SEARCH · PubMed Health

Results for “Observer Variation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources

PubMed1985

An international collaborative study on foot and mouth disease virus assay methods. 2. Quantification of 146S particles.

Workers in 11 laboratories in Europe and one in North America participated in a collaborative study to assess the variability of a sucrose gradient procedure used for the quantification of foot and mouth disease virus (FMDV). To this end, a range of standards was distributed from one of the participating laboratories. A series of adenine preparations were used to assess the various spectrophotometers/UV monitors and it showed most to be accurate and linear in their responses. The FMDV and MS2 ribophage standards were used to assess the sucrose gradient procedure and indicated low levels of within laboratory variation whereas between laboratory variation was greater. Recalculation of results from the unprocessed data in the coordinating laboratory permitted the identification and reduction of one source of between laboratory variation. Despite the observed variations, the results indicated that meaningful comparisons could be made between the data of different laboratories provided that a procedure similar to the one described in this report is used.

Adenine↗

PubMed2000

Statistical testing of drug accumulation in skin tissues by linear regression versus contents of stratum corneum lipids.

This investigation is a contribution to standardization in in vitro drug penetration measurements using excised human skin and to statistical treatment of the observations. The wide variations observed in measurements of drug accumulation in and drug permeation through the stratum corneum are caused not only by analytical errors but also by the variability of the horny layer lipid composition. The last-mentioned systematic influence can be compensated for by stepwise (multiple) linear regression using the contents of the main lipid classes as independent variables. In consequence, the S.E. of estimate given by the regression calculation is lower than the S.E. of the means of the observations. Significant differences in drug quantities accumulated in skin tissues (stratum corneum and dermis) are sensitively detected by Chow's F-test of structural change. Accumulation data of flufenamic acid and hydrocortisone penetrated from different bases are given as examples. The calculation mode is exemplarily explained and discussed. The results of the test for structural change, two-independent-groups t-test and paired-samples t-test are compared. The F-test of structural change proves to be a helpful statistical method suitable to the assessment of biopharmaceutical quality parameters and to measurements using biological materials.

Administration, Topical↗

PubMed1983

Sequential mutations in hemagglutinins of influenza B virus isolates: definition of antigenic domains.

Comparative analysis of the amino acid sequences of hemagglutinins (HAs) of influenza B/Lee/40, B/Md/59, and B/HK/73 viruses has allowed examination of the molecular basis of antigenic variation in type B viruses. As seen with influenza type A viruses, antigenic drift in influenza B viruses proceeds mostly through the accumulation of amino acid substitutions within the HA1 portion of the HA molecule. However, the rate of variation observed among the influenza B virus HAs appears to be significantly lower than the observed rate of variation among influenza A virus HAs. The overall rate of amino acid change in the HA1s of the influenza B viruses studied is 2% per 10 years, whereas the HA1s of H3 influenza A viruses vary by 9.2% per 10 years. The sequences of the influenza B HAs were also examined in relation to the three-dimensional model for the A/Aichi/2/68 HA. When the primary amino acid sequences are compared, it appears that most of the important structural features of the type A HAs--such as the sialic acid binding site, the disulfide linkages, and the stem structure of the trimer--are conserved in the influenza B virus HAs. Regions are also identified where extensive amino acid substitutions have occurred among the three antigenically distinct influenza B virus HAs. The locations of these areas in the B HA structure correspond to antigenic regions proposed for the A virus HAs. In addition, modulation of antigenic regions in B virus HAs may also occur through amino acid deletions and variation in glycosylation sites.

Amino Acid Sequence↗

PubMed2003

Tree species of the Central Amazon and soil moisture alter stable isotope composition of nitrogen and oxygen in nitrous oxide evolved from soil.

