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Biomedical subjects

B Leijnse

Publications and source records attributed to B Leijnse.

At least 55 records · Page 3Linked to original sources
PubMed1983

Preparation and evaluation of a 7-parameter intralaboratory control blood of 4-month stability.

Sterile, fresh concentrates of human red blood cells suspended in a specially designed sterile preservation medium have a stability of all six red blood cell parameters of over four months as measured in the Coulter Model S-Plus II. Substitution under sterile conditions of the unstable white blood cells for (commercially available) fixed (human) red blood cells is a well-established method to obtain simulated white blood cell suspensions of long-term stability.

Blood Cell Count↗
PubMed1983

Direct determination of total serum cholesterol by on-column gas-liquid chromatographic analysis without previous derivatisation compared with WHO-CDC reference method.

A method for the direct determination of total serum cholesterol by on-column gas-liquid chromatography is described. The French reference method developed by Gambert et al. served as a model for our method, which is fast and less laborious than the well-known CDC reference method of Cooper et al. based on the Abell-Kendall technique. The accuracy and precision of our on-column gas-liquid chromatographic method and the CDC reference method are comparable. The obvious advantage of this proposed gas-liquid chromatographic reference method is its increased analytical speed. The problem of the specificity of our method in relation to cholestanol is discussed.

Cholestanol↗
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↗
PubMed1983

Evaluation of accuracy of 20 different test kits for the enzymic determination of cholesterol.

We evaluated the accuracy of 20 different test kits for the enzymic determination of cholesterol. Using a selected set of standards, we found mean values differing by -9.9 to + 10.7% from values obtained by the Abell-Kendall procedure. Nine kits gave values with a relative bias of less than 2.5%. In the case of the other 11 kits, recalculation with secondary serum standards resulted in values within 5% of the reference values. Depending on the kit used, two different commercially available standard solutions produced results differing by, at most, 8.7%. We obtained indirect evidence that use of esterase of bacterial origin is associated with low values. We ascribe the high values obtained with some kits to positive interference by stabilizers or unspecified compounds in the reagents.

Cholesterol↗
PubMed1982

Unstable glycosylated hemoglobin in patients with diabetes mellitus.

Incubation of washed erythrocytes for 4 h at 37 degrees C in saline resulted in the disappearance of an unstable glycosylated fraction. In a reference group, its amount was very small, but its presence had a significant influence on the upper level of the reference range. In non-diabetic pregnant women, the unstable fraction was significantly higher than in the non-pregnant individuals, which resulted in a lower reference range for the stable HbA1. In diabetic patients, the average unstable HbA1 was about 10% of the "unincubated" level, with marked differences between individuals (0--30%), even in patients with a slightly elevated HbA1. Therefore it is important to determine the concentration of stable HbA1.

Diabetes Mellitus↗
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↗
PubMed1981

Polynuclear iron compounds in human transferrin preparations.

During commonly used saturation procedures of transferrin with iron compounds, both as ferri and ferrous, polynuclear iron compounds are easily formed, even when nitrilotriacetate (NTA) is used as a strong iron ligand. The presence of these nonspecific bound irons is demonstrated with Mossbauer spectroscopy and with electronic optical spectroscopy. But no evidence, however, has been found of two different iron binding sites. Because dialysis is not able to remove all polynuclear iron, an easy method with gel filtration has been developed that does remove the polynuclear iron. Some notes are made about the often used method, in transferrin biochemistry, of saturation determination, i.e. the quotient of the absorbances of 470 and 280 nm.

Binding Sites↗
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

Influence of zinc ions addition to different lots of 2-amino-2-methyl-1-propanol (AMP) buffer on the alkaline phosphatase activities.

The influence of Zn2+ on the inactivation of alkaline phosphatase [orthophosphoric monoester phosphohydrolase (alkaline optimum), EC 3.1 3.1] in serum during preincubation with 2-amino-2-methyl-1-propanol (AMP) buffers was investigated. Addition of Zn2+ to the buffer before preincubation increases the enzyme activity. An optimum Zn2+ concentration different for each lot of AMP buffer can be found, at which the enzyme activities are restored to a level equal to activities measured without preincubation. There is a relation between the inactivating properties of the different AMP buffers and the amount of Zn2+ needed to prevent this inactivation. Since Zn2+ chelating substituted diamines are held responsible for the inactivation by removing Zn2+ from the enzyme, we assume that the addition of Zn2+ to the buffer prevents this removal. As Zn2+ itself is an inhibitor of the enzyme, the addition of both too much or too little Zn2+ results in lower enzyme activities after preincubation with AMP buffer.

Alkaline Phosphatase↗
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↗