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PubMed1997

Growth assessment in school-children of Villa Cubas, Catamarca Argentine.

An anthropometric study of the growth in schoolchildren aged 5 to 14 years, belonging to the Villa Cubas district of the capital of the province of Catamarca, has been carried out. Villa Cubas presents average/low socioeconomic characteristics and is situated in a peripheral sector to the Center of the Capital. Male and female students have been evaluated. The measurements were turned to "Z" scores. The aims of this work were: 1) To determinate the state of growth in comparison with the national reference standards and 2) To analyze the competence of the use of such standards in the clinical and nutrition assessment in the province of Catamarca. The results showed that the body weight and height had no difference with the standards, while the sitting presented higher values than the standards. The results are interpreted as a consequence of the food deficit that affected the height and the inferior height part. The standards of reference are considered to be out-of-date and inappropriate for the clinic assessment in the province of Catamarca, inasmuch as they do not show the changes that have taken place in the population in the last 20 years.

Adolescent↗
PubMed2001

A method to standardize a reference of scalp EEG recordings to a point at infinity.

The effect of an active reference in EEG recording is one of the oldest technical problems in EEG practice. In this paper, a method is proposed to approximately standardize the reference of scalp EEG recordings to a point at infinity. This method is based on the fact that the use of scalp potentials to determine the neural electrical activities or their equivalent sources does not depend on the reference, so we may approximately reconstruct the equivalent sources from scalp EEG recordings with a scalp point or average reference. Then the potentials referenced at infinity are approximately reconstructed from the equivalent sources. As a point at infinity is far from all the possible neural sources, this method may be considered as a reference electrode standardization technique (REST). The simulation studies performed with assumed neural sources included effects of electrode number, volume conductor model and noise on the performance of REST, and the significance of REST in EEG temporal analysis. The results showed that REST is potentially very effective for the most important superficial cortical region and the standardization could be especially important in recovering the temporal information of EEG recordings.

Algorithms↗
PubMed2004

Mass value assignment of total and subclass immunoglobulin G in a human standard anthrax reference serum.

An anti-Anthrax Vaccine Adsorbed (anti-AVA) standard human reference serum pool, AVR414, has been prepared, and the total and protective antigen (PA)-specific immunoglobulin G (IgG) were quantified. AVR414 was prepared by plasmapheresis of healthy adults who had received a minimum of four subcutaneous injections of AVA. Mass values (in milligrams per milliliter) for total IgG and IgG subclasses 1 to 4 were determined by radial immunodiffusion. Anti-PA-specific IgG assignment (in micrograms per milliliter) was done by consensus of two complementary approaches: homologous enzyme-linked immunosorbent assay (ELISA) with affinity-purified anti-PA IgG as a calibrator and summation of mean PA-specific IgG subclass concentrations determined by IgG subclass-specific ELISA using the United States National Reference Preparation for Human Serum Proteins as a standard. The total IgG concentration assigned to AVR414 reference serum was 8.33 mg/ml. IgG subclass concentrations were the following: for IgG1, 4.48 mg/ml; for IgG2, 3.35 mg/ml; for IgG3, 0.37 mg/ml; and for IgG4, 0.30 mg/ml. The assigned mass value for total anti-PA-specific IgG was 141.2 microg/ml. Anti-PA-specific IgG subclass concentrations were the following: for IgG1, 79.6 microg/ml; for IgG2, 35.3 microg/ml; for IgG3, 3.2 microg/ml; and for IgG4, 25.3 microg/ml. Human reference serum pool AVR414 will have direct application in the standardization of anthrax serological assays, in reagent qualification, and as a standard for quantification of PA-specific IgG in humans who have been vaccinated with or otherwise exposed to Bacillus anthracis PA.

Anthrax Vaccines↗
PubMed2026

Diagnostic Performance of Machine Learning for Systemic Lupus Erythematosus: Systematic Review and Meta-Analysis.

