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PubMed1999

Rationale for time-qualified reference standards for 24-hour blood pressure values and their circadian rhythms in Japanese normotensive adults: a study by the Ambulatory Blood Pressure Monitoring Research Group.

The aim of this study was to demonstrate that blood pressure (BP) has to be standardized according to its circadian variability, including the properties shown in its circadian rhythm. The BP time-qualified standards were derived from a sample of 644 clinically healthy normotensive Japanese subjects (320 males, 324 females; age range, 18-93 years), stratified by age-group and gender, who underwent noninvasive ambulatory monitoring according to a fixed protocol. The monitored data series shows that BP exhibits a within-day variability at any age of life in both males and females. Additionally, the monitored data series shows that BP exhibits a significant circadian rhythm at any age of life in both males and females. The age- and sex-related reference limits for the BP within-day variability constitute the time-qualified standards against which both the casual and monitored BP measurements can be compared in order to detect whether or not they are compatible with normotension. The reference limits for the BP circadian rhythm represent the rhythmometric standards against which the BP oscillatory curve can be compared in order to detect whether or not they are compatible with a physiological circadian rhythm.

Adolescent↗
PubMed2004

Stable oxygen isotopes from theropod dinosaur tooth enamel: interlaboratory comparison of results and analytical interference by reference standards.

Although previous work has demonstrated that biological phosphates ('biophosphates') record significant changes in delta18O associated with variations in local climate and seasonality, the repeatability of these analyses between laboratories has not previously been tested. We serially sampled enamel on four Cretaceous dinosaur teeth for phosphate delta18O analysis at up to three different facilities. With the exception of one set of unprocessed enamel samples, the material supplied to each laboratory was chemically processed to silver phosphate. Each laboratory analyzed sample sets by pyrolysis (thermochemical decomposition) in a ThermoFinnigan TC/EA attached to a ThermoFinnigan Delta Plus mass spectrometer. Significant interference between phosphate samples and the NIST reference material 8557 barium sulfate (NBS 127) distorts some of the results. Samples analyzed immediately following NBS 127 may be depleted by 6 per thousand isotopically and in instrument peak amplitude response by 80%. Substantial interference can persist over the subsequent 20 silver phosphate samples, and can influence the instrument peak amplitude response from some organic standards. Experiments using reagent-grade silver phosphate link these effects to divalent cations, particularly Ca2+ and Ba2+, which linger in the reactor and scavenge oxygen evolved from pyrolysis of subsequent samples. Unprocessed enamel includes 40 wt% calcium and self-scavenges oxygen, disrupting the isotopic measurements for the first half of a set and depleting subsequent organic standards by up to 9 per thousand. In sets without NBS 127 or calcium, such interference did not occur and an interlaboratory comparison of results from enamel shows reproducible, significantly correlated peaked delta18O patterns with a 2-3 per thousand dynamic range, consistent with previous results from contemporaneous teeth. Whereas both unprocessed enamel and the NBS 127 barium sulfate should be applied to biological phosphate ('biophosphate') stable isotope research with caution, seasonal variations in enamel phosphate delta18O are a paleoecologically valuable, reproducible phenomenon in theropod dinosaur teeth.

Animals↗
PubMed1993

Retrospective analysis of the use of a standardized reference form in admissions to a dietetics internship program.

Although the letter of recommendation is the most commonly requested information relating to the personal qualities of applicants to dietetics internship programs, little research has focused on its value in selection decisions. The purpose of this study was to review how 318 letters of recommendation submitted on a standardized form related to the source of the reference and to the admission status of the applicants. The form contained 40 attributes that raters assigned to one of six categories. Nine of the 40 attributes were not rated by more than 75% of the raters, and 3 of the attributes were rated as outstanding by more than 60% of the raters. We concluded that these attributes did little to distinguish among applicants. The attribute maturity correlated 0.70 with 5 attributes and 0.99 with 2 attributes, so duplication of information existed. Raters were categorized as follows: adviser, major professor, other professor, employer, and other. The highest mean ratings were given by advisers; major professors rated students lowest. Analysis of variance supported a significant difference in rating by type of rater. Our findings suggest that fewer items should be used on a standardized form and that the type of rater should be specified if references are to distinguish among applicants.

Analysis of Variance↗
PubMed1999

A comparison of nutritional indices of children in Chitungwiza, Zimbabwe, with the international reference standard.

