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X Fuentes-Arderiu

Publications and source records attributed to X Fuentes-Arderiu.

At least 19 recordsLinked to original sources
PubMed1999

Indirect reference limits estimated from patients' results by three mathematical procedures.

Presently, only a few clinical laboratories produce their own reference values, while the great majority use reference intervals reported in the literature. An alternative to this unsatisfactory situation is to estimate indirect reference limits by means of mathematical/statistical procedures from patients' results obtained routinely in the laboratory. The procedures of Bhattacharya (A simple method of resolution of a distribution into Gaussian components. Biometrics 1967;23:115-135) Martin et al. (Reference values based on populations accessible to hospitals. In: Gräsbeck R, Alström T, editors. Reference Values in Laboratory Medicine. Chischester: Wiley, 1981:233-262) and Kairisto et al. (Generation of reference values for cardiac enzymes from hospital admission laboratory data. Eur J Clin Chem Clin Biochem 1994;32:789-796) were applied to 14 biochemical quantities. In order to verify these procedures, the indirect reference limits obtained from patients' results were validated by statistical comparison with reference limits estimated from a reference sample according to recommendations of the International Federation of Clinical Chemistry (IFCC). Calculated indirect reference limits for most quantities studied were reliable, but indirect reference limits for bilirubins and potassium ion substance concentrations, alanine aminotransferase, and aspartate aminotransferase catalytic concentrations in serum were not suitable. We conclude that indirect reference limits can be obtained from patients' results by all procedures studied when skewness and kurtosis of mixed distribution are not too large, but other factors also seem to have an influence on the reliability of these procedures.

Adult↗
PubMed1998

Annual rhythmic variations of follitropin, lutropin, testosterone and sex-hormone-binding globulin in men.

The annual rhythmic variations of the serum concentrations of follitropin, lutropin, sex-hormone-binding globulin and testosterone, the ratio between the serum concentrations of testosterone and sex-hormone-binding globulin, and the salivary concentration of testosterone were investigated in a group of 20 apparently healthy men. Venous blood and salivary specimens were collected at 1-month intervals during 12 months. The annual rhythms were studied by using a periodic function resulting from the sum of three cosine functions with periods of 365, 182.5 and 121.66 days. For the salivary concentration of testosterone and for the ratio between the serum concentrations of testosterone and sex-hormone-binding globulin, only the cosine function with a period of 365 days was significant, and for the serum concentration of lutropin, only the cosine function with a period of 121.66 days was significant. Serum concentrations of follitropin, sex-hormone-binding globulin and testosterone were significantly affected by 365 and 121.66 rhythmic components. The salivary concentration of testosterone and the serum concentration of follitropin are the quantities with the greatest annual rhythmic variation of those studied.

Adult↗
PubMed1998

Elecsys CEA, PSA and AFP. Clinical results of a multicentre evaluation.

Three tumormarker assays, Elecsys CEA, PSA and AFP, have been evaluated in an international multicentre study to characterize their clinical performance and to verify the comparability with the corresponding tests of the Enzymun-Test product line and other methods. For each of the markers results were obtained from four laboratories. On the basis of 314 and 199 specimens respectively, (preliminary) reference ranges could be established for CEA and PSA. For the prostate marker, the age dependence of the antigen level could be clearly confirmed. Mean concentrations range between 0.51 ng/ml (< 40 years) and 3.57 ng/ml (> 70 years). Referring to CEA, 95th percentiles of 4.31 ng/ml and 2.69 ng/ml were elaborated for smokers and nonsmokers. In general, good to excellent correlations (r > 0.98) were found between the Elecsys and Enzymun-Tests. Regarding the systematic comparability of both systems, most of the slopes derived from the individual method comparison studies are within the +/- 10% range of the respective standardization results. The specific distribution pattern of the individual tumormarker values elaborated with sample material of known clinical background, reflects the well established categorization of different benign and malignant diseases according to their characteristic marker levels. Of utmost importance, however, is the excellent comparability of the Elecsys assays with the corresponding Enzymun-Tests and the FDA approved AIA 1200 tests from TOSOH in follow-up studies. Almost superimposable concentration curves guarantee that identical diagnostic information is derived from all three methods. Especially for PSA, a series of measurements on sera of prostatectomized patients proved the usability and clinical value of the test also for this particular indication. For either one of the Elecsys tests, the feasibility of using plasma as sample material was verified.

Adult↗
PubMed1997

Properties and Units in the Clinical Laboratory Sciences. IX. Properties and Units in Trace Elements (IUPAC-IFCC Technical report 1997). International Union of Pure and Applied Chemistry and International Federation of Clinical Chemistry. rita.cornelis@rug.ac.be.

This document is the first recommendation on the presentation of trace elements and their values in clinical laboratory sciences from IFCC and IUPAC. It forms part of the ongoing effort to standardize requests and reporting of laboratory data for transmission across cultural and linguistic domains, without attempting to standardize the language used by clinicians and laboratory practitioners. Subsequent documents deal with syntax, kinds-of-property, and properties and units used in other areas of clinical laboratory sciences.

Chemistry, Clinical↗
PubMed1997

Evaluation of a new measurement procedure for the concentration of ferritin in serum.