The use of stable isotopes of N and O in N2O has been proposed as a way to better constrain the global budget of atmospheric N2O and to better understand the relative contributions of the main microbial processes (nitrification and denitrification) responsible for N2O formation in soil. This study compared the isotopic composition of N2O emitted from soils under different tree species in the Brazilian Amazon. We also compared the effect of tree species with that of soil moisture, as we expected the latter to be the main factor regulating the proportion of nitrifier- and denitrifier-derived N2O and, consequently, isotopic signatures of N2O. Tree species significantly affected delta15N in nitrous oxide. However, there was no evidence that the observed variation in delta15N in N2O was determined by varying proportions of nitrifier- vs. denitrifier-derived N2O. We submit that the large variation in delta15N-N2O is the result of competition between denitrifying and immobilizing microorganisms for NO3(-). In addition to altering delta15N-N2O, tree species affected net rates of N2O emission from soil in laboratory incubations. These results suggest that tree species contribute to the large isotopic variation in N2O observed in a range tropical forest soils. We found that soil water affects both 15N and 18O in N2O, with wetter soils leading to more depleted N2O in both 15N and 18O. This is likely caused by a shift in biological processes for 15N and possible direct exchange of 18O between H2O and N2O.

Brazil↗

PubMed1995

Stability of debrisoquine (CYP2D6) phenotype in liver transplant patients.

Liver metabolism may be modified after liver transplantation according to the phenotype of the donor and may be influenced by posttransplantation complications. The CYP2D6 phenotype was assessed in 13 patients (group I) before and after liver transplantation using debrisoquine. CYP2D6 activity was also assessed in vitro on microsomes from the liver of the recipients and the donors, using dextromethorphan. Twelve patients were extensive metabolizers both before and after transplantation. One apparently poor metabolizer was transplanted with the liver of another poor metabolizer. The intrinsic clearance of dextromethorphan (CL(int)) measured on recipient liver microsomes was significantly lower than that on donor liver microsomes (p < 0.05). In extensive metabolizers, the debrisoquine metabolic ratio was correlated with CL(int) before (r = 0.78, p < 0.05) and after (r = 0.89, p < 0.0005) transplantation. Debrisoquine phenotype was measured repeatedly in nine additional patients (group II) up to 3 years after liver transplantation. Their phenotype was stable during the follow-up observation, although the variations observed may be clinically relevant. Therefore, no change in CYP2D6 phenotype (extensive/poor metabolizer) was observed because of the liver transplantation, and the debrisoquine log metabolic ratio was largely unaffected by the liver complications observed during the posttransplantation follow-up observation.

Cytochrome P-450 CYP2D6↗

PubMed2004

Major histocompatibility complex and microsatellite variation in two populations of wild gorillas.

In comparison to their close relatives the chimpanzees and humans, very little is known concerning the amount and structure of genetic variation in gorillas. Two species of gorillas are recognized and while the western gorillas number in the tens of thousands, only several hundred representatives of the mountain gorilla subspecies of eastern gorillas survive. To analyse the possible effects of these different population sizes, this study compares the variation observed at microsatellite and major histocompatibility complex (MHC) loci in samples of wild western and mountain gorillas, collected using a sampling scheme that targeted multiple social groups within defined geographical areas. Noninvasive samples proved a viable source of DNA for sequence analysis of the second exon of the DRB loci of the MHC. Observed levels of variation at the MHC locus were similar between the two gorilla species and were comparable to those in other primates. Comparison of results from analysis of variation at multiple microsatellite loci found only a slight reduction in heterozygosity for the mountain gorillas despite the relatively smaller population size.

Animals↗

PubMed1997

A novel image cytometric method for quantitation of immunohistochemical staining of cytoplasmic antigens.

Evaluation of molecular markers by immunohistochemical labelling of tissue sections has traditionally been performed by qualitative assessment by trained pathologists. For those markers with a staining component present outside of the nucleus, there has been no image histometric method available to reliably and consistently define cell interfaces within the tissue. We present a new method of approximating cellular boundaries to define cellular regions within which quantitative measurements of staining intensity may be made. The method is based upon Voronoi tessellation of a defined region of interest (ROI), and requires only the position of the nuclear centroids within the ROI. Here we describe the VORSTAIN software which has been developed based on the Oncometrics CytoSavant Automated Image Cytometry System. To demonstrate this technique, human breast cancer sections immunohistochemically stained for bcl-2 protein and counter-stained with nuclear methyl green stain were evaluated. Intra-observer variation in the measured values was between 1.5-2.6% and inter-observer variation was between 1.8-4.4%. The primary source of variability was due to difficulties in interpreting the exact position of the nuclear centroids. Analysis of mean staining densities for each slide correlated well with subjective scoring performed by two independent pathologists. Using VORSTAIN, significant variation of staining intensities between regions within the same slide was measured for some sections, indicating a large degree of heterogeneity within the tumours. The ability to accurately quantitate the degree of heterogeneity of molecular marker expression within tumours may be a valuable tool in prognostication.

