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At least 1,621 records · Page 90Linked to original sources
PubMed1997

An actual use comparison of condoms meeting Australian and Swiss standards: results of a double-blind crossover trial.

The performance of condoms in actual use has been poorly researched in the past, especially in comparing condoms that met different quality control standards as indicated by laboratory testing. The present study used a double-blind crossover design to compare the performance of 2 types of condoms in actual use; one that met the Australian and International Organization for Standardization (ISO) standards for condom quality and one that met the more stringent Swiss Quality Seal requirements. Ninety-two men recruited from Metropolitan Melbourne completed a self-report diary sheet after each condom was used which assessed the performance of the condom and the conditions under which it was used. From a total of 1917 condom uses, there was an overall breakage risk of 2.7%. The breakage risk ratio (Australian/ISO:Swiss) for all types of use was 1.16 (95% confidence interval 0.68-1.99). When subanalyses by method of entry were performed, the condoms meeting the Swiss standard appeared to fare better than the Australian/ ISO standards for anal sex (RR = 4.84, 95% CI 1.07-21.8, P = 0.022), while the opposite was the case for vaginal sex (RR = 0.74, 95% CI 0.35-1.53, P = 0.41). The result for anal use was statistically significant at the 5% level, despite being based on fewer condom trials than that for vaginal use, but this result needs to be replicated. Although the participants appeared representative of the general male population in Melbourne in the age bracket 18-46 years, there was a significant history of condom usage reported. This may have influenced the risk of breakage.

Adult↗
PubMed2004

Assessing the accuracy of OSHA's projections of the benefits of new safety standards.

BACKGROUND: In the preambles to the safety and health standards that it has issued since 1987, the Occupational Safety and Health Administration (OSHA) projected that new safety standards would prevent over 2,600 death each year. For six safety standards issued since 1990, we compare OSHA's projections of the impact of full compliance on fatalities with actual fatality changes and examine the reasons for the differences. METHODS: We reviewed the preambles to OSHA standards and the Regulatory Impact Analyses (RIAs) prepared for them to identify the baseline and the prevention factor that the agency used to project the number of deaths that would be prevented. We used three data sources to track the relevant categories of fatalities: the Census of Fatal Occupational Injuries (CFOI), the National Traumatic Occupational Fatality program, and OSHAs Fatality/Catastrophe investigations. RESULTS: For all six standards, OSHA appeared to overestimate the number of deaths prevented. The availability of CFOI led to better estimates of the fatality baseline, but the prevention factor was always overestimated, especially for standards which emphasized training. CONCLUSIONS: OSHA needs to develop better methods for projecting injury impacts. Research is needed to help OSHA predict the effects of behavioral requirements (e.g., training) on actual work practices and injury outcomes. For non-fatal injuries, new methods of data collection will be required.

Accidents, Occupational↗
PubMed1991

Interlaboratory study of cellular fluorescence intensity measurements with fluorescein-labeled microbead standards.

To determine the precision of cellular fluorescence intensity (FI) measurements derived from labeled microbead standards, FI results were compared from 43 different flow cytometers in 34 laboratories. All laboratories analyzed prepared aliquots of fluoresceinated calf thymocyte nuclei (Fluorotrol), human lymphocytes stained with fluoresceinated anti-CD4 antibody, and fluoresceinated microbeads used as both internal and external standards. Measurements were conducted by most laboratories on the third and fourth days after sample preparation. Results for percent of events within the gates and the histograms returned by participants indicated that the samples had remained stable and that gated populations had been properly identified. All standard curves showed strong linearity, and the pooled results from all standards produced a best-fit curve that was in close agreement with the assigned values. Nonetheless, results for cellular FI were highly variable, with CVs of 20-34%. Agreement within lab/instrument was much better, with CVs ranging from 3.0 to 9.9%. The overall variability was not obviously attributable to differences in the types of cytometer, nor could it be explained by attributes of the standard curves or any other single variable examined. However, the application of a corrective factor based on FI results for Fluorotrol allowed a two-fold improvement in the precision of FI measurements on CD4-stained lymphocytes, with an overall CV of 11%. Uncharacterized differences in the operating conditions of flow cytometers can influence cellular FI measurements, but consistent results can be obtained if a stained cellular calibrator is analyzed in addition to the proper microbead standards.