The aim of this study was the evaluation of an immunoturbidimetric measurement procedure for the concentration of ferritin in serum, based on the new Tina-quant Ferritin reagents kit (Boehringer Mannheim) in which the antibody-coated latex particles have been modified with regard to the previous Tina-quant Ferritin reagents kit. The evaluation was carried out using the BM/Hitachi 917 Analyzer. The evaluation included the within-run and between-day imprecisions estimation, the comparison of measurement procedures and the assessment of the measuring range. An additional study of between-day imprecision was done using 4 microl and 20 microl of sample. Detection limit was studied using BM/Hitachi 917 (4 microl and 20 microl of sample), ES 300 and Cobas-Core analyzers. The coefficients of variation obtained in the between-day imprecision study are lower when 20 microl of sample is used instead of 4 microl. In the measurement procedure using 20 microl, the coefficient of variation observed at physiological concentrations is 2.4%. The detection limit with 20 microl of sample is lower than with 4 microl. Therefore, in ferropenic anaemia studies it is convenient to use the measurement procedure with 20 microl sample volumes, since it possesses the best metrological characteristics for this purpose.

Evaluation Studies as Topic↗
PubMed1997

Evaluation of the VALAB expert system.

The validation of a clinical laboratory report is a process that guarantees the results contained in the report have been obtained under satisfactory metrological conditions and that they are compatible with the information available on the patient. This validation is generally carried out manually by a clinical laboratory professional, but also may be done by an expert system properly programmed, such as the VALAB system. The evaluation presented in this article consists of comparing human and system decisions of validation for 500 randomly selected clinical laboratory reports from hospitalized patients. In this evaluation, 84.8% of the reports examined by the VALAB are accepted directly without any human aid, and only 15.2% require examination by clinical biochemists.

Clinical Chemistry Tests↗
PubMed1997

Multicentric reference values: shared reference limits.

In order to obtain shared reference limits, three laboratories in the same geographical area with a homogeneous population have developed a proposal to produce multicentric reference values. The strategy simulates a virtual laboratory, actually formed by the laboratories involved; the reference limits produced in the virtual laboratory are in fact derived from the blend of reference values obtained by each laboratory. Each laboratory has chosen its own reference sample and has measured the biochemical quantities under study. Reference individuals (n = 171) and 15 biochemical quantities among the most measured in clinical laboratories were selected. The reference values obtained in each laboratory were blended when permitted by the Harris & Boyd test (Clin Chem 1990; 36:265-70). The multicentric reference limits obtained by the virtual laboratory for each quantity were estimated according to the recommendations of the International Federation of Clinical Chemistry. For each quantity, each laboratory, with the results observed in their reference sample, estimated the diagnostic specificity, using as cut-off values the corresponding multicentric reference limits. Each observed value of diagnostic specificity was compared with the theoretical diagnostic specificity value, equal to 0.975, that should be observed when a reference limit is used as cut-off value. The multicentric reference limits obtained by the virtual laboratory are valid in all cases with the exception of the upper reference limit for the concentrations of calcium(II) and urate in serum in one of the laboratories.

Adult↗
PubMed1997

Intra- and inter-individual biological variability data bank.

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.

Chemistry, Clinical↗
PubMed1996

Daily rhythmic and non-rhythmic variations of follitropin, lutropin, testosterone, and sex-hormone-binding globulin in men.

The circadian rhythmic variations of the serum concentrations of follitropin, lutropin, sex-hormone-binding globulin and testosterone, the ratio between the serum concentrations of testosterone and sex-hormone-binding globulin, and the salivary concentration of testosterone were investigated in a group of 13 apparently healthy men. Venous blood and salivary specimens were collected at 4-h intervals over a 24-h period. The circadian rhythms were studied by using a periodic function resulting from the sum of two cosine functions with periods of 24 and 12 h. The serum concentrations of follitropin and lutropin showed no significant rhythmic variations. For the salivary concentration of testosterone and for the ratio between the serum concentrations of testosterone and sex-hormone-binding globulin, only the cosine function with a period of 24 h was significant. Serum concentrations of sex-hormone binding globulin and testosterone were significantly affected by 24- and 12-h rhythmic components. Of the quantities studied, the salivary concentration of testosterone showed the greatest daily rhythmic variation (28.8% of the mean estimated over rhythm).

Adult↗
PubMed1994

Analytical goals for rectilinear calibration functions.

Analytical goals for rectilinearity based on within-subject biological variation have not yet been advocated. On the other hand, the statistical tests to evaluate rectilinearity may be too restrictive for clinical purposes. If rectilinearity of the least-squares regression is rejected by the statistical test used, we propose to compare the systematic error introduced using such a regression line as the calibration function, with the allowable total error. Since total error ideally should be less than the within-subject biological coefficient of variation (C.V.Bw) the goal for rectilinearity we propose is that the maximum allowable systematic relative error produced by the calibration function (LoRi) when a lack of rectilinearity really occurs is: LoRi < C.V.Bw -1.96 C.V.M, where C.V.M is the between-run metrological coefficient of variation of the measurement procedure, corresponding to the value of concentration under study.

Algorithms↗