Biomarkers, Tumor↗

PubMed1994

Myocardial blood flow rate and capillary permeability for 99mTc-DTPA in patients with angiographically normal coronary arteries. Evaluation of the single-injection, residue detection method with intracoronary indicator bolus injection and the use of a mobile gamma camera.

The aims of the present study were to quantitate myocardial perfusion and capillary permeability in the human heart by means of the single-injection, residue detection method using a mobile gamma camera. With this method, the intravascular mean transit time and the capillary extraction fraction (E) can be determined in one experiment and in the same myocardial region. Eighteen patients with a history of chest pain episodes and angiographically normal coronary arteries were studied after intracoronary bolus injections of 99mTc-DTPA during elective coronary angiography. Two measurements were performed at a 15-min interval during resting conditions, and a third measurement was made during atrial pacing. Regions of interest were drawn in the left anterior descending (LAD) and the circumflex (CX) coronary artery perfusion beds. Sources of variation in plasma flow rate (fpl), E, and the calculated capillary permeability area product (PS) were determined. Spontaneous 15 min variations (mean of two values) for the LAD and the CX territory, respectively, gave a mean fpl(LAD) of 74.2 (measurement 1) and 77.8 ml.(100 g.min)-1 (measurement 2) (SD of the difference 7.5 ml.(100 g.min)-1) and fpl(CX) of 82.7 and 92.1 ml. (100 g.min)-1, respectively (SD of the difference 16.1 ml.(100 g.min)-1), and E(LAD) was 51.0 and 55.7%, respectively (SD of the difference 8.4%), and E(CX) was 52.9 and 50.4%, respectively (SD of the difference 5.9%). During atrial pacing, the rate-pressure product increased by 97%, and in the LAD area fpl increased by 46% (p < 0.05), E decreased by 6% (NS), and PS increased by 39% (NS), whereas in the CX region flow increased by only 9% (p < 0.01), E decreased by 15% (p < 0.05), and PS decreased by 15% (NS) compared with baseline values. Both the spontaneous variation and the observer variation are low. The reduced vasodilator response in the CX region in combination with the decrease in E, which reduce the supply of nutrients, may play a role in the symptoms of these patients.

Adult↗

PubMed1992

Strain-cross response of heavy male broilers to dietary lysine in the finisher feed: live performance and further-processing yields.

A total of 2,560 male broilers from eight commercial strain-crosses were growth to 42 days of age on common starter (1 to 21 days; 23.06% CP, 3,217 kcal ME/kg) and grower (21 to 42 days; 20.14% CP, 3,224 kcal ME/kg) rations. All strain-crossed subsequently received finisher diets (17.95% CP; 3,186 kcal ME/kg) containing either .85 or .95% lysine from 42 to 53 days of age. Further-processing yields were determined on 12 birds per pen, selected within +/- 10% of the replicated pen (8 pens per strain-cross, 40 birds per pen) average weight. The strain-crosses differed significantly (P less than .05) in BW (1, 21, 42, and 53 days), weight gain (WG), feed:gain ratio (1 to 21 and 21 to 42 days), and mortality rate (1 to 21 days). The lysine effect during the finisher period was significant for 53-day BW and WG from 1 to 53 days. Chilled carcass (CC) and abdominal fat (AF) weights, CC yield (percentage, excluding AF), AF yield (percentage of CC weight), Pectoralis major, Pectoralis minor, total deboned breast (TDB), drumstick, thigh, wing, and residual "cage" and skin yields varied among the strain-crosses. A significant weight and yield response to lysine was observed for TDB. Variation observed among strain-cross in live performance, further-processing yields, and response to additional lysine is attributed to differences in rate of growth and degree of maturity at market age. Furthermore, the lysine requirement during the finisher period for optimum breast meat yield may be higher than that recommended by the National Research Council in 1984.