CD4-Positive T-Lymphocytes↗
PubMed1997

A novel standardization method for two-dimensional DNA fingerprints.

Two-dimensional (2-D) DNA fingerprinting is a technique that allows for parallel genome analysis through the simultaneous detection of up to 500 mini- or microsatellite loci on a 2-D gel. Separation is performed according to size and melting temperature in the gel. In the application of this technique in genome analysis, a standardized method for the identification of individual spots is required. However, due to the polymorphic nature of up to 80% of the spots, existing standardization methods that have been primarily developed for 2-D protein patterns are not suitable for this task. We developed a robust method that standardizes 2-D DNA fingerprint spots on the basis of melting temperature - or denaturing gradient position - and fragment size. An external marker was used as a basis for standardization. A normalization surface was calculated over the gel dimensions by adapting an established numerical iteration technique previously used in physics termed "relaxation method". The relaxation method works robustly with the irregularly spaced marker spots. The evaluation of the method for a spot of preknown position derived from the TP53 gene revealed a median observed error below 1% for fragment length and denaturing gradient position. The search for candidate minisatellite loci in genomic difference analysis depends on the reliable identification of alleles of this locus in different individuals. We proved experimentally that alleles of a single minisatellite locus cloned from a 2-D gel cluster on an isothermal line can be reliably identified using the presented standardization method. In conclusion, a standardization tool for a broader application of 2-D DNA fingerprinting in both tumor analysis and possibly parallel mutation screening is now available.

Alleles↗
PubMed2002

Development and inter-rater reliability of a standardized verbal instruction manual for the Chinese Geriatric Depression Scale-short form.

The Geriatric Depression Scale (GDS) is a common screening tool for elderly depression in Hong Kong. This study aimed at (1) developing a standardized manual for the verbal administration and scoring of the GDS-SF, and (2) comparing the inter-rater reliability between the standardized and non-standardized verbal administration of GDS-SF. Two studies were reported. In Study 1, the process of developing the manual was described. In Study 2, we compared the inter-rater reliabilities of GDS-SF scores using the standardized verbal instructions and the traditional non-standardized administration. Results of Study 2 indicated that the standardized procedure in verbal administration and scoring improved the inter-rater reliabilities of GDS-SF.

Aged↗
PubMed2003

Liquid chromatography/tandem mass spectrometry methods for quantitation of mevalonic acid in human plasma and urine: method validation, demonstration of using a surrogate analyte, and demonstration of unacceptable matrix effect in spite of use of a stable isotope analog internal standard.

Selective, accurate, and reproducible liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods were developed and validated for the determination of mevalonic acid, an intermediate in the biosynthesis of cholesterol and therefore a useful biomarker in the development of cholesterol lowering drugs, in human plasma and urine. A hepta-deuterated analog of mevalonic acid was used as the internal standard. For both methods, calibration standards were prepared in water, instead of human plasma and urine, due to unacceptably high levels of endogenous mevalonic acid. The lower quality control (QC) samples were prepared in water while the higher QC samples were prepared in the biological matrices. For the isolation/purification of mevalonic acid from the plasma and urine matrices, the samples were first acidified to convert the acid analyte into its lactone form. For the plasma samples, the lactone analyte was retained on and then eluted off a polymeric solid-phase extraction (SPE) sorbent. For the urine method, the sample containing the lactone analyte was passed through a C-18 SPE column, which did not retain the analyte, with the subsequent analyte retention on and then elution off a polymeric SPE sorbent. Chromatographic separation was achieved isocratically on a polar-endcapped C-18 analytical column with a water/methanol mobile phase containing 0.5 mM formic acid. Detection was by negative-ion electrospray tandem mass spectrometry. The standard curve range was 0.500-20.0 ng/mL for the plasma method and 25.0-1,000 ng/mL for the urine method. Excellent accuracy and precision were obtained for both methods at all concentration levels tested. It was interesting to note that for certain batches of urine, when a larger sample volume was used for analysis, a high degree of matrix effect was observed which resulted not only in the attenuation of the absolute response, but also in a change of analyte/internal standard response ratio. This demonstrated that, under certain conditions, the use of a stable isotope analog internal standard does not, contrary to conventional thinking, guarantee the constancy of the analyte/internal response ratio, which is a prerequisite for a rugged bioanalytical method. On the other hand, under conditions where the sample matrix does not have such a deleterious effect, we have found that a stable isotope analog could serve as a surrogate (substitute) analyte. Thus, we have shown that using calibration standards prepared by spiking plasma with tri-deuterated or tetra-deuterated mevalonic acid, instead of mevalonic acid itself (the analyte), plasma QC samples that contain mevalonic acid can be successfully analyzed for the accurate and precise quantitation of mevalonic acid. The use of a surrogate analyte provides the opportunity to gauge the daily performance of the method for the low concentration levels prepared in the biological matrix, which otherwise is not achievable because of the endogenous concentrations of the analyte in the biological matrices.

