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Biomedical subjects

B G Blijenberg

Publications and source records attributed to B G Blijenberg.

At least 73 records · Page 4Linked to original sources
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↗
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↗
PubMed1987

Reflections on the standardization of total bilirubin in neonatal serum.

A study is described on the standardization of the determination of neonatal total bilirubin. A wide variation in results was shown in surveys held in The Netherlands and Germany and the reasons for this variation were sought. The suitability of commercial bilirubin standards and direct reading instruments, widely used in the neonatal field, was tested by comparing all measurements with those obtained with the candidate reference method. We found differences between the stated values and those obtained by the reference method. However, a bias was also shown to exist between the results measured with the direct reading instruments and those obtained with the reference method, explaining at least qualitatively, the variation seen in the surveys. In addition, problems in the calibration of the DuPont ACA are discussed.

Adult↗
PubMed1985

Spinal fluid protein revisited: a reappraisal of the biuret procedure.

In this study our previously described selected method, a biuret procedure with deproteinization, for the determination of spinal fluid protein is thoroughly discussed against the background of the results found with a number of Lowry modifications. The use of various separation techniques, i.e. deproteinization, ultrafiltration and chromatography (HPLC), for protein analysis led to the question as to whether low molecular weight proteins in cerebrospinal fluid play an important role or not with respect to the choice of a selected method for the determination of total protein.

Biuret Reaction↗
PubMed1984

The introduction of bromocresol purple for the determination of serum albumin on SMAC and ACA, and the standardization procedure.

The bromocresol purple methods for the determination of serum albumin on the Technicon SMAC and the DuPont ACA systems were evaluated and compared with the corresponding bromocresol green methods, a radial immunodiffusion (RID) and an electrophoresis technique. The linearity and precision of the dye binding methods were comparable. The bromocresol purple methods were more influenced by lipaemia and to a lesser extent by high bilirubin concentrations. The specificity of the bromocresol purple methods was superior to that of the bromocresol green methods and showed excellent correlations with the radial immunodiffusion method: bromocresol purple: SMAC = 1.03 (RID) + 0.32; bromocresol purple: ACA = 1.00 (RID) + 1.27. The bromocresol purple methods intercorrelated better than the bromocresol green methods. Freeze-dried sera can be used for albumin standardization. Analysis of the albumin fractions of freeze-dried and liquid sera by high-performance liquid chromatography (HPLC) did not reveal significant differences in albumin polymerization. Purified albumin reacted, irrespective of the degree of polymerization, very differently in the dye-binding methods. The bromocresol purple methods showed an overestimation of purified albumin, the bromocresol green methods an underestimation. The reason for these differences is unclear. Non-human albumin reacted poorly with bromocresol purple in contrast with bromocresol green.

Animals↗
PubMed1984

Surveys of neonatal bilirubin. An evaluation.

Experience in surveying the neonatal bilirubin determination in the Netherlands is described. Initially it was organized as a local activity (the Rotterdam area), then later enlarged to a national scale (some 150 participants). A number of items is discussed i.e. the initial improvements, which stabilized at an interlaboratory imprecision of about 8%, and further changes that could improve this rather high imprecision.

Bilirubin↗
PubMed1983

Spectrophotometric analysis of CSF after subarachnoid hemorrhage: limitations in the diagnosis of rebleeding.

We studied the course of CSF xanthochromia after subarachnoid hemorrhage by serial spectrophotometric analysis of lumbar CSF in 15 patients without clinical or CT evidence of rebleeding. The xanthochromic index rose in some patients up to the seventeenth day, and the proportion of oxyhemoglobin or the absolute concentration of hemoglobin often fluctuated. Therefore, rebleeding can be demonstrated in lumbar CSF only by increased xanthochromia, if previous samples had shown a decrease. These criteria could be applied in only 6 of 17 consecutive patients with rebleeding as demonstrated by CT, and they were met in 5.

Bilirubin↗
PubMed1983

Application of reference methodology: determination of total protein in serum.

A study is described on the calibration of the Technicon SMAC for the determination of total protein. Various results of external quality control programmes showed a bias between our value and the mean mentioned in the survey report. A difference of 4 g/l was found to exist between our calibration value and the value mentioned by the manufacturer. The question arises as to which methodology should be chosen in solving the problems described in this article.

Autoanalysis↗
PubMed1983

The influence of the label on the quality of a solid-phase immunoassay: evaluation of a commercial ELISA kit for serum ferritin.

A new Enzyme Linked Immuno Sorbent Assay (ELISA) kit for the determination of serum ferritin has been compared with another ferritin kit based on the Immuno Radio-Metric Assay (IRMA) approach, both assays containing similar antibodies. Based on these studies, we found the within-run precision of the ELISA (and IRMA) to have coefficients of variation of 4-10% and 2-6% respectively, over a concentration range of 12-600 micrograms/l. The between-run precision for the same concentration range exhibited a CV range of 9-13% and 7-11% respectively. The sensitivities were found to be 1.4 micrograms/l and 0.9 microgram/l. The mean recovery was 103% for the ELISA procedure. It was found that, using the serum dilution technique, the linearity reached to 1000 micrograms/l. In the ELISA procedure no influence from the so-called "high dose hook effect" was observed. While EDTA-plasma produced 6% lower values than serum in the ELISA technique, no interference from albumin, gamma-globulins and mild haemolysis was observed. Stability problems with the ELISA kit were not encountered. A comparative analysis of multiple specimens demonstrated nearly identical values with r = 0.994 and y = 0.87 x1.01. The quality and ease of operation of the ELISA approach compared with other techniques are discussed. In conclusion it is possible to replace a radio-label in an immunoassay with an enzyme-label with the same degree of reliability and other parameters of quality control exhibited by radioimmunoassays.

