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G T Sanders

Publications and source records attributed to G T Sanders.

At least 37 records · Page 2Linked to original sources
PubMed1997

[Laboratory testing virtually centralized to benefit both patients and drug research].

Laboratory analyses in multicentre safety studies of new drugs usually are performed in central laboratories outside the Netherlands. Patient care requires local (hospital) laboratory tests. In the so-called Virtually Centralized Laboratory the Dutch local laboratories report their results after data communication and data transformation in such a way that they seem to form one laboratory. The local analytical results are transformed by calibrating the local methods using standard preparations, thus reducing the inter laboratory variation. This concept may lead to one set of national reference values for all general clinical chemical and haematological laboratory tests.

Blood Chemical Analysis↗
PubMed1997

Precision of the magnesium determination in mononuclear blood cells and erythrocytes.

OBJECTIVE: Establishing the analytical variation and reproducibility of the intracellular magnesium (Mg) assay in mononuclear blood cells (MBC) and erythrocytes (RBC). DESIGN AND METHODS: We assessed the analytical variation of the several determination steps, and the reproducibility for the complete intracellular Mg-assay (combination of preanalytical, analytical, and biological variation). The influence of platelets was determined by comparing Mg concentrations obtained from heparinized blood and defibrinated blood. RESULTS: Coefficients of variation of the several determination steps used in the MBC- and RBC-assay were < or = 5.4%. The overall analytical variation was 5.0-6.8%, and reproducibility of the complete Mg-assay 11.6-14.0%. Mg measurements in MBC (expressed as fmol/cell) obtained from heparinized blood showed significantly higher values than those obtained from defibrinated blood. CONCLUSION: This is the first study to describe in detail reproducibility data for the individual steps in the overall procedure to measure intracellular magnesium. It is shown that results obtained in daily practice should be interpreted with care. Moreover, the removal of platelets is essential in the determination of Mg in MBC.

Blood Specimen Collection↗
PubMed1997

Critical difference between serial measurements of CK-MB mass to detect myocardial damage.

To assess the critical difference in serial measurements of CK-MBmass and the ability of this critical difference to detect myocardial damage, we studied 110 patients in whom an acute myocardial infarction (AMI) had been ruled out. Blood samples were drawn at 3, 4, 5, 6, 7, 8, 12, 16, 20, and 24 h after onset of symptoms. With a critical difference of 72.6%, an increase of >2.0 microg/L between two CK-MBmass measurements was determined to be significant. Twenty-three of the non-AMI patients had an increase in CK-MBmass >2.0 microg/L, but five of these did not have an abnormal concentration of troponin T (i.e., not >0.1 microg/L). Also among the 110 non-AMI patients, 22 did have an abnormal troponin T value, 18 of whom (82%) also had CK-MBmass increased by >2.0 microg/L. In 20 of the 23 patients with an increase in CK-MBmass >2.0 microg/L, this increase was detected from the values for two samples collected at 5 and 12 h after onset of symptoms. In conclusion, using the critical difference for CK-MBmass defined as an increase >2.0 microg/L detected myocardial damage in patients without AMI.

Adult↗
PubMed1997

The clinical value of lactate dehydrogenase in serum: a quantitative review.

The aim of this article is to describe guidelines for rational use of lactate dehydrogenase and its isoenzymes, in the diagnostic processes and during follow-up, based on a systematic review of relevant literature. Sources of data for this study were English-language scientific publications, obtained from the database of the National Library of Medicine (Medline), concerning the clinical application (diagnosis, monitoring or treatment of disease) of lactate dehydrogenase and lactate dehydrogenase isoenzyme measurements in serum in the following main clinical fields: cardiology, hepatology, haematology and oncology. For acceptance in the present review, studies had to include: a proper definition of the tested patient population, diagnostic criteria, sampling time, sampling frequency, and test characteristics. Estimation of the relation between lactate dehydrogenase or lactate dehydrogenase isoenzymes and specific diseases expressed as sensitivity, specificity, survival or remission rate were extracted. The application of serum lactate dehydrogenase is relevant in the diagnosis of myocardial infarction (late detection), haemolytic anaemia, ovarian dysgerminoma and testicular germ cell tumor. For monitoring the progress of a disease lactate dehydrogenase is relevant in establishing the survival duration and rate in Hodgkin's disease and non-Hodgkin's lymphoma, and in the follow-up of ovarian dysgerminoma. Rational use of lactate dehydrogenase can be achieved when requests for its determination are limited to the above mentioned conditions. No rationale could be found for measuring lactate dehydrogenase isoenzymes.

