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PubMed1985

Standard electromotive force of the H2-AgCl;Ag cell in 30, 40, and 50 mass% glycerol/water from -20 to 25 degrees C: pK2 and pH values for a standard "mops" buffer in 50 mass% glycerol/water.

Data are presented regarding the establishment of the pH (designated pH*) of a standard buffer solution suitable as a pH reference in 50 mass% glycerol/water mixtures at temperatures ranging from -20 to 25 degrees C. The buffer material selected was the ampholyte Mops [(3-N-morpholino)-propane sulfonic acid], and the reference standard consists of equal molal amounts of Mops and its sodium salt. The assignment of pH* values is based on measurements of the electromotive force (emf) of cells without liquid junction of the type: Pt;H2(g, 1 atm) / Mops, Na Mopsate, NaCl / AgCl;Ag and the pH* was derived from a determination of K2, the equilibrium constant for the dissociation process (Mops) +/- in equilibrium with (Mopsate)- + H+. The standard emf of the silver-silver chloride electrode in 30, 40, and 50 mass% glycerol/water mixtures was determined from emf measurements of the cell at subzero temperatures with HCl solutions replacing the buffer-chloride mixtures.

Buffers↗

PubMed2006

Preconcentration of Pb(II), Cr(III), Cu(II), Ni(II) and Cd(II) ions in environmental samples by membrane filtration prior to their flame atomic absorption spectrometric determinations.

A method for separation-preconcentration of Pb(II), Cr(III), Cu(II), Ni(II) and Cd(II) ions by membrane filtration has been described. The method based on the collection of analyte metal ions on a cellulose nitrate membrane filter and determination of analytes by flame atomic absorption spectrometry (FAAS). The method was optimized for several parameters including of pH, matrix effects and sample volume. The recoveries of analytes were generally in the range of 93-100%. The detection limits by 3 sigma for analyte ions were 0.02microgL(-1) for Pb(II), 0.3microgL(-1) for Cr(III), 3.1microgL(-1) for Cu(II), 7.8microgL(-1) for Ni(II) and 0.9microgL(-1) for Cd(II). The proposed method was applied to the determination of lead, chromium, copper, nickel and cadmium in tap waters and RM 8704 Buffalo River Sediment standard reference material with satisfactory results. The relative standard deviations of the determinations were below 10%.

Cadmium↗

PubMed1983

Adaptation of microvolume EMIT assays for theophylline, phenobarbital, phenytoin, carbamazepine, primidone, ethosuximide, and gentamicin to a CentrifiChem chemistry analyzer.

We have developed microvolume EMIT procedures for theophylline, phenobarbital, phenytoin, carbamazepine, primidone, ethosuximide, and gentamicin using a centrifugal analyzer (CentrifiChem and Pipettor 1000) to reduce the manufacturer's recommended manual reagent consumption by one-sixth. In addition to developing the EMIT procedure, the performance of the analyzer and pipettor were verified. The analyzer and pipettor are capable of producing within-run precision at a 3-microliters sample volume and 210-microliters analyzer cuvette volume equal to or less than 1.5%. The performance of the EMIT procedures on the analyzer yielded spike drug recoveries of 90.8 to 106.1% for drug concentrations throughout the calibration concentration range of each assay. The percent error on standard reference material of the National Bureau of Standards ranged from a +12.0% to a -0.6% for ethosuximide, phenobarbital, phenytoin, and primidone. Patient comparison data yielded slopes from 0.930 to 1.110 for all assays. The other important feature of the adapted EMIT assay is its simplicity for use on a routine basis.

Anticonvulsants↗

PubMed2006

[The effect of intrauterine development and nutritional status on intrauterine and neonatal mortality].