Enzyme-Linked Immunosorbent Assay↗
PubMed1983

A comparative study of five different methods for the determination of 3-methoxy-4-hydroxymandelic acid in urine.

Five different methods for the determination of 3-methoxy-4-hydroxymandelic acid (vanilmandelic acid, VMA) in urine were compared: a GLC-FID catecholamine metabolite profiling method, an HPLC method with electrochemical detection, the method of Pisano et al. [1962) Clin. Chim. Acta 7, 285-291), a one dimensional paper chromatographic method with diazotized p-nitroaniline staining and the commercially available Bio-Rad VMA by Column Test. The comparison consisted of an imprecision study, a linearity check, a recovery study, a split sample comparison and an interference study. The best results of the imprecision study (n = 8) were found with the Bio-Rad and the HPLC method (within-run imprecision had a coefficient of variation (CV) of 5.1% and 1.4%; between-days CV of 5.9% and 6.0% respectively for values of 32.4 mumol/l and 24.5 mumol/l). The Pisano method had the poorest within-run CV (14.6%) and between-days CV (16.8%) for a value of 23.2 mumol/l. All methods showed good linearity. The mean recovery of the HPLC method was 101.3%; the mean recovery of the other four methods ranged from 93.9%-96.0%. The split sample comparison showed that the accuracy of the HPLC, the GLC and the Pisano method is comparable. The accuracy of the paper chromatographic method and the Bio-Rad method had a positive bias compared with the HPLC method. Especially the positive bias of the Bio-Rad method can be very large. The HPLC method was not influenced by the compounds tested in the interference study, whereas the GLC method in some cases only suffered from overloading problems. The Pisano and the Bio-Rad method were most influenced by the interfering compounds tested. We conclude that the HPLC and the GLC methods are superior to the other three VMA methods. From an analytical point of view HPLC is the method of choice for determining 3-methoxy-4-hydroxymandelic acid in urine.

Chromatography, Gas↗
PubMed1982

Evaluation of the Technicon bound uricase method for the determination of uric acid in urine.

We have evaluated the Technicon bound uricase method for the determination of uric acid in urine with the AutoAnalyzer II. The general analytical characteristics of the method, and the effect of urine on the immobilized uricase nylon tube reactor were investigated. The method was found to be a linear up to 7.0 mmol/l with aqueous standards and up to 5.0 mmol/l with urine samples. Between-days imprecision had a coefficient of variation (CV) of 1.6% for values of about 1.2 mmol/l, and 0.8% for values above 3.5 mmol/l. Within-run imprecision gave a CV of 0.7% for values of 1.07 and 2.95 mmol/l and a CV of 0.4% for a value of 4.77 mmol/l. The mean analytic recovery was 99.1% (range 93.8-103.0%). The sample interaction was 0.9%. The correlation with the phosphotungstate method and the manual Dutch standard method was good, but the enzymatic values were 20% lower than the phosphotungstate values. Storing the immobilized uricase nylon tube reactor at 4 degrees C, when not in use, prolonged the lifetime by nearly 50%. Urine samples were not different from aqueous uric acid standards in their effect on the stability of the uricase nylon tube reactor.

Enzymes, Immobilized↗
PubMed1980

A survey report on the determination of total bilirubin in neonatal samples.

Three surveys were organized in the Rotterdam area with respect to the determination of total bilirubin in neonatal sera. Fifteen hospital laboratories participated. The coefficients of variation dropped from about 15% (survey 1) to about 8% (survey 3). This improvement was reached by discussing the techniques used, and in some cases by changing them.

Bilirubin↗
PubMed1980

Evaluation of an enzyme-immuno-assay for the determination of total serum estrogens in pregnancy.

We have evaluated a new diagnostic kit for the determination of total estrogens in serum or plasma of pregnant women by means of an enzyme-immuno-assay. Within-run precision had a coefficient of variation of 4.7-4.9% for total estrogen concentrations of 400 to 2000 nmol/l. For the same range of concentrations, day-to-day precision was found to be 5.9-8.9%. Mean analytic recovery of unconjugated estriol was 102%. Enzymatic hydrolysis of different estrogen conjugates was shown to be virtually complete. The antiserum used in the assay has the same affinity for estrone, estradiol and estriol. Preliminary clinical studies included 14 pregnant women. The results suggest that the determination of total estrogens in pregnancy plasma can be used to monitor fetoplacental function in much the same way as urine total estrogens are used.

Estradiol↗
PubMed1979

Evaluation of a new diagnostic kit for the enzymatic determination of creatinine.

We have evaluated a new diagnostic kit for the enzymatic determination of creatinine in serum, plasma and urine. The method was found to be linear up to 1000 mumol/l. Within-run precision had a coefficient of variation of 3.1--5.6% for normal to slightly elevated values and of 2.3--3.3% for values of about 320 mumol/l. Day-to-day precision was found to be 7.8 and 5.7% for values of 94 and 141 mumol/l, respectively. Mean analytic recovery was 98%. Bilirubin and hemoglobin did not interfere in concentrations up to 490 and 240 mumol/l, respectively. The influence of lipids was studied. Correlation studies were done with two other methods, the Technicon SMA 12/60 method and the Dutch standard manual method.

Amidohydrolases↗