OBJECTIVES: To examine the hypothesis that, the fifth, 50th and 95th percentiles of the weights and heights of primary school children of Chitungwiza Municipality, (a town 30 km south west of Harare, Zimbabwe), did not differ from those of the NCHS reference population of children. DESIGN: A descriptive cross sectional study. SETTING: Chitungwiza Municipality. SUBJECTS: Primary school children aged five to 16 years. MAIN OUTCOME MEASURES: Height for age < 90%, weight for height < 80% and the comparability of mean weights and heights between the study children and the NCHS reference children. RESULTS: Low rates were found for height for age < 90% (stunting) and for weight for height < 80% (wasting) among the Chitungwiza children, 3.5% (95% CI 2.8%, 4.7%) and 1.9% (CI 0.9%, 3%), respectively. The differences between age and sex matched pairs of the sample mean heights and reference mean heights, and of the sample mean weights and reference mean weights at the fifth, 50th and 95th percentiles, were significant. Chitungwiza children consistently dropped below the NCHS mean weight and height for all three percentiles. CONCLUSION: This study has demonstrated that stunting and wasting is low among Chitungwiza primary school children but that the spread of their heights and weights lies lower than the spread of the heights and weights of the NCHS reference children. We recommend that wider cross sectional and longitudinal anthropometric assessments in a nation wide sample of primary school children be carried out to shed more light on the growth potential of Zimbabwean children.

Adolescent↗
PubMed2001

[Need and quality assurance: can the introduction of the new generation mobile systems change the reference standards?].

The new generation of radiological mobile systems, by lowering the installation and depreciation expenses, has led to start new low volume catheterization laboratories. These equipments allow to obtain good quality images, but they are not so reliable for extended performances, so that they are not suitable for interventional procedures. On the other hand, the extension of the indications to coronary angiography and angioplasty, with the related increase in the population needs, leads the resetting of the reference areas to start new catheterization laboratories. Anyhow lowering of expenses and of the extension of the reference areas does not change the need for maintaining high activity levels of centers and first operators in order to guarantee the quality of diagnostic and interventional procedures. The optimal levels of centers in national standards are 800 coronary angiographies and 400 coronary angioplasties per year: these numbers indicate the experience necessary to warrant the quality of procedures, with optimal results and low rate of complications, therefore they should not be changed. The spreading of laboratories due to the new low cost radiological equipments leads to an increase in inappropriate procedures and in the total expenses for the management of cardiac patients, without a proportional advantage in prognosis and quality of life. In order to ensure a quick diagnostic and therapeutic process to all the patients who need invasive procedures, instead of starting new centers, it is worthwhile to perfect the efficiency of links among small and main centers following shared pathways.

Angioplasty↗
PubMed2000

Estimation of the prevalence of low bone density in Canadian women and men using a population-specific DXA reference standard: the Canadian Multicentre Osteoporosis Study (CaMos).

The Canadian Multicentre Osteoporosis Study (CaMos) is a prospective cohort study which will measure the incidence and prevalence of osteoporosis and fractures, and the effect of putative risk factors, in a random sample of 10,061 women and men aged > or = 25 years recruited in approximately equal numbers in nine centers across Canada. In this paper we report the results of studies to establish peak bone mass (PBM) which would be appropriate reference data for use in Canada. These reference data are used to estimate the prevalence of osteoporosis and osteopenia in Canadian women and men aged > or = 50 years. Participants were recruited via randomly selected household telephone listings. Bone mineral density (BMD) of the lumbar spine and femoral neck were measured by dual-energy X-ray absorptiometry using Hologic QDR 1000 or 2000 or Lunar DPX densitometers. BMD results for lumbar spine and femoral neck were converted to a Hologic base. BMD of the lumbar spine in 578 women and 467 men was constant to age 39 years giving a PBM of 1.042 +/- 0.121 g/cm2 for women and 1.058 +/- 0.127 g/cm2 for men. BMD at the femoral neck declined from age 29 years. The mean femoral neck BMD between 25 and 29 years was taken as PBM and was found to be 0.857 +/- 0.125 g/cm2 for women and 0.910 +/- 0.125 g/cm2 for men. Prevalence of osteoporosis, as defined by WHO criteria, in Canadian women aged > or = 50 years was 12.1% at the lumbar spine and 7.9% at the femoral neck with a combined prevalence of 15.8%. In men it was 2.9% at the lumbar spine and 4.8% at the femoral neck with a combined prevalence of 6.6%.

Absorptiometry, Photon↗
PubMed2001

Isotope-ratio measurements of lead in NIST standard reference materials by multiple-collector inductively coupled plasma mass spectrometry.