BACKGROUND: Early and accurate diagnosis of systemic lupus erythematosus (SLE) and its organ involvement is essential. Previous reviews of machine learning (ML) in SLE combined heterogeneous tasks and validation strategies and may have overinterpreted model performance. OBJECTIVE: This study evaluated the diagnostic performance of ML and deep learning (DL) models for 3 clinically distinct SLE-related tasks: SLE classification or diagnosis, lupus nephritis (LN) diagnosis, and neuropsychiatric systemic lupus erythematosus (NPSLE) discrimination. We also assessed methodological quality and certainty of evidence. METHODS: PubMed, Embase, Cochrane Library, Web of Science, and IEEE Xplore were searched from January 2014 to April 2026. Eligible peer-reviewed diagnostic accuracy studies developed or validated ML or DL models for 1 of the 3 prespecified tasks, used an accepted reference standard, and provided data for a 2×2 contingency table. Bivariate random-effects meta-analyses with the Hartung-Knapp-Sidik-Jonkman adjustment were used to pool sensitivity and specificity. We reported 95% prediction intervals (PIs), assessed risk of bias using the Quality Assessment of Diagnostic Accuracy Studies for Artificial Intelligence tool (QUADAS-AI; Viknesh Sounderajah [Imperial College London]), and evaluated certainty of evidence using the Grading of Recommendations Assessment, Development, and Evaluation framework for diagnostic test accuracy. RESULTS: Twenty-nine studies were included: 17 for SLE classification, 5 for LN diagnosis, and 7 for NPSLE discrimination. In the primary task-stratified analysis, pooled sensitivity was 0.91 (95% CI 0.86-0.94; 95% PI 0.56-0.99), and pooled specificity was 0.94 (95% CI 0.91-0.96; 95% PI 0.69-0.99), with low heterogeneity (I²=23.9% and 22.9%, respectively). DL models showed a sensitivity of 0.93 and specificity of 0.95, compared with 0.88 and 0.94 for traditional ML models. Certainty of evidence was high for most analyses but low for LN diagnosis because of inconsistency and imprecision. All studies were retrospective, and only 9 of 29 (31%) performed independent external validation. Overall risk of bias was high or unclear in 22 of 29 (75.9%) studies. No study reported model calibration, decision-curve analysis, or net clinical benefit. CONCLUSIONS: ML models showed promising diagnostic accuracy across 3 distinct SLE-related tasks, but wide PIs, limited external validation, and pervasive risk of bias restrict conclusions about real-world generalizability. Prospective multicenter studies with standardized tasks and reference standards, independent external validation, and formal assessment of calibration and clinical utility are required before clinical implementation.

Humans↗
PubMed2002

Zinc and iron interactions evaluated between different mineral sources in different nutritional matrixes.

We compared the absorption of BioZn, SFE-171, SO4Fe (reference standard) and SO4Zn (reference standard) alone or in combination in water and in an infant dessert. When mineral interactions were evaluated, zinc and iron were administered in a 1:1 molar relation. There 160 rats divided in 16 groups of 10 animals each which received: SO(4)65Zn, Bio65Zn, SO(4)65Zn + SO4Fe, Bio65Zn + SFE-171, SO(4)59Fe, 59SFE-171, SO(4)59Fe + SO4Zn and 59SFE-171 + BioZn either in water or an infant dessert. The results showed that BioZn has bioavailability similar to SO4Zn both in water (23.36 +/- 3.14% vs. 21.48 +/- 6.03%. respectively) and in an infant dessert (19.89 +/- 3.27% vs. 18.31 +/- 4.76%, respectively). When these zinc compounds were administered with iron no statistical difference of zinc absorption was found (Bio65Zn + SFE-171 in water 22.70 +/- 6.30%, Bio65Zn + SFE-171 in the infant dessert 18.07 +/- 5.89%, SO(4)65Zn + SO4Fe in water 24.67 +/- 5.70% and SO(4)65Zn + SO4Fe in the infant desert 20.56 +/- 5.20%). For iron, the absorption of 59SFE-171 in water was higher (p < .01) than SO(4)59Fe in water and 59SFE-171 + BioZn in water (32.35 +/- 8.32% vs. 26.27 +/- 8.83% vs. 23.69 +/- 8.37%, respectively). Iron absorption from SO(4)59Fe in water was higher (p < .01) than SO(4)59Fe + SO4Zn in water (26.27 +/- 8.83% vs. 20.21 +/- 8.72%, respectively). Iron absorption in the infant dessert was higher (p < .01) for 59SFE-171 + BioZn than SO(4)59Fe, 59SFE-171 and SO(4)59Fe + SO4Zn (22.81 +/- 6.97% vs. 16.12 +/- 6.14% vs. 16.90 +/- 6.23% vs. 15.04 +/- 6.25%, respectively). Statistical differences (p < .01) were found between iron absorption from 59SFE-171 in water and the infant dessert (32.35 +/- 8.32% vs. 16.90 +/- 6.23%, respectively) and for SO(4)59Fe (26.27 +/- 8.83% vs. 16.12 +/- 6.14% respectively). Zinc and iron interactions evaluated in a 1:1 molar relation of the minerals were observed only for iron absorption in water but not in infant dessert. No negative effect was found for zinc absorption neither in water nor in infant dessert.

