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At least 1,711 records · Page 95Linked to original sources
PubMed1996

Consensus of a group of professional societies and diagnostic companies on guidelines for interim reference ranges for 14 proteins in serum based on the standardization against the IFCC/BCR/CAP Reference Material (CRM 470). International Federation of Clinical Chemistry. Community Bureau of Reference of the Commission of the European Communities. College of American Pathologists.

The release in 1993 of a new reference material for serum proteins, CRM 470/RPPHS 5 has given rise to a great improvement in the between-laboratory variability of serum protein measurements worldwide. Conversion to the new reference material results in significant changes in reference values for some proteins. The establishment of new reference ranges will take a considerable time, and in the interim several professional societies and diagnostic companies have agreed to use consensus reference ranges based on studies already undertaken.

Blood Proteins↗
PubMed1989

A growth velocity standard for Chinese children in Hong Kong.

Racial differences in the size of children make it questionable that a widely used Caucasian velocity reference standard can be used for Chinese children. In the present study, the growth velocity in 935 healthy Chinese children aged 4-6 was examined, showing that height velocity was significantly lower than Tanner's references. With the Caucasian velocity standard, Chinese children might be misinterpreted as growing abnormally slowly. In order to detect growth and endocrine disorders of childhood and adolescence, a Chinese growth velocity standard for children of 0 to 18 years must be established.

Asian People↗
PubMed1996

Pattern of growth in children with cerebral palsy.

OBJECTIVE: To provide a growth reference standard for children with quadriplegic cerebral palsy (QCP). Growth references specific to children with cerebral palsy would facilitate uniformity in clinical appraisal of their growth and nutritional status and would simplify comparative interpretation of growth data. DESIGN: Weights and lengths were obtained according to standardized procedures. Measurements were taken at time of visit to an orthopedic clinic and from retrospective review of charts. SUBJECTS: Three hundred sixty children with QCP. Growth data were based on 1,630 observations. ANALYSIS: Growth curves representing the 10th, 50th, and 90th percentiles were estimated using a smoothing splines technique. Statistical bootstrapping was performed to confirm significant differences from the growth charts of the National Center for Health Statistics (NCHS). RESULTS: Growth charts were constructed for boys and girls, aged 0 to 120 months, depicting length for age, weight for age, and weight for length. Average differences in length for age, weight for age, and weight for length between children with QCP and NCHS standards were -2.3 z, -2.4 z, -1.3 z for boys, and -2.1 z, -2.1 z, -1.1 z for girls. Children with QCP fell progressively behind in stature and weight. Compared with their NCHS counterparts, they were 5% shorter at 2 years of age and more than 10% shorter at 8 years of age. APPLICATION: Charts representing the pattern of growth in children with QCP should be accessible to parents and health care professionals to facilitate evaluation and monitoring of nutritional status.

Anthropometry↗
PubMed1968

Standardization of submaximal exercise tests.

It is often impossible to measure the reference standard of cardiorespiratory fitness (the maximum oxygen intake) directly, and there is thus a need for subsidiary standard procedures based on body responses to submaximal exercise. In order to reach agreement on such procedures, a recent international working party has compared a variety of possible tests involving step, bicycle, and treadmill exercise; criteria of comparison included the extent of habituation and learning with each procedure, the physiological responses, and practical considerations. There was little to commend submaximal exercise on the treadmill. Anxiety and learning were least on the bicycle ergometer, but significant anaerobic metabolism developed at loads of more than 55% of aerobic power; the main role of the bicycle was thus in laboratory tests requiring arm immobilization. The step test was cheap and portable, subjects showed relatively little anxiety or learning, and good-quality electrocardiograms were obtained: it thus seemed the procedure of choice for field tests. The results of all forms of submaximal test should be extrapolated to maximum oxygen intake in order to overcome difficulties arising from differences in the age and fitness of subjects. Four common extrapolation procedures, based respectively on one to four measurements of oxygen consumption and pulse rate, yielded similar predictions of maximum oxygen intake. A single progressive test, in which the exercise load was increased at the end of every third minute, gave an identical prediction of maximum oxygen intake to that obtained from a series of 4 discontinuous tests. The progressive test was thus the preferred procedure; however, in subjects with some circulatory delay, it might be necessary to replace the four 3-min loads by three 4-min loads.