Adipose Tissue↗

PubMedDate not supplied

[Chronopharmacokinetic study of lidocaine in the rat (author's transl)].

1. The aim of the present study was to investigate an eventual influence of the hour of administration on lidocaine kinetics in the rat. 280 Wistar AF SPF adult male rats were used for this study and maintained under controlled environmental conditions (LD: 06.00-18.00) during the month of October. A single 50 mg . kg-1 dose of lidocaine was given by intramuscular route, at four different fixed time points of a 24-hour period (i.e.: 10.00, 16.00, 22.00 and 04.00) to 70 rats. At each specified time point blood samples were taken 5, 15, 30 min., 1, 2, 4 and 6 hours after the drug administration. Lidocaine plasma levels (free and bound) were determinated according to a specific gas chromatographic method. 2. Our data showed circadian variations of pharmacokinetic parameters (Formula: see text) 3. Lidocaine free fraction varied with time and the protein binding of lidocaine showed a circadian variation. 4. The observed variations may be related to 1) daily fluctuations of absorption or binding of the drug 2) to diurnal variation of the hepatic drug metabolising enzymes responsible for the inactivation of the drug and/or 3) to diurnal variations in excretion rate of lidocaine. Finally our results agree with those of Lutsch and Morris who found a circadian periodicity in susceptibility to lidocaine in the mouse with maximal convulsant activity at 21.00.

Animals↗

PubMed1991

Some observations on variations in filament overlap in tetanized muscle fibres and fibres stretched during a tetanus, detected in the electron microscope after rapid fixation.

Anomalous tension development which would not be predicted from the descending limb of the length-tension curve occurs during prolonged tetani and after stretch during a tetanus. Variations in filament overlap might account for all or part of the tension enhancement. Fibres isolated from frog skeletal muscle were rapidly fixed during a tetanus with mercuric chloride in ethanol and chloroform so that the correct alignment of the filaments in the overlap zones was preserved. The fibres were examined in polarized light with compensation, and in the electron microscope. There were variations in striation spacing along the length of the fibres, and severe shortening with contraction bands near the tendon insertions, confirming observations made by others on live fibres. Many variations in filament overlap which would not be detectable by light microscopy or laser diffraction were seen in the electron microscope. In a pilot study we measured differences in the width of the overlap zones between half-sarcomeres in a small area and within individual half-sarcomeres. In the latter case the variations were greater in a fibre which developed creep of tension and one which did not. Even greater variations were seen in three fibres stretched during a tetanus, and, in two of these, there were some grossly elongated half-sarcomeres in which the filaments had pulled out of the overlap zones, leaving gaps.

Animals↗

PubMed2003

Variation between observed and true Terminal Restriction Fragment length is dependent on true TRF length and purine content.

Terminal Restriction Fragment (TRF) pattern analysis has become a widely used and informative tool for studying microbial communities. Variation between sequence-determined or true TRF length and observed TRF length (TRF drift) has been previously reported and can significantly affect identification of bacterial species using TRF lengths predicted from sequence databases. In this study TRF drift was determined for 21 bacterial species using an ABI 310 Genetic Analyzer. TRF drift was positively correlated with true TRF length and negatively correlated with TRF purine content. This implies that subtle differences in molecular weight, whether from purine content or dye label, can significantly affect the observed TRF length.

Bacteria↗

PubMed1999

Interobserver and intraobserver variation in endoscopic assessment of GERD using the "Los Angeles" classification.

