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PubMed1990

Construction of growth reference standards for urban slum children in developing countries.

A cross-sectional sample of 2987 children in the age group of 1 to 10 years were selected from urban slums of Delhi for measurement of weight and height. Males and females were 53 and 47% respectively. Mean weight and height were calculated for both the sexes. Comparison of percentiles of weight and height with NCHS and ICMR standards showed that the 75th percentiles weight and height of the present study were comparable with 80 and 90% of 50th percentile of NCHS respectively. Hence, upper 25% of the sample arranged in ascending order of magnitude were used for the construction of reference standards of weight and height. Comparison of percentiles drawn from the top 25% of the sample demonstrated that 50th percentile of the present study corresponded to 80% of 50th percentile of the NCHS for weight and 90% of 50th percentile of NCHS of the height for both boys and girls. Also the 50th percentile of ICMR for weight and height for both the sexes. Standards constructed from such sample would be better suited for two important uses: (i) monitoring of Nutrition Programme, and (ii) to detect a child with abnormal growth at the earliest.

Body Height↗
PubMed2003

Certification of standard reference material 970, ascorbic acid in serum, and analysis of associated interlaboratory bias in the measurement process.

BACKGROUND: The accurate and reproducible measurement of ascorbic acid is essential in delineating the role of ascorbic acid as a diagnostic tool for human disease and for the comparison of data acquired by different laboratories. A stabilized pair of standards of ascorbic acid in human serum, which is compatible with most analytical methods, have been prepared. METHODS: The certification was based on the gravimetric addition of ascorbic acid to metaphosphoric acid-stabilized, ascorbic acid-depleted serum and NIST liquid chromatography-electrochemical measurements. The NIST results were analyzed statistically for homogeneity, and the expanded uncertainty of each SRM was calculated using all of the NIST data. An interlaboratory comparison exercise was also performed. RESULTS: These materials, Standard Reference Material (SRM) 970 Ascorbic Acid in Serum, Level I and Level II, are homogeneous and are certified to contain (10.07 +/- 0.21) and (30.57 +/- 0.28) mmol ascorbic acid/L of solution (expanded uncertainty), respectively. In the interlaboratory comparison (n = 17), the relative SDs for the two materials were 22% and 19%. CONCLUSIONS: Two lots of serum, each containing different amounts of ascorbic acid stabilized in metaphosphoric acid, have been prepared and characterized. Many laboratories provide inaccurate results.

Ascorbic Acid↗
PubMed2005

Japanese standard reference material for JDS Lot 2 haemoglobin A1c. I: Comparison of Japan Diabetes Society-assigned values to those obtained by the Japanese and USA domestic standardization programmes and by the International Federation of Clinical Chemistry reference laboratories.

BACKGROUND: The Committee on Standardization of Laboratory Testing Related to Diabetes Mellitus of the Japan Diabetes Society (JDS) previously recommended use of the primary calibrator (JDS Lot 1) prepared by the former Committee for Standardization of Glycohemoglobin for standardizing the measurement of haemoglobin A1c (HbA1c). Owing to the depletion of vials of Lot 1 in March 2001, the present committee certified a new reference material, Lot 2, now distributed by the Health Care Technology Foundation (HECTEF). The standardization programme for HbA1c measurement in Japan is currently based on Lot 2, which has values assigned from within Lot 1; the Lot 1 values were consensus values based on assays by laboratories in the Japanese national quality control programme. In this study, for the purpose of international comparison and standardization, Lot 2 was assayed by the JDS reference laboratories, the National Glycoprotein Standardization Program (NGSP) in the USA, and by reference laboratories approved by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). METHOD: The HbA1c values of JDS Lot 2 were transferred from those assigned to Lot 1 using KO500, a high-resolution HPLC method, at three laboratories approved by the JDS committee. Subsequently, vials of JDS Lot 2 were shipped to and assayed by the NGSP in the USA and 10 IFCC reference laboratories. RESULT: The JDS-assigned HbA1c values (from Lot 1) are 4.04 for Level 1, 5.38 for Level 2, 7.32 for Level 3, 9.88 for Level 4, and 12.63 for Level 5, all expressed as a percentage of total haemoglobin. The values obtained by NGSP and the IFCC laboratories gave the following formulas: NGSP value(%)=JDS value(%)+0.3%; IFCC value(%)=1.068xJDS value(%)-1.741%. CONCLUSION: Although the values obtained by the IFCC laboratories are significantly lower than the values assigned to Lot 2 by the JDS, the relationship is linear. In addition, standardization of HbA1c based on JDS Lot 2 is currently at a satisfactory level in Japan. As a result, the reassignment of values for Lot 2 to agree with the IFCC values should be relatively easy and will be done after all relevant parties agree to the change.