Adult↗
PubMed1993

Quantitation of c-myc gene amplification by a competitive PCR assay system.

Gene amplification is a common event in the progression of human cancers. The detection and quantitation of certain amplified oncogenes has been shown to have prognostic importance in certain human malignancies. A method is described that utilizes the principles of competitive PCR for quantitation of the c-myc gene copy number in relation to the copy number of a reference gene (tissue plasminogen activator [t-PA] gene) located on the same chromosome (8) as the c-myc gene. This ratio gives the true level of amplification of the c-myc gene, accounting for variables such as cell number, cell cycle phase, and chromosome 8 ploidy. The determination of gene amplification depends on the precise measurement of the ratio of target and reference genes. An important feature of this assay is that the competitive reference standards used for target gene c-myc and reference gene t-PA have been linked to form a hybrid. This simple modification guarantees that both reference gene and target gene assay tubes get identical amounts of the competitive template for each gene, thereby eliminating a significant source of error. This method has the same desirable attributes of standard PCR in that very small sample sizes are required and that results can easily be obtained in < 24 hr. In addition, this technique does not require the use of radioactivity or expensive DNA detection kits, and thus, may give it wider applicability for the study of human cancers.

Base Sequence↗
PubMed1995

Evanescent fluorobiosensor for the detection of polyaromatic hydrocarbon based on DNA intercalation.

A flow-injection analysis (FIA) system coupled with an evanescent wave (EW) biosensor employing total internal reflection of fluorescence radiation (TIRF) for the detection of polyaromatic hydrocarbon that intercalates into DNA is reported. A highly fluorescent intercalator, "ethidium bromide," has been used as the reference compound for detection. The EW biosensor was developed according to the procedure described earlier (1,2). Data on the analysis of Naphthalene, 3-methylcholanthrene, 7,12-dimethylbenz(a)anthracene, 1,2-benzanthracene, and some standard reference materials supplied by the National Institute of Standards and Technology are reported. The relative ability of the polyaromatic hydrocarbon to displace ethidium bromide, based on the relative binding ratio, is found to be on the order of 7,12-dimethylbenz[a]anthracene > 3-methylcholanthrene > 1,2-benzanthracene > napthalene.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2001

Using multiples of the median to normalize serum protein measurements.

Quantification of serum proteins is useful in the diagnosis and clinical management of many disorders. With the introduction of automated analyzers and standardized reference materials, one of the last barriers to more widespread utilization of these measurements is the lack of availability of reliable and transferable age- and gender-specific reference ranges. One normalization method that deserves consideration is converting values to multiples of the median (MoM) for age and gender. When two analytic methods agree, or differ only by a proportional amount, conversion to MoM can be used to simplify the clinical interpretation of serum protein results. As a test of this method, assay results for IgG, transferrin, and albumin from three Swedish hospitals were normalized using published reference ranges from the United States. All assays were standardized to CRM 470. IgG results were in agreement in mass units, and transferrin measurements were proportionally different. However, there were important, non-proportional differences in albumin measurements. After converting IgG and transferrin measurements to MoM, published reference ranges were appropriate for the Swedish Hospitals.

Blood Proteins↗
PubMed2000

Estimating food and nutrient intake from food frequency questionnaire data by reference to a standard weighed diet survey.

INTRODUCTION: The food frequency questionnaire is widely regarded as more appropriate for ranking and grouping individuals according to levels of nutrient intake than for estimating absolute nutrient amounts. AIMS: To develop a method for estimation of amount of nutrient intake from food frequency questionnaires by reference to an independent weighed dietary survey. METHOD: Six stages of the method are described and illustrated in the estimation of total dietary fat from the 1984-85 Health and Lifestyle Survey using the 1986-87 Dietary and Nutritional Survey of British Adults as the reference standard. RESULTS: Several points support the validity of the approach although limitations are identified.

