Causes of unsatisfactory performance in proficiency testing.
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BACKGROUND: Proficiency testing (PT) provides a measure of the effectiveness of laboratory quality assurance programs. Test reports are released from processes that the laboratory judges to be in conformance with quality specifications; an evaluation of unsatisfactory performance (UNSAT) by a PT provider is an unexpected outcome for the laboratory. An understanding of the root cause(s) of testing errors provides an opportunity for the continuous improvement of laboratory services. METHODS: We used participant data from the New York State Department of Health PT program to characterize the quality of testing in the toxicology specialty. Outcomes from laboratory investigations into causes of UNSAT and information on quality control practices collected from all program participants were used to identify the root causes of error. RESULTS: Two classes of error were encountered: spurious test results caused by lapses in standard operating procedures and instrument malfunctions (300 per million assays) and common-cause analytic error (7000 per million assays or 0.7% rate of UNSAT). Causes of spurious results included inaccurate mathematical correction for specimen dilution, misinterpretation of instrument codes, and instrument sampling errors. Calibration drift was most frequently cited as the common-cause analytic error. Approximately one-half of the laboratories used an allowable error for the quality control of analytical systems that exceeded the threshold error specified by manufacturers for stable instrument performance. CONCLUSIONS: The causes of spurious results suggest the need for ongoing competency testing of analysts where analyst intervention is required in an otherwise automated process, and for continued diligence in mistake-proofing instrument design. The intrinsic quality of laboratory testing is unlikely to improve until the allowable error in quality control is consistent with manufacturer specifications for stable system performance. (+info)
Ethical review of regulatory toxicology guidelines involving experiments on animals: the example of endocrine disrupters.
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The safety assessment of new chemicals (including medicines, pesticides, food additives, and industrial chemicals) relies on the results of animal experiments. Because the safety of those exposed to these products and the welfare of the experimental animals used are considered critically important, both testing requirements and the welfare of experimental animals are controlled by law. In the U.K., projects that propose to use animals for experimental purposes, including for the testing of chemicals, have been controlled by law for over a century, with the most recent legislation (Animals [Scientific Procedures] Act of 1986) requiring a cost/benefit assessment before it may proceed. New regulations introduced in 1998 will require an ethical review process for all projects from April 1999. Such ethical review will have to take account of the toxicity testing methods and schemes that are required by the legislation aimed at protecting human health. Neither national nor international proposals for toxicity testing methods and schemes are generally subjected to ethical review from the point of protecting animal welfare. The international nature of the chemical and pharmaceutical industry means that testing requirements from one of the major national regulatory agencies (USA, EU, or Japan) or the international organizations (Organization for Economic Co-operation and Development [OECD]or the International Conference on Harmonization [ICH]) have an impact on the testing carried out by industrial organizations in all countries. The recent proposals for screening and testing chemicals to identify endocrine disrupters (ED) from the Endocrine Disrupter Screening and Testing Advisory Committee (EDSTAC) of the U.S. Environmental Protection Agency (EPA) are used as an example of the interaction between regulatory proposals and animal welfare issues. The current proposals are the most extravagant in the use of animals. Between 0.6 and 1.2 million animals would be required for each 1000 chemicals tested. The EPA, before incorporating them into regulation, is subjecting the recommendations to further review. This will undoubtedly moderate the number of animals actually used from the worst-case calculation. The variables that have the greatest impact on the number of animals required for testing are the prevalence of ED chemicals in the chemicals to be tested, and the sensitivity and specificity of the testing methods. The modeling demonstrates, for example, that increasing the prevalence from 10 to 50% reduces the number of animals used to detect one ED from 10,000 to 2700. Knowledge of the prevalence of EDs in the chemicals to be tested would allow rational selection of tier one screening based on the sensitivity and specificity of the screening tests. The EDSTAC proposals are difficult to justify from an ethical perspective, as equally effective detection rates may be achieved with fewer animals. National and international regulatory testing proposals should be subjected to formal independent ethical review before they are finalized, with a view to improving animal welfare. (+info)
Evaluation of the EDSTAC female pubertal assay in CD rats using 17beta-estradiol, steroid biosynthesis inhibitors, and a thyroid inhibitor.
