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Results for “Observer Variation”

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PubMed1995

Inter-examiner variation in the assessment of age-related factors in teeth.

Inter-observer variations in the registration of dental age-related characteristics have not previously been studied. Examination and registration were made by 6 dentists with varying experience in age estimation. A total of 13 age-related dental characteristics in 30 teeth extracted from adults were assessed macroscopically, by stereomicroscope and from radiographs. The measurements were analysed in a microcomputer, using the SPSS/PC+ statistical package. The results showed that, except for the score on surface roughness, significant differences were found between some of the observers for all types of measurements, when a paired t-test analysis was made. The correlation coefficients between the observers varied and were rather weak for the surface roughness score. The study revealed systematic differences among the observers as well as differences in interpreting the definitions of the scores for the different parameters. Thus age estimation using statistical methods is seen to be dependent upon the experience of the individual observer and interpretation. Care should therefore be taken not to rely too much upon the results of an odontological age estimation. The possible implications of these results for forensic work are also discussed.

Adolescent↗

PubMed2007

Fracture healing assessment comparing stiffness measurements using radiographs.

Based on published reports, we presumed radiographs would be unreliable as a sole measure of fracture healing. To confirm this presumption we correlated radiographic fracture healing assessments with fracture stiffness measurements. We showed 100 plain radiographs of fractures with corresponding fracture stiffness measurements to 92 observers. The radiographs were shown twice to assess intraobserver variation. Observers were divided into three groups and asked to determine whether each fracture had healed (union corresponded to a fracture stiffness greater than 15 nm/degrees). Group 1 based fracture healing on the general appearance of healing. Groups 2 and 3 assessed fracture healing based on the number of cortices bridged by callus. In Group 2, the fracture was considered healed if two or more cortices were bridged on both radiographic views and in Group 3 if three or more cortices were bridged by callus. All groups performed poorly. There was no difference in terms of correct prediction of healing between methods, although there was a trend toward more reliability with cortical callus bridging assessment. We found substantial intraobserver variability, which improved using cortical bridging methods. Observers were less reliable at predicting healing when there was a metaphyseal extension to a diaphyseal fracture.

Bony Callus↗

PubMed1991

Using replicate observations in observer agreement studies with binary assessments.

By introducing replicate observations into observer agreement studies, one can obtain better measures of observer agreement than heretofore possible. New methodology based on the analysis of latent variables allows a separation of within- and between-observer variation for binary measures of assessment among pairs of observers. Maximum likelihood estimation and hypothesis testing are discussed. The methodology is illustrated using data on the assessment of dysplasia by pathologists.

Biometry↗

PubMed2002

Reproducibility of evaluation of the uterus by transvaginal sonography, hysterosonographic examination, hysteroscopy and magnetic resonance imaging.

BACKGROUND: The aim was to evaluate and compare inter-observer reproducibility by magnetic resonance imaging (MRI), transvaginal ultrasonography (TVS), hysterosonographic examination (HSE) and hysteroscopy (HY). METHODS: Different observers consecutively evaluated MRI, TVS, HSE and HY independently in 51 pre-menopausal women, who underwent hysterectomy for benign diseases. RESULTS: Inter-observer agreement (kappa) was as follows: Exclusion of uterine cavity abnormalities: MRI 0.97, TVS 0.68, HSE 0.48 and HY 0.63; submucous myomas: MRI 0.97, TVS 0.59, HSE 0.60 and HY 0.67; polyps: MRI 0.49, TVS 0.48, HSE 0.35 and HY 0.50; identification of myometrial myomas: MRI 0.97, TVS 0.74; adenomyosis: MRI 0.73 and TVS 0.38. Mean difference between observers in number of observed myomas was (absolute values) MRI 0.58, TVS 0.93. Agreement on evaluation of abnormalities in the uterine cavity, submucous myomas, number of myomas and adenomyosis was significantly greater by MRI than by any of the other techniques, whereas agreement was in line by TVS, HSE and HY. CONCLUSIONS: Inter-observer disagreement reached substantial levels only for exclusion of uterine cavity benign abnormalities by HY, TVS and HSE. Strategies should be adopted to reduce observer variation of common gynaecological imaging techniques or the less observer-dependent MRI technique could be favoured.