The capability of a second-generation Nu Instruments multiple collector inductively coupled plasma mass spectrometer (MC-ICP-MS) has been evaluated for precise and accurate isotope-ratio determinations of lead. Essentially the mass spectrometer is a double-focusing instrument of Nier-Johnson analyzer geometry equipped with a newly designed variable-dispersion ion optical device, enabling the measured ion beams to be focused into a fixed array of Faraday collectors and an ion-counting assembly. NIST SRM Pb 981, 982, and 983 isotopic standards were used. Addition of thallium to the lead standards and subsequent simultaneous measurement of the thallium and lead isotopes enabled correction for mass discrimination, by use of the exponential correction law and 205Tl/203Tl = 2.3875. Six measurements of SRM Pb-982 furnished the results 206Pb/204Pb = 36.7326(68), 207Pb/204Pb = 17.1543(30), 208Pb/204Pb = 36.7249(69), 207Pb/206Pb = 0.46700(1), and 208Pb/206Pb = 0.99979(2); the NIST-certified values were 36.738(37), 17.159(25), 36.744(50), 0.46707(20), and 1.00016(36), respectively. Direct isotope lead analysis in silicates can be performed without any chemical separation. NIST SRM 610 glass was dissolved and introduced into the MC-ICP-MS by means of a micro concentric nebulizer. The ratios observed were in excellent agreement with previously reported data obtained by TIMS and laser ablation MC-ICP-MS, despite the high Ca/Pb concentration ratio (200/1) and the presence of many other elements at levels comparable with that of lead. Approximately 0.2 microg lead are sufficient for isotope analysis with ratio uncertainties between 240 and 530 ppm.

Journal Article↗
PubMed1998

Automatic quantification of immunohistochemically stained cell nuclei based on standard reference cells.

A fully automatic method for quantification of images of immunohistochemically stained cell nuclei by computing area proportions, is presented. Agarose embedded cultured fibroblasts were fixed, paraffin embedded and sectioned at 4 microm. They were then stained together with 4 microm sections of the test specimen obtained from bladder cancer material. A colour based classifier is automatically computed from the control cells. The method was tested on formalin fixed paraffin embedded tissue section material, stained with monoclonal antibodies against the Ki67 antigen and cyclin A protein. Ki67 staining results in a detailed nuclear texture with pronounced nucleoli and cyclin A staining is obtained in a more homogeneously distributed pattern. However, different staining patterns did not seem to influence labelling index quantification, and the sensitivity to variations in light conditions and choice of areas within the control population was low. Thus, the technique represents a robust and reproducible quantification method. In tests measuring proportions of stained area an average standard deviation of about 1.5% for the same field was achieved when classified with classifiers created from different control samples.

Automation↗
PubMedDate not supplied

[Development of a plastic capillary tube for Saling fetal blood analysis. Evaluation of pH-metry with standard references].

In order to avoid mouth suction and danger of glass breakage during collection and to avoid mixing of the sample with a piece of wire and an external magnet immediately after collection, an unbreakable plastic capillary tube was designed with increased heparin coating and surface and reduced diffusion distance. For assessing agreement between pH measurements of blood samples obtained with the new plastic capillary tube and a commercial glass capillary tube, umbilical blood pH-values of 41 births were analyzed simultaneously by both methods. The mean difference between paired pH-values, the corresponding 95%-confidence interval and the true limits of agreement were calculated. The pH-values obtained with the plastic capillary tube are systematically lower, with a mean pH decrease of 0.009 units, and there is an additional random variation with a standard deviation of 0.009 pH units. The true limits of agreement: [-0.031, 0.013] represent the interval of the worst expected pH difference. The increased heparin availability in the plastic capillary tube may be the reason for the systematic pH deviation of -0.009 units. However this difference does not seem to be clinically relevant and the statistical evaluation shows a sufficiently good agreement between the pH measurements.

Acid-Base Equilibrium↗
PubMed1986

Potentiating paired stimulation of cardiac muscle in vitro as positive inotropic reference standard.

In rabbit papillary muscles, potentiating paired stimulation was used as a standard positive inotropic intervention. Pairs of depolarizing electrical stimuli were applied, equal in strength and with a coupling interval of the functional refractory period plus 10 msec. After five successive pairs at a basic driving rate of 0.5 Hz, maximum potentiation amounting to a two- to threefold increase in the contraction amplitude was reached. The potentiating paired stimulation was rapid in both onset and reversibility and was reproducible. Potentiating paired stimulation is sparing since internal Ca2+ pools are utilized to increase force. Using potentiating paired stimulation-induced increase in force of contraction as a new reference, the following order of potency of positive inotropic agents was obtained: ouabain greater than DPI 201-106 greater than IBMX greater than APP 201-533. Effects of these drugs on rested-state contractions and frequency-force relationship were also investigated.