Animals↗
PubMed2006

Accuracy of FVIII: C assay by one-stage method can be improved using hemophilic plasma as diluent.

BACKGROUND: the basic prerequisite of Factor VIII clotting assay (FVIII:C) by One-Stage Method is that all other than FVIII clotting factors are present in constant concentration in each dilution of both standard reference and patient's plasma curves. On the contrary, the plasma content of each dilution is decreasing as the dilution factor increases. OBJECTIVES AND METHODS: to keep exactly constant the plasma content in each mixture, we performed all dilutions of both standard reference and patient's plasma with FVIII deficient plasma and further with a fixed amount of buffer (method B). To show the discrepancies between this method and regular method A, using buffer to make dilutions, a comparative study was conducted on FVIII: C assay on samples at known FVIII concentration and in patients' plasma. Imidazole or Owren's buffers and five different aPTT reagents were employed, both in method A and B. RESULTS: a discrepancy between FVIII: C assays obtained by method A and B was observed, mainly when Pathrontin SL and Imidazole buffer were used. The assays derived from method B always better fit with the expected, calculated, values of FVIII:C concentrations. Furthermore, FVIII: C was assayed in 60 patients: the outcome of method A was always higher than values of method B. The discrepancy between the two methods was higher at FVIII concentrations below 50 U/dL but null at 100 U/dL. The A slope was steeper than B slope and the difference was statistically significant starting from the 1/10 dilution. Accordingly, FVIII: C of patients' plasma obtained by method A was always higher that those obtained by method B, even 2 or 3 times for FVIII level < or = 10 U/dL or 1.4-1.6 times for FVIII levels between 10 and 25 U/dL. CONCLUSIONS: only method B is able to give FVIII: C assays in agreement with the expected values. The dilution of reference standards and samples with FVIII deficient plasma is crucial to accurately evaluate the post-infusion FVIII concentrations in pharmacokinetic studies or the trough level during prophylactic therapy and to investigate the discrepancy among different FVIII: C assays. In addition, the assessment of severity and classification of hemophilia should be reviewed.

Blood Coagulation↗
PubMed1975

Collaborative study of the determination of available lysine in proteins and feeds.

In the proposed method 1-fluoro-2,4-dinitrobenzene (DNFB) is reacted with the free epsilon-amino groups in protein of form DNFB-epsilon-amino lysine which is stable to acid hydrolysis. The sample is acid hydrolyzed and unavailable lysine is determined with an amino acid analyzer; total lysine is determined on the untreated sample. The available lysine, which was bound by DNFB, is determined by difference. The available lysine has been determined in 3 samples of 44% protein soybean meal by 5 collaborators, following the method outlined. The range for available lysine in reference standard 1 was 2.02-2.14%, in reference standard 2, 2.59-2.73% and in reference standard 3, 0.55-0.91%. The method has been adopted as official first action.

Animal Feed↗
PubMed2005

Proton nuclear magnetic resonance spectroscopy (NMR) methods for determining the purity of reference drug standards and illicit forensic drug seizures.

