SEARCH · PubMed Health

Results for “Reproducibility”

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 505 records · Page 28Linked to original sources

PubMed1991

Evaluation of the reproducibility of the revised 1988 International Federation of Gynecology and Obstetrics grading system of endometrial cancers with special emphasis on nuclear grading.

An intraobserver and interobserver analysis of the reproducibility of the revised 1988 International Federation of Gynecology and Obstetrics (FIGO) grading system of endometrial cancers was performed in 47 endometrial cancers (94 biopsy specimens). In the revised FIGO grading system the growth pattern still serves as the basic parameter, but nuclear atypia inappropriate for the architectural grade, raises the grade by 1. Ninety-four slides were graded twice by two pathologists. Analysis by the kappa statistics (corrected for agreement by chance) showed an acceptable result for interobserver reproducibility: kappa value 0.65 (95% confidence interval, 0.480 to 0.818). Further study showed this to be a reflection of the reproducibility of the architectural grade: kappa 0.70 (95% confidence interval, 0.565 to 0.850), whereas the reproducibility of the nuclear grade was poor: kappa value 0.55 (95% confidence interval, 0.383 to 0.713). Review of the literature showed great variability in the definition of nuclear grading, indicating that the revised 1988 FIGO grading system is not applicable as standard of reference for studies of endometrial cancers, before agreeing to the definition of inappropriate nuclear atypia.

Adenocarcinoma↗

PubMed1997

Histologic/histochemical grading system for osteoarthritic articular cartilage: reproducibility and validity.

OBJECTIVE: To evaluate the reproducibility and validity of the histologic/histochemical grading system (HHGS) for osteoarthritis (OA) developed by Mankin and coworkers. METHODS: Sections of human articular cartilage from macroscopically normal and osteoarthritic femoral heads were graded by the HHGS (0-14 scale) twice by 3 observers, and intra- and interobserver reproducibility was determined. RESULTS: The exact intra- and interobserver reproducibilities ranged from 22% to 33% and from 13% to 25%, respectively. Intra- and interobserver variation ranged from -7 to 5. Although scores were generally higher in cartilage from osteoarthritic joints as compared with cartilage from normal joints, the difference reached statistical significance for only 2 observers. Additionally, the average scores from all observers were within the definitive range for OA (>5) in 30% of sections from normal joints, and in only 47% of sections from OA joints. CONCLUSION: The results indicate that the reproducibility and the validity of the HHGS are inadequate, and an improved histopathologic grading system for OA is needed.

Adult↗

PubMed2001

Reproducibility of intravascular ultrasound and intracoronary Doppler measurements.

The aim of this study was to evaluate the reproducibility of intravascular ultrasound (IVUS) and intracoronary (IC) Doppler flow velocity measurements. The use of IVUS and IC Doppler has been suggested as a means for percutaneous coronary intervention (PCI) guidance in a series of studies. This would require an acceptable level of accuracy and reproducibility of these two methods for lesion evaluation. In this study, the main focus was on the issue of reproducibility. One hundred and eight patients referred for PCI entered into the study. Inter- and intraobserver variability was measured. Catheter difference was assessed. On-line and off-line measurements were compared. MUSIC criteria were assessed off-line, twice. Calculated and measured diameters were compared. After having obtained initial IC Doppler measurements, the Doppler wire was immediately withdrawn and repositioned for reacquisition of Doppler measurements. IVUS measurements are reproducible and reliable off-line and, to a slightly lesser degree, on-line. Area measurements should be performed more than once and the mean used for vessel description. Lumen diameters should be calculated from the mean of the area measurements. A measuring technique consensus should be reached and adhered to. CFR measurements can be used to determine reduced vs. normal flow reserve. In this study, it was found that proximal to distal velocity ratio and diastolic to systolic velocity ratio variability made these parameters unsuitable for PCI guidance.

Blood Flow Velocity↗

PubMed2005

Improving the reproducibility of diagnosing micrometastases and isolated tumor cells.

