This study aimed to assess currently used evaluation procedures for haemoglobin concentration and... more This study aimed to assess currently used evaluation procedures for haemoglobin concentration and leukocyte concentration in European external quality assessment schemes (EQAS). Participating EQAS organizers were asked to complete a questionnaire gathering information on the statistical procedures used to assess the performance of participants, and to analyse an Excel file with 262 results for haemoglobin concentration and leukocyte concentration. Responses
International Journal of Hygiene and Environmental Health, 2014
The aim of this study was to evaluate the association between persistent organic pollutants (POPs... more The aim of this study was to evaluate the association between persistent organic pollutants (POPs) and thyroid hormones in an aging population. Forty-eight women and 66 men, aged 55-74 years and living in upper Hudson River communities completed a questionnaire and provided blood specimens. Serum was analyzed for thyrotropin (thyroid stimulating hormone, TSH), free (fT4) and total thyroxine (T4), total triiodothyronine (T3), and for POPs. POPs included 39 polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) determined by gas chromatography with electron capture detection (GC-ECD), and nine polybrominated diphenyl ethers (PBDEs) determined by high-resolution gas chromatography with high-resolution mass spectrometry detection (HRGC-HRMS). Multivariable linear regression analysis was used to evaluate associations between thyroid hormones and sums of POPs, adjusted for covariates and stratified by sex. Effects were expressed as differences in thyroid hormone levels associated with a doubling in the level of exposure. Among women, DDT+DDE increased T4 by 0.34μg/dL (P=0.04) and T3 by 2.78ng/dL (P=0.05). Also in women, sums of PCBs in conjunction with PBDEs elicited increases of 24.39-80.85ng/dL T3 (P<0.05), and sums of PCBs in conjunction with DDT+DDE elicited increases of 0.18-0.31μg/dL T4 (P<0.05). For men estrogenic PCBs were associated with a 19.82ng/dL T3 decrease (P=0.003), and the sum of estrogenic PCBs in conjunction with DDT+DDE elicited an 18.02ng/dL T3 decrease (P=0.04). Given age-related declines in physiologic reserve, the influence of POPs on thyroid hormones in aging populations may have clinical implications and merits further investigation.
Scandinavian Journal of Clinical & Laboratory Investigation, 1991
Immunoassay systems require calibration protocols that are normally more sophisticated than many ... more Immunoassay systems require calibration protocols that are normally more sophisticated than many analytical techniques in routine clinical use. Calibrators used in such assays may differ significantly from the analyte in clinical specimens. Differences in the properties of calibrators, or reference materials, from those of clinical specimens may include: species origin of the calibrator for an analyte; integrity of the molecular species; matrix of the calibration solution; addition of preservative agents. Owing to the large number of potential differences in the properties of calibrators and those of serum specimens that may affect immunoassay results, the concept of commutability that we originated and first applied to enzyme activity measurements can readily be applied to immunoassay determinations. We specifically examined the properties of calibration materials in nine commercial immunoassay tests for human thyrotropin. Significant non-commutability of materials was demonstrated. The measured results obtained with authentic patient sera differed by a factor of approximately two fold between the techniques exhibiting the lowest and greatest numeric results. Considerably larger intermethod biases were found for calibration materials. Multivariate analysis revealed that the patient sera formed a highly focussed pattern. The calibration materials for one instrument system also focussed in this group. Other calibrators formed three foci indicating similar patterns of commutability within each of the three groups. Clustering was independent of the amount of thyrotropin in the patient specimens, but appeared to be concentration-dependent for at least some of the calibrators. Thus the availability of a common calibration material appears feasible, but not presently available in many commercial products. A processed human serum, a candidate material for use in our proficiency testing program, was projected in the same cluster as authentic patient sera indicating that this material has intermethod properties identical to patient sera (i.e. fully commutable).
A simple technique is described that is suitable for rapid screening of hybridoma microculture fl... more A simple technique is described that is suitable for rapid screening of hybridoma microculture fluids for monoclonal antibody producing hybrids. The procedure measures increase in light scatter due to the antigen-antibody reaction on a surface of indium metal coated upon glass and does not require use of a labeled second antibody. Techniques minimizing nonspecific binding in such assays are presented. The procedure was used to screen hybridoma microculture fluids containing mouse monoclonal antibodies directed against human mitochondrial isoenzyme of aspartate aminotransferase (EC 2.6.1.1). The technique was compared to an enzyme-linked immunosorbent assay, and similar semi-quantitative results were found for sample cultures tested in the two procedures. The new screening procedure affords a simple screening assay without sacrificing sensitivity or specificity of standard methods.
