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PubMed1998

Balneotherapy and quality assessment: interobserver reliability of the Maastricht criteria list and the need for blinded quality assessment.

This study investigates aspects of the reliability of the Maastricht criteria list for quality assessment in systematic reviews, and whether blinded reviewing is necessary to prevent review bias. We used the data set of 12 articles from a systematic review concerning the efficacy of balneotherapy in patients with arthritis. Twenty reviewers participated of which two reviewers, who have been involved in developing the Maastricht criteria list, acted as reference standard. Half of all assessments were performed blindly. A high level of agreement was found between the reviewers and a high level of correlation with the reference standard. The quality scores between the blinded and unblinded assessment did not differ much. Based on the results we conclude that the Maastricht criteria list is a reliable instrument in quality assessment of clinical trials. Within the limits of this study we found no evidence that blinding is necessary to prevent review bias.

Arthritis↗
PubMed1982

Methylene unit calibration for analysis of organic acids by gas--liquid chromatography/mass spectrometry.

We describe a method for automatic computation of "methylene unit" retention-time indices in real time on a computer-controlled gas chromatograph/mass spectrometer system. The calculation is based on the exponential relationship between the methylene unit values of hydrocarbon reference standards and the oven temperature at their elution. Using this mathematical relationship, we calculated calibration factors, which eliminates the need to include a set of methylene unit reference standards with each run and simplifies and speeds identification of unknown peaks in chromatograms. Long-term stability and good precision of the calibration factors were observed during the six-month period of study.

Carboxylic Acids↗
PubMed1999

[Adult body height in women in Cordoba, Argentina, and exploration of the current trend (1978-198)].

The objective of this work was to contribute local data concerning the full adult height of women in Cordoba, Argentina, and to explore the possibility of a secular trend in their heights. For the study, 513 women were examined during May and June 1994. All of the women were between 18 and 40 years of age and were mothers of children who were included in a study on lactation, feeding, growth, and development in Córdoba. The measurements were carried out applying standardized techniques and using as a reference standard the 50th-percentile level data from the U.S. National Center for Health Statistics. The mean full height of the Córdoba population studied was 157.9 cm, 0.97 standard deviation (SD) below the reference norm. For the women from the highest of six socioeconomic strata, the mean height was 159.7 cm (-0.67 SD); the mean for women from the lowest stratum was 156.2 cm (-1.25 SD). The difference in the means of those two socioeconomic groups was statistically significant (P < 0.001). Of the population studied, 2.3% (6.4% of the lowest social stratum) were shorter than 145 cm. In order to explore the possibility of a secular trend, the resulting data were categorized into two groups according to the mother's age at the time of the anthropometric examination, one group with a mean age of 24 and a second group with a mean age of 34. The younger women had a mean adult height 0.4 cm greater than that of the older women (P = 0.47). This secular increase in height is notably smaller than that reported for other Argentine provinces (1.2 and 1.4 cm/decade) and somewhat lower than the average reported in population studies in Australia, Belgium, the United States, Japan, and Norway (0.6 cm/decade). The authors conclude that in the period analyzed, 1978-1988, the living conditions in the city of Córdoba have not improved in a way that is reflected in a significant increase in the height of adult women. The authors recommend that maternal health and nutrition programs concentrate their resources on the mothers from the lowest socioeconomic stratum who are shorter than 145 cm.

Adolescent↗
PubMed2004

Collaborative field study on the utility of a BDD factor VIII concentrate standard in the estimation of BDDr Factor VIII:C activity in hemophilic plasma using one-stage clotting assays.

