Biomedical subjects

P Volkers

Publications and source records attributed to P Volkers.

9 recordsLinked to original sources

PubMed2006

Bacterial contamination of platelet concentrates prepared by different methods: results of standardized sterility testing in Germany.

BACKGROUND AND OBJECTIVES: National guidelines for monitoring the bacterial contamination rate of blood components were introduced in Germany in 1997. The objective of this study was to present and evaluate the results of sterility testing of platelet concentrates (PCs) prepared by different methods. MATERIALS AND METHODS: The analysis of results of sterility testing of blood component production from transfusion medicine centres in Germany in 1998 and 2001 was based on information collected using standardized questionnaires. RESULTS: The bacterial contamination rates for single-donor PCs derived from whole blood and apheresis (0.210% vs. 0.156%) were comparable and showed no significant difference. However, pooled PCs produced from four buffy coats using the sterile docking procedure showed a significantly higher bacterial contamination rate compared with single-donor PCs derived from whole blood and apheresis (0.184% vs. 0.604%). CONCLUSIONS: Use of standardized methods for sterility monitoring is sufficient to assess collection and production processes in terms of hygiene and yields reliable data on bacterial contamination rates of blood components. The methods described are suitable for using to analyse the efficiency of newly introduced methods to reduce bacterial contamination rates of blood components (e.g. diversion, bacteria screening and pathogen inactivation).

Bacterial Infections↗

PubMed2005

[Regulatory aspects of clinical trials with emphasis on biologicals].

Clinical trials play a central role in clinical development for achieving marketing authorization for a drug. Carefully planned and carried out clinical trials allow for valid conclusions on the efficacy and/or safety of a drug. In order to do so, various requirements have to be fulfilled: clinical studies are to be planned and conducted in accordance with Good Clinical Practice, scientifically sound methods have to be applied, the patients' safety has to be ensured, trial objectives and results have to be clinically relevant, quality and transparency of all steps from planning to reporting a clinical study have to be ensured. For biologicals, special attention has to be paid to specific aspects, such as their mode of action or possible impact on the environment. Various guidelines reflecting regulatory aspects are available to support drug development. In addition, specific questions on drug development might be discussed directly between study sponsors and regulatory agencies. Due to the changes imposed by the 12th law amending the German Drug Law (Arzneimittelgesetz), the relevant German authorities will be more involved in the planning and conduct of clinical trials.

Adverse Drug Reaction Reporting Systems↗

PubMed2004

[Thiomersal and immunisations].

Thiomersal was used in the 1930s for the first time for the preservation of vaccines to prevent bacterial and fungal contamination. Thiomersal is an organic compound containing 49% mercury (Hg) by weight. It is generally well known that mercury and its compounds, including thiomersal, ethylmercury, and methylmercury, act as nephro- and neurotoxicants, however, at much higher doses than used in vaccines. In the 1990s the question of toxicity of thiomersal in vaccines was reassessed since the numbers of vaccines recommended for routine administration to infants and children, and therefore the cumulative thiomersal dose in children, increased in some countries. Various international committees (European Agency for the Evaluation of Medicinal Products, EMEA, US Public Health Service/American Academy of Pediatrics, Institute of Medicine, IOM) concluded after an extensive risk/benefit analysis that scientific evidence is inadequate to reject or explicitly recommend thiomerosal-containing vaccines for children. However (in line with the global goal of reducing exposure to mercury), they recommended promoting the elimination of thiomerosal from paediatric vaccines. This has largely been achieved in Germany. Today a child in Germany can be immunised in accordance with the official recommendations (STIKO) almost without the administration of thiomerosal (residual amounts). Results of new pharmacokinetic and epidemiological studies are discussed. The evidence available to date does not support the hypothesis of a potential relationship between neurodevelopmental disorders and thiomersal-containing vaccines.

Adverse Drug Reaction Reporting Systems↗

PubMed2004

Plasma quality after whole-blood filtration depends on storage temperature and filter type.