Adult↗

PubMed1993

A computerized technique for vertebral morphometry.

A new technique for morphometric measurement of vertebral bodies has been described, in which a computerized image analysis system was used to digitize and measure standardized lateral radiographs of the thoracic and lumbar spine. The sources of error in the radiographic system and the image analysis system were assessed using vertebral phantoms and test images. Oblique projection in the radiographic image of a vertebra did not produce a significant error in the measured area. The radiographic magnification was approximately 35%. Optical non-uniformity was detected in the image analysis system, and was ascribed to the lens optics. The maximum intra-observer and inter-observer variations in vertebral area were 3.1% and 5.3% respectively for experienced observers. The technique is applicable to clinical studies of large populations, and has value in investigating vertebral deformity in the management of metabolic bone disease.

Female↗

PubMed2001

A biophysical analysis of stem and root diameter variations in woody plants.

A comprehensive model of stem and root diameter variation was developed. The stem (or root) was represented using two coaxial cylinders corresponding with the mature xylem and the extensible tissues. The extensible tissues were assumed to behave as a single cell separated from the mature xylem by a virtual membrane. The mature xylem and the extensible tissues are able to dilate with temperature and grow. Moreover, the extensible tissues are able to shrink and swell according to water flow intensity. The model is mainly based on the calculation of water volume flows in the "single cell" that are described using the principles of irreversible thermodynamics. The elastic response to storage volume and plastic extension accompanying growth are described. The model simulates diameter variation due to temperature, solute accumulation, and xylem, water potential. The model was applied to the peach (Prunus persica) stem and to the plum (Prunus domestica x Prunus spinosa) root. The simulation outputs corresponded well with the diameter variation observed. The model predicts that variations of turgor pressure and osmotic potential are smaller than the variations of xylem water potential. It also demonstrates correlations between the xylem water potential, the turgor pressure, the elastic modulus, and the osmotic potential. The relationship between the diameter and the xylem water potential exhibits a substantial hysteresis, as observed in field data. A sensitivity analysis using the model parameters showed that growth and shrinkage were highly sensitive to the initial values of the turgor pressure and to the reflection coefficient of solutes. Shrinkage and growth were sensitive to elastic modulus and wall-yielding threshold pressure, respectively. The model was not sensitive to changes in temperature.

Biophysical Phenomena↗

PubMed2001

Evaluation, selection, and follow-up of live kidney donors: a review of current practice in French renal transplant centres.

BACKGROUND: A resurgence of interest in the concept of live-donor renal transplantation has prompted a closer look at methods of live donor evaluation, selection, and follow-up. The aim of this study was to describe these methods in all 46 French renal transplant centres. METHODS: Questionnaires were sent to all chief renal physicians. RESULTS: The survey was completed by 78% of centres, which accounted for 95% of all live-donor renal transplants carried out in France in 1995 and 1996. There was a substantial variation in all three steps of live-donor management. For example, we observed variations in the screening for specific short- or long-term risk factors (especially cardiovascular or thrombotic risk factors and diabetes). In addition the exclusion criteria differed, especially the cut-off age for donation, which ranged from 45 to 75 years. The composition of teams evaluating and selecting potential donors and the role of the potential donors in the decision-making process varied greatly among centres. Finally, we observed less variation in the methods of donor follow-up. CONCLUSIONS: The current survey revealed a marked disparity in the management of live donors in France. It raises the question of whether these practices should be codified into a set of guidelines for live-donor transplantation.

Adult↗

PubMed2006

Experimental determination of subjective similarity for pairs of clustered microcalcifications on mammograms: observer study results.