Blood Chemical Analysis↗
PubMed2006

Microheterogeneity evaluation of polycyclic aromatic hydrocarbons in particulate standard reference materials.

With the emergence of highly sensitive analytical techniques, the microanalysis of natural-matrix materials employing smaller sample sizes is increasingly more common, which subsequently warrants a homogeneity assessment for the individual components at the appropriate sampling level. Pressurized liquid extraction (PLE) in combination with gas chromatography/mass spectrometry (GC/MS) has been used to determine the sampling constants and evaluate the relative homogeneity of trace levels of polycyclic aromatic hydrocarbons (PAHs) for two previously certified particulate standard reference materials, SRM 1649a Urban Dust and SRM 1650b Diesel Particulate Matter, in the milligram sampling range. Fluoranthene, pyrene, benz[a]anthracene and benzo[e]pyrene within SRM 1650b Diesel Particulate Matter were deemed to be homogeneous, based on relatively small sampling constants (K (S)<100 mg), whereas the larger sampling constants (K (S)>100 mg) obtained for all PAHs in SRM 1649a Urban Dust suggest more material heterogeneity. The material heterogeneity of ten individual PAHs (phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene) was also described via nonlinear relationships (i.e., power law) between subsampling error S (s) (%) and sample mass, which are used to predict analyte-specific minimum sample masses that result in a specific level of analytical uncertainty.

Journal Article↗
PubMed2006

Bone ALP and OC reference standards in adult baboons (Papio hamadryas) by sex and age.

BACKGROUND: Serum bone-specific alkaline phosphatase (bone ALP) and intact osteocalcin (OC) are markers of bone formation of interest because of easy measurability and potential utility as identifiers of those at risk for fractures associated with bone metabolism disorders. The baboon (Papio hamadryas) exhibits extensive biological similarities to humans making it particularly well suited to studies of bone maintenance and turnover. METHODS: We measured serum bone ALP and OC in 591 baboons. RESULTS: We report significant sex and age effects and present reference ranges and percentile distributions for these markers. CONCLUSIONS: This study is the first to characterize normal variation in bone ALP and OC levels in baboons and to assess the age and sex effects on this variation. The results provide much-needed reference standards to allow researchers to evaluate the status of their animals in cross-sectional studies and assess the meaning of changes in bone ALP and OC levels in longitudinal studies.

Age Factors↗
PubMed1994

Review of the problems involved in using enzymes in blood group serology--provision of freeze-dried ICSH/ISBT protease enzyme and anti-D reference standards. International Council for Standardization in Haematology. International Society of Blood Transfusion.

Proteolytic enzyme preparations and techniques used routinely in blood group serology for the detection of atypical patient antibodies prior to transfusion vary widely and are often poorly standardised. Recent advances have been made in the use of biochemical methods to standardise and stabilise the potency of the enzyme preparations used. A joint working party of the International Council for Standardization in Haematology (ICSH) and the International Society of Blood Transfusion (ISBT) has investigated possibilities for the provision of standards for the protease preparations and techniques. The specification for these standards was that the performance of enzyme reference preparation in the reference technique should be of equivalent sensitivity to the ICSH/ISBT LISS spin indirect antiglobulin test using a titration series of a reference weak anti-D, and be free from false-positive reactions. The working party circulated materials for evaluation in inter-laboratory trials, followed by a laboratory workshop meeting to achieve agreement on the specification for reference materials and methods. Reference freeze-dried papain at 0.6 azoalbumin units and weak anti-D preparations (91/562) have been prepared and validated to meet these specifications. The performance of a test enzyme preparation in the technique for which it is recommended for use should be at least equal to that of the reference papain preparation, by the reference two-stage technique in terms of sensitivity, using a titration series of the reference anti-D, and freedom from false-positive reactions, using six fresh inert sera. The reference papain and weak anti-D can also be used to calibrate the level of proteolytic activity required in other procedures in blood group serology, such as new technology methods for antibody detection, and automated and microplate cell grouping procedures. These preparations and an agreed method for their use are now available from listed centres as ICSH/ISBT and Food and Drug Administration reference materials.

Blood Grouping and Crossmatching↗
PubMed2003

Definition of a population-specific DXA reference standard in Italian women: the Densitometric Italian Normative Study (DINS).