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The Endocrine Disrupter Screening and Testing Advisory Committee has recommended the female pubertal onset assay as a Tier I test to detect potential endocrine-disrupting chemicals (EDs). We evaluated this assay's ability to detect EDs acting through various mechanisms. In two similar experiments, weanling female rats were dosed for 20 days by gavage with vehicle (0.5% methocel) or the following test compounds (mg/kg/day): 17beta-estradiol (E2; 0.1, 2, or 4), ketoconazole (KETO; 24, 50, or 100), finasteride (FIN; 20), testolactone (TL; 220), fadrozole (FAD; 0.6, 1.2, or 6.0) or 6-propylthiouracil (PTU; 240). In vehicle-treated females, mean age at pubertal onset, as evidenced by vaginal opening (VO), varied interexperimentally from 32.3+/-1.6 days to 33.5+/-1.8 days. At 0.1 mg/kg E2, age at VO was reduced slightly to 31.0+/-1.6 days, but not significantly (alpha=0.05). Higher E2 doses (2.0 and 4.0) reduced age at VO to 28 days. KETO delayed VO, but this delay was significant only at 100 mg/kg (39.7+/-2.4 days). FIN and TL had no effect on age at pubertal onset; however, FAD significantly delayed VO. PTU delayed VO to 34.2+/-1.1 days and altered thyroid weight, histology, and hormone levels. With each compound, significant changes in age at VO were accompanied by decreased uterine or ovarian weights. Thus, although this assay did not detect TL or lower doses of E2 (0.1 mg/kg) or KETO (< or = 50 mg/kg), it was capable of detecting EDs operating through a variety of mechanisms. (+info)
An integrative approach to neurotoxicology.
(20/791)
Exposure of human populations to a wide variety of chemicals has generated concern about the potential neurotoxicity of new and existing chemicals. Experimental studies conducted in laboratory animals remain critical to the study of neurotoxicity. An integrative approach using pharmacokinetic, neuropathological, neurochemical, electrophysiological, and behavioral methods is needed to determine whether a chemical is neurotoxic. There are a number of factors that can affect the outcome of a neurotoxicity study, including the choice of animal species, dose and dosage regimen, route of administration, and the intrinsic sensitivity of the nervous system to the test chemical. The neurotoxicity of a chemical can vary at different stages of brain development and maturity. Evidence of neurotoxicity may be highly subjective and species specific and can be complicated by the presence of systemic disease. The aim of this paper is to give an overview of these and other factors involved in the assessment of the neurotoxic potential for chemicals. This article discusses the neurotoxicity of several neurotoxicants (eg, acrylamide, trimethyltin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, manganese, and ivermectin), thereby highlighting a multidisciplinary approach to the assessment of chemically induced neurotoxicity in animals. These model chemicals produce a broad range of effects that includes peripheral axonopathy, selective neuronal damage within the nervous system, and impaired neuronal-glial metabolism. (+info)
GC-MS identification of sympathomimetic amine drugs in urine: rapid methodology applicable for emergency clinical toxicology.
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A method was developed that permitted rapid identification in urine of the following sympathomimetic amines: amphetamine, benzphetamine, cathinone, desmethylsegiline, diethylpropion, ephedrine, fenfluramine, mazindol, methylenedioxyamphetamine, methylenedioxyethylamphetamine, methylenedioxymethamphetamine, mescaline, methamphetamine, methcathinone, methylaminorex, methylphenidate, pemoline, phendimetrazine, phenylepherine, phentermine, phenylpropanolamine, pseudoephedrine, and selegiline. In addition, two alpha-phenylethylamine-like monoamine oxidase inhibitors, phenelizine and tranylcypromine, were studied. Those sympathomimetic amines containing a primary or secondary amine, a hydrazine, and/or hydroxyl (except mazindol) functional groups were derivatized effectively using an on-column derivatization technique that used a reagent consisting of 10% fluoroanhydride in hexane, whereas the other sympathomimetic amines, including mazindol, were analyzed underivatized. Three different fluoroanhydrides, trifluoroacetic (TFAA), pentafluoropropionic (PFPA), and heptafluorobutyric (HFBA), and three different injection-port temperatures (160, 200, and 260 degrees C) were investigated. Both TFAA and PFPA gave sympathomimetic amine derivatives with essentially identical retention times, whereas HFBA gave longer retention times and better separation of individual compounds. The base fragmentation ion was noted to increase 50 amu (CF2) for each derivatized sympathomimetic amine as the length of the carbon-fluorine chain increased. Fragmentation ion abundance was maximized at an injection-port temperature of 260 degrees C, and this enhanced sensitivity coupled with the better chromatographic resolution of the individual sympathomimetic amines prompted the selection of HFBA as the derivatizing agent of