Advances in production technologies of factor (F)VIII concentrates during the last two decades has resulted in very pure and safe products. In assessment of recombinant FVIII:C, inconsistent assay values are found comparing one-stage assays with two-stage (e.g. amidolytic) methods. Such discrepancies have been quite prominent in the case of a B-domain deleted recombinant FVIII (BDDrFVIII, ReFacto). In order to alleviate this assay variance, a product-specific reference standard [the ReFacto Laboratory Standard (RLS)], was established for laboratory use with either one-stage clotting or chromogenic substrate assays for the measurement of FVIII:C in ReFacto-containing patient samples. The primary objective of the current study was to assess, under field laboratory conditions, the accuracy and precision of the one-stage clotting assay for the determination of FVIII:C in ReFacto-containing samples employing the new concentrate standard. A secondary goal was to assess whether use of the RLS would minimize the discrepancy between one-stage clotting and chromogenic substrate assays. Thirty-one clinical laboratories worldwide participated in the study of severe-hemophilic plasma (SHP) samples that had been spiked with ReFacto to target levels of 0.9, 0.6 and 0.2 IU mL(-1). FVIII:C levels were determined against both the RLS and the local in-house plasma standard (IHS). The results showed good agreement between laboratories in FVIII:C levels obtained by one-stage clotting assays utilizing the RLS, and a good degree of accuracy was found compared with the intended target values. Consistent with previously published data, a discrepancy of approximately 30% was observed between one-stage clotting and chromogenic potencies when the IHS was used as the calibrator. The discrepancy between one-stage and chromogenic assay methodologies was significantly reduced when the RLS was employed as calibrator in the one-stage assay. In conclusion, the study demonstrates that accurate and precise FVIII:C results can be obtained for ReFacto-containing SHP samples by clinical laboratories using a product-specific standard in one-stage clotting assays. In addition, the product-specific reference standard significantly reduced the discrepancy between the one-stage clotting and the chromogenic substrate assay for ReFacto.

Blood Coagulation↗
PubMed2003

Assessment of the accuracy of diagnostic tests: the cross-sectional study.

In diagnostic accuracy studies, the contrast of interest can be one of the following: one single test contrast; comparing two or more single tests; further testing in addition to previous diagnostics; and comparing alternative diagnostic strategies. The clinical diagnostic problem under study must be specified. Studies of "extreme contrasts" (as early phase evaluations) and studies in "clinical practice" settings (assessing clinical value) should be distinguished. Design options are (1) survey of the total study population, (2) case-referent approach, or (3) test-based enrollment. Data collection should generally be prospective, but ambispective and retrospective approaches are sometimes appropriate. In addition to determinants of primary interest [the test(s) under study] possible modifiers of test accuracy and confounding variables must be specified. The reference standard procedure should be independent from the test results. Applying a reference standard can be difficult in case of classification errors, lack of a clear pathophysiologic concept, incorporation bias, or invasive or complex investigations. Possible solutions are: an independent expert panel, and the delayed type cross-sectional study (clinical follow-up). Also, a prognostic criterion can be chosen. For studies to be relevant for practice, inclusion criteria must be based on "intention to diagnose" or "intention to screen." The recruitment procedure is preferably a consecutive series of presenting patients or a target population screening, respectively. Sample size estimation should be routine. Analysis has to be focused on the contrast of interest. Estimating test accuracy and prediction of outcome need different approaches. External (clinical) validation requires repeated studies in other, similar populations. Also, systematic reviews and meta-analysis have a role. To enable readers of diagnostic research reports to evaluate whether methodological key issues were addressed, authors are advised to follow the STARD guidelines.

Cross-Sectional Studies↗
PubMed1989

Associations of genetics and sampling time with levels of interleukin-2 activity.

The interleukin-2 (IL-2) assay has become a useful tool for examining the cellular immune response. Because of a lack of avian IL-2-dependent cell lines, the avian IL-2 assay in its present state, however, is not currently as powerful as its mammalian counterpart in effectively evaluating levels of IL-2 activity. The use of an avian IL-2 reference standard, Percoll-enriched populations of lymphoblasts, and sample collection times were examined to optimize the assay for comparing levels of IL-2 activity in a large number of birds. The reference standard was effective in accounting for assay-to-assay variance. Percoll-enriched populations of responding lymphoblasts were more sensitive to IL-2 than nonseparated populations of cultured peripheral blood lymphocytes. Levels of IL-2 activity of cells isolated from the same bird did not change within a 1-week period, although differences did approach significance. In addition, levels of IL-2 activity differed between genetically distinct populations.