A rapid, sensitive, accurate, precise, reproducible, and versatile method for determining the purity of reference drug standards and the routine analysis of illicit drugs and adulterants using proton (1H) Nuclear Magnetic Resonance (NMR) Spectroscopy is presented. The methodology uses a weighed sample dissolved in a deuterated solvent or solvent mixture containing a high purity internal standard. The NMR experiment employs 8 scans using a 45 second delay and 90 degrees pulse. In the determination of purity of reference standards, the number of quantitative determinations available is equal to the number of peak groups that are baseline resolved. The relative standard deviation (RSD) of these signals is usually < 1% for pure standards, and the results agree well with other purity determining methods. This method can also aid in the determination of correct molecular weight for standards containing an unknown number of waters of hydration or an unknown number of acids per drug in salts. Because the molar response for the hydrogen nucleus is 1 for all compounds, and since no separation media are used, only one linearity study is required to test a probe. In the presented study, the linearity of the NMR probe was determined using methamphetamine HCl dissolved in deuterium oxide (D2O) with maleic acid as the internal standard (5 mg) for a range of concentrations from 0.033 to 69.18 mg/ml with a resulting correlation coefficient of >0.9999 for all 6 methamphetamine peak groups. The spectra of complex illicit heroin, methamphetamine, MDMA, and cocaine samples are presented, as well as an extensive list of compounds, their solubilities and the solvent(s) and internal standard used.

Journal Article↗
PubMed2000

Comparison testing of current (PPD-S1) and proposed (PPD-S2) reference tuberculin standards.

Since 1951, the tuberculin PPD-S1 has been used to standardize commercial PPD reagents and perform special tuberculin surveys. PPD-S1 is now in short supply and a new standard (PPD-S2) has been manufactured. To determine if PPD-S2 is equivalent and can replace PPD-S1, we conducted a double-blind clinical trial. Between May 14 and October 28, 1997, 69 subjects with a history of culture-proven tuberculosis (TB patients) and 1,189 subjects with a very low risk for TB infection were enrolled, received four skin tests (with PPD-S1, PPD-S2, and one each of the commercially available PPDs), and had reactions measured by two trained observers. Among the TB patients, we found statistically indistinguishable immunogenicity (mean reaction size +/- standard deviation): 15.6 +/- 6.6 mm for PPD-S1 and 14.8 +/- 5.6 mm for PPD-S2. Among low-risk subjects, the tests had equally high specificities (PPD-S1, 98.7% and PPD-S2, 98. 5%), using a 10-mm cutoff. The number of discordant (negative versus positive) interpretations for PPD-S2, assuming that low-risk subjects who had a >/= 10 mm reaction to PPD-S1 were truly infected, was low (0.5%) and indistinguishable from the rate of discordant interpretations of the same test when read by two different observers (0.8%). The study results indicate that PPD-S2 is qualified to be used as the new U.S. reference standard for PPD tuberculin.

Adult↗
PubMedDate not supplied

Cross-mapping between three terminologies with the international standard nursing reference terminology model.

PURPOSE: The International Standards Organization's (ISO) International Standard IS 18104 should assist the nursing profession to integrate their terminologies into computer systems and healthcare reference terminologies. The purpose of this study is to cross-map between different terminologies; that is, to determine if concepts in one terminology are similar to concepts in another terminology. METHODS: The ISO standard was used to test the degree to which three terminologies could be cross-mapped to each other. Concepts and terms were selected, their equivalence determined by experts, and the specific concepts were dissected or broken down to their constituent parts. RESULTS: Based on experts' selections from the three classifications, equivalent concepts were identified. Those concepts deemed equivalent were dissected, thus revealing whether the components of the nursing diagnostic concepts such as focus, judgment, and other attributes of the ISO standard matched. Based on the dissection of each diagnosis, the decision was made whether mapping was possible or not. CONCLUSIONS: The dissection revealed that several nursing diagnostic concepts can easily be interchanged, while others cannot or can be mapped only for specific purposes (e.g., clinical or aggregate use). This implies that for some concepts it does not matter which terminology is used, and in other cases it does because of different meanings.