BACKGROUND: A new endoscopic classification of gastroesophageal reflux disease (GERD) has been proposed, and the term mucosal break has been introduced to describe mucosal damage. This new classification was evaluated by endoscopists with different levels of experience. METHODS: Fifty endoscopic photographs for each of 20 randomly selected patients with GERD were assessed retrospectively by three groups of seven endoscopists classified by experience: group 1 (100 to 500 procedures), group 2 (500 to 3000), and group 3 (more than 3000). The new classification was modified by adding grade 0 to describe healed mucosal breaks, so that there were five grades. All photographs were assessed twice at an interval of more than 1 week, and kappa statistics were used to determine observer variation. RESULTS: Interobserver variation within group 3 (kappa = 0.39, n = 21) and between groups 3 and 2 (kappa = 0.36, n = 49) was significantly different (p < 0.01) from that between groups 3 and 1 (kappa = 0.26, n = 49). Intraobserver variation in group 1 (kappa = 0.39, n = 7) was significantly different (p < 0.01) from that in group 2 (kappa = 0.51, n = 7) and group 3 (kappa = 0.54, n = 7). CONCLUSIONS: Observer variation depends on level of endoscopic experience. Only experienced endoscopists should use the new classification for grading of GERD.

Adult↗

PubMed1993

Ontogeny of a circadian rhythm in body temperature in newborn lambs reared independently of maternal time cues.

To investigate the ontogeny of a circadian rhythm in body temperature, we performed 24-h temperature measurements at six postnatal ages in ten newborn lambs reared independently of their ewes. At 18 to 48 h of age, a significant time-of-day variation in body temperature was found, the variation achieving a peak between 5.00 pm and 6.00 pm. Over the next two weeks, this time-of-day variation disappeared, reappearing at 18 days of age, although the phase had shifted such that the peak temperature was achieved between 8.00 am and 9.00 am. At 26 days of age, the time-of-day variation in body temperature was still present, maintaining the same phase relationship as at 18 days of age. It is possible that the significant time-of-day variation observed in the two oldest groups is due to the emergence of a discernable circadian rhythm in body temperature entrained to the light-dark cycle during the second or third week of life, whereas the time-of-day variation observed in the 18 to 48-h old is due to residual effects of entrainment to maternal zeitgebers. We speculate that the lack of any observable time-of-day variation in the 4, 6 and 11 days-old lambs may denote the presence of no rhythm or possibly a free-running rhythm in body temperature in subjects not yet able to entrain to photic zeitgebers.

Animals↗

PubMed1994

[Dysmorphic erythrocytes in urinary sediment in differentiating urological from nephrological causes of hematuria].

OBJECTIVE: To determine the significance of dysmorphic erythrocytes in the urinary sediment for discrimination between urological and nephrological causes of haematuria. DESIGN: Evaluation of diagnostic test. SETTING: Departments of Nephrology and Pathology, University Hospital Nijmegen. METHOD: Of 107 patients with haematuria in whom renal parenchymal or urological disease was diagnosed, the percentage of dysmorphic erythrocytes was estimated in the unstained urinary sediment with normal light microscopy. By using a Receiver Operating Characteristic curve the cutoff point that provided the highest diagnostic value of the erythrocyte morphology was determined. In addition, the inter-observer variation was estimated in a separate series of 26 urinary sediments. RESULTS: At a cutoff value of 40% dysmorphic erythrocytes the sensitivity for urological pathology was 100% and the specificity 66.7%. When presence of erythrocyte, haemoglobin or fatty casts was also considered as a criterion for a nephrological diagnosis, the specificity for urological pathology rose to 88.1%. The inter-observer variation showed a correlation coefficient of 0.90 (kappa: 0.77). CONCLUSION: Evaluation of the erythrocyte morphology in the urinary sediment is a reliable aid in determining the strategy to be followed in patients with haematuria. It is important, however, that strict criteria for establishing erythrocyte dysmorphism are applied.

Adolescent↗

PubMed2003

Magnetic resonance imaging in the radiation treatment planning of localized prostate cancer using intra-prostatic fiducial markers for computed tomography co-registration.