Animals↗
PubMed2005

Screening US and CT for blunt abdominal trauma: a retrospective study.

OBJECTIVE: To assess the accuracy of screening US and CT in patients with blunt abdominal trauma admitted to the trauma centre of our General Hospital. MATERIALS AND METHOD: The abdominal US reports of 864 primary trauma patients (139 with major and 725 with minor injuries) and 162 CT reports of a subgroup of the same subjects (64 with major and 98 with minor injuries) were reviewed and compared to the best available reference standard. The accuracy of screening US was assessed by evaluating its overall ability to distinguish negative from positive cases by showing at least one of the lesions documented by the reference standard and its specific ability to depict all lesions; CT reports were evaluated only for the method's performance in depicting all lesions. RESULTS: Screening US exhibited a satisfactory overall ability to distinguish negative from positive patients (91.5% sensitivity and 97.5% specificity in major trauma patients versus 73.3% sensitivity and 98.1% specificity in the minor trauma group) and a satisfactory specific ability to depict all injuries in major trauma patients. In minor trauma cases sensitivity was satisfactory for free fluid but unsatisfactory for organ injuries. Of the 21/864 false negative reports (5 in patients with major and 16 in cases with minor traumas), only one affected patient management, a major trauma case, by delaying an emergency laparotomy. The performance of CT in detecting each single lesion was predictably excellent in both patient groups. CONCLUSION: Its satisfactory accuracy for major trauma suggests that US could be employed not only to screen cases for emergency laparotomy but also as an alternative to CT. However, since major traumatic injuries generally carry an imperative indication for CT, especially as regards neurological, thoracic and skeletal evaluation, US should be employed to perform a prompt preliminary examination using a simplified technique in the emergency room simultaneously with resuscitation.

Abdomen↗
PubMed2005

Evaluation of capillary electrophoresis for determining the concentration of dissolved silica in geothermal brines.

The determination of silica concentrations in geothermal brines is widely recognized as a difficult analytical task due to its complex chemical polymerization kinetics that occurs during sample collection and chemical analysis. Capillary electrophoresis (CE) has been evaluated as a new reliable analytical method to measure silica (as silicates) in geothermal brines. Synthetic and geothermal brine samples were used to evaluate CE methodology. A capillary electrophoresis instrument, Quanta 4000 (Waters-Millipore) coupled with a Waters 820 workstation was used to carry out the experimental work. The separation of silicates was completed in approximately 5.5 min using a conventional fused-silica capillary (75 microm i.d. x 375 microm o.d. x 60 cm total length). A hydrostatic injection (10 cm for 20 s at 25 degrees C) was employed for introducing the samples. The carrier electrolyte consisted of 10 mM sodium chromate, 3 mM tetradecyltrimethyl-ammonium hydroxide (TTAOH), 2 mM sodium carbonate, and 1 mM sodium hydroxide, adjusted to a pH 11.0 +/- 0.1. Silicates were determined using an indirect UV detection at a wavelength of 254 nm with a mercury lamp and with a negative power supply (-15 kV). A good reproducibility in the migration times (%R.S.D. approximately 1.6%) based on six non-consecutive injections of synthetic brine solutions was obtained. A linear response between silica concentration and corrected peak area was observed. Ordinary (OLR) and weighted (WLR) linear regression models were used for calculating silica concentrations in all samples using the corresponding fitted calibration curves. The analytical results of CE were finally compared with the most probable values of synthetic reference standards of silica using the Student's t-test. No significant differences were found between them at P = 0.01. Similarly, the atomic absorption spectrometry (AAS) results were also compared with the most probable concentrations of the same reference standards, finding significant differences at P = 0.01.

Calibration↗
PubMed2006

Diagnosis of gonococcal infection in high risk women using a rapid test.