The study evaluated the quality of plasma obtained after whole-blood filtration with four different polyester filters and one polyurethane filter. The activities of coagulation factors and proteinase inhibitors were not or only negligibly affected by filtration, in all experiments. Filtration did not increase markers of clotting and fibrinolysis. Only a strong neutrophil and complement activation was observed, which depended on the type of filter and whole-blood storage conditions. However, as neutrophil elastase-specific degradation products did not increase and the complement-derived anaphylatoxin C3a was found in its inactivated form, C3a-desArg, these filtration-dependent changes apparently have little impact on the therapeutic quality of whole-blood-filtered fresh frozen plasma for transfusion.

Antithrombins↗

PubMed2004

Control of Clostridium perfringens vaccines using an indirect competitive ELISA for the epsilon toxin component - examination of the assay by a collaborative study.

Investigations on the replacement of the mouse neutralisation test for proving vaccine batches of Clostridium (C.) perfringens toxoid vaccines were performed since several years. The European Pharmacopoeia (Ph. Eur.) monograph Clostridium perfringens vaccines for veterinary use (0363) is prescribing a potency test by immunisation of rabbits and checking the induction of specific antibodies against the toxins in a mouse neutralisation test. Since the monograph was revised, immunochemical methods are favoured to detect directly specific antibodies in the rabbit sera. An indirect competitive ELISA using a monoclonal antibody was established at the Paul-Ehrlich-Institut for the detection of antibodies against the epsilon toxin component of C. perfringens. It was revised using the Clostridia rabbit antiserum Ph. Eur. Biological Reference Preparation (BRP) Batch 1 as reference serum. With a defined content of 11 International Units (IU) of C. perfringens epsilon antitoxin this reference serum enables the calculation of the potency of rabbit sera under test. For the collaborative study vaccine products of different composition licensed for the German and European markets were used. Seven international laboratories were included. Aim was to make a prediction on the transferability and precision of the test method. The results showing a satisfactory intermediate precision and transferability of the test confirmed the applicability of the ELISA method for the batch control of C. perfringens vaccines. Therefore a replacement of the mouse neutralisation test is available.

Animals↗

PubMed2003

Validation of flow cytometry to quantify the potency of anti-D immunoglobulin preparations.

BACKGROUND AND OBJECTIVES: Flow cytometry has been recommended as an alternative to that of autoanalyser methodology for estimation of anti-D potency. This investigation was performed to validate the flow cytometry method based on a quality assurance system. MATERIALS AND METHODS: A flow cytometry method based on indirect labelling of Rh(D)-positive red blood cells was validated using the parameters precision and accuracy and was compared to the autoanalyser data of manufacturers of anti-D immunoglobulin preparations. RESULTS: The experiment first investigated the possible differences between assays from single donors compared with a pooled assay. Red blood cells of four individual donors and their pooled red blood cells were interchangeable. There was no significant difference between donors, on one hand, and between the use of a single donation and the pooled red blood cells, on the other hand (P = 0.695). The two-sided 95% confidence intervals (CIs) of the difference between single donors and the pool ranged from -4.6% to 4.7%. The intermediate variability was determined by standard deviation (SD) = 48.4 IU/ml [coefficient of variation (CV) = 3.8%]; the repeatability was SD = 34.3 IU/ml (CV = 2.7%). Using a spiking experiment, the second part of the experiment investigated recovery of a known anti-D potency. The recovery of samples spiked with defined amounts of reference preparation was 97.7-101%, with a mean bias of -1.3 (95% CI: -4.1 to 1.6). The results of the flow cytometry assay, as compared to those of the autoanalyser performed by the manufacturers of anti-D immunoglobulin preparations for those manufacturers who have their method validated in-house, ranged from 87 to 129%, indicating good correlation. CONCLUSIONS: Flow cytometry is a suitable quality control method for polyclonal anti-D immunoglobulins, which can be standardized in a quality control laboratory using a quality assurance system.

Automation↗

PubMed2001

Collaborative study for the establishment of erysipelas ELISA coating antigen. European Biological Reference Preparation batch no. 1.