Animals↗
PubMed1997

The European Register for Clinical Chemists. (European Communities Confederation of Clinical Chemistry, Working Group on Registration).

To ensure freedom of movement in the European Union, a limited number of professions is regulated by a so-called Sectorial Directive; all other disciplines, including clinical chemistry, fall under a General Directive. However, clinical chemists in the EU wish their specialty to be more specifically regulated; this means that common standards of education, training, experience and compliance with continuing professional developments must be guaranteed. Therefore, the European Communities Confederation of Clinical Chemistry (EC4) is about to implement the European Register for clinical chemists, and has composed a guide to this Register. The document describes the conditions for entry to specialty training, the minimum standards for registration (university education and postgraduate vocational training with a minimum total of eight years), the competencies of those qualifying for registration, and the operation of the register. Registration guarantees professional and managerial competencies; the title conferred is "European Clinical Chemist". EC4 recognises the existing national registers as far as they are based on the minimal requirements as indicated. An EC4 Register Commission (EC4RC) will maintain and control the European Register, supported by National Clinical Chemistry Registration Committees (NCCRC). An NCCRC controls the quality of the education in each country and assesses candidates. An individual (EU citizen or non-EU citizen trained in an EU country) applies privately for the European Register to EC4RC and, where applicable, the application is accompanied by a document from the NCCRC of the country of registration, stating that the applicant has the necessary qualifications. For EU citizens trained outside the EU the final decision is with EC4RC; non-EU citizens not trained in an EU country are not eligible for registration. Registration is renewed once every five years.

Chemistry, Clinical↗
PubMed1996

Magnesium fractions in serum of healthy individuals and CAPD patients, measured by an ion-selective electrode and ultrafiltration.

OBJECTIVES: Validation and comparison of a magnesium ion-selective electrode (ISE) with a cation-exchange resin technique, followed by determination of all magnesium fractions in serum of healthy volunteers and continuous ambulatory peritoneal dialysis (CAPD) patients. DESIGN AND METHODS: The analytical aspect has been studied by measuring the influence of complexing agents on the fraction ionized magnesium (friMg2+). A theoretical approximation of friMg2+, based on mass equilibria and complexation constants, was calculated and compared with the measurements. RESULTS: ISE measurements showed good agreement with theory. Reference values of the ionized, protein-bound, and complexed magnesium fractions were (mean +/- SD) 0.65 +/- 0.04, 0.27 +/- 0.04, and 0.08 +/- 0.03, respectively. Fractions obtained in the CAPD group were 0.62 +/- 0.04, 0.22 +/- 0.05, and 0.16 +/- 0.05, respectively, and differed significantly from the values of the reference population. CONCLUSIONS: All known serum magnesium parameters can be established by a combination of ultrafiltration, atomic absorption spectrometry, and ISE measurements. Unknown complexing compounds most probably account for the increased fraction of complexed magnesium in the serum of CAPD patients.

Adult↗
PubMed1996

Prognostic value of troponin T, myoglobin, and CK-MB mass in patients presenting with chest pain without acute myocardial infarction.

OBJECTIVE: To assess the prognostic value of minor myocardial damage in patients presenting with chest pain without myocardial infarction. DESIGN: The relative risk of suffering a cardiac event in the next six months was assessed in patients with minor myocardial damage assessed by the cardiac markers CK-MB, myoglobin, and troponin T. SETTING: Emergency department of a large university hospital. PATIENTS: In 128 consecutive patients with chest pain, acute myocardial infarction (by WHO criteria) was ruled out; of these, 39 had a rise and fall of one or more markers, indicating minor myocardial damage. The presence of a documented history of coronary artery disease was assessed on admission. RESULTS: 24 patients had a subsequent event (cardiac death, acute myocardial infarction, percutaneous transluminal coronary angioplasty, coronary artery bypass grafting) in the next six months. An abnormal troponin T predicted a subsequent event while abnormal CK-MB or myoglobin did not. The relative risk for troponin T was 2.8 (95% confidence interval: 1.0 to 7.9), for myoglobin 1.0 (0.3 to 3.2), and for CK-MB 0.9 (0.2 to 3.4). A documented history of coronary artery disease predicted subsequent events with a relative risk of 3.9 (1.3 to 11.3). CONCLUSIONS: Troponin T was the only marker that predicted future events, but a documented history of coronary artery disease was the best predictor in patients in whom an acute myocardial infarction had been ruled out.