Presentation of images of lesions similar to that of an unknown lesion might be useful to radiologists in distinguishing between benign and malignant clustered microcalcifications on mammograms. Investigators have been developing computerized schemes to select similar images from large databases. However, whether selected images are really similar in appearance is not examined for most of the schemes. In order to retrieve images that are useful to radiologists, the selected images must be similar from radiologists' diagnostic points of view. Therefore, in this study, the data of radiologists' subjective similarity for pairs of clustered microcalcification images were obtained from a number of observers, and the intra- and inter-observer variations and the intergroup correlations were determined to investigate whether reliable similarity ratings by human observers can be determined. Nineteen images of clustered microcalcifications, each of which was paired with six other images, were selected for the observer study. Thus, subjective similarity ratings for 114 pairs of clustered microcalcifications were determined by each observer. Thirteen breast, ten general, and ten nonradiologists participated in the observer study; some of them completed the study multiple times. Although the intraobserver variations for the individual readings and the interobserver variations for pairs of observers were not small, the interobserver agreements were improved by taking the average of readings by the same observers. When the similarity ratings by a number of observers were averaged among the groups of breast, general, and nonradiologists, the mean differences of the ratings between the groups decreased, and good concordance correlations (0.846, 0.817, and 0.785) between the groups were obtained. The result indicates that reliable similarity ratings can be determined by use of this method, and the average similarity ratings by breast radiologists can be considered meaningful and useful for the development and evaluation of a computerized scheme for selection of similar images.

Breast Diseases↗

PubMed2004

Chromosomal instability and marker chromosome evolution in oral squamous cell carcinoma.

Squamous cell carcinoma of the head and neck and its subset, oral squamous cell carcinoma (OSCC), arise through a multistep process of genetic alterations as a result of exposure to environmental agents, such as tobacco smoke, alcoholic beverages, and viruses, including human papillomavirus. We and others have shown that the karyotypes of OSCC are near-triploid and contain multiple structural and numerical abnormalities. However, despite a background of clonal chromosomal aberrations, individual cells within a culture express many nonclonal numerical and structural abnormalities, termed chromosomal instability (CIN). To evaluate CIN in oral cancer cells, we isolated clones from two OSCC cell lines and carried out classical cytogenetic analysis, fluorescence in situ hybridization using centromere-specific probes, and spectral karyotyping. We observed variation in chromosome number within clones and between clones of the same cell line. Although similar numbers of centromeric signals for a particular chromosome were present, "homologs" of a chromosome varied structurally from cell to cell (marker chromosome evolution) as documented by classical and spectral karyotyping. In addition to the numerical chromosome variations within a clone, we observed marker chromosome evolution by structural chromosome alterations. It appears that both intrinsic structural alterations and extrinsic cytoskeletal factors influence chromosome segregation, resulting in individual tumor cells that express unique karyotypes. We show that CIN and marker chromosome evolution are essential acquired features of neoplastic cells. Proliferation of this heterogeneous cell population may provide some cells with the ability to evade standard therapies.

Biomarkers↗

PubMedDate not supplied

Genetics of apolipoprotein H (beta2-glycoprotein I) polymorphism in India.

BACKGROUND: Human apolipoprotein H (beta(2)-glycoprotein I, apoH, protein; APOH, gene) is a single-chain glycoprotein that has been implicated in several metabolic pathways, including lipid metabolism, coagulation and production of antiphospholipid antibodies and many disease phenotypes. The structural, molecular and genetic bases of APOH have been studied in detail but population studies, especially from the Indian subcontinent, are limited. OBJECTIVE: This study seeks to enlarge our understanding of APOH genetic diversity in human populations from different regions and social groups of India. Also, we examine the level and extent of genetic variation at this locus in world populations and its utility as a population genetic marker. SUBJECTS AND METHODS: Blood samples from 1381 unrelated and randomly selected individuals were screened for APOH genetic polymorphism. Eleven populations from North India (Brahmins, Banias, Jat Sikhs, Khatris, Scheduled Castes, Lobanas and Rajputs), West India (Brahmin and Patels) and Central India (Brahmins and Baiga tribe) were studied for APOH polymorphism using isoelectric focusing. Allele frequencies were calculated by the gene counting method. The results were statistically evaluated using chi-square statistics for regional and ethnic variation. Genetic distances were computed on Indian populations to determine the population affinities. Correspondence analysis was used to assess ethnic variation in world populations. RESULTS: An interesting and wide genetic variation at this locus was observed in Indian populations. The frequency distribution of three observed alleles ranged from 0.034 to 0.091 for APOH*1, 0.852 to 0.917 for APOH*2 and 0.027 to 0.075 for APOH*3. The world's highest APOH*2 allele frequency was observed in the Patel (0.917) caste group from West India. CONCLUSIONS: Overall, the observed variation at this locus in Indian populations is comparable to many Caucasian populations. An analysis of world populations showed that APOH is a useful genetic marker for population and anthropological studies.