The authors study to what extent bodily development and nutritional status influence the viability of foetuses and neonates, that is, their perinatal mortality. They developed a new method, the MDN system (MDN: Maturity, Development, Nutritional status) to determine the weight and length standard positions of neonates in relation to reference standards on the basis of their gestational ages, birth weights and lengths. The system contains a chessboard-like matrix (or MDN Table) comprising 64 cells arranged in eight horizontal lines of the most common zones of weight percentile standards and eight vertical columns of the length percentile standards. Depending upon its weight and length, each neonate can be positioned in one of the cells of the MDN Table. The table allows differentiating the major neonate groups with significantly different developmental and nutritional statuses. The authors used a computerised program to process in one MDN table the data of 680,947 neonates born in the 7 five years from 1997 to 2003 in Hungary. When the ratio of body length and weight was considered, 90.6% of this neonate population was found normally (proportionally) nourished. 4.9% of the population was relatively over-nourished, while 4.5% was relatively undernourished. Then, the authors computed the intrauterine and neonatal mortality rate of the newborns in each cell of the MDN Table. Intrauterine (neonatal) mortality rate in the neonate group with an absolute average development was 3,6 per thousand (4,4 per thousand), that in the proportionally retarded group under weight and length percentiles 10 was 21 per thousand (14 per thousand). This rate was 41 per thousand (24 per thousand) under weight and length percentiles 3. The mortality rate was 51 per thousand (49 per thousand) in the extremely overnourished group and 124 per thousand (78 per thousand) in the extremely undernourished group. The authors believe that the MDN system including the MDN table is a suitable method to differentiate the most endangered groups of neonates on the basis of their development and nutritional status.

Birth Weight↗

PubMed1965

The applicability of North American growth standards in developing countries.

For the purpose of developmental evaluation of growing children and the nutritional assessment of individuals or populations, reliance on current North American standards for size, maturational timing, body fatness or osseous development may be unwise not only with respect to various African, Asiatic and Pacific populations but often with respect to adults and children in North America. In particular, the dental development and early ossification progress of most human groups are in advance of contemporary North American standards. The use of stature as a reference standard and the simple ratio of weight to height are both unsatisfactory measures except within clearly defined population samples. At the very least, age-size tables based on parental statures would be more realistic and useful for children of known parentage, whereas present-day averages that neglect parental size are most applicable to foundlings and illegitimate children.

Adolescent↗

PubMedDate not supplied

Standardization of serum protein analyses.

A brief historical review is presented of the development of bovine serum albumin as a standard for the determination of serum total protein. Bovine serum albumin is now available as a standard reference material from the National Bureau of Standards. Also reviewed is the present status of the immunoglobulin standards.

Biuret Reaction↗

PubMed1994

Comparative study of the stability of saxitoxin and neosaxitoxin in acidic solutions and lyophilized samples.

Paralytic shellfish poison (PSP) has historically been a problem for the shellfish industry. In order to prevent the marketing of contaminated seafood products, governments have implemented monitoring programs where standards of toxins are necessary. The stability of these standard toxins is very important. In this paper we analysed the stability of saxitoxin (STX) and neosaxitoxin in acidic solution and lyophilized samples. Individual toxins were determined in each sample using a high-performance liquid chromatographic procedure employing post-column oxidation of the toxins to form fluorescent derivatives. Our results demonstrate that STX is very stable in solution samples and could be adopted as a reference standard. This toxin can be kept in dilute acidic solutions for 18 months without loss of potency. However, neosaxitoxin is unstable, possibly due to transformation to other toxins.

Animals↗

PubMed1992

An alternative approach to contrast-detail testing of X-ray image intensifier systems.

The difficulties of making the results of threshold contrast-detail diameter tests on X-ray image intensifier systems consistent with published performance standards are discussed. The current approach to contrast-detail testing is described and an alternative method intended to give greater consistency for all image intensifier input field diameters proposed. The current and alternative test conditions are compared on two image intensifier systems. The results obtained show that the contrast-detail curves for image intensifier systems with a wide range of input field diameters can be effectively normalized to be directly comparable to a common reference standard by applying the proposed alternative test conditions. The implications of this result on the interpretation of the contrast-detail test are discussed.

Quality Control↗

PubMed1995

Preliminary investigation of glycosylated proteins by capillary electrophoresis and capillary electrophoresis/mass spectrometry using electrospray ionization and by matrix-assisted laser desorption ionization/time-to-flight mass spectrometry.