Aged↗
PubMed1995

Value of myoglobin, troponin T, and CK-MBmass in ruling out an acute myocardial infarction in the emergency room.

BACKGROUND: Ruling out acute myocardial infarction (AMI) on the basis of rapid assays for cardiac markers will allow early triage of patients and cost-effective use of available coronary care facilities. METHODS AND RESULTS: We studied the value of myoglobin, creatine kinase (CK)-MBmass, and troponin T in ruling out an AMI in the emergency room in 309 consecutive patients presenting with chest pain. The gold standard for AMI was the combination of history, ECG, and a typical curve of the CK-MB activity (CK-MBact). Myoglobin was the earliest marker, and its negative predictive value (NPV) was significantly higher than for CK-MBmass and troponin T from 3 to 6 hours after the onset of symptoms (myoglobin versus CK-MBmass, P < .03; myoglobin versus troponin T, P < .01). The NPV of myoglobin reached 89% 4 hours after the onset of symptoms. The NPV of CK-MBmass reached 95% 7 hours after the onset of symptoms. Troponin T was not an early marker for ruling out AMI, and NPV changed over time, together with CK-MBact. The early NPV was higher in a subgroup of patients with a low probability of the presence of AMI for the three markers. Cardiac markers rise earlier in patients with large infarcts than in patients with small infarcts as indicated by the cumulative proportion of the marker above the upper reference limit at each time point (myoglobin, P = .04; CK-MBmass, P = .013; troponin T, P = .016). CONCLUSIONS: For ruling out AMI in the emergency room, myoglobin is a better marker than CK-MBmass or troponin T from 3 until 6 hours after the onset of symptoms, but the maximal NPV reaches only 89%. At 7 hours, the NPV of CK-MBmass is 95%. The test characteristics are influenced by the probability of the presence of AMI in the patients studied and by the size of their AMI. Infarct size of AMI patients should be reported in studies evaluating cardiac markers.

Aged↗
PubMed1995

Kinetics of prostate-specific antigen after manipulation of the prostate.

Kinetics of prostate-specific antigen (PSA) were investigated after manipulation of the prostate in two groups of patients: those treated with digital rectal examination (DRE), and those with needle biopsy. 8 patients had serial PSA measurements to study the effect of DRE (group 1). 7 of 8 patients had PSA baseline values < 10 ng/ml. Blood samples were taken at 1 min, 30 min, 1, 3, 6, 12 and 24 h after DRE. Some patients were further monitored for 5 days with one blood sample taken at the same time each day. Statistically significant increased PSA levels were found after DRE (P < 0.001). Maximal increase was 70%. In most patients, peak levels were found between 30 and 60 min after DRE. Based on the results, it is concluded that after DRE it is prudent to wait 3 days before PSA is determined. 7 patients had serial PSA measurements after transrectal prostate needle biopsy (group 2). PSA sampling was similar as in the previous group. All patients had increased PSA levels after biopsy (range 1.3-9.5-fold). After 5 days, only 2 of 7 patients had returned to baseline levels. We conclude that biopsies of the prostate induce an important and long-lasting PSA elevation.

Adenocarcinoma↗
PubMed1995

Evaluation of the Hitachi 911 for routine urine analysis and for measurement of various special serum analytes.

The Boehringer Mannheim Hitachi 911 is a selective analyzer for 35 different methods including 3 ion-selective electrode (ISE) methods. We have evaluated this analyzer primarily to obtain objective information on its applicability for routine urine analyses in our laboratory. We also implemented appropriate assays for various special serum- and whole blood-tests, some for the first time on the Hitachi 911 and some with modified settings. Analytical evaluation involved NCCLS EP5-T2 (imprecision), NCCLS EP6-P (linearity), Krouwer 27 (multifactor) and Passing & Bablok (method comparison) evaluation protocols. With the exception of evidence of systematic erroneous sample predilution, overall results were favourable. Practicability of the Hitachi 911 was judged by simulating daily routine. During a period of two weeks, daily urine samples were rerun on the Hitachi 911, leading to a gain of about 50% in total processing time. It was concluded that the Hitachi 911 meets the requirements in terms of analytical performance, reliability, versatility and speed for an analyzer to be used in a routine (urine) setting, while having a distinct role in special (serum/whole blood) measurements.

Blood Chemical Analysis↗
PubMed1994

Clinical biochemistry training in The Netherlands.