BACKGROUND: The latest edition of the tumor-lymph node-metastasis (TNM) classification of malignant tumors distinguishes between isolated tumor cells (pN0) and micrometastases (pN1mi). The reproducibility of these categories has not been assessed previously. METHODS: Digital images from 50 cases with low-volume lymph node involvement from axillary sentinel lymph nodes were circulated twice for evaluation (Evaluation Rounds 1 and 2) among the members of the European Working Group for Breast Screening Pathology, and the members were asked to categorize lesions as micrometastasis, isolated tumor cells, or something else and to classify each case into a pathologic lymph node (pN) category of the pathologic TNM system. Methods for improving the low reproducibility of the categorizations were discussed between the two evaluation rounds. kappa Statistics were used for the assessment of interobserver variability. RESULTS: The kappa value for the consistency of categorizing low-volume lymph node load into micrometastasis, isolated tumor cells, or neither of those changed from 0.39 to 0.49 between Evaluation Rounds 1 and 2, but it was slightly lower for the pN categories (0.35 and 0.44, respectively). Interpretation of the definitions of isolated tumor cells (especially with respect to their localization within the lymph node), lack of guidance on how to measure them if they were multiple, and lack of any definitions for multiple simultaneous foci of lymph node involvement were listed among the causes of discordant diagnoses. CONCLUSIONS: The results of the current study indicated that the definitions available have minor contradictions and do not permit a reproducible distinction between micrometastases and isolated tumor cells. Refinement of these definitions, therefore, is required. One refinement that may improve reproducibility is suggested in this report.

Biopsy, Needle↗

PubMedDate not supplied

Positional reproducibility of protein spots in two-dimensional polyacrylamide gel electrophoresis using immobilised pH gradient isoelectric focusing in the first dimension: an interlaboratory comparison.

An intra- and interlaboratory comparison of positional reproducibility of protein spots in two-dimensional electrophoresis using immobilised pH gradients (IPG) in the first dimension (IPG-DALT) was made. Aliquots of two different samples, human cardiac and barley leaf proteins, were separated in two different laboratories (London and Munich), using 180 mm long IPG gel strips, pH 4-8, for the first dimension and homogeneous SDS-PAGE gels (12% T) for the second dimension. Subsets of 340 (cardiac) and 200 (barley) well-resolved spots distributed across the 2-D gel patterns were selected for computer analysis (PDQUEST) of positional reproducibility. The IPG-dimension was highly reproducible in each laboratory, with a mean standard deviation of about 1 mm for both types of sample. Interlaboratory comparisons revealed identical results for barley with a mean standard deviation along the x-axis of about 1 mm, whereas the cardiac matchset showed slightly more variability (mean standard deviation approximately 1.5 mm). Nevertheless, IPG-DALT provides significantly improved reproducibility of spot positions compared to conventional isoelectric focusing with synthetic carrier ampholytes.

Electrophoresis, Gel, Two-Dimensional↗

PubMed2004

Capillary isoelectric focusing--reproducibility and protein adsorption.

Capillary isoelectric focusing (CIEF) is an important tool for the quality assurance of biotechnologically maintained drugs and for proteome analysis. The critical performance parameters of this technique are the precisions of isoelectric point (pI) values and peak areas. Compared to capillary zone electrophoresis (CZE), where precise results can be obtained (e.g., 0.5% relative standard deviation (RSD) for peak areas, n = 60), only few data are available for CIEF experiments. So far, reproducible data of pI values (RSD = 0.5%) have been acquired, but peak areas show inferior results (about 3-15% RSD). Nonstable capillary coatings and protein adsorption have been discussed as possible reasons. Recent work of Righetti et al. [25, 27] has proven that the use of coated capillaries can reduce the adsorption of proteins by 50% but cannot prevent it. In our CIEF experiments irregular and poorly reproducible peak patterns have been observed. In a long-time experiment of 106 repeated runs, an overall RSD of 10% was obtained for peak areas, RSD of 2% only in series of about 10 consecutive replicates. Especially at higher concentrations the reproducibility deteriorates. This seems to be the result of a self-amplifying process, induced by adsorbed protein molecules, leading to further agglomerations. CZE control experiments in linear polyacrylamide (LPA)-coated capillaries proved a strong pH dependency of these effects within a small range. Compared to bare fused-silica surfaces, adsorption effects are reduced but not inhibited. An enhancement of reproducibility in CIEF experiments can be achieved only by controlling the interactions of proteins and capillary walls.

Adsorption↗

PubMed2007

Event-related functional near-infrared spectroscopy (fNIRS) based on craniocerebral correlations: reproducibility of activation?

