PubMed Health⌕ Search

Biomedical subjects

X Fuentes-Arderiu

Publications and source records attributed to X Fuentes-Arderiu.

At least 19 recordsLinked to original sources
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↗
PubMed1994

Circadian rhythmic variations in serum concentrations of clinically important lipids.

Twenty-five apparently healthy adults (13 men and 12 women), mean age 29.5 years (SD 3.6 years), served as subjects in a 24-h study conducted in Barcelona (Spain) in spring of 1990. Six blood samples were collected from each subject at 4-h intervals over a 24-h period, beginning at 1000. The oral temperature was measured at 2-h intervals to facilitate an independent biological time reference. The serum concentrations of apolipoprotein (apo) A-I, apo B, cholesterol, high- and low-density lipoprotein cholesterol, and triglyceride were measured. The circadian rhythms of these quantities were studied with use of a periodic function resulting from the sum of two cosine functions of 24 and 12 h. For serum concentrations of apo A-I and apo B, only the 24- or 12-h components, respectively, were significant. However, the other quantities studied were significantly affected by both rhythmic components. The maximum daily rhythmic variation ranged from 5% (with respect to the daily mean) for apo A-I to 63% for triglyceride concentration. In all cases except triglyceride, the daily maximum values were measured in the afternoon samples, near the time of maximum oral temperature.

Adult↗
PubMed1993

Diagnostic accuracy evaluation using ROC curve analysis.

The diagnostic accuracy of a biochemical quantity is inversely related to the overlapping zone between the values of the population suffering from a disease and the population which does not. The ROC curves are an indirect measure of the overlapping zone between both populations. Specimens (plasma and urine) taken from 928 patients with symptoms of acute abdominal pain were used and the catalytic concentration of alpha-amylase, pancreatic alpha-amylase and triacylglycerol lipase (determined by two methods) were measured. Definitive diagnosis was obtained by following the directives of expert groups on the evaluation of diagnostic tests. Diagnostic accuracy was characterized by calculating the diagnostic sensitivity and specificity, by representing the ROC curves and by quantifying the areas under the ROC curves. The catalytic concentration of pancreatic alpha-amylase in plasma was the quantity with a greater area under the ROC curve (A = 0.9740) and then the one which had greatest diagnostic accuracy. If we considered the upper limit of the reference interval to be the cut-off value, the catalytic concentration of pancreatic alpha-amylase in plasma had a diagnostic sensitivity and specificity values of 0.96 and 0.88 respectively for the acute pancreatitis.

Acute Disease↗
PubMed1993

Circadian rhythms of serum concentrations of 12 enzymes of clinical interest.

A total of 25 apparently healthy adults (13 men and 12 women), 29.5 years (SD = 3.6 years) of age, served as subjects in a 24-h study conducted in Barcelona, Spain, in the spring of 1990. The group had a homogeneous pattern of meals, activity, and behavior. Six blood samples were collected at 4-h intervals over a single 24-h period beginning at 10:00 h. The oral temperature was measured at 2-h intervals to facilitate an independent biological time reference for the local population being studied. The serum concentration of 12 enzymes of clinical interest were measured in each sample: creatine kinase, creatine kinase 2, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyltransferase, alkaline phosphatase, cholinesterase, lactate dehydrogenase, lactate dehydrogenase 1, 5'-nucleotidase, pancreatic alpha-amylase, and triacylglycerol lipase. We supposed that all experimental data obtained for a quantity came from a single "hypothetical subject" that represented the central tendency of the population and then these data were analyzed for circadian rhythm by single cosinor. A statistically significant circadian rhythm was detected in all quantities studied (p < or = 0.05) except for serum concentrations of pancreatic alpha-amylase and triacylglycerol lipase. The maximum daily rhythmic variation was approximately 10% (interval, 6-14%) for all quantities studied except pancreatic alpha-amylase (2.6%). This rhythmic variation is greater than the analytical variation except for 5'-nucleotidase and pancreatic alpha-amylase. The acrophases for the quantities studied (except that of triacylglycerol lipase) coincide with times near those of the oral temperature acrophase (18:01 local time). The results of this study will doubtless contribute to further documentation of the structure of the human circadian timing system and to establishment of time-qualified reference intervals for a defined group of subjects.

5'-Nucleotidase↗
PubMed1993

Within- and between-subject biological variations of follitropin, lutropin, testosterone, and sex-hormone-binding globulin in men.

The within-subject and between-subject biological variation 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 concentration of testosterone in saliva have been studied in a group of 20 men during 12 months. The between-subject coefficients of variation (CVs) were 36.0% for follitropin, 37.0% for lutropin, 42.7% for sex-hormone-binding globulin, 21.3% for testosterone in serum, 28.8% for testosterone in saliva, and 51.6% for the ratio between serum concentrations of testosterone and sex-hormone-binding globulin. The medians of the within-subject CVs for the respective analyses and ratio were 17.3%, 24.0%, 12.1%, 10.9%, 17.3%, and 9.4%. These data were used to calculate the desirable imprecision, the critical difference for significant change detection, and the index of individuality.