1-Methyl-3-isobutylxanthine↗
PubMed2000

Serial echocardiographic measurements of the pulmonary autograft in the aortic valve position after the Ross operation in a pediatric population using normal pulmonary artery dimensions as the reference standard.

Serial echocardiographic measurements of the annulus and sinus were obtained in children before the Ross operation, and early and late postoperatively. Values were compared with normal standards for the aorta and pulmonary artery (PA). There was no significant difference between PA annulus measurements before surgery and the corresponding autograft immediately afterward (1.73 +/- 0.60 cm preoperatively; 1. 63 +/- 0.58 cm postoperatively, p = NS). Late after surgery the mean annulus diameter was enlarged compared with the normal aorta (DeltaZ 1.9 +/- 2.4), but remained relatively unchanged compared with the normal PA (DeltaZ 0.7 +/- 1.1, p <0.01). In contrast, the autograft sinus was dilated early after surgery (1.83 +/- 0.58 cm preoperatively; 2.18 +/- 0.73 cm postoperatively, p <0.01). Mean sinus Z score further increased compared with both the aorta (DeltaZ 1.3 +/- 1.7) and PA (DeltaZ 1.3 +/- 1.6). Use of standard PA measurements may be important in the assessment of autograft enlargement. Minimal change in autograft Z scores over time suggests that annulus enlargement is mainly due to somatic growth. In contrast, the autograft sinus showed an immediate and continued disproportionate increase in size over time, suggesting that sinus enlargement is largely due to passive dilation.

Adolescent↗
PubMed1980

Determination of reference standards for adrenal steroids excretion in normal prepuberal children.

An improved method of gas-liquid chromatography (GLC) for routine estimation of adrenal steroids in urine is presented. It was applied to the exploration of steroid output in 120 normal prepuberal children to both sexes aged 3 months-12 years. Urinary data were compared to plasmatic values of adrenal hormones estimated by radio-immuno-assays (RIA). Analysis of the relationships between steroids outputs and bone age revealed that the excretion of cortisol catabolites was expressed by a saturation curve whereas that of delta 4-3 keto androgens catabolites were expressed by geometrical pregression curves; urine dehydroepiandrosterone (DHEA) and plasma DHEA-sulfate showed outbreaks of high values beyond 6 years of age which ruled out all curve fitting attempts. The computation of these relationships allowed to determine the confidence belts of the various regressions which appear as a useful tool to estimate the delayed or accelerated character of adrenal activity in prepuberal childhood. Comparison of the various urinary (GLC) and plasmatic (RIA) parameters enabled us to comment on adrenal puberty.

Adrenal Cortex Hormones↗
PubMed2005

Correlation of office-based cystoscopy and cytology with histologic diagnosis: how good is the reference standard?

OBJECTIVES: To evaluate the accuracy of cystoscopy and cytology in predicting the histopathologic features of suspicious cystoscopic lesions. METHODS: We reviewed the bladder biopsy records at two institutions from July 2001 to July 2004. Intraoperative biopsies were performed for positive (papillary or sessile) (n = 155) and equivocal (n = 101) lesions found during office cystoscopy. The specimens were submitted for histopathologic analysis, and the results were correlated with the preceding office-based cystoscopy and cytology findings. RESULTS: Malignancy was found in 27 (26.7%) of 101 equivocal lesions and 128 (82.5%) of 155 sessile or papillary lesions. Of the 72 biopsies performed for equivocal lesions in patients with a history of transitional cell carcinoma (TCC), 24 (33%) had malignancy compared with 3 (10.3%) of 29 biopsies performed in patients without a history of TCC. For patients with no history of TCC and equivocal lesions, cytology was able to identify all neoplasms (100% sensitivity) and negative cytology always predicted a normal biopsy result (100% negative predictive value). However, for patients with a history of TCC and equivocal lesions, cytology had a sensitivity and negative predictive value of 81.8% and 88.2%, respectively. CONCLUSIONS: Our findings suggest that patients without a history of TCC who have an equivocal lesion at cystoscopy may avoid an unnecessary operation if they have normal cytology findings. A large number of patients with equivocal cystoscopic findings undergo unnecessary biopsies in the operating room, and future studies should be performed to assess the value of other bladder markers in predicting oncologic status in this setting.

Cystoscopy↗