Alleles↗

PubMed1993

Allelic diversity at minisatellite MS205 (D16S309): evidence for polarized variability.

We have determined the allelic structures on 106 Caucasian chromosomes at the minisatellite locus MS205 (D16S309). In addition to the internal structures deduced by minisatellite variant repeat (MVR) mapping, the genotypes at six flanking substitutional polymorphic sites have been analysed. The minisatellite structures show a polarity of variation at MS205, with most observed variation due to differences at one extremity of the tandem repeat array. This locus, therefore, provides a further example of polarity of variation at human minisatellites. Analysis of haplotypes at flanking polymorphic sites suggests that there may be a higher frequency of exchange near the highly unstable end of the minisatellite, and thus that exchanges of flanking polymorphisms may be due to co-conversion or recombination events occurring during unequal exchanges between minisatellite alleles.

Alleles↗

PubMed1992

Effect of different culture techniques used to induce capacitation on the chromatin stability of human sperm.

To validate an in-vitro bioassay for assessing chromatin stability of human sperm, 38 semen samples from infertile men were studied using sodium dodecyl sulphate, an anionic detergent which disorganizes only the cytoplasmic membrane. Assay sensitivity was 50 sperm, whilst the within- and between-assay variation, and the between-observer variation were found to be within the accepted range for this type of bioassay. The influence of different in-vitro treatments currently used in some clinical assisted fertilization programmes was evaluated: a destabilizing effect occurred in Grade I (stable) and Grade III (swollen) sperm. In the former, all treatments reduced stable sperm; in the latter, a significant (P less than 0.001) increase in swollen sperm was shown with two methods that used Ham's F-10 as culture medium. Different chromatin patterns found in the treated sperm suggest the possibility that the recovered samples could be modified compared to their status at the time of isolation.

Biological Assay↗

PubMed2002

Morphological diversity of androgenic carrot plants.

The aim of this study was to evaluate phenotypic variation of R0 androgenic plants obtained from four seed sources and donor plants by anther culture. Several morphological traits (leaf size, petiole length, leaf division, cortex colour) and the range of diversity were evaluated. There was large variation in all traits among the donor varieties. Especially leaf division and cortex colour differed significantly among the androgenic plants that came from different seed sources. The plants regenerated from four donor plants of variety 62 were significantly different in most traits except for leaf width and cortex colour. Evaluation of R1 plants will demonstrate whether the R0 variation observed is due to genetic variation or physiological differences from tissue culture.

Androgens↗

PubMed1980

[Absolute bioavailability of theophylline (Euphylline)].

The pharmacokinetics and bioavailability of theophylline have been investigated in eight healthy subjects following application of the drug in form of a tablet, a retard tablet (enteric-coated), and a suppository (Euphyllin) in comparison with an intravenous preparation. Peak plasma concentrations were measured 1.5 hours (tablet), 6 hours (retard tablet) and 4 hours (suppository) after drug administration, respectively. The absolute bioavailability was of th tablet 105 +/- 25%, of the retard table 81 +/- 23%, of the suppository 74 +/- 25%. The variations observed were primarily due to variations in the other pharmacokinetic parameters, only to a lesser extent to variable absorption of theophylline.

Adult↗

PubMed1996

Determination of prostatic volume with transrectal ultrasound: A study of intra-observer and interobserver variation.