In recent years, the biotechnological industry has emerged as the major source of new human therapeutic proteins. Although the great majority of these occur naturally as glycoproteins, it has been observed that glycosylation of the recombinantly produced proteins could be fundamental for their in vivo activity (e.g. tissue plasminogen activator, erythropoietin) or, on the contrary, insignificant (e.g. interleukin-1 receptor antagonist, gamma-interferon, granulocyte macrophage-colony-stimulating factor). The inherent heterogeneity of these complex biomolecules presents an exciting challenge in the analytical field for both their structural analysis and the development of suitable analytical methods to guarantee consistency of their production. Owing to this ever increasing therapeutic interest in proteins and glycoproteins, this paper compares the information provided by different analytical techniques (i.e. high-performance liquid chromatography, sodium dodecyl sulphate polyacrylamide gel electrophoresis, capillary electrophoresis, capillary electrophoresis/electrospray ionization mass spectrometry, matrix-assisted laser desorption/ionization time-of flight mass spectrometry and high-performance liquid chromatography/matrix-assisted laser desorption/ionization time-of flight mass spectrometry when used for the analysis of proteins and glycoproteins. For the sake of simplicity, reference standard proteins and glycoproteins were used as samples.

Chromatography, High Pressure Liquid↗

PubMed2001

Protein microarrays for highly parallel detection and quantitation of specific proteins and antibodies in complex solutions.

BACKGROUND: We have developed and tested a method for printing protein microarrays and using these microarrays in a comparative fluorescence assay to measure the abundance of many specific proteins in complex solutions. A robotic device was used to print hundreds of specific antibody or antigen solutions in an array on the surface of derivatized microscope slides. Two complex protein samples, one serving as a standard for comparative quantitation, the other representing an experimental sample in which the protein quantities were to be measured, were labeled by covalent attachment of spectrally resolvable fluorescent dyes. RESULTS: Specific antibody-antigen interactions localized specific components of the complex mixtures to defined cognate spots in the array, where the relative intensity of the fluorescent signal representing the experimental sample and the reference standard provided a measure of each protein's abundance in the experimental sample. To test the specificity, sensitivity and accuracy of this assay, we analyzed the performance of 115 antibody/antigen pairs. 50% of the arrayed antigens and 20% of the arrayed antibodies provided specific and accurate measurements of their cognate ligands at or below concentrations of 0.34 microg/ml and 1.6 microg/ml, respectively. Some of the antibody/antigen pairs allowed detection of the cognate ligands at absolute concentrations below 1 ng/ml, and partial concentrations of 1 part in 106, sensitivities sufficient for measurement of many clinically important proteins in patient blood samples. CONCLUSIONS: These results suggest that protein microarrays can provide a practical means to characterize patterns of variation in hundreds of thousands of different proteins in clinical or research applications.

Immunoassay↗

PubMed2000

Bioimpedance and inferior vena cava diameter for assessment of dialysis dry weight.

It is essential to carry out a clinical assessment of dry body weight in dialysis-dependent children in order to develop a suitable dialysis prescription. Bioimpedance analysis and inferior vena cava diameter (IVCD) have been evaluated and utilized in adults as noninvasive parameters for the assessment of dry weight and extracellular volume. Since there are no data available for normal children, we performed a prospective study to establish reference standards for a pediatric population (111 females and 95 males, aged 6.8-16 years). We found strong correlations of both resistance and IVCD with age, height, weight, and, in particular, with body surface area. IVCD and resistance also correlated with each other. We also investigated 28 pediatric dialysis patients who showed growth retardation and delayed puberty. Applying age-related reference intervals to pediatric dialysis patients resulted in an underestimation of overhydration. The combination of both methods using body surface area-related reference limits with the clinical features of deviation of dry weight will serve as an adjunct to the assessment of post-dialysis dry weight.

Adolescent↗

PubMed1978

Reference preparation to standardize results of serological tests for rheumatoid factor.