PURPOSE: To assess the feasibility, and potential implications, of using intra-prostatic fiducial markers, rather than bony landmarks, for the co-registration of computed tomography (CT) and magnetic resonance (MR) images in the radiation treatment planning of localized prostate cancer. METHODS: All men treated with conformal therapy for localized prostate cancer underwent routine pre-treatment insertion of prostatic fiducial markers to assist with gross target volume (GTV) delineation and to identify prostate positioning during therapy. Six of these men were selected for investigation. Phantom MRI measurements were obtained to quantify image distortion, to determine the most suitable gold alloy marker composition, and to identify the spin-echo sequences that optimized both marker identification and the contrast between the prostate and the surrounding tissues. The GTV for each patient was contoured independently by three radiation oncologists on axial planning CT slices, and on axial MRI slices fused to the CT slices by matching the implanted fiducial markers. From each set of contours the scan common volume (SCV), and the scan encompassing volume (SEV), were obtained. The ratio SEV/SCV for a given scan is a measure of inter-observer variation in contouring. For each of the 18 patient-observer combinations the observer common volume (OCV) and the observer encompassing volume (OEV) was obtained. The ratio OEV/OCV for a given patient-observer combination is a measure of the inter-modality variation in contouring. The distance from the treatment planning isocenter to the prostate contours was measured and the discrepancy between the CT- and the MR-defined contour recorded. The discrepancies between the CT- and MR-defined contours of the posterior prostate were recorded in the sagittal plane at 1-cm intervals above and below the isocenter. RESULTS: Phantom measurements demonstrated trivial image distortion within the required field of view, and an 18K Au/Cu alloy to be the marker composition most suitable for CT-MRI image fusion purposes. Inter-observer variation in prostate contouring was significantly less for MR compared to CT. The mean SEV/SCV ratio was 1.58 (confidence interval (CI): 1.47-1.69) for CT scans and 1.37 (CI: 1.33-1.41) for MR scans (paired t-test; P=0.036). The overall magnitude of contoured GTV was similar for MR and CT; however, there were spatial discrepancies in contouring between the two modalities. The greatest systematic discrepancy was at the posterior apical prostate border, which was defined 3.6 mm (SD 3.5 mm) more posterior on MR- than CT-defined contouring. CONCLUSIONS: Prostate contouring on MR is associated with less inter-observer variation than on CT. In addition, we have demonstrated the feasibility of using intra-prostatic fiducial markers, rather than bony landmarks, for the co-registration of CT and MR images in the radiation treatment planning of localized prostate cancer. This technique, together with on-line correction of treatment set-up according to the fiducial marker position on electronic portal imaging, may enable a reduction in the planning target volume (PTV) margin needed to account for inter-observer error in target delineation, and for prostate motion.

Biomarkers↗

PubMedDate not supplied

Inter-observer agreement and clinical diagnosis of leprosy for prophylaxis studies.

Clinical diagnosis is still the most useful tool for detecting early cases of leprosy in field research. In prophylaxis studies accuracy of clinical diagnosis of leprosy is important during intake as well as for measuring efficacy of the intervention. This paper reports our observations regarding the extent of inter-observer variations in clinical diagnosis of leprosy and its implications for a prophylaxis study. Information on 225 suspects and cases of leprosy, each examined independently by three senior workers after initial standardization, was used for this purpose. Agreement among the examiners regarding the presence of skin patch, thickened nerve trunk and sensory deficit was fairly high (Kappa = 0.7). Agreement on the presence of infiltration in a skin patch was not satisfactory (Kappa = 0.4-0.5). It was observed that in clinical diagnosis of leprosy, presence of skin patch and sensory deficit, as well as thickened nerve trunk and related anaesthesia were correlated observations. The influence of inter-observer variations on defining leprosy problem in the community can be quite large. The paper suggests some ways of overcoming the problem.

Adult↗

PubMedDate not supplied

Substantial genetic variation in southern African black rhinoceros (Diceros bicornis).

Thirty protein-coding loci of southern African black rhinoceros (Diceros bicornis) from four isolated populations were studied using starch gel electrophoresis and polyacrylamide gel electrophoresis. Gene diversity estimates varied between 0.036 and 0.058, with the Zambezi Valley population having the largest amount of protein variation. These levels are higher than those in other studies of genetic variation in black rhinoceros and are similar to the amount of genetic variation observed for outbred natural populations that are not genetically depauperate. Because the observed levels of genetic variation vastly exceed the expectations for current effective population sizes, the current levels apparently reflect large black rhinoceros populations which have existed until recently. Observed levels of genetic variation within populations are consistent with the expectations when recent demographic events are taken into account.

Africa, Southern↗