PURPOSE: We assessed the intra-observer and interobserver variation in measurements of prostatic volume using transrectal ultrasound. MATERIALS AND METHODS: Two volume estimations were performed by 1 observer in 40 patients and by 2 observers in 75. RESULTS: Mean prostatic volumes measured ranged from 18.9 to 87.0 ml. (median 39.8) for 1 observer and from 15.5 to 95.4 ml. (median 42.4) for 2 observers. The mean difference plus or minus standard deviation and limits of agreement between the paired volume estimations were 0.1 +/- 3.3 ml. and -6.5 +/- 6.7 ml., respectively, for 1 observer, and -0.3 +/- 5.3 ml and -10.9 to 10.3 ml., respectively, for 2 observers. The mean difference was 9.8% for 2 observers. The mean difference was 9.8% for 2 observers compared to 4.6% for 1. CONCLUSIONS: The results show that there is considerable variation in repeated measurements of prostatic volume and the variation is greatest for 2 observers compared to 1 observer.

Adult↗

PubMed1976

Variation in basal arteries of the brain in polecat (Mustela putorius putorius L.).

Observations carried out on 106 polecat brains showed that the system of basilar arteries of the brain is similar to those in other cornivorous species. The observed variation was manifested in a differentiation connections of the vessels, in occurence of some variations and in asymmetry. Some cases of such variations were hitherto observed only in some ruminants.

Animals↗

PubMed2004

Between-method variation in human chorionic gonadotropin test results.

BACKGROUND: Results on sera and calibrators vary 1.4- to 2.3-fold among commercial human chorionic gonadotropin (hCG) assays. The relative contributions of calibrators, standards, hCG charge isoforms, and major structural variants to this variation have not been quantified. METHODS: Purified hCG was separated by isoelectric focusing into four fractions with pI ranges of 3-4, 4-5, 5-6, and 6-7. These four fractions together with pure hCG, hyperglycosylated hCG, hCG beta-subunit (hCGb), nicked hCG, and hCGb core fragment (hCGbcf) were tested in nine commonly used commercial serum assays for hCG. The compositions of pure hCG preparations, standards, and commercial hCG preparations were determined by immunoassay. RESULTS: The three pure hCG preparations and the four hCG charge isoforms each showed parallel responses in the nine commercial hCG assays. Although wide variations were found in the detection of hCG structural variants by the nine assays (range for hyperglycosylated hCG, 468-1544 IU/L; for hCGb, 3187-5535 IU/L; for nicked hCG, 2736-4240 IU/L; and for hCGbcf, <2-130 IU/L), this did not correlate with the between-method variation observed in results for the three pure hCG preparations. Commercial preparations of hCG and calibrators showed great variation in their content of hCG structural variants (from 34% to 100% intact hCG). CONCLUSIONS: Intermethod differences in hCG results were not explained by changes in responses attributable to hCG charge isoforms or to hCG structural variants, but wide variation was observed in concentrations of hCG structural variants in calibrators and in detection of these structural variants. Differences in assay specificity and in composition of the calibrators are the most likely sources of between-method variation.

Calibration↗

PubMed1994

Quantification of patient to patient variation of skin erythema developing as a response to radiotherapy.

A method is described to determine accurately skin redness during a course of radiotherapy using reflectance spectroscopy utilizing information from across the visible spectrum according to the L*a*b* color coordinate system. The method was used to quantify the development of skin erythema during and after electron beam irradiation of the chest wall following mastectomy. A number of factors were identified which could influence the wide variation in response seen between patients. These were: intra- and inter-observer variation; intra- and inter-patient variation and variation in the actual dose delivered. Statistical analysis, including an analysis of variance of inter- and intra-patient variation, revealed that the major factor that accounts for the observed difference between patients is a true inter-patient variation, with a coefficient of variation, corrected for intra-patient variation, of 43%. Within the narrow dose range administered in this study, there was no demonstrable dose-effect relationship, raising questions about the role of cell death in the basal layer of the epidermis in the pathogenesis of radiation induced erythema.

Adult↗