 85 mumol/l and 102 mumol/l, respectively. Carry-over inhibitory effect of benzethonium chloride can be avoided by washing the cuvettes, after protein determination by the benzethonium chloride method, with 5 ml/l Triton X-100, 5 ml/l Tween 20 or 10 g/l sodium dodecyl sulphate. The latter has a disadvantage in that it precipitates out at low temperatures. The dry slide method (Johnson & Johnson) for serum choline esterase is free of the inhibitory effect until the concentration of benzethonium chloride in the sample reaches about 200 mumol/l.

In this study we evaluated a Fourier transform IR spectrometer (Bio-Rad, USA) equipped with a search system for the analysis of urinary stones. We constructed a database of the stone library with the help of results found with X-ray diffraction analysis. In total, we included 223 stone results (213 natural and 10 spurious stones) consisting of single and composite nature. Regarding the latter we used many comparable and many diverging combinations. Applying 60 artificial referee samples that were used in the urinary stone surveys as organized by the German Society for Clinical Chemistry, we found the instrument hit quality index alone, as a measure of best spectral match not entirely sufficient in relation to acceptable performance. This was also caused by the absence of some rare components. Of those 60 survey samples, 17 did not meet the guidelines of the survey organization. These guidelines are: qualitatively correct and quantitatively within tolerance limits +/-20%. Though a number of these samples seemed irrelevant in a clinical setting, they nevertheless represent a challenge for better performance. In the second round, therefore, we included new entries and human expertise as well, which resulted in an upgrading of the score. We only missed, finally, 4 combinations, mainly related to the purine molecule, i.e. uric acid, sodium urate and ammonium urate. In conclusion, based on extension of the library, we consider the search system as acceptable. Despite that, human interpretation proved to be necessary.