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Biomedical subjects

B Leijnse

Publications and source records attributed to B Leijnse.

At least 19 recordsLinked to original sources
PubMed1992

A network thermodynamic model of the concentrating properties of the rabbit/rat kidney in the steady state using the electronic network simulation program SPICE.

A model for the simulation of the diluting and concentrating properties of the rabbit and rat kidney is developed. Translation of the physical model into an electronic one brings the model into a form that can be handled by the electronic network simulation program SPICE. The steady state responses of both kidneys to various inputs are calculated under certain conditions.

Animals↗
PubMed1991

Occupational allergy to pancreatic powder: characterization of IgE-binding antigens in pancreatic extract by immunoblotting.

The IgE response to inhaled dust of pancreatic powder was studied with sera from two employees of a pharmacy. IgE from both sera was directed against both porcine and bovine trypsin preparations. The major IgE-binding structures had an isoelectric point in the pH 8 to 9 range. The molecular weight of the IgE-binding structures was different for both patients. In one patient, most IgE was directed against a 28 to 30 kd structure, whereas the second patient had IgE directed against components with a molecular weight of 35 and 45 kd, respectively.

Adult↗
PubMed1991

Graphical non-linear representation of multi-dimensional laboratory measurements in their clinical context.

A polygon-based graphical representation of laboratory test results using nonlinear scaling is described. It is argued that the nonlinearity of the scale and the use of colors in the representation facilitates interpretation of the test result in its relationship to the standard reference range and critical clinical decision levels. Preliminary results suggest that this representation may be fruitfully used to enhance the efficiency of the information transfer from the clinical chemistry laboratory to clinicians. Other applications, inside as well as outside the medical field, may easily be imagined.

Chemistry, Clinical↗
PubMed1991

Calibration of Technicon Chem 1 multitest analysers.

Recently, two Technicon Chem 1 multitest clinical chemistry analysers were introduced after an evaluation in our laboratory. Calibration according to the instructions of the manufacturer resulted in significant differences between the assay results of the two Chem 1 analysers for twelve of twenty-two methods. To remove these differences we used an additional procedure based on the NCCLS EP-9P protocol for method comparison. Four reference methods were used as comparison methods. Our results indicate that, for three of these methods, the results on both Chem 1 analysers are biased in slope and intercept, and corrections of these parameters are necessary to produce results comparable to the reference method values. For the remaining eighteen assays, methods in routine use in our laboratory were used as comparison methods. In fifteen of eighteen assays, corrections of slope and (or) intercept were necessary to prevent changes in the cumulative average patient data produced by our laboratory. An adjustment of the slopes and intercepts, according to the multi-point calibration procedure presented here, resulted in significant differences between system-specific values measured in our laboratory and those assigned by the manufacturer for ten of thirteen methods. We conclude that the use of the multi-point calibration procedure presented in this article (based on calibration according to the instructions of the manufacturer and NCCLS EP-9P) greatly improves the intra-laboratory comparability and therefore should be part of multi-centre evaluations.

Autoanalysis↗
PubMed1990

A candidate reference method for coupled sodium-water determination in human serum.

A candidate reference method is described for coupled sodium-water determination based on ion-exchange sodium separation from the serum matrix followed by gravimetry as Na2SO4, and serum water determination by means of microwave evaporation. For sera with normal sodium and water contents, the mean relative standard deviation is 0.6% (0.8 mmol/l). Mean inaccuracy for the coupled sodium-water determination is -0.3% (0.4 mmol/l). The candidate reference method can be considered a reference method because the reference method value did not differ significantly from the definitive value, there is no known source for interferences or bias, and misinterpretation due to abnormal protein or lipid levels is excluded because serum sodium is determined on a plasma water basis. Sodium concentrations determined by the candidate reference method are used for comparing field methods with the candidate reference method. If the resulting regression equation is used in the calibration procedure, good correlation between all (in)direct field methods and the candidate reference method is ensured, and accurate results are produced. Results of proficiency testing show a good correlation between (in)direct field methods and the candidate reference method, because sera with approximately normal water contents are used.

Chemistry Techniques, Analytical↗
PubMed1990

Experiences with a new assay for pancreas specific alpha-amylase.