The purpose of the present study was to assess the retest reliability of cortical activation detected by event-related functional near-infrared spectroscopy (fNIRS) based on craniocerebral correlations. Isolated functional activation was evoked in the motor cortex by a periodically performed finger-tapping task. During 44-channel fNIRS recording, 12 subjects performed 30 trials of right and left index finger tapping in two sessions. The retest interval was set to 3 weeks. Simple correlations of the contrast t-values supplemented by scatterplots, channel-wise intraclass correlation coefficients (ICC), as well as reproducibility indices for the size and the location of the detected activation were calculated. The results at the group level showed sufficient single measure ICCs (up to 0.80) and excellent reproducibility of the size and the location (up to 89% were reproducible). Comparisons of the intersession group amplitudes demonstrate that the fNIRS signals were stable across time in a retest study design: the number of significant differences was less than randomly occurring false-positive activated channels if an alpha level of 5% is chosen. Effect size analyses indicated that the intersession amplitude differences are small (mean < 0.25). For deoxyhemoglobin and oxyhemoglobin distinct statistical power profiles were revealed regarding the activation vs. baseline contrast as well as the intersession amplitude differences, indicating a higher sensitivity of deoxyhemoglobin for local hemodynamic changes. The results suggest that sensorimotor activation assessed by event-related fNIRS based on craniocerebral correlations is sufficiently reproducible at the group level.

Adult↗

PubMed1993

Quantitative microscopical and confocal laser scanning microscopy for intermediate endpoint biomarkers in breast cancer: potential and reproducibility.

Diagnostic quantitative pathological (QP) determinations are increasingly used in our hospital. The number of requests for QP for reference materials is rising rapidly. This is understandable; quantitative assessments have a strong prognostic value and can be very reproducible, depending on the care taken with a number of factors including cell and tissue processing, application of the appropriate stains, and the measurement protocol used. As to the latter, systematic random sampling gives the best intra- and interobserver agreement (with correlation coefficients between observers for certain features > or = 0.94). Flow cytometric determinations are often regarded as more reproducible than interactive morphometry due to the high speed of the assessments, the large number of objects measured per specimen, and the lack of observer interaction. Indeed, flow cytometrically assessed DNA ploidy is very reproducible, even though the % S-phase fraction is much more variable. Unlike image cytometry (ICM), visual inspection of cells is not easily accomplished with flow cytometry (FCM). With ICM, the fully automated measurement of DNA in thousands of cells is possible in 3-5 minutes, with a very low coefficient of variation (< or = 2% for the diploid and tetraploid peak of liver cell nuclei). ICM also allows measurement of texture features. However, quantitative immunohisto/cytochemical determinations may not always be as reproducible as sometimes believed. Recently, we found large variations in the measurements, made by a commercially available image processing instrument, of the estrogen and progesterone receptors, Ki-67, cathepsin D, and neu protein overexpression in breast cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Neoplasms↗

PubMed2005

Diffusion-weighted MRI of the lung with hyperpolarized helium-3: a study of reproducibility.

PURPOSE: To determine the reproducibility of several parameters of the ADC measurement by calculating the scan-to-scan intrasubject variability. MATERIALS AND METHODS: Measurements were performed using a gradient-echo sequence with a bipolar gradient for diffusion weighting (b=3.89 sec/cm2). Five patients with pulmonary emphysema, and six healthy-lung volunteers were included in the study. Images were acquired after inspiration of 3He during a single inspiratory breath-hold. To assess the reproducibility, the measurement was performed twice (time between measurements=20 minutes) without repositioning the subjects. Analysis was performed on the basis of region-of-interest (ROI) analysis and global lung ADC histograms. RESULTS: The mean ADC of a ROI varied by 5.1% between two measurements for volunteers and by 6.1% for patients. In the global evaluation, the 75th percentile demonstrated the best reproducibility (2%), while other parameters showed variations up to 12%. Only the variation of the standard deviation (SD) and the measure of homogeneity of the ADC map showed a significant difference between patients and volunteers. CONCLUSION: Diffusion-weighted imaging (DWI) is a well-reproducible method for assessing the lung microstructure.

Administration, Inhalation↗

PubMed1996

Reproducibility of isometric trunk extension torque, trunk extensor endurance, and related electromyographic parameters in the context of their clinical applicability.