OBJECTIVE: To assess the performance and acceptability for patients and health care workers of the NGThermo Biostar (GC OIA) to diagnose gonococcal infection compared with culture using modified Thayer Martin medium. METHODS: This study involved 326 high-risk women presenting with vaginal discharge or referral by sexual partner with urethral discharge at a sexually transmitted infections (STI) clinic in Manaus, Brazil. Endocervical swabs collected from the women were tested with both the NG Biostar and modified Thayer Martin culture as the reference standard test. Clinic staff were trained to perform the NG Biostar on site and the culture was performed in the laboratory of the clinic. RESULTS: The prevalence of gonococcal infection as measured by the reference standard was 15% (50/326) overall. Among asymptomatic participants, the prevalence of infection was 17.7% (25/141) and among symptomatic women it was 13.5% (25/185) (p = 0.3). Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the NG Biostar test, with 95% confidence intervals (CI), were 60% (46.4% to 73.6%), 89.9% (86.2% to 93.6%), 55.6% (42.4% to 68.8%), and 92.6% (89.5% to 95.7%), respectively; 98.8% of study participants were willing to wait approximately 1 hour in the clinic for test results. CONCLUSION: Syndromic management protocols for treatment of STI in developing countries require refinement because, as currently described, they lead to over-treatment of cervical infection. A rapid test done during patients' initial presentation and leading to immediate treatment if positive would help improve the accuracy of diagnosis and could also be used to screen asymptomatic women. Even though the NG Biostar had a low sensitivity and PPV, which is less than ideal, it could still improve the rates of treatment over the gold standard test that requires return visits for patients to receive results and to benefit from treatment. Cost-effectiveness studies using rapid point-of-care tests for Neisseria gonorrhoeae infection compared to the syndromic approach should be carried out to assess their value in STI diagnosis and treatment in developing nations.

Adolescent↗
PubMed2005

Evaluation of four mass spectrometric methods for the gas chromatographic analysis of polychlorinated n-alkanes.

The suitability of four mass spectrometric methods for the gas chromatographic analysis of polychlorinated n-alkanes (PCAs, also called chlorinated paraffins) was evaluated and compared using spiked and fish liver samples. Electron ionization tandem mass spectrometry (EI-MS/MS) as well as electron capture negative ionization (ECNI) combined with low and high resolution mass spectrometry and CH4/CH2Cl2-negative ion chemical ionization (NICI) low resolution mass spectrometry were investigated. All methods showed an accuracy of <21% for the analysis of spiked fish samples. However, the analysis of real samples showed deviations of up to 46% between the four mass spectrometric methods. The influence of the selected reference standard on quantification was also evaluated. The use of a quantification standard with a degree of chlorination deviating from that of the sample can result in differences of > 100% for the ECNI methods. EI-MS/MS and CH4/CH2Cl2-NICI led to errors of maximum 17% and 33%, respectively, independent from the degree of chlorination of the used reference standard.

Alkanes↗
PubMed2004

[Diagnostic kits in parasitology: which controls?].