This study aimed to assess currently used evaluation procedures for haemoglobin concentration and... more This study aimed to assess currently used evaluation procedures for haemoglobin concentration and leukocyte concentration in European external quality assessment schemes (EQAS). Participating EQAS organizers were asked to complete a questionnaire gathering information on the statistical procedures used to assess the performance of participants, and to analyse an Excel file with 262 results for haemoglobin concentration and leukocyte concentration. Responses
International Journal of Hygiene and Environmental Health, 2014
The aim of this study was to evaluate the association between persistent organic pollutants (POPs... more The aim of this study was to evaluate the association between persistent organic pollutants (POPs) and thyroid hormones in an aging population. Forty-eight women and 66 men, aged 55-74 years and living in upper Hudson River communities completed a questionnaire and provided blood specimens. Serum was analyzed for thyrotropin (thyroid stimulating hormone, TSH), free (fT4) and total thyroxine (T4), total triiodothyronine (T3), and for POPs. POPs included 39 polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE) determined by gas chromatography with electron capture detection (GC-ECD), and nine polybrominated diphenyl ethers (PBDEs) determined by high-resolution gas chromatography with high-resolution mass spectrometry detection (HRGC-HRMS). Multivariable linear regression analysis was used to evaluate associations between thyroid hormones and sums of POPs, adjusted for covariates and stratified by sex. Effects were expressed as differences in thyroid hormone levels associated with a doubling in the level of exposure. Among women, DDT+DDE increased T4 by 0.34μg/dL (P=0.04) and T3 by 2.78ng/dL (P=0.05). Also in women, sums of PCBs in conjunction with PBDEs elicited increases of 24.39-80.85ng/dL T3 (P<0.05), and sums of PCBs in conjunction with DDT+DDE elicited increases of 0.18-0.31μg/dL T4 (P<0.05). For men estrogenic PCBs were associated with a 19.82ng/dL T3 decrease (P=0.003), and the sum of estrogenic PCBs in conjunction with DDT+DDE elicited an 18.02ng/dL T3 decrease (P=0.04). Given age-related declines in physiologic reserve, the influence of POPs on thyroid hormones in aging populations may have clinical implications and merits further investigation.
Scandinavian Journal of Clinical & Laboratory Investigation, 1991
Immunoassay systems require calibration protocols that are normally more sophisticated than many ... more Immunoassay systems require calibration protocols that are normally more sophisticated than many analytical techniques in routine clinical use. Calibrators used in such assays may differ significantly from the analyte in clinical specimens. Differences in the properties of calibrators, or reference materials, from those of clinical specimens may include: species origin of the calibrator for an analyte; integrity of the molecular species; matrix of the calibration solution; addition of preservative agents. Owing to the large number of potential differences in the properties of calibrators and those of serum specimens that may affect immunoassay results, the concept of commutability that we originated and first applied to enzyme activity measurements can readily be applied to immunoassay determinations. We specifically examined the properties of calibration materials in nine commercial immunoassay tests for human thyrotropin. Significant non-commutability of materials was demonstrated. The measured results obtained with authentic patient sera differed by a factor of approximately two fold between the techniques exhibiting the lowest and greatest numeric results. Considerably larger intermethod biases were found for calibration materials. Multivariate analysis revealed that the patient sera formed a highly focussed pattern. The calibration materials for one instrument system also focussed in this group. Other calibrators formed three foci indicating similar patterns of commutability within each of the three groups. Clustering was independent of the amount of thyrotropin in the patient specimens, but appeared to be concentration-dependent for at least some of the calibrators. Thus the availability of a common calibration material appears feasible, but not presently available in many commercial products. A processed human serum, a candidate material for use in our proficiency testing program, was projected in the same cluster as authentic patient sera indicating that this material has intermethod properties identical to patient sera (i.e. fully commutable).
A simple technique is described that is suitable for rapid screening of hybridoma microculture fl... more A simple technique is described that is suitable for rapid screening of hybridoma microculture fluids for monoclonal antibody producing hybrids. The procedure measures increase in light scatter due to the antigen-antibody reaction on a surface of indium metal coated upon glass and does not require use of a labeled second antibody. Techniques minimizing nonspecific binding in such assays are presented. The procedure was used to screen hybridoma microculture fluids containing mouse monoclonal antibodies directed against human mitochondrial isoenzyme of aspartate aminotransferase (EC 2.6.1.1). The technique was compared to an enzyme-linked immunosorbent assay, and similar semi-quantitative results were found for sample cultures tested in the two procedures. The new screening procedure affords a simple screening assay without sacrificing sensitivity or specificity of standard methods.
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