Testing the capacity of the trunk extensor muscles may be useful in the diagnosis of low back pain. In the present study, the reproducibility of measurements of maximum trunk extension force, trunk extension endurance, and related electromyographic parameters was investigated. Intraclass correlations indicated that the reproducibility of maximum force and endurance time was satisfactory. Nevertheless, the smallest difference in these parameters that could be attributed, with 95% confidence, to a change in the condition of a patient was, in general, more than 20%. On the electromyograms, the slopes of amplitude and frequency content appeared to be related to endurance time. The reproducibility of these parameters in terms of the intraclass correlation was again satisfactory; however, the smallest detectable difference generally exceeded 50%. The clinical applicability of the parameters studied is severely limited by a lack of reproducibility.

Adult↗

PubMed2003

Reproducibility study of 3D geometrical reconstruction of the human carotid bifurcation from magnetic resonance images.

The combined magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) modeling approach is playing an increasingly important role in advancing our understanding of the relationship between hemodynamics and arterial disease. Nevertheless, such a modeling approach involves a number of uncertainties associated with various stages of the process. The present study is concerned with the reproducibility of geometry reconstruction, one of the most crucial steps in the modeling process. The reproducibility test was conducted on the right carotid bifurcation of eight normal human subjects, each of whom were scanned twice using the same MR protocol with an in-plane resolution of 0.625 mm. Models constructed from different scans of the same subject were compared and assessed using four quantitative measures: centerline distance, cross-sectional area, contour shape factors, and mean radius difference. The difference in the maximum carotid bulb area between the two scans was found to be <8.1% for all subjects. Shape factors (measuring the dissimilarity between two contours) of <10% were achieved in most of the common carotid arteries (CCAs) and internal carotid arteries (ICAs). The mean radius difference between the two scans was <0.4 mm for all subjects. Among the three vessels, the geometry of CCA was well reproduced by the reconstruction procedure in most of the cases, while the external carotid artery (ECA) showed the worst reproducibility. The impact of geometrical differences on CFD-predicted flow patterns and wall shear stress (WSS) will be investigated and discussed in a separate paper.

Adult↗

PubMed2003

Accuracy and reproducibility in phase contrast imaging using SENSE.

The purpose of this study was to evaluate the accuracy and reproducibility of phase contrast imaging using the sensitivity encoding (SENSE) method at different reduction factors. Analytical expressions were derived that state how reproducibility is influenced for velocity and flow measurements. Computer simulations, and in vitro and in vivo studies were performed in order to validate these expressions and to assess how accuracy is affected when different reduction factors are applied. It was shown that reproducibility depends on the reduction and geometry factors. Since the geometry factor varies spatially, so does the reproducibility for phase contrast imaging. In areas with high geometry factors, the standard deviation (SD) may become so large that aliasing occurs. The accuracy of phase contrast imaging is not influenced directly when SENSE is used, but may be indirectly influenced due to high SDs of the measured phase that may subsequently cause aliasing. The current results show that it is possible to achieve accurate flow measurements even at high reduction factors. By taking the geometry factor into account, it may be possible to find areas where phase contrast imaging is accurate even at high reduction factors.

Blood Flow Velocity↗

PubMed1996

Reproducibility of high spatial resolution proton magnetic resonance spectroscopic imaging in the human brain.

The application of proton (1H) magnetic resonance spectroscopic imaging (MRSI) allows for noninvasive, localized analyses of brain biochemistry; however, minimal work has been devoted to the evaluation of 1H MRSI reproducibility. This study examined the reproducibility of 1H MRSI from five normal subjects on two occasions, separated by 10 days. Reproducibility of the MR signal was evaluated in the context of automated shimming, automated processing, and accurate subject repositioning. Reliability measures for physicochemical indices (choline moieties, creatine, N-acetylaspartate, and myo-inositol) were moderately concordant across repeat studies. Gain variation and repositioning results were excellent. It has been concluded that 1H MRSI reproducibility is adequate for serial studies of brain metabolism.

Adult↗

PubMed1992

Autonomic surface potential analysis: assessment of reproducibility and sensitivity.