Chromatography, Liquid↗
PubMed2005

Stable isotopically labeled internal standards in quantitative bioanalysis using liquid chromatography/mass spectrometry: necessity or not?

It appears to be a general belief that stable isotopically labeled (SIL) internal standards yield better assay performance results for quantitative bioanalytical liquid chromatography/mass spectrometry (LC/MS) assays than does any other internal standard. In this article we describe our experiences with structural analogues and SIL internal standards and their merits and demerits. SIL internal standards are the first choice, but deuterium-labeled compounds may demonstrate unexpected behavior, such as different retention times or recoveries, than the analyte. In addition, a SIL internal standard with identical chemical properties as the analyte may cover up assay problems with stability, recovery, and ion suppression. Since SIL internal standards are not always available or are very expensive, structural analogues can be used, however, with consideration of several issues, which are usually displayed during method validation.

Acetamides↗
PubMed1999

Mapping of central D2 dopamine receptors in man using [11C]raclopride: PET with anatomic standardization technique.

D2 dopamine receptors are of interest in the pathophysiology of schizophrenia. For group comparisons of neuroreceptor distribution measured by PET on a pixel-by-pixel basis, an anatomic standardization technique is required. The aim of the present study is to build a database of normal D2 dopamine receptor distribution using [11C]raclopride and an anatomic standardization technique. In each subject, two PET measurements were performed with rapid bolus injection and with continuous infusion of [11C]raclopride. The radioactivity of the PET images were integrated in the time interval. Integrated images were normalized by the radioactivity of the cerebellum, providing a measure of the binding potential (BP) in each pixel. Each PET image was transformed into a standard brain anatomy using a Computerized Brain Atlas system. From the standardized PET images, the sample mean and the SD of the BP were calculated in each pixel. On the anatomically standardized average images for the both rapid bolus injection and continuous infusion, high BP was observed in the putamen and the caudate nucleus, whereas low BP was observed in the cerebral cortices. The BP for the thalamus and the substantia nigra were slightly higher than those for the cerebral cortices. This regional distribution is in good agreement with the distribution of D2 dopamine receptors known from in vitro studies. The anatomic standardization technique permits to build a database of the normal D2 dopamine receptor distribution in the living human brain. This technique can be applied for group comparisons on a pixel-by-pixel basis.

Adult↗
PubMed1994

Standardization of reagents and methods used in cytological and histological practice with emphasis on dyes, stains and chromogenic reagents.

The need for the standardization of reagents and methods used in the histology laboratory is demonstrated. After definitions of dyes, stains, and chromogenic reagents, existing standards and standards organizations are discussed. This is followed by practical instructions on how to standardize dyes and stains through the preparation of reference materials and the development of chromatographic methods. An overview is presented of the problems concerned with standardization of the Romanowsky-Giemsa stain for cytological and histological application. Finally, the problem of how to convince routine dye and stain users of the need for standardization in their histology laboratories is discussed.