Journal Article↗
PubMedDate not supplied

Salmonella mutagenicity of three complex mixtures assayed with the microsuspension technique. A WHO/IPCS/CSCM study.

In a collaborative study on complex mixtures, three complex mixtures and two pure compounds were assayed with the Salmonella microsuspension technique. The two pure compounds were benzo[a]pyrene (BaP) and 1-nitropyrene (1-NP). The three complex mixtures were standard reference materials (SRMs) from the U.S. National Institute of Standards and Technology, SRM 1649, SRM 1650 and SRM 1597. The two samples SRM 1649, an urban dust particulate matter, and SRM 1650, a diesel particulate matter, were sonicated with dichloromethane. Sample SRM 1597 was an extract of a coal tar sample with a complex mixture of polycyclic aromatic hydrocarbons. The microsuspension assay was performed with Salmonella strains TA98 and TA100 according to Kado et al. (1983) with minor modifications (Löfroth et al., 1988). The results showed that the microsuspension technique is a more sensitive assay than the plate incorporation method. Depending on sample, strain and metabolic condition the mutagenic responses were 3-37 times higher in the microsuspension assay than in the conventional plate incorporation assay. The microsuspension method is thus useful for environmental samples which are often available in only small amounts.

Air Pollutants↗
PubMed1995

Cervical cell recognition and morphometric grading by image analysis.

Cervical cell recognition by morphometric image analysis was compared to human visual cell recognition on the same 6,375 cells from 40 dysplastic, CIS, invasive, and 10 normal pap smears. The experimental approach defined receiver operating characteristic (ROC) curves for morphometric image analysis which could be rigorously compared to previously established human visual cell recognition ROCs on the same cells. Overall performance was measured Az, the area under the ROC curves in the two instances. For morphometric image analysis cell recognition, Az = 0.91, and for human visual cell recognition, Az = 0.87. These results clearly demonstrated that morphometric image analysis is equivalent to experienced human observers in ability to recognize isolated cells from cervical smears. An approach was also developed to link the ROC analytic methods of this study to a cytopathological or histopathological grading system, or "scale", that could be expressed in terms of normal deviate units of morphometric descriptors. This approach has the advantage of describing the grading scale in terms of its ROC characteristics; in essence, it describes performance for that grading scale at any decision point along the scale, if used for two-category classification. Additionally, This concept provides for a uniform final scale, regardless of which cells or tissues are graded. Also, this type of grading scale would automatically adjust itself for measurement variance for different types of cells or tissue, by reference to normal cells or tissues, so that a standard reference could be maintained.

Carcinoma in Situ↗
PubMed1993

Computerized assessment of verbal skill.

This paper describes a computerized diagnostic test for the assessment of basic literacy skills in Dutch. Central in this test is a skill labeled word image, referring to the subject's implicit knowledge of orthographic structure. Test norms were obtained in a group of reference subjects. The most notable trend found in the standardization study was that the development of word image performance showed a nonlinear, U-shaped trend. Two case studies are reported. A supplementary validation study, based on test data collected from standard reference groups of normal and poor readers, demonstrated that word image performance is significantly related to between-group differences.

Child↗
PubMed2006

Diagnosis-dependent misclassification of infections using administrative data variably affected incidence and mortality estimates in ICU patients.

OBJECTIVE: To determine the accuracy of hospital discharge diagnoses in identifying severe infections among intensive care unit (ICU) patients, and estimate the impact of misclassification on incidence and 1-year mortality. STUDY DESIGN AND SETTING: Sepsis, pneumonia, and central nervous system (CNS) infections among 7,615 ICU admissions were identified using ICD-9 and ICD-10 diagnoses from the Swedish hospital discharge register (HDR). Sensitivity, specificity, and likelihood ratios were calculated using ICU database diagnoses as reference standard, with inclusion in sepsis trials (IST) as secondary reference for sepsis. RESULTS: CNS infections were accurately captured (sensitivity 95.4% [confidence interval (CI)=86.8-100] and specificity 99.6% [CI=99.4-99.8]). Community-acquired sepsis (sensitivity 51.1% [CI=41.0-61.2] and specificity 99.4% [CI=99.2-99.6]) and primary pneumonia (sensitivity 38.2% [CI=31.2-45.2] and specificity 98.6% [CI=98.2-99.0]) were more accurately detected than sepsis and pneumonia in general. One-year mortality was accurately estimated for primary pneumonia but underestimated for community-acquired sepsis. However, there were only small differences in sensitivity and specificity between HDR and ICU data in the ability to identify IST. ICD-9 appeared more accurate for sepsis, whereas ICD-10 was more accurate for pneumonia. CONCLUSION: Accuracy of hospital discharge diagnoses varied depending on diagnosis and case definition. The pattern of misclassification makes estimates of relative risk more accurate than estimates of absolute risk.