Osteoporosis is currently defined on the basis of the T-score by dual-energy X-ray absorptiometry (DXA). Despite its limitations, this definition is applied worldwide. However, the normal values provided by manufacturers may not be fully representative of specific local populations. So far, there are no normative data in the Italian population using Hologic densitometers. The Densitometric Italian Normative Study (DINS) is an ongoing multi-center study that aims to establish reference values for bone densitometry with dual-energy X-ray absorptiometry (DXA) in the male and female Italian population. In this paper we report the results of the lumbar vertebrae (L2-L4) and proximal femur in 1,622 women aged 20-79 years. Bone mineral density (BMD) was determined using dual-energy X-ray absorptiometry (DXA) on Hologic bone densitometers (Hologic, Waltham, Mass.). Most of the subjects were examined with a QDR 4500. The BMD of the lumbar vertebrae was virtually constant between 20 and 49 years (test for trend: P=0.66); the BMD values between 20-45 in premenopausal women (mean 1.036; SD 0.109 g/cm(2)) were thus defined as the peak bone mass values, significantly lower compared to the Hologic reference curve (mean 1.079, SD 0.11 g/cm(2)). The mean BMD values of the femoral neck were virtually identical to those of the NHANES study in the first 3 decades; after the age of 50 the BMD values were slightly greater than those of the NHANES subject. The subject classification according to the WHO criteria was similar using the DINS and NHANES reference values for the femur; for the spine, the Hologic reference values classified a larger proportion of women as osteoporotic (21 vs. 16%) or osteopenic (42 vs. 38%) compared to DINS.

Absorptiometry, Photon↗
PubMed2002

Comparison of gravimetry and hydrolysis/derivatization/gas chromatography-mass spectrometry for quantitative analysis of fat from standard reference infant formula powder using supercritical fluid extraction.

This paper describes a comparative study of the gravimetric versus hydrolysis/derivatization/gas chromatography-mass spectrometry determination of fat in infant formula. Fat was extracted using supercritical carbon dioxide modified with a small amount of ethanol, the extract was weighed, and the total fat was determined gravimetrically. Subsequently, another sample of the supercritical fluid fat extract was hydrolyzed to yield free fatty acids, which were converted to their methyl ester derivatives (FAMEs). Quantification was performed by GC-MS. NIST Standard Reference Material (SRM-1846) was used to validate both fat determination methods. Results showed that the gravimetric average percent fat was 26.86%, whereas the GC-MS method yielded 24.64%. Some peaks were detected in the ion chromatogram from the GC-MS that were identified as nonfatty acids such as aldehydes, which may account for the higher percentage fat measured as weight of extract rather than measured as FAMEs expressed as triglycerides.

Carbon Dioxide↗
PubMed2003

Solid phase speciation of arsenic by sequential extraction in standard reference materials and industrially contaminated soil samples.

Availability, mobility, (phyto)toxicity and potential risk of contaminants is strongly affected by the manner of appearance of elements, the so-called speciation. Operational fractionation methods like sequential extractions have been applied for a long time to determine the solid phase speciation of heavy metals since direct determination of specific chemical compounds can not always be easily achieved. The three-step sequential extraction scheme recommended by the BCR and two extraction schemes based on the phosphorus-like protocol proposed by Manful (1992, Occurrence and Ecochemical Behaviours of Arsenic in a Goldsmelter Impacted Area in Ghana, PhD dissertation, at the RUG) were applied to four standard reference materials (SRM) and to a batch of samples from industrially contaminated sites, heavily contaminated with arsenic and heavy metals. The SRM 2710 (Montana soil) was found to be the most useful reference material for metal (Mn, Cu, Zn, As, Cd and Pb) fractionation using the BCR sequential extraction procedure. Two sequential extraction schemes were developed and compared for arsenic with the aim to establish a better fractionation and recovery rate than the BCR-scheme for this element in the SRM samples. The major part of arsenic was released from the heavily contaminated samples after NaOH-extraction. Inferior extraction variability and recovery in the heavily contaminated samples compared to SRMs could be mainly contributed to subsample heterogeneity.

Arsenic↗
PubMed1996

Studies on the role of urinary macromolecules in urolithiasis: review of methodologies and a proposal for a standard reference crystallization system.

In this study, urine from a calcium oxalate kidney stone former was ultrafiltered (10 kD cut-off). Crystallization was induced in the ultrafiltrate and retentate fractions as well as in a sample of the whole urine. The progress of crystallization was monitored by Coulter Counter and flow cytometry techniques. (The latter has not been used in studies of the role of urinary macromolecules in urolithiasis). Deposited crystals were examined by scanning electron microscopy. Results indicated that urinary macromolecules in this subject are inhibitors of nucleation and aggregation. These results agree with the findings of some workers but disagree with those of others. Indeed, studies on the role played by urinary macromolecules in promoting or inhibiting urolithiasis have failed to produce consistent findings. Examination of the literature reveals that a wide variety of experimental techniques and crystallization systems have been used in these studies and that this might be the cause of the inconsistencies. Based on reported experiences and those of the present study, a standard reference crystallization system is proposed. The key elements of this system involve the use of real urine, ultrafiltration, continuous crystallizer equipment, Coulter Counter procedures and scanning electron microscopy.