Animals↗
PubMed1993

Cross-calibration of liquid and solid QCT calibration standards: corrections to the UCSF normative data.

Quantitative computed tomography (QCT) has been shown to be a precise and sensitive method for evaluating spinal bone mineral density (BMD) and skeletal response to aging and therapy. Precise and accurate determination of BMD using QCT requires a calibration standard to compensate for and reduce the effects of beam-hardening artifacts and scanner drift. The first standards were based on dipotassium hydrogen phosphate (K2HPO4) solutions. Recently, several manufacturers have developed stable solid calibration standards based on calcium hydroxyapatite (CHA) in water-equivalent plastic. Due to differences in attenuating properties of the liquid and solid standards, the calibrated BMD values obtained with each system do not agree. In order to compare and interpret the results obtained on both systems, cross-calibration measurements were performed in phantoms and patients using the University of California San Francisco (UCSF) liquid standard and the Image Analysis (IA) solid standard on the UCSF GE 9800 CT scanner. From the phantom measurements, a highly linear relationship was found between the liquid- and solid-calibrated BMD values. No influence on the cross-calibration due to simulated variations in body size or vertebral fat content was seen, though a significant difference in the cross-calibration was observed between scans acquired at 80 and 140 kVp. From the patient measurements, a linear relationship between the liquid (UCSF) and solid (IA) calibrated values was derived for GE 9800 CT scanners at 80 kVp (IA = [1.15 x UCSF] - 7.32).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2001

Standardization of bone mineral density at femoral neck, trochanter and Ward's triangle.

The International Committee for Standards in Bone Measurement (ICSBM) has published standardization formulas for total hip bone mineral density (BMD). In many applications, however, BMD of hip subregions, such as femoral neck (FN), trochanter (TR), and Ward's triangle (WT), are commonly measured. This paper addresses whether the standardization formulas for total hip BMD can be adequately used for hip subregions. We used data from 100 healthy women, from 20 to 80 years old, who had hip BMD measured in both the total hip and hip subregions by a Hologic QDR 2000, a Lunar DPX, and a Norland XR26 Mark II. The same women were used by ICSBM for the standardization of total hip BMD. In addition, we used data of 3139 patients from a clinical trial to validate our results. We derived standardization formulas for FN, TR, and WT using the same statistical method as that used for total hip BMD. We applied both total hip calibration formulas and subregion-specific formulas to the data and compared the corresponding effect. We found that the total hip calibration formulas can partially reduce BMD differences between the Hologic and Lunar as well as the Lunar and Norland scanners in hip subregions, but increase differences between the Hologic and Norland scanners. The subregion calibration formulas are most appropriate for calibrating subregion BMD values and their absolute changes, and should be adopted. Standardization is unnecessary for BMD percentage changes in our clinical trial data.

Absorptiometry, Photon↗
PubMed1990

International Standards for salmon calcitonin, eel calcitonin, and the Asu1-7 analogue of eel calcitonin: calibration by international collaborative study.

Regulatory specifications in most countries require that the potency of salmon calcitonin (sCT) clinical products be expressed in International Units (IU) defined by the World Health Organization (WHO) International Standard. The first ampouled standard was prepared in 1972 and has been distributed world-wide since then. A batch of ampoules to serve as the replacement standard is now required. Other piscine calcitonins, eel calcitonin (eCT) and an amino-suberic acid analogue of eCT (Asu1-7 eCT) are now clinical products in some countries and international standards are required for these peptides which are similar to, but not identical with, sCT. This paper describes the preparation of three new ampouled standards and their biological calibration by international collaborative study comprising 17 participants from 10 countries. Following the recommendations in the final report of the collaborative study, the 2nd International Standard (IS) for sCT, the 1st IS for eCT and the 1st IS for Asu1-7 eCT were recently established by WHO, each with an assigned potency in IU, and are now available for issue.

Animals↗
PubMed2004

Development and application of Marinelli beaker standards for monitoring radioactivity in Dairy-Products by gamma-ray spectrometry.