Adult↗
PubMed1992

Within-subject and between-subject biological variation of prothrombin time and activated partial thromboplastin time.

The within-subject and between-subject biological variation of prothrombin time (PT) and activated partial thromboplastin time (APTT) have been studied in a group of 19 women and 20 men over a period of 9 months. All measurements were performed with a mechanical coagulometer. The between-subject coefficients of variation were 6.8% for PT and 8.9% for APTT. The medians and the 90th percentiles of within-subject coefficients of variation were 1.7% and 5.9%, respectively, for PT, and 0.0% and 6.1% for APTT. These data were used to calculate the critical difference for significant change detection and the desirable between-day imprecision.

Adult↗
PubMed1992

Biological variation of the leukocyte differential count quantities.

The biological variation of the blood concentration and number fraction of the different kinds of leukocytes have been estimated, over a one-year period in a group of 19 women and 20 men, apparently healthy volunteers. All measurements have been performed with a Toa E-5000 haematological analyser. The medians of the within-subject biological coefficients of variation, separated by sex when significant differences exist, are the following for concentrations: 9.4% in men and 15.4% in women for the leukocytes, 16.9% in men and 26.9% in women for the neutrophils, 12.3% for the lymphocytes, 14.9 for the basophils+eosinophils+monocytes (as measured by Toa E-5000); and for number fraction are the following: 8.6% for neutrophils, 0% in men and 7.2% in women for lymphocytes, and 16.7 for basophils+eosinophils+monocytes (as measured by Toa E-5000). With these data the index of individuality, the critical difference for significant change detection and the desirable imprecision have been calculated.

Adult↗
PubMed1992

Within-subject biological variation of hematological quantities and analytical goals.

For several common hematological quantities, the within-subject biological variation during a 1-year period was estimated in a group of 39 apparently healthy volunteers: 19 women and 20 men. All measurements were performed with a hematological analyzer (Toa E-5000, Toa Medical Electronics, Kobe, Japan). The means of the within-subject biological coefficients of variation, separated by sex when significant difference was shown, were as follows: 2.8% for hemoglobin concentration; 3.0% for erythrocyte concentration; 2.9% for erythrocyte volume fraction; 1.1% for mean erythrocyte volume; 1.9% for arbitrary SD of erythrocyte volume; 1.6% for mean erythrocyte hemoglobin concentration; 1.3% for mean erythrocyte hemoglobin; 10.8% in men and 15.7% in women for leukocyte concentration; and 6.7% in men and 8.6% in women for platelet concentration. The desirable between-day imprecisions for the measurement of each quantity were established as one half of the average of within-subject biological variation.

Adult↗
PubMed1992

Results of the multicenter evaluation of the CEDIA Phenytoin assay.

Thirteen clinical evaluation sites in Europe and U.S.A. investigated the CEDIA Phenytoin assay on Boehringer Mannheim/Hitachi analyzers with respect to imprecision, recovery of control sera, interlaboratory survey, linearity and method comparisons using patient samples. The linear dose-response relationship up to 40 micrograms/mL was confirmed by all participants. Imprecision at therapeutic analyte concentrations equalled that of other routine methods. Recovery of controls was found in a +/- 6% range for target values assigned by the CEDIA assay. The good interlaboratory transferability of the CEDIA assay was confirmed with control material and human samples. The reconstituted reagent can be used up to one month using weekly recalibration. In method comparison studies good correlations to other routine methods were obtained. Results in analyte-free human sera did not deviate systematically from the zero-point. Thus, the accuracy in patient sera has been shown for the CEDIA Phenytoin assay.

Dose-Response Relationship, Drug↗
PubMed1992

Biological variation data applied to the selection of serum lipid ratios used as risk markers of coronary heart disease.

The biological variation of several relative lipid quantities, calculated as the ratios between the concentrations of various serum lipids and apolipoproteins, has been estimated over a one-year period. The medians of the within-subject biological coefficient of variation, separated by sex when significant differences exist, were 15.4% for [apolipoprotein A-I]/[apolipoprotein B], 6.8% for [high-density lipoprotein (HDL)-cholesterol]/[cholesterol], 10.5% and 17.6% (women and men, respectively) for [HDL2-cholesterol]/[HDL-cholesterol], 13.6% for [HDL2-cholesterol]/[HDL3-cholesterol], 10.6% for [low-density lipoprotein (LDL)-cholesterol]/[apolipoprotein B], 10.6% and 8.7% (women and men, respectively) for [LDL-cholesterol]/[cholesterol], and 6.3% for [LDL-cholesterol]/[HDL-cholesterol]. From these data, we have calculated the critical difference for significant change detection, the index of individuality, and the goal for the between-day imprecision. Concerning within-subject biological variation, the best ratios for the detection of risk of coronary heart disease and the monitoring of intervention are [LDL-cholesterol]/[HDL-cholesterol] and [HDL-cholesterol]/[cholesterol]. The index of individuality obtained in this study indicates that the use of population-based reference values is inadequate for interpreting the ratios studied.

Adult↗