Cause of Death↗
PubMed1994

Factors limiting large-scale localisation.

The mechanisms mediating relative spatial localisation in the visual system are still unclear. There is a growing amount of evidence that this capability is not merely limited by the processing of the front-end visual system. Models of localisation should, therefore, include higher-level processing stages. A careful study of the sources of error in localisation tasks may further our understanding of the nature of these processes. A study is reported in which the possible role of higher-order processing in relative spatial localisation is explicitly addressed. For this purpose the error sources of threshold performance were investigated for two similar relative-spatial-localisation tasks: two-dot separation discrimination and two-dot orientation discrimination. Fovea-centered stimuli with large dot separations were used. The front-end processing for these stimuli is probably identical in both tasks. Hence, differential effects of the variation of the experimental parameters on threshold performance for both tasks may reveal the characteristics of the higher-level processing involved. The effects of dot separation, stimulus orientation, and experimental procedure (single-stimulus binary forced choice versus two-alternative forced choice) on threshold performance for both tasks are reported. The results show that thresholds for both tasks increase proportionally with dot separation. However, separation-discrimination thresholds are always significantly higher than orientation-discrimination thresholds. Thresholds for separation discrimination are independent of stimulus orientation. In contrast, orientation-discrimination thresholds show an oblique effect: thresholds are consistently lower for horizontal stimuli. Both tasks also show a different dependency of threshold behaviour on the experimental procedure. For a horizontal stimulus orientation, separation discrimination is better with an explicit (physical) reference standard, whereas orientation discrimination is better with an implicit referent. These differential effects cannot be explained by any of the known characteristics of the front-end visual system. They suggest that large-scale spatial-localisation performance is probably limited at a processing level at which spatial relations are explicitly represented.

Adult↗
PubMed1997

Predicting realistic RBE values for clinically relevant radiotherapy schedules.

To consider the therapeutic potential of radiation effect modifiers it is necessary to balance the modification of the injury in tumours with that in different types of normal tissue. It is especially important to ensure that the effects that have been demonstrated in preclinical experiments are both qualitatively and quantitatively relevant for the radiation doses that will be used in clinical schedules. Most radiobiology studies are initially performed with large single doses or a few large fractions, and from those results predictions have sometimes been made of the potential clinical benefit from a radiation modifier. In the clinic they will be used with many repeated small fractions of about 2 Gy over a period of several weeks. The effects will be quantitatively different in these two dose ranges for a variety of reasons. No modifiers of radiation effect are truly dose-modifying over the whole dose spectrum. They all have a differential effect on the type of damage inflicted at high and low dose levels, i.e. those described by the linear and quadratic terms in the LQ model. This means that every modifier has a dose or dose per fraction dependence on the magnitude of the sensitization or protection. The details of that dose dependence will vary with the alpha/beta ratio of the tissue under consideration. Furthermore all tissues and tumours contain a mixture of cells, with different proliferative, redox and other characteristics that influence their sensitivity to radiation and their susceptibility to the radiomodifier. The influence of different subsets of cells changes as a fractionated treatment progresses and the sensitive cells are eradicated, leaving more resistant survivors. The overall response to a fractionated schedule then depends critically on whether there is re-assortment of cells from the resistant phase into more sensitive or modifiable phases before the next fraction in the series. In addition, the magnitude of dose modification depends totally on the standard curve against which the comparison is made. The reference standard is different in preclinical laboratory studies and in conventional clinical experience. Those differences must be considered when moving from the laboratory to the clinic and back again. The effect of these different factors is considered using the linear quadratic model to dissect the components. Examples are provided to demonstrate the clinical relevance.