A unique situation for clinical biochemistry exists in the Netherlands, since it is nearly fully practised by science-oriented professionals. They are enlisted in the Register of Recognized Clinical Biochemists supervised by the Netherlands Society of Clinical Chemistry. Training as a clinical biochemist consists of a 4-year period in a hospital laboratory; it is not a specific university education. Strictly specified requirements exist for trainee, tutor, laboratory and hospital to maintain the quality of our profession. The candidate has to become acquainted with the following aspects: general clinical biochemistry (including haematology), fundamental research, clinical orientation and management. Passing the yearly examination and publishing two articles in international journals are an obligation. Continuing education is not yet compulsory, but is well formalized within our society. European unification asks for one regulation of clinical biochemistry on a European level, both for professionals with a medical and a science-oriented background.

Biochemistry↗
PubMed1994

Biological half-life of prostate-specific antigen after radical prostatectomy.

The disappearance pattern of prostate-specific antigen from serum after a standard radical prostatectomy was studied in eight patients with cancer confined to the prostate. The results were used to plot an elimination curve and calculate the best fit. A biphasic pattern was found with an average biological half-life of 1.63 hours in the alpha-phase, and 4.63 days in the beta-phase. Based on these results it is concluded that determination of prostate-specific antigen concentrations less than one month after a standard radical prostato-vesiculectomy has no value for the detection or exclusion of residual malignant processes.

Aged↗
PubMed1994

Analytical evaluation of Kone Microlyte determination of ionized magnesium.

We performed an analytical evaluation of a commercially available instrument for determining ionized magnesium through use of a neutral carrier, liquid-membrane-based ion-selective electrode. Reproducibility (CV 2-4%), linearity (0.30-2.50 mmol/L), lower limit of detection (0.30 mmol/L), and absence of interference from Ca2+ indicate adequate performance for measuring ionized magnesium in plasma or serum samples in the normal to high-concentration range. Sodium in excess of 150 mmol/L caused a negative bias, which can be explained by ionic strength-induced changes in activity coefficients. The use of heparin as an anticoagulant must be restricted to concentrations < 15 units/mL because of the binding of magnesium to heparin. The mean +/- SD concentration of ionized magnesium and its fraction of total magnesium in 76 healthy volunteers were 0.56 +/- 0.05 mmol/L and 0.65 +/- 0.04, respectively.

Adolescent↗
PubMed1993

Evaluation of the creatinine assay on the Reflotron analyser under centralized and non-centralized conditions.

The creatinine assay, performed on Reflotron "dry chemistry" analysers in six offices of general practitioners, was evaluated as part of a project on the quality of laboratory determinations in decentralized situations. The method itself was evaluated before this investigation was started. Differences were noticed between Reflotron machines, batches of strips, and various types of sample, viz. heparin-treated blood or plasma gave higher results than serum of EDTA-treated samples. All Reflotron results were lower in comparison with wet chemistry methods. The "dry chemistry" technique was not influenced by the presence of glucose or bilirubin (below 170 mumol/l); haemoglobin interfered. By simultaneous sampling, all creatinine determinations performed on whole EDTA blood in the general practitioners offices were repeated on serum in centralized laboratories using "wet chemistry" techniques. In this comparison 3% of all creatinine determinations in general practitioners offices were outside the 95% confidence interval. We conclude that the creatinine determination on the Reflotron may be used in general practitioners office testing as long as the general practitioner is aware of its limitations and can rely on a "reference" laboratory for training, quality control and repetition of unexpected results.

Bilirubin↗
PubMed1992

Clinical evaluation of a pancreatic lipase mass concentration assay.

An immunoactivation assay for determining pancreatic lipase mass concentration was clinically evaluated and compared with results obtained by measuring total amylase and pancreatic amylase activity. A group of 30 patients with pancreatitis was compared with a control group of 32 patients in which this disease was suspected but excluded. Both lipase mass concentration and pancreatic amylase activity exhibit good sensitivity (0.93 each) and specificity (0.94 and 0.97, respectively) at cutoff concentrations of 200 micrograms/L and 200 U/L, respectively. The median increase in lipase mass concentration (37.1 times the upper limit of the reference interval) in the pancreatitis group was higher than that for either total amylase or pancreatic amylase activity (5.94 and 14.5 times, respectively) but showed a similar time to peak value. We conclude that the lipase assay is the method of choice for diagnosing pancreatitis.

Acute Disease↗