Animals↗
PubMed2002

Impedance vector distribution by sex, race, body mass index, and age in the United States: standard reference intervals as bivariate Z scores.

Bioelectrical impedance measurements were collected in the Third National Health and Nutrition Examination Survey (NHANES III), but their results have not been published. In the NHANES III population, resistance (R) and reactance (Xc) values at 50-kHz frequency were obtained with a Valhalla Scientific meter (model 1990B; San Diego, CA, USA). The RXc graph method was used to identify bivariate pattern distributions of mean vectors (95% confidence ellipses by sex, race, age, and body mass index [BMI]), and individual impedance vectors (50%, 75%, and 95% tolerance ellipses). Data from 10 222 adults (5261 men and 4961 women) formed 90 four-way classification groups, with two sexes, three races or ethnicities (non-Hispanic white, non-Hispanic black, Mexican American), five age classes (20-29, 30-39, 40-49, 50-59, and 60-69 y), and three BMI classes (19-24.9, 25-29.9, and 30-34.9 kg/m(2)). Sex, race or ethnicity, BMI and age, in decreasing order, influenced the vector distribution pattern. Mean vectors in women were significantly longer than those in men. Within each sex, the mean vector of non-Hispanic white subjects was shorter and with a smaller phase angle than that of corresponding BMIs from the two other race/ethnic populations. Tolerance ellipses were calculated from sex- and race-specific reference populations 20 to 69 y old and 19 < or = BMI < 30 kg/m(2) (8022 subjects, 4226 men and 3796 women). After transformation of impedance vector components into bivariate Z scores (standardized deviates, as differences from the mean divided by the standard deviation of the reference population), we constructed one standard, reference, RXc-score graph (50%, 75%, and 95% tolerance ellipses) that can be used with any analyzer in any population. The pattern of impedance vector distribution and reference bivariate intervals for the individual impedance vector are presented for comparative studies (free software at E-mail: apiccoli@unipd.it).

Adult↗
PubMedDate not supplied

Echo reference standards in ophthalmic ultrasonography.

The use of different echo standards in ophthalmic ultrasonography is discussed. The acoustical properties of the W38 Hema reflector made out of soft corneal contact lens material are determined and verified in several independent measurements. It is shown that this material meets the requirements for plane echo interfaces which are mandatory for reflectors considered to serve as echo standards. A conversion diagram is given for echo references presently used in ophthalmic ultrasonography. Finally, an example for an application of the W38 reflector in performance control and calibration measurements on ultrasonic instruments is presented.

Calibration↗
PubMed2004

The accuracy of digital-video retinal imaging to screen for diabetic retinopathy: an analysis of two digital-video retinal imaging systems using standard stereoscopic seven-field photography and dilated clinical examination as reference standards.

PURPOSE: To evaluate the accuracy of two digital-video retinal imaging (DVRI) systems to detect diabetic retinopathy. METHODS: A prospective, masked, technology assessment was conducted for two DVRI systems at a tertiary care Veterans Affairs Medical Center. Group A (n = 151 patients) was imaged with a 640x480 resolution system and group B (n = 103 patients) with an 800x600 resolution system. Four retinal evaluations were performed on each patient: DVRI with undilated pupils using one imaging field (U-DVRI), DVRI with dilated pupils using three imaging fields (D-DVRI), dilated clinical examination, and Early Treatment Diabetic Retinopathy Study stereoscopic seven-field photography (ETDRS-P). Two analyses of accuracy were conducted, one using ETDRS-P as a "gold standard" (ETDRS-GS) and one using dilated clinical examination as a "gold standard" (C-GS). RESULTS: For group A, using the ETDRS-GS, sensitivities of U-DVRI and D-DVRI were 0.66 and 0.66; specificities of U-DVRI and D-DVRI were 0.66 and 0.86. Using the C-GS, sensitivities of U-DVRI and D-DVRI were 0.79 and 0.80; specificities of U-DVRI and D-DVRI were 0.68 and 0.85. For group B, using the ETDRS-GS, sensitivities of U-DVRI and D-DVRI were 0.76 and 0.85; specificities of U-DVRI and D-DVRI were 0.45 and 0.80. Using the C-GS, sensitivities of U-DVRI and D-DVRI were 0.81 and 0.87; specificities of U-DVRI and D-DVRI were 0.45 and 0.69. For both groups, dilation significantly improved specificities. CONCLUSIONS: The 800x600 resolution DVRI system offers an accurate method of detecting diabetic retinopathy, provided there is adequate pupillary dilation and three retinal images are taken. DVRI technology may help facilitate retinal screenings of growing diabetic populations.

Aged↗