The development of new diagnostic tools particularly for some parasitic "neglected diseases", is slowed or even hindered by limited resources assigned for basic and applied research in public institution and private sector. Even if the time-line and costs needed for developing a new In Vitro Diagnostic (IVD) test are generally lower compared to vaccines or new drugs, industry is poorly engaged in investing resources due to the perception of limited markets. To accelerate the development of diagnostics for the world's most deadly diseases, the World Health Organization's (WHO) Special Programme for Research and Training in Tropical Diseases (TDR), the United Nations Development Programme, the World Bank and the Gates Foundation, last year launched a new initiative, FIND (Foundation for Innovative New Diagnostics, www.finddiagnostics.org). The aim is to "apply the latest biotechnology innovations to develop and validate affordable diagnostic tests for diseases of the developing world". Ideally, a new diagnostic test should be accurately evaluated prior to use in medical practice. The first step would be a pre-clinical evaluation, an analytic study to determine its laboratory performance. A crucial point in this phase is the calibration of reagents (antigens, antibodies, DNA probes, etc.) against a standard reference preparation. WHO, through the WHO International Laboratories for Biological Standards, "provides International Biological Reference Preparations which serve as reference sources of defined biological activity expressed in an internationally agreed unit" (www.who.int/biologicals/IBRP/index.htm). Standardization allows "comparison of biological measurements worldwide" and ensures the reliability of diagnostic procedures. These preparations are generally intended for use in the characterization of the activity of secondary reference preparations (regional, national or in-house working standards). Unfortunately, international reference standards for parasitic diseases are not available at present, except for Toxoplasma antibodies. The first international standard reagent for Anti-Toxoplasma Serum was established in 1968 and at present, an international standard reference serum, Anti-toxoplasma serum, human TOXM is available at the National Institute for Biological Standards and Control (NIBSC) in UK. Several collaborative, multicenter studies were carried out to assess the performance of different methods and commercial tests for the diagnosis of toxoplasmosis, by providing to participating laboratories a panel of well-defined sera to be tested. A four-phase process following well-accepted methodological standards for the development of diagnostics, analogous to those internationally accepted for drugs and vaccines was recently proposed. The pre-clinical evaluation, the analytic study to assess sensitivity, specificity, predictive values in laboratory (phase I), should be followed by a proof of principle study to distinguish diseased from healthy persons in easily accessible populations (phase II). The evaluation of test performance in populations of intended use (phase III), and finally the delineation of cost-effectiveness and societal impact of new tests in comparison with existing tools (phase IV) should complete the validation procedure. In this context, national regulatory agencies play a major role in pre-market approval and post-market surveillance of IVDs. The European Community in 1998 approved a directive (Directive 98/79/EC) which rules the marketing of IVD medical devices, in order to harmonise the performance levels and standards in European countries. But, among IVDs for parasitic diseases, only those to detect congenital toxoplasmosis are submitted to defined procedures to provide the verification of products before their placing on the market and the surveillance after their marketing by a notified body, which perform appropriate examinations, tests and inspections to production facilities to verify if the device meets the requirements of the directive. In U.S.A., the Food and Drug Administration (FDA), through the Office of In Vitro Diagnostic Device Evaluation and Safety (OIVD), provides a comprehensive and regulatory activity for IVDs through pre-market evaluation and post-market surveillance. In developing countries, the scarcity of resources limits the procedures through which the national control authority can assure safety, quality and efficacy of products marketed, both imported and locally manufactured.

Animals↗
PubMed1994

Reference preparations in the standardisation of HIV-1 PCR--an international collaborative study.

Following the recent developments in diagnostic polymerase chain reaction (PCR) technology, we have assessed a set of HIV-1 DNA reference standards using the first commercial diagnostic test kit for the detection of HIV-1 (Amplicor, Roche) in an international collaborative study. Nineteen laboratories in 11 countries analysed a set of ten (re-coded) HIV-1 DNA reference standards, whose performance had been validated in a previous collaborative study (Bootman and Kitchin, 1992). Results from the current study show that, using the diagnostic kit, 84% of laboratories (16/19) obtained correct diagnoses for all ten test samples. One additional laboratory failed only to detect the sample containing ten copies of target template. Test results from the remaining two laboratories were declared void in accordance with the Amplicor quality control guidelines.

DNA, Viral↗
PubMed2006

Assessment of iodine status using dried blood spot thyroglobulin: development of reference material and establishment of an international reference range in iodine-sufficient children.