The evaluation of an enzymatic colorimetric method to measure pancreas amylase activity in serum using two monoclonal antibodies that specifically inhibit salivary amylase is described. The assay is quick, easy to perform and can be automated easily. Within-run and day-to-day precision studies gave CVs of less than or equal to 1.5 p. cent and less than or equal to 2.6 p. cent respectively. The test is linear up to 2,150 U/L. Salivary amylase activities up to 20,000 U/L did not contribute more than 2 p. cent to pancreatic amylase activity present in a serum sample. A significant interference by bilirubin is found. Reference values were established for both pancreatic and total amylase activities in serum and used for interpreting the results of pancreatic amylase and total amylase in 72 randomly selected patients. Results obtained by this method agree well with a lectin inhibition method (r = 0.9886).

Acute Disease↗
PubMed1990

Detection of aberrant observations in a background of an unknown multidimensional Gaussian distribution.

An exploratory iterative technique for the detection of aberrant observations on a background of a multidimensional Gaussian distribution is described. Its development was motivated by the analysis of a set of three measurements reflecting the acid-base metabolism in the blood of 2,402 intensive care patients. This new, three-dimensional treatment of such data yields a meaningful description. A technical evaluation of the method, using artificially generated data is also presented. It is shown that the model parameters of the underlying Gaussian distributions are determined with good accuracy and that the accuracy with which the contamination is estimated increases with increasing distance of the contaminating observations from the mean.

Acid-Base Equilibrium↗
PubMed1990

Accuracy of serum ferritin determinations in tissue preparations and human serum.

Introduction of the NBSB 80/602 reference preparation for the calibration of ferritin immunoassays has reduced the inter-assay variability, and represents the first important step towards standardisation of ferritin immunoassays. However, our investigations show that comparison between assay results is still impossible, owing to differences in assay methodology and performance, differences in the specificities of the antibodies and antigens used and other possible interfering substances. We conclude that all kits detect mainly the more basic isoferritins in serum, and that all isoferritins (acidic, intermediate and basic) are systematically underestimated. Since we also showed possible immunological differences between reference or kit standards and serum ferritin, we conclude that the present kits have poor accuracy. To diminish inter-assay variability and to increase the accuracy of serum ferritin determinations, a method is needed that detects all basic, intermediate and acidic isoferritins and measures the true ferritin concentration in serum under normal and pathological circumstances. This reference method can be used to evaluate interference and systematic errors in routine methods. The introduction of a reference method, in combination with the NBSB 80/602 human liver reference preparation, is the second important step towards the accurate standardisation of ferritin immunoassays.

Antibodies↗
PubMed1989

An evaluation of the improved Technicon Chem 1 system.

The improved selective multitest analyser Technicon Chem 1 was evaluated according to the ECCLS guidelines in our laboratory. Twenty two routine parameters were examined. The trial also included a clinical evaluation. About 50,000 measurements were performed during six weeks. The following conclusions can be drawn: 1. The changes made in the system (mainly software) led to genuine improvements. 2. The precision of the system can be rated as good. With a few exceptions (alkaline phosphatase, lactate dehydrogenase, creatine kinase, albumin and total bilirubin) all between-day coefficients of variation are lower than 3%. 3. Excellent agreement was found between the results obtained from the Chem 1 and from the comparison methods. 4. No drift was observed. Once calibrated the Chem 1 can be used for at least fifteen days without renewed calibration, except for the analysis of sodium, potassium and calcium. 5. No carry-over was observed, either specimen-related, or reagent-related. 6. Though not all methods were examined in detail, in general the linearity was found to agree with the manufacturer's claims. 7. The influence of interfering substances proved to be moderate. 8. The practicability of the system was good. A more complete judgement is given in the Discussion Section.

Blood Chemical Analysis↗
PubMed1988

Alterations in carbohydrate composition of serum IgG from patients with rheumatoid arthritis and from pregnant women.

The carbohydrate composition of IgG purified from serum of patients with rheumatoid arthritis (RA), pregnant women, and blood donors has been determined by gas-liquid chromatography. Comparison of the results indicates that IgG from patients with RA contains significantly less galactose but more N-acetylglucosamine than normal IgG, whereas the fucose and sialic acid contents are not changed. The carbohydrate content of IgG in RA is reduced. IgG in pregnancy contains more galactose and more sialic acid than normal IgG, whereas fucose, N-acetylglucosamine, and the total carbohydrate content are not changed. These data suggest a temporal compensation of the RA associated undergalactosylation of IgG in female patients with RA during pregnancy, a period during which remission of the disease is often observed.

Acetylglucosamine↗
PubMed1988

Immunoblot analysis of IgE-binding antigens in spices.