Marinelli (reentrant) beakers are recommended for measurement of low-activity radioactive environmental samples, in both liquid and solid phase. The preparation of Marinelli beaker standards of milk powder containing 232ThO2 at secular equilibrium with its daughter radionuclides was studied. Standards were prepared by mixing of known amounts of solid ThO2 and milk powder. The densities of the standards were 0.5-0.7 kg dm(-3). Measurements of calibrated Marinelli beaker standards with HPGe detector showed that the energy dependence of the efficiency is similar to that of a point source, i.e. an almost linear dependence of log-efficiency vs. log-energy in the 200-2000 keV range, however the parabolic correlation fits better. The validity of these standards was checked by comparison with certified standard reference material IAEA-152-Milk powder containing radiocesium and radiopotassium. The results obtained were found to be in a good agreement with the published certified data. The limit of detection for the determination of radiocesium by gamma ray spectrometry under the prevailing experimental conditions is 0.03 Bq (i.e. 0.8 pCi), for samples of dairy products having lower densities of 0.7 kg dm(-1).

Dairy Products↗
PubMed2005

Development of a two-color laser fluorescence detector. On-line detection of internal standards and unknowns by capillary electrophoresis within the same sample.

A two-laser, two-color detector has been developed for the simultaneous detection of naturally occurring and recombinant (internal standards) cytokines within the same biological sample. The internal standards were labeled with Bimane and detected with a 408 nm laser while the natural cytokines were labeled with AlexaFluor633 and detected with a 633 nm laser. The two resulting electropherograms were plotted as overlaid traces and quantification of the natural materials determined by comparison with the standards. Using this system, recovery of all four cytokine standards was greater than 94% in both saline and cytokine-depleted plasma. These recoveries could be achieved with intra- and inter-assay coefficients of variance (c.v.) of less than 4.5 and 5.6, respectively. Application of this system to the examination of clinical samples demonstrated that measurement of the four pro-inflammatory cytokines could distinguish between normals, sub-clinical and clinical inflammation. An advantage of this approach is that direct calculation of unknowns by comparison to identical internal standards can shorten analytical time by eliminating the need for additional standard or calibration runs.

Color↗
PubMed2005

Improvements for comparative analysis of changes in diversity of microbial communities using internal standards in PCR-DGGE.

The use of internal standards both during DNA extraction and PCR-DGGE procedure gives the opportunity to analyse the relative abundance of individual species back to the original sample, thereby facilitating relative comparative analysis of diversity. Internal standards were used throughout the DNA extraction and PCR-DGGE to compensate for experimental variability. Such variability causes decreased reproducibility among replicate samples as well as compromise comparisons between samples, since experimental errors cannot be differentiated from actual changes in the community abundance and structure. The use of internal standards during DNA extraction and PCR-DGGE is suitable for ecological and ecotoxicological experiments with microbial communities, where relative changes in the community abundance and structure are studied. We have developed a protocol Internal Standards in Molecular Analysis of Diversity (ISMAD) that is simple to use, inexpensive, rapid to perform and it does not require additional samples to be processed. The internal standard for DNA extraction (ExtrIS) is a fluorescent 510-basepair PCR product which is added to the samples prior to DNA extraction, recovered together with the extracted DNA from the samples and analysed with fluorescence spectrophotometry. The use of ExtrIS during isolation of sample DNA significantly reduced variation among replicate samples. The PCR internal standard (PCR(IS)) originates from the Drosophila melanogaster genome and is a 140-basepair long PCR product, which is amplified by non-competitive primers in the same PCR reaction tubes as the target DNA and analysed together with the target PCR product on the same DGGE gel. The use of PCR(IS) during PCR significantly reduced variation among replicate samples both when assessing total PCR product and when comparing bands representing species on a DGGE gel. The entire ISMAD protocol was shown to accurately describe changes in relative abundance in an environmental sample using PCR-DGGE. It should, however, be mentioned that despite the use of ISMAD some inherent biases still exist in DNA extraction and PCR-DGGE and these should be taken into consideration when interpreting the diversity in a sample based on a DGGE gel.