CONTEXT: Thyroglobulin (Tg) may be a valuable indicator of improving thyroid function in children after salt iodization. A recently developed Tg assay for use on dried whole blood spots (DBS) makes sampling practical, even in remote areas. OBJECTIVE: The study aim was to develop a reference standard for DBS-Tg, establish an international reference range for DBS-Tg in iodine-sufficient children, and test the standardized DBS-Tg assay in an intervention trial. DESIGN, PARTICIPANTS, AND INTERVENTIONS: Serum Tg reference material of the European Community Bureau of Reference (CRM-457) was adapted for DBS and its stability tested over 1 yr. DBS-Tg was determined in an international sample of 5- to 14-yr-old children (n = 700) who were euthyroid, anti-Tg antibody negative, and residing in areas of long-term iodine sufficiency. In a 10-month trial in iodine-deficient children, DBS-Tg and other indicators of iodine status were measured before and after introduction of iodized salt. RESULTS: Stability of the CRM-457 Tg reference standard on DBS over 1 yr of storage at -20 and -50 C was acceptable. In the international sample of children, the third and 97th percentiles of DBS-Tg were 4 and 40 microg/liter, respectively. In the intervention, before introduction of iodized salt, median DBS-Tg was 49 microg/liter, and more than two thirds of children had DBS-Tg values greater than 40 microg/liter. After 5 and 10 months of iodized salt use, median DBS-Tg decreased to 13 and 8 microg/liter, respectively, and only 7 and 3% of children, respectively, had values greater than 40 microg/liter. DBS-Tg correlated well at baseline and 5 months with urinary iodine and thyroid volume. CONCLUSIONS: The availability of reference material and an international reference range facilitates the use of DBS-Tg for monitoring of iodine nutrition in school-age children.

Adolescent↗
PubMed2003

A multicenter pharmacokinetic study of the B-domain deleted recombinant factor VIII concentrate using different assays and standards.

When the one-stage clotting assay is used in comparison with the chromogenic and immunological assays, plasma levels of factor (F)VIII are underestimated by 40-50% after infusion of B-domain deleted recombinant FVIII (BDD-rFVIII) in patients with hemophilia. A possible way to counteract the underestimation of FVIII levels by the one-stage assay is the adoption of a recombinant FVIII reference standard instead of a plasma standard. To evaluate the usefulness of such a standard [ReFacto Laboratory Standard (RLS)], the pharmacokinetic parameters of a single dose of BDD-rFVIII (25 U kg(-1)) were evaluated in a multicenter study carried out in 18 patients with severe hemophilia A. The very low in vivo recovery, obtained with the combination of the one-stage assay and plasma reference standard, was increased up to the values obtained by the chromogenic assay when the results were expressed in terms of RLS. When the plasma standard was used, the one-stage/chromogenic ratio was 0.82 +/- 0.12 for FVIII levels above 25 U dL(-1) and 1.42 +/- 0.99 for FVIII levels below 25 U dL(-1). Using the RLS, the one-stage/chromogenic ratio increased to 1.01 +/- 0.19 at FVIII levels above 25 U dL(-1), as a consequence of a complete overlap of the two decays; however, at FVIII levels below 25 U dL(-1), the one-stage/chromogenic ratio was still 1.6 +/- 0.85. After the twelfth hour, FVIII concentrations obtained by chromogenic assay were always lower than those resulting from the one-stage clotting assay, independently of the standard used. Results obtained by chromogenic assay were not affected by the type of standard used. Compared with those obtained by the one-stage assay, higher values of clearance, lower volume of distribution area and shorter plasma half-life or mean residence time were obtained by chromogenic assay because of a shape change of the decay curve due to a shift to higher values in the first part (time interval 0-12 h) and to lower values in the second part of the decay curve (time interval 12-48 h). As a consequence, the slope of the decay curve obtained by means of chromogenic assay was steeper. In conclusion, the more homogeneous results of in vivo recovery and pharmacokinetic analysis, due to the decrease of discrepancy between the two methods when RLS was used, make the cheaper and more widely used one-stage assay preferable to the more expensive chromogenic assay, on condition that the ReFacto specific standard has used.

Adult↗
PubMed2004

Setting up standards and a reference map for the alkaline proteome of the Gram-positive bacterium Lactococcus lactis.

