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G J Boerma

Publications and source records attributed to G J Boerma.

At least 37 records · Page 2Linked to original sources
PubMed1991

Multicentre comparison of the Novo Biolabs immunometric CK-MB assay with four established methods.

The analytical performance of a new immunometric CK-MB assay from Novo Biolabs was evaluated in three hospitals. Comparisons were made with another immunometric assay, an immune inhibition/precipitation technique, an immune inhibition method, and a column separation method. The Novo assay exhibited good precision (CV 3-7%) at all concentration levels tested (6-150 micrograms/L) and was found to be linear over the range 0-200 micrograms/L. Comparison of the Novo kit with the other methods using patients' sera showed acceptable correlation between the methods over a wide concentration range (r = 0.96-0.99). We conclude that the assay is a useful adjunct to the specific measurement of CK-MB, particularly in routine laboratories with a high throughput of such determinations.

Creatine Kinase↗
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

The Reflotron Total Cholesterol assay in heparinized venous and capillary blood.

We recently evaluated the Reflotron Total Cholesterol dry chemistry assay by examining the calibration and the accuracy of the assay in serum, whole venous EDTA-blood and capillary EDTA blood. We now describe a study on the analysis in heparinized venous and heparinized finger stick blood. Cholesterol assays in venous serum and plasma, and in finger capillary blood and plasma (all with heparin) were compared. Finger capillary blood was obtained in two ways: 1. in heparinized capillaries; 2. in a Becton Dickinson microtainer that could be centrifuged for separation of the plasma. Venous blood was obtained in plain tubes (for serum) and heparinized tubes to obtain venous whole blood and also venous plasma. We did not, on average, find large differences between the concentrations of cholesterol in the various materials. The regression equations for finger capillary whole blood and venous whole blood however show higher slopes than the others. Inaccuracy due to the sampling technique appears to be no greater for finger capillary samples than for venous samples.

Capillaries↗
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

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↗
PubMed1986

Minimizing interlaboratory variation in routine assays of serum cholesterol through the use of serum calibrators.

A cholesterol standardization program was developed in The Netherlands for clinical laboratories that use their analytical results as indicators of cardiovascular risk. Participants with sufficient precision but inaccurate results are encouraged to use serum-based calibrators as a means to decrease bias. A regional pilot survey and thereafter a national one were carried out in 31 and 138 laboratories, respectively, to investigate whether use of the serum-calibration procedure could improve routinely performed cholesterol measurements. To participants in our national quality-control surveys were mailed three calibrators (pooled human serum) and five human-serum controls, for analysis of cholesterol on four different days. Reference method values had been assigned to the calibrators by the Netherlands Reference Laboratory, applying the U.S. Centers for Disease Control modification of the Abell-Kendall procedure. Using the calibration curves based on results for the serum calibrators decreased the between-laboratory variation (SD) by at least 50%, with improved accuracy for non-enzymatic methods. The initial within-laboratory precision was generally good, and improvements in it were small. To our knowledge, standardization results involving so many routine hospital laboratory procedures have not been previously reported.

Calibration↗
PubMed1985

Improved preparation of cholesterol calibration and control sera.

We prepared several serum batches with various cholesterol concentrations, to be used as calibrators and controls in a proficiency testing program of an organization in The Netherlands that is in charge of the standardization of cholesterol determinations for epidemiological purposes. The sera were of human origin, to avoid abnormal matrix effects. To decrease the cholesterol content in some samples, we adsorbed them onto colloidal silicic acid. To increase it, we added lipoproteins that had been precipitated from human serum with heparin and calcium ions. The precipitation method we used allowed us to dilute the serum as little as possible and to keep the final concentrations of calcium and heparin as low as possible, while maintaining a high cholesterol content. By mixing these sera having high and low cholesterol concentrations, we could prepare batches with any desired concentration. The stabilities of these sera were excellent. We used the sera to calibrate enzymic determinations of cholesterol.

Calcium↗
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

Suitability of various control sera for use in testing the accuracy of cholesterol determination with enzymic kits.

We used 20 different commercial enzymic kits to measure cholesterol in 19 commercial control sera and in a pooled specimen of human serum and compared the relative biases, with the Abell -Kendall procedure as reference. Our purpose was to select those sera in various enzymic kits showing behavior similar to that of human serum and which thus can be used to measure the accuracy of these kits. The overall mean relative biases obtained with each of the 20 kits for the pooled human serum on the one hand and for a given control serum on the other generally correlated significantly. On the basis of the correlation coefficients and regression equations, we could select the control sera best suited for measurement of accuracy. They were all human-serum based, with cholesterol concentrations greater than 5 mmol/L. Animal sera with above-normal lipid values produced by feeding special diets appeared to be less reliable control sera in this respect.

Animals↗
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↗