Activities of Daily Living↗
PubMedDate not supplied

Cyanide assay: statistical comparison of a new gas chromatographic calibration method versus the classical spectrophotometric method.

This work compares two different methods for assaying hydrogen cyanide, a spectrophotometric method and a headspace gas chromatographic method, each with its own reference standard generation. In the first method, the reference standards are cyanide solutions. In the second method, the reference standards are based upon the in situ reduction of ethyl thiocyanate by dithiothreitol to produce hydrogen cyanide. Furthermore, hydrogen cyanide concentration in the blood of patients who were poisoned by smoke inhalation or who committed suicide by cyanide ingestion is determined using both methods. Results are discussed using statistical comparison.

Calibration↗
PubMed2002

Hepatic metastases in patients with colorectal cancer: relationship between size of metastases, standard of reference, and detection rates.

PURPOSE: To determine the relationship between the size of hepatic metastases, the standard of reference, and the reported detection rate in patients with colorectal cancer. MATERIALS AND METHODS: With use of a MEDLINE search (January 1994 to January 2001), articles were selected that contained original results on detection of hepatic metastases of colorectal cancer, categorized for size in at least two categories, with use of helical computed tomography (CT), helical CT at arterial portography, or magnetic resonance imaging. Results were compared with the size distribution of hepatic metastases in 47 consecutive patients with colorectal carcinoma, which were detected by using a combination of intraoperative ultrasonography (US) and palpation. RESULTS: Seven studies met all predefined criteria. Four studies involved intraoperative US in all patients and demonstrated a significant negative correlation (-0.988) between detection rate and fraction of small metastases. These studies had a higher fraction and lower detection rate of small metastases and a lower overall detection rate. A majority (58% [145 of 252]) of metastases in the study population were smaller than 20 mm. CONCLUSION: Few articles adequately describe the standard of reference and size distribution of hepatic lesions. Hepatic metastases of colorectal cancer are frequently smaller than 20 mm. When the standard of reference is suboptimal, many small metastases are excluded from analysis, and detection rates are therefore inflated.

Carcinoma↗
PubMed1990

Pulmonary function testing reference values and interpretations in pediatric training programs.

A questionnaire was sent to all pediatric training programs to evaluate the use of pulmonary function reference standards and the interpretation of pulmonary function test results. Responses were obtained from 107 of 130 institutions, and 94 of these had pulmonary function laboratories available. Of the 94, 60 used one of three reference standards. The primary reason the reference standards were chosen was either unknown or because they came with the spirometer (24), were recommended by another person or were those used in that person's training (34), or were thought to be the best standards available or most applicable to the population to be tested (31). To define abnormality, most used an 80% predicted cutoff for forced vital capacity, forced expiratory volume in 1 second, and forced expiratory flow at 25% to 75% vital capacity. For a change in an individual through time, most used a 10% change for forced vital capacity, forced expiratory volume in 1 second, and forced expiratory flow at 25% to 75% vital capacity. Thirteen used statistical methods to define abnormal individuals and none used statistical methods to define a significant change over time. Although there are a few guidelines for reference standards and interpretations of pulmonary function tests, it appears that most laboratories are not using those guidelines and that further guidelines and education are needed.

Adolescent↗
PubMedDate not supplied

Design and implementation of a collaborative study of the mutagenicity of complex mixtures in Salmonella typhimurium.

In 1987, the International Programme on Chemical Safety (IPCS) in collaboration with the U.S. Environmental Protection Agency (U.S. EPA) and the U.S. National Institute of Standards and Technology (U.S. NIST) initiated an international collaborative study of the mutagenicity of complex environmental mixtures in the Ames Salmonella typhimurium mutation assay. The objectives of this study were: (1) to estimate the inter- and intra-laboratory variability associated with the extraction of mixtures for bioassay, (2) to estimate the inter- and intra-laboratory variability associated with the Salmonella typhimurium bioassay when applied to complex mixtures, and (3) to determine whether standard reference complex mixtures would be useful in mutagenicity studies and to evaluate whether reference or certified mutagenicity values determined from this collaborative study should be reported. The complex mixtures used in this study were selected from standard reference materials (SRMs) which had previously been issued by the U.S. NIST as SRM 1597 (coal tar), SRM 1649 (diesel particulate matter) and SRM 1650 (urban air particulate matter) with certified values for polycyclic aromatic hydrocarbons. These SRM complex mixtures are available to scientists as reference standards for analytical chemistry research and are under consideration as SRMs for mutagenicity studies of complex environmental mixtures. This paper briefly describes the final study design, protocol, selection of the complex mixtures, and implementation of this international study.