Animals↗
PubMed1985

Correlation between bioassay and radioimmunoassay for erythropoietin in human serum and urine concentrates.

Both immunoreactive erythropoietin (Ep) and biologically active Ep were measured in 23 samples of human serum and 21 concentrates of human urine. Immunoreactive Ep was measured by radioimmunoassay (RIA). Biological activity was determined in the plethoric mouse bioassay in which 59Fe incorporation was converted to units of Ep from standard reference curves. Low values for Ep were determined from standard curves plotted as probits to improve sensitivity for levels of Ep as low as 30 mU/ml. Ep levels in 35 samples ranged between 30 and 1000 mU/ml by both assays; in 9 samples Ep was 15.2-37.5 mU/ml by RIA but was not detectable by bioassay. Analysis of the data for the 35 samples in which Ep could be measured by both assays showed a strong correlation between the values obtained by the two assays. These results indicate that the RIA used in these experiments detects biologically active Ep in human serum and urine when it is present in amounts only moderately higher than normal. The ultrafiltration method used for preparation of urine samples was effective in concentrating Ep in some urines, but the results were too erratic and nonquantitative to permit its use as a method for quantifying human urinary Ep excretion.

Biological Assay↗
PubMed2005

A micellar electrokinetic capillary chromatography method for monitoring mycophenolic acid in serum of transplant recipients.

Mycophenolic acid (MPA), the active metabolite of the immunosuppressive agent mycophenolate mofetil (MMF), was for the first time quantified in the serum of transplant recipients using micellar electrokinetic capillary chromatography (MEKC). Sample preparation was carried out with solid phase extraction (SPE) using octadecyl-modified endcapped silica (C18 EC) as sorbent. Extremely varying recovery rates in preliminary experiments showed both the importance of pH monitoring during the single SPE steps and the necessity of an internal standard. MPA carboxy butyl ether (CBE), a specifically developed reference standard, was employed. Furthermore, optimisation of the MEKC parameters detection wavelength and injection time was of primary importance in order to enable the quantitation of therapeutic trough serum levels of MPA in the range lower than 5 microg x mL(-1). Under optimised conditions, a limit of quantitation of 1.0 microg x mL(-1) was achieved allowing the determination of MPA in the serum of patients.

Algorithms↗
PubMedDate not supplied

Flame atomic absorption spectrometric determination of serum zinc: collaborative study.

A method for determining serum zinc concentrations was collaboratively studied by 9 laboratories. Serum samples in polypropylene tubes are directly diluted with 0.03% Brij 35, and zinc is determined by flame atomic absorption spectrophotometry (AAS). A certified standard reference material serves as an external control. Repeatability relative standard deviations (RSDr) were 1.2 and 11.4% and reproducibility relative standard deviations (RSDR) were 6.1 and 12.9% for serum zinc concentrations of 6.36 and 0.63 micrograms/mL, respectively. The method has been approved interim official first action by AOAC.

Humans↗
PubMed1980

[Development of a radioimmunoassay for thyrotropin (TSH) in dried blood spots together with a comparison of 7 commercial kits (author's transl)].

The blood-spot thyrotropin RIA for detection of congenital hypothyroidism has been established as a screening programme. This article describes the problems in hand, namely optimisation of the method and a comparison of the performance in 7 commercial kits on the West German market. The following factors have been investigated: a. Shelf-life of standards and samples b. Effect of filter paper quality and weight c. Size of paper disc d. Blood sampling time e. Time of removal of paper disc f. Effect on the results of washing the precipitate. The commercial kits at present on the market differ widely in method and price. Apart from this, there was no agreement between the results obtained, and the difference between the standard concentration given by the firm compared with the reference standard MRC 68/38 varied from 22--185%. Methodological guidelines and quality control measures, both internal and external, are suggested.

Blood Specimen Collection↗