The variance of between-laboratory results for rheumatoid factor tests was reduced through the use of a reference serum preparation. Two separate proficiency testing surveys have shown reduction of 58 to 81% in variance with samples of differing levels and composition. Reduction of variance was seen in data from laboratories in which the same methods and reagents were used, but greater reduction in variance was seen in results from laboratories using different methods and reagents. This study demonstrates that comparability of results of rheumatoid factor tests can be significantly improved through the use of a standard reference serum preparation and that confidence in such results can therefore be increased. A serum rheumatoid factor level of approximately 50 IU/ml is equivalent to a titer of 160 in the Singer-Plotz latex test, which has traditionally been accepted as evidence of rheumatoid arthritis.

Arthritis, Rheumatoid↗

PubMed1994

Effects of agars on determination of potency of polymyxin B sulfate by the agar plate diffusion method.

The effects of agars on the determination of the potency of polymyxin B sulfate by the agar plate diffusion method were investigated. The results showed that there were significant differences in the potency of polymyxin B sulfate between agars produced by different manufacturers. In order to investigate this phenomenon, two major components of polymyxin B sulfate, namely, the polymyxin B1 and B2 fractions, were isolated and purified by preparative high-pressure liquid chromatography, and the effects of agars on the potencies of these two components were individually examined. The results showed that there were significant differences in the relative potency of the B1 component versus that of the B2 component between the agar preparations produced by different manufacturers. On the basis of the relative potency of each of the components and the composition of the components, we developed a theoretical equation with which we could calculate the activity of polymyxin B sulfate on a certain agar. The values computed from the equation were consistent with those obtained from actual measurements. It was concluded that the effects of agars on the determination of polymyxin B sulfate activity will become evident only when the composition of the reference standard significantly differs from that of the samples. When the standard and samples have the same compositions, the sources of the agar preparation exert no effect on the determination of the potency by the agar plate diffusion method.

Agar↗

PubMed2000

A new method for the simultaneous analysis of growth and death of immunophenotypically defined cells in culture.

BACKGROUND: Internal standards have been used in flow cytometry methods to enumerate lymphoid subsets and hemopoietic progenitor cells ex vivo. However, the currently available methods cannot be readily applied to the analysis of cultured cells because of the frequent occurrence of cell death during in vitro assays. METHODS: This paper reports a new method for the enumeration of both viable and nonviable cells in culture. Cells were counted with the aid of an internal reference standard of microbeads, and live versus dead cell discrimination was performed using 7-amino-actinomycin D which allows the double staining of surface antigens. RESULTS: The method is more precise, accurate and sensitive than either conventional light microscopy-based or automated cell counting. Additionally, it may be used to accurately measure the number of apoptotic cells in a culture. RESULTS: Through the enumeration of surviving cells it is demonstrated that, when applied to the study of mitogen-activated T lymphocytes, current flow cytometry techniques (which do not use internal standards) for the study of the viability and apoptosis overestimate the fraction of viable cells and underestimate both the fraction of dead and apoptotic cells. CONCLUSIONS: The new method overcomes these limitations and is of use in the in vitro study of cell growth and apoptosis.

Apoptosis↗

PubMed1987

Quantitation of ceftetrame in human plasma and urine by high-performance liquid chromatography.

A method is described for quantifying ceftetrame, the acid metabolite of methylene (6R,7R)-7-[(Z)-2-(2-amino-4-thiazolyl)-2-(methoxyimino)acetamido]-3- [(5-methyl-2H-tetrazol-2-yl)-methyl]-8-oxo-5-thia-1-azabicyclo[4.2 .0]oct-2-ene-2-carboxylate pivalate, an orally active cephalosporin. Sodium benzylpenicillin is added to the plasma as the reference standard. The compounds are extracted from plasma or urine using a Bond Elut phenyl column. An aliquot of the methanol eluate is analyzed by high-performance liquid chromatography using a Waters Nova-Pak phenyl column and a UV detector set to 225 nm. The ratios of the peak heights for ceftetrame and sodium benzylpenicillin are calculated and converted to concentrations of analyte with calibration curves that are generated from the analysis of analyte-free plasma or urine fortified with various amounts of ceftetrame and a fixed amount of sodium benzylpenicillin. For plasma, the limit of quantitation for the assay is 0.48 microgram/ml and the inter-assay precision (relative standard deviation) is 9.3%. For urine, the limit of quantitation for the assay is 19.1 micrograms/ml, and the inter-assay precision is 4.9%.