Laboratories↗
PubMed1998

Modification of the ferrozine technique to analyze iron contents in different foods: comparative study using an internal standard as reference methodology.

A methodology for the determination of iron in foods fortified with this element or in nutritional products is important and has to be sensitive and rapid. In developing countries, an inexpensive and reliable methodology is also required. For this purpose, the Gordon's Ferrozine technique was slightly modified and assayed with yogurt, dry powdered milk, and cereal mixtures, all of them fortified with iron, using an internal standard as the reference methodology. The obtained results demonstrate a close correlation between the standard curve interpolation method and the internal standard reference method (correlation coefficient r2 = 0.9950) in a wide range of concentrations. The slope (0.9998+/-0.0040) demonstrates that both procedures measure equal amounts of iron. The conclusion is that the proposed technique is a reliable, practical, and inexpensive methodology for iron determination in different foods fortified with iron.

Ferrozine↗
PubMed2006

Genomic DNA as a general cohybridization standard for ratiometric microarrays.

Feature variability on ratiometric microarrays is accommodated by simultaneous cohybridization of a labeled reference standard with a labeled experimental sample. An optimal reference standard would provide full and equal representation for all array features from a given genome so that it would function on any array, would represent all features with similar signal intensity, and would be highly reproducible-both technically and biologically-from preparation to preparation and laboratory to laboratory. A low cost and a good shelf life are also highly desirable. Finally, providing for straightforward recovery of RNA prevalence information and for integration of data across multiple, initially unrelated studies would be significant advances over current methods. For virtually all ratiometric array studies published to date the reference standard has been some kind of RNA sample assembled from a number of different cell lines, tissues, or experimental time points. These RNA references fall short of the desired universality, uniformity, and reproducibility criteria, which then affect data quality and integration across studies. Also, the various mixed RNA standards cannot be used to derive RNA prevalence information from an experimental sample. In contrast, genomic DNA is a natural choice to meet all the criteria, although it has not yet been widely exploited for eukaryotic array experiments. Principal stumbling blocks have been achieving high enough absolute signals for large mammalian and plant genomes and finding a way to stabilize labeled DNA so that it can be stored and used with ease. This chapter describes two genomic DNA-labeling methods that make it possible to use genomic DNA as a universal microarray cohybridization standard. The indirect labeling method permits production of a large quantity of a stable genomic DNA standard that can then be quality tested and stored frozen. This optimizes experimental consistency and significantly improves ease of use. This chapter also shows that the genomic DNA reference standard can deliver RNA prevalence measurements from ratiometric array platforms.

Animals↗
PubMed1989

Identification of intrauterine growth retardation among low birth weight preterm infants.

This study describes an attempt to define intrauterine growth retardation low birth weight preterm infants by comparing reference standards for intrauterine growth in weight, length, and head circumference on their variability across ethnic groups and cities, and on their specificity in independently classifying infants as short, thin, or having small heads. The sample consisted of 985 inborn preterm low birth weight infants enrolled at eight participating sites in a randomized clinical trial using uniform sampling criteria. When gestational age was used as the reference standard, striking differences were found by ethnicity and site in the prevalence of low weight infants at birth. These differences, as well as the potentially false overlap of classification, were attenuated when the use of gestational age as a reference standard was used only for birth length, while length itself was used (as an alternative to gestational age) as the reference standard for birth weight, and weight was used as the reference standard for head circumference. These results raise questions about the use of gestational age as the primary or only reference standard in assessing weight and head circumference at bith.

Black or African American↗