Bacteria↗
PubMed2006

Thermal stability of the WHO international standard of interferon alpha 2b (IFN-alpha 2b): application of new reporter gene assay for IFN-alpha 2b potency determinations.

A World Health Organization requirement for biological standards is that they should exhibit long-term stability at their recommended storage temperature. Thermal stability is usually predicted in accelerated thermal degradation studies, where ampoules of the lyophilized standard are stored at elevated temperatures for relatively short times before testing. To confirm the predicted thermal stability of the 2nd international standard of human interferon alpha 2b (IFN-alpha2b; 95/566), we tested the potency of the ampouled contents of this standard after 9 years storage at the customary storage temperature of -20 degrees C in comparison with ampoules of the IS which had been stored continuously at temperatures ranging from -150 degrees C to 56 degrees C. Since IFN-alpha2b potency estimates derived from the results of antiviral assays (AVA) showed high within-assay variability, we investigated a novel reporter gene assay (RGA) based on induction of secreted alkaline phosphatase (SEAP) for comparability and precision of such estimations. We show that this RGA generated comparable estimates with overall lower variation. Additionally, the SEAP conversion of p-nitrophenyl phosphate to yellow product could be followed kinetically. Absorbance readings were shown to increase with time in proportion with increasing concentration of IFN-alpha2b. When the time-dependent increments of absorbance were plotted graphically, the slopes of lines corresponded to concentration. This approach enabled single dilutions of IFN samples, identical in molecular structure to an IFN-alpha2b standard, to be used for potency estimates by interpolation of slope value against those of the standard at fixed concentrations. It appears attractive for high through-put potency testing of various R&D IFN-alpha2b samples.

Cell Line, Tumor↗
PubMed2003

Standardization of diagnostic PCR for the detection of foodborne pathogens.

In vitro amplification of nucleic acids using the polymerase chain reaction (PCR) has become, since its discovery in the 1980s, a powerful diagnostic tool for the analysis of microbial infections as well as for the analysis of microorganisms in food samples. However, despite its potential, PCR has neither gained wide acceptance in routine diagnostics nor been widely incorporated in standardized methods. Lack of validation and standard protocols, as well as variable quality of reagents and equipment, influence the efficient dissemination of PCR methodology from expert research laboratories to end-user laboratories. Moreover, the food industry understandably requires and expects officially approved standards. Recognizing this, in 1999, the European Commission approved the research project, FOOD-PCR (http://www.PCR.dk), which aims to validate and standardize the use of diagnostic PCR for the detection of pathogenic bacteria in foods. The present review focuses on the harmonization procedure and standardization criteria for detection of foodborne pathogens by PCR. The progress of standardization so far and future perspectives of diagnostic PCR are discussed.

Bacteria↗
PubMed1990

Nervonic acid versus tricosanoic acid as internal standards in quantitative gas chromatographic analyses of fish oil longer-chain n-3 polyunsaturated fatty acid methyl esters.

Tricosanoic acid (23:0) and cis-15-tetracosenoic acid (nervonic acid, 24:1 n-9) were compared as choices suitable for use as internal standards in the quantitation of eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids. Experiments conducted included: (a) comparison of the flame ionisation detector responses of the two fatty acid methyl esters; (b) estimation of accurately weighed quantities of EPA and DHA using both 23:0 and 24:1 separately as internal standard; (c) determination of EPA and DHA contents of commercially available fish oil ethyl ester capsules using the two as internal standard. The results suggest that both 23:0 and 24:1 methyl esters behaved similarly in the flame ionization detector of the gas chromatograph and are comparable internal standards for use in quantitation of EPA and DHA. This includes the analysis of ethyl ester mixtures as long as interesterification of sample with solvent methanol is complete. The relatively poor solubility of the saturated 23:0 is countered by its greater stability. A possible drawback of 24:1 could be the presence of more than one positional isomer in either a 24:1n-9 standard or in the actual sample. In principle any fatty acid could serve as an internal standard as long as the limitations involved in the use of each are taken into account.

Chromatography, Gas↗