Adult↗

PubMed2005

MRI of the olfactory bulbs and sulci in human fetuses.

BACKGROUND: There is limited knowledge of the MRI pattern of the development of fetal olfactory bulbs and sulci. OBJECTIVE: To describe the MRI appearance of olfactory bulbs and sulci in normal in vivo fetuses according to gestational age. MATERIALS AND METHODS: Olfactory bulbs and sulci were retrospectively assessed on brain MRI examinations of 88 normal fetuses between 24 and 39 weeks gestational age. Two reference centres were involved in the study and both used routine protocols that included axial and coronal T2- and T1-weighted sequences at 1.5 T. The results were compared both with the commonly used neuropathological data in the literature and with personal neuropathological data. Pearson's chi-squared test or Fisher's exact test were performed. One case of olfactory agenesis associated with CHARGE syndrome was identified. RESULTS: T2-weighted coronal sequences were the most sensitive for detecting olfactory bulbs and sulci. Olfactory sulci were significantly better detected from 30 weeks onwards (90.9-100%; P<0.001). MRI showed a posteroanterior development of these sulci. Olfactory bulbs were better detected from 30 to 34 weeks (80-90.9%; P<0.002). Comparison with neuropathological data confirmed the posteroanterior development of the sulci and showed an important delay in detection of the olfactory structures (bulbs and sulci). No difference was observed between the two centres involved. CONCLUSIONS: To date, fetal MRI can depict olfactory sulci from 30 weeks gestational age onwards and olfactory bulbs from 30 to 34 weeks gestational age. This preliminary reference standard is useful to assess the normality of the olfactory system and to diagnose olfactory agenesis.

Fetus↗

PubMed1998

Guidelines for organisation and management of external quality assessment using proficiency testing. Expert Panel on Cytometry of the International Council for Standardization in Haematology.

This document is intended to assist towards the WHO objective that external quality assessment (EQA) schemes be established at national and/or regional levels world-wide. Quality assurance is defined as all steps taken by the director of a laboratory to ensure reliability of laboratory results and to increase accuracy, reproducibility and between-laboratory comparability. This includes the use of internal quality control procedures and participation in external quality assessment. Internal quality control provides the means for evaluation of analytic test results at the time of testing in order to decide whether they are reliable enough to be released to the requesting clinicians. EQA, on the other hand, refers to a system of retrospective and objective comparison of results from different laboratories by means of proficiency testing (PT) organised by an external agency. The main purpose is to establish between-laboratory and between-method (including between-instrument) comparability, and agreement with a reference standard where one exists. Internal quality control and EQA complement each other and must never be considered as alternatives.

Animals↗

PubMed2000

Chlamydia pneumoniae serology: interlaboratory variation in microimmunofluorescence assay results.

The lack of standardization in chlamydia serology has made interpretation of published data difficult. This study was initiated to determine the extent of interlaboratory variation of microimmunofluorescence (MIF) test results for the serodiagnosis of Chlamydia pneumoniae infections. Identical panels of 22 sera were sent to 14 laboratories in eight countries for the determination of IgG and IgM antibodies by MIF. Although there was extensive variation in the numeric titer values, the overall percentage agreement with the reference standard titers from the University of Washington was 80%. For results by serodiagnostic category, the best agreement was for four-fold rise in IgG titers, while the lowest agreement was for negative or low IgG titers. Agreement for IgM titers was 50%-95%. Four laboratories failed to discern false-positive IgM titers possibly because of the presence of rheumatoid factor. Further studies are underway to determine the source of interlaboratory variation for the MIF test.

Antibodies, Bacterial↗