The development and validation of suitable alternatives for the replacement of in vivo challenge testing in the evaluation of vaccines is an important goal for national authorities and manufacturers involved in the assessment of quality, safety and efficacy of such products. To that end, 13 laboratories from 9 European countries, including 5 manufacturers, 7 authorities and EDQM, have taken part in a collaborative study to evaluate the suitability of a candidate reference preparation of erysipelas coating antigen for ELISA as a European Pharmacopoeia Biological Reference Preparation (Ph. Eur. BRP No. 1). The new Ph. Eur. BRP is intended for use in a serological assay, which would significantly reduce the suffering of animals in the potency assays of inactivated erysipelas vaccines. Participants were provided with sufficient study material, including the candidate coating antigen, and a panel of test sera from mice which had been immunised with vaccines representative of products on the European market, in order to evaluate the performance of the coating antigen in an enzyme-linked immunosorbent assay (ELISA) which had previously performed successfully in a prevalidation study [1] and in an international validation study [2]. Results of the collaborative study indicate that the candidate batch of erysipelas ELISA coating antigen is suitable to act as a Ph. Eur. biological reference preparation. The final study report was presented at the 110th session of the Ph. Eur. Commission (June 19-21, 2001) and the material was duly adopted as Erysipelas ELISA Coating Antigen Ph. Eur. BRP No. 1 for use in the enzyme-linked immunosorbent assay in the context of the serological potency assay for inactivated erysipelas vaccines.

Animals↗

PubMed1998

Rationale and design of the International Verapamil SR/Trandolapril Study (INVEST): an Internet-based randomized trial in coronary artery disease patients with hypertension.

OBJECTIVES: The primary objective of the International Verapamil SR/Trandolapril Study (INVEST) is to compare the risk for adverse outcomes (all-cause mortality, nonfatal myocardial infarction [MI] or nonfatal stroke) in hypertensive patients with coronary artery disease (CAD) treated with either a calcium antagonist-based or a noncalcium antagonist-based strategy. BACKGROUND: Treatment recommendations for hypertension include initial therapy with a diuretic or beta-adrenergic blocking agent, for which reductions in morbidity and mortality are documented from randomized trials but are less than expected from epidemiologic data. For this reason, recent attention has focused on calcium antagonists or angiotensin-converting enzyme inhibitors. While these agents reduce blood pressure, outcome data from large randomized trials are lacking, but some case-control data, dominated by short-acting dihydropyridines, suggest an increased risk of cardiovascular events. These studies had methodologic limitations and did not differentiate among calcium antagonist types and formulations. Several studies differentiating among calcium antagonist types and an overview of published randomized trials show no increased risk with verapamil and suggestion for benefit in CAD patients. METHODS: A total of 27,000 CAD patients with hypertension will be randomized at 1,500 primary care sites to receive either a calcium antagonist-based (verapamil) or beta-blocker/diuretic-based (atenolol/hydrochlorothiazide) antihypertensive care strategy. The study uses a novel, electronic "paper-less" system for direct on-screen data entry, randomization and drug distribution from a mail pharmacy linked to the coordination center via the Internet. RESULTS: Contract negotiations with the United States and international sites are ongoing. Patients being enrolled are predominantly elderly (72% aged 60 years or older) men (54%), with either an abnormal coronary angiogram or prior MI (71%). In addition to hypertension, CAD and elderly age, most patients (89%) have one or more associated conditions (diabetes, dyslipidemia, smoking, cerebral or peripheral vascular disease, etc.) contributing to increased risk for adverse outcome. While 26% have diabetes, most of these are noninsulin dependent. Using the protocol strategies, target blood pressures (according to JNC VI) have been reached in 58% at the fourth visit, and as expected most (89%) are requiring multiple antihypertensive drugs. CONCLUSION: The design and baseline characteristics of the initial patients recruited for a prospective, randomized, international, multicenter study comparing two therapeutic strategies to control hypertension in CAD patients are described.

Aged↗

PubMed1989

Comparison of two combined diuretics in the treatment of essential hypertension.

The efficacy and safety of two combination drugs, consisting of a diuretic + a K-sparing agent, were investigated in the treatment of essential hypertension. A double-blind, randomized, parallel group study design was employed. After randomization, 14 patients were treated with 10 mg xipamide + 30 mg triamterene (A) and 16 with 25 mg hydrochlorothiazide + 50 mg triamterene (B). The patients suffered from essential hypertension with a systolic blood pressure (SBP) at entry of greater than or equal to 150 mmHg and a diastolic blood pressure (DBP) of greater than or equal to 95 mmHg. After 6 weeks, mean decline in DBP was 12% in group A and 9% in group B, respectively. With treatment A, one patient became hypokalemic and with treatment B one patient became hyperkalemic.

Adult↗