choice. Assignments were made for the fragmentation ions produced by each derivatized drug. The developed method was adapted to analyze urine specimens that might be encountered in emergency toxicology testing. For identification of sympathomimetic amines requiring derivatization, 0.1 mL of the patient specimen had amphetamine-d5 and methamphetamine-d5 added as internal standard followed by adjustment of pH to 9.3 with borate buffer, extraction with 9:1 chloroform/isopropanol, centrifugation and separation of the organic phase, addition of 10% methanolic HCI and evaporation under nitrogen, reconstitution with HFBA reagent, and on-column derivatization during gas chromatographic-mass spectrometric (GC-MS) analysis. For those sympathomimetic amines not requiring derivatization, 1.0 mL of urine specimen had diazepam-d5 added as internal standard followed by the same extraction procedure and reconstitution accomplished with ethyl acetate. Because precolumn derivatization was eliminated and only 8 min was required for GC-MS analysis, complete analysis time was approximately 30 min, making the method suitable for clinical emergency toxicology purposes. (+info)
Stand-alone automated solutions can enhance laboratory operations.
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Clinical laboratory automation has developed over the past decade as one means of consolidating testing, reducing costs, and improving the effectiveness of laboratory testing. Most of the developments have been aimed at core clinical laboratory operations, and have primarily addressed preanalytical and analytical processing of traditional specimens arriving in blood collection or similar aliquot tubes. Much less attention has been given to specialized applications such as processing specimens for urine toxicology, and only recently have vendors attacked the problems associated with sorting and maintaining the laboratory's inventory of specimens. This report highlights selected developments in these areas, describes one approach to cost-effective custom platform development, and discusses the advantages and pitfalls to solving problems with laboratory automation. (+info)
New horizons: future directions in neurotoxicology.
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Neurotoxicology is a relatively young discipline that has undergone significant growth during the last 25 years. During the late 1970s and 1980s, numerous national and international conferences and meetings were devoted to the topic of neurotoxicology, the formation of societies or specialty sections related to neurotoxicology, and the establishment of two independent peer-reviewed journals devoted to neurotoxicology. This decade was also associated with a rapid increase in our knowledge of chemical effects on the structure and function of the nervous system. During the 1990s, regulatory agencies such as the U.S. Environmental Protection Agency accepted neurotoxicology as a crucial end point and neurotoxicity testing and risk assessment guidelines were published. Neurotoxicology has also been accepted at the international level as evidenced by environmental criteria documents published by the International Programme on Chemical Safety and testing guidelines by the Organization of Economic Cooperation and Development. In recent years, there has been increased concern that the etiology of some neurodegenerative diseases may be associated with exposure to neurotoxic agents and that subpopulations of humans such as children and the elderly may be differentially sensitive to neurotoxic exposure. In the future, mechanistic information derived from basic research will be used in the identification and characterization of chemicals with neurotoxic potential. (+info)
Use of transgenic animals for carcinogenicity testing: considerations and implications for risk assessment.
(24/791)
Advances in genetic engineering have created opportunities for improved understanding of the molecular basis of carcinogenesis. Through selective introduction, activation, and inactivation of specific genes, investigators can produce mice of unique genotypes and phenotypes that afford insights into the events and mechanisms responsible for tumor formation. It has been suggested that such animals might be used for routine testing of chemicals to determine their carcinogenic potential because the animals may be mechanistically relevant for understanding and predicting the human response to exposure to the chemical being tested. Before transgenic and knockout mice can be used as an adjunct or alternative to the conventional 2-year rodent bioassay, information related to the animal line to be used, study design, and data analysis and interpretation must be carefully considered. Here, we identify and review such information relative to Tg.AC and rasH2 transgenic mice and p53+/- and XPA-/- knockout mice, all of which have been proposed for use in chemical carcinogenicity testing. In addition, the implications of findings of tumors in transgenic and knockout animals when exposed to chemicals is discussed in the context of human health risk assessment. (+info)