The IgE response to coriander and other spices was studied by immunoblotting, after separation of the spice extracts by isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A major IgE-binding component from coriander had an isoelectric point of pH5. After incubation of SDS-PAGE-separated spice extracts with serum from a patient with an occupational allergy to spices, a closely related pattern of IgE binding to coriander, dill and anise extract was observed. These results suggest that the botanically related spices, coriander, anise and dill, contain common IgE-binding structures.

Antigens↗
PubMed1988

Measurement of total serum protein by near-infrared reflectance spectroscopy.

This study describes the measurement of total protein in serum by near-infrared reflectance spectroscopy. With an algorithm, generated by the calibration procedure, the protein content of serum samples was calculated from absorbance data at various wavelengths in the near-infrared. A good correlation (r = 0.993) was found between near-infrared reflectance spectroscopy measurement of serum protein and analysis by the biuret reaction.

Blood Proteins↗
PubMed1988

Use of the Reflotron system for cholesterol assay in capillary blood, venous blood, and serum--evaluation of accuracy and lot-to-lot reagent comparability.

Since its recalibration in 1987, the Reflotron "dry-chemistry" cholesterol method can produce accurate results. Here we report how cholesterol concentrations in venous blood, plasma, and serum determined with Reflotron compare with values determined for fingerstick samples. When no EDTA is used in the latter, accurate results may meet the WHO/CDC criterion of a maximum bias less than or equal to 5%. Reflotron users should avoid use of EDTA. Lot-to-lot variation among the solid-phase reagent carriers was evaluated in four lots of these strips. The largest difference, 0.4 mmol/L, was seen in a commercial quality-control serum with a cholesterol concentration of approximately 7 mmol/L. The maximum differences in results for several serum pools were not always found between the same reagent lots, although the highest results in five of six materials occurred with a single lot of strips. As in all clinical chemical testing, regular quality control is necessary.

Cholesterol↗
PubMed1988

Revised calibration of the Reflotron cholesterol assay evaluated.

We evaluated the Boehringer Mannheim (B.M.) Reflotron Total Cholesterol "dry-chemistry" method after its recalibration in 1987. Reports in the literature up to 1986-1987 of a negative bias (up to -10%) in the method prompted a revision of the factory-set calibration of the Reflotron. For this, B.M. prepared a new set of calibrators with 12 different concentrations of cholesterol. We checked in two ways whether accuracy had been achieved: (a) The values assigned to the calibrators by B.M. were checked with the manual Abell-Kendall Reference Method (MAK) performed in an official Reference Center. These were shown to be correct. (b) Concurrently, a direct comparison was made by analyzing 200 fresh samples of human serum. Reflotron cholesterol values obtained for these samples proved to be accurate, meeting the current World Health Organization/Centers for Disease Control criterion of maximum bias less than or equal to 5%. Orthogonal regression analysis yielded the following correlation: Reflotron = 0.985 MAK + 0.238 mmol/L (y = ax + b). Reflotron mean = 6.26 mmol/L; MAK mean = 6.09 mmol/L. SDa = 0.015 mmol/L; SDb = 0.120 mmol/L, and r = 0.989.

Autoanalysis↗
PubMed1987

Lectin-enzyme immunoassay of transferrin sialovariants using immobilized antitransferrin and enzyme-labeled galactose-binding lectin from Ricinus communis.

A heterologous lectin-enzyme immunoassay is described. Microtiter plate wells were coated with affinity-purified antibodies to human transferrin. After incubation with transferrin sialovariants, prepared by limited neuraminidase treatment and separated with chromatofocusing, a lectin-enzyme-streptavidin complex was added. A good correlation was obtained between the number of terminal galactose groups on transferrin and the response in the lectin-enzyme immunoassay using Ricinus communis agglutinin as the galactose-binding lectin. The results indicate that characterization of glycosylation is possible with less than a microgram of the glycoprotein available, using lectin-enzyme immunoassays.

Enzyme-Linked Immunosorbent Assay↗
PubMed1987

Irrelevant IgE binding to cellulose discs in RAST.

This study describes two sera that showed irrelevant IgE binding to all allergen-coated cellulose discs tested. This irrelevant IgE binding was not observed when allergen extracts were coupled to agarose beads. Such irrelevant IgE binding can be detected using human serum albumin-coated discs.

Adult↗
PubMed1987

Further studies on the standardization of neonatal bilirubin.

Certain problems in the standardization of direct-reading instruments (bilirubinometers) were investigated. It was shown that the combination of wavelength setting and choice of pH is very important with respect to the standard to be used. It is emphasized that in fact there is no synthetic bilirubin standard which can be used as primary standard. Reasons are given why the only pragmentic solution proved to be a pool of neonatal serum.

Adult↗