Despite the fact that almost 39% of the theoretical expressed proteins of Lactococcus lactis have a predicted isoelectric point above 7, these proteins have not been studied in previous proteome analyses. In the present study, we set up a reference map of alkaline lactococcal proteins by using immobilized pH gradients (IPG) spanning pH 6 to 12 and 9 to 12, and protein identification by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). Different electrophoresis systems for isoelectric focusing were evaluated to optimize the first dimension. Best results were obtained by sample application using cup-loading at the anodic side and increasing the final voltage up to 8000 V for IPGs, using N,N-dimethylacrylamide as monomer. After two-dimensional gel electrophoresis of extracts obtained from exponentially growing cells, about 200 protein spots were selected for identification by peptide mass fingerprinting. With MALDI-TOF MS, 153 proteins were identified that were the products of 85 different genes. Their predicted isoelectric points range from as high as 11.31 to as low as 6.34. Ribosomal proteins, hypothetical proteins and proteins with unknown function represent the largest groups of identified proteins. For further classification, the codon adaptation index (CAI) and grand average of hydropathicity (GRAVY) for each lactococcal protein were calculated. The protein with the lowest CAI identified in this study is the manganese ABC transporter ATP-binding protein. Less than 10% of the alkaline lactococcal proteins have a smaller CAI. The highest GRAVY for an identified protein is 0.26. The complete in silico data of Lactococcus lactis as well as clickable reference maps are available at www.wzw.tum.de/proteomik/lactis.

Bacterial Proteins↗
PubMed2001

Certification of the chlorine content of the isotopic reference materials IRMM-641 and IRMM-642.

The Slovak Institute of Metrology and the Institute for Reference Materials and Measurements have collaborated in the certification of the two chlorine reference materials IRMM-641 and IRMM-642. Until now no isotopically enriched chlorine isotopic reference material certified for isotopic composition and content has been available commercially. The isotopic reference materials IRMM-641 and IRMM-642 described herein are certified for isotopic composition and for chlorine content. The chlorine content of the reference material IRMM-641 was certified by use of high-precision argentometric coulometric titration at the Slovak Institute of Metrology. The base material used for IRMM-641 is NIST Standard Reference Material 975. The chlorine content of the reference material IRMM-642 was measured by isotope dilution, using negative thermal ionization mass spectrometry at the Institute for Reference Materials and Measurements. Both standard reference materials were prepared by dissolving NaCl in water. The reference material IRMM-641 contains 0.025022 +/- 0.00011 mol kg(-1) chlorine of natural isotopic composition with an n(37Cl)/n(35Cl) ratio of 0.31977 +/- 0.00082. The reference material IRMM-642 contains 0.004458 +/- 0.000028 mol kg(-1) chlorine with an n(37Cl)/n(35Cl) ratio of 0.01914 +/- 0.00088.

Journal Article↗
PubMed1975

Measurement of IgE antibodies by the radioallergosorbent test. II. Analyses of quantitative relationships in the test.

IgE antibodies have been measured by the radioallergosorbent test (RAST) and the relative amounts present in serum determined by comparison with reference standards. In this study we analyzed the quantitative aspects of the binding of IgE antibody to solid-phase ragweed antigens. With the volumes of allergic serum usually tested, IgE antibodies are in excess in the first step of the RAST. The inability of solid-phase antigens to remove IgE antibody appeared to be due to an insufficient quantity of antigen on the particles rather than steric interference with binding of IgE antibody. Dose-response curves with serums from several ragweed-sensitive subjects were not parallel when plotted on a semilog scale. In contrast, log-log plots of dose-response curves with serums from ragweed-sensitive subjects were nearly parallel. Log-log plots of dose-response curves with serums from subjects with ragweed and grass sensitivity and tested with the appropriate solid-phase antigens also were nearly parallel. Because of the latter finding, RAST could be standardized using a reference serum in every assay and plotting the results on a log-log scale. Finally, because IgE antibody is in excess in the RAST as it is usually performed, the final result reflects both the quantity and the affinity of the IgE antibody.

Allergens↗
PubMed1986

Standardization of U.S. Reference Rh0 (D) Immune Globulin by quantitative automated hemagglutination.

An automated hemagglutination procedure was used to assess the relative potency of US Reference Rh0 (D) Immune Globulin, Lot 3, with respect to the International Reference Preparation, WHO Anti-D immunoglobulin, Lot 68/419. A value of 300 international units (IU) of anti-D per ampoule has been assigned to Lot 68/419. In 25 assays, the mean value for Lot 3 was 820 IU anti-D per milliliter when tested in parallel with Lot 68/419.

Automation↗