There has been recent interest in measuring sympathetic sudomotor function by autonomic surface potential analysis. The purpose of the present study was to assess factors affecting the reproducibility of the test. We determined the within-day and between-day reproducibility in 24 healthy volunteers. We used an increasing rather than a constant electrical stimulus to minimize habituation. The amplitudes were still highly variable (an average within-day coefficient of variation in the soles of 35%). Habituation did not, however, affect the latencies of the responses, which were much more reproducible (an average within-day coefficient of variation in the soles of 8%). Studies of between-day reproducibility revealed that the mean amplitudes were lower on day 2 vs. day 1 (0.706 +/- 0.10 vs. 0.85 +/- 0.10 mV in the soles, P less than 0.01) but the mean latencies were similar on the different testing days (2.09 +/- .04 seconds for the soles on day 1 vs. 2.16 +/- .05 seconds on day 2). We also assessed the sensitivity of surface potential analysis and report the results of testing 35 patients with far advanced autonomic neuropathy.

Aged↗

PubMed2002

Inter-laboratory and inter-observer reproducibility of immunohistochemical assessment of the Ki-67 labelling index in a large multi-centre trial.

Proliferative activity of tumour cells, as assessed by the Ki-67 labelling index, has been suggested as a potential prognostic indicator in many neoplastic diseases. Meaningful application of the immunohistochemically determined tumour cell growth fraction in clinical decision-making requires information about its inter-laboratory reproducibility. To assess the reproducibility of Ki-67 determined growth fraction, a multi-centre immunohistochemical trial was performed with 172 participating laboratories, each testing 30 different tissue samples. Evaluating 5160 Ki-67 labelling indices with a newly developed tissue microarray, good inter-observer reproducibility but high inter-laboratory variability was found. Reassessment of all stainings revealed considerable inter-laboratory differences in the intensity and frequency of labelled nuclei, suggesting that antigen retrieval or staining techniques are predominantly responsible for the inter-laboratory variability found in this trial. Consequently, cut-off levels for Ki-67, suggested to distinguish prognostic subgroups in tumours, appear to have limited reproducibility in a multi-centre approach. It is concluded that there is a need to standardize the immunohistochemical determination of the Ki-67 labelling index when it is used as a prognostic indicator in surgical pathology.

Biomarkers, Tumor↗

PubMed2005

A robust, streamlined, and reproducible method for proteomic analysis of serum by delipidation, albumin and IgG depletion, and two-dimensional gel electrophoresis.

Serum is a readily available source for diagnostic assays, but the identification of disease-specific serum biomarkers has been impeded by the dominance of human serum albumin and immunoglobulins (Igs) in the serum proteome. There is a need to reduce the technical variation in serum processing and analysis to allow for a reproducible analysis of large cohorts. To this end, we have developed a rapid and reproducible procedure for sample preparation and high-resolution two-dimensional gel electrophoresis to analyze human serum. Serum is centrifuged at high speed to remove lipids and aggregated proteins, incubated with protein G resin to remove IgG, precipitated with NaCl/ethanol to deplete albumin, and slowly resolubilized in a sodium dodecyl sulfate (SDS)/N-(2-hydroxyethyl)piperazine-2'-(2-ethanesulfonic acid) (HEPES) buffer. The delipidated and IgG/albumin depleted serum proteins are focused on pH 4-7 linear large immobilized pH gradient strips, and then resolved by Bis-Tris SDS-polyacrylamide gel electrophoresis. The robustness and reproducibility of the optimized procedure was determined for three individual serum samples on three consecutive days. An image analysis of the nine silver-stained gels demonstrated that the intensity and localization of protein spots are highly reproducible. Our IgG and albumin depletion procedure will aid in screening the patient sera for normal biological variation and disease-specific biomarkers.

Blood Proteins↗

PubMed2002

Evaluation of protocols for reproducible electrospray in-source collisionally induced dissociation on various liquid chromatography/mass spectrometry instruments and the development of spectral libraries.

Mass spectral libraries provide a tool for identifying unknown compounds using both molecular weight and fragmentation information. Mass spectrometers with electrospray ionisation (ESI) and atmospheric chemical ionisation (ApCI) sources have the capability to produce data of this type using in-source collisionally induced dissociation (CID), and in-source CID libraries can be created. Due to the variation in electrospray source design from different instrument manufacturers, the production of reproducible in-source CID spectra that can be used in libraries for all instrument types is not a trivial task. To date, the evaluation of the production of in-source CID libraries has tended to focus on similar instruments from one manufacturer. The studies have also tended to focus on specific compound classes, with a limited molecular weight range.This report describes the findings from the investigation of protocols for the creation of mass spectral libraries using ESI in-source CID on six instruments from four different manufacturers. The overall goal was to create a spectral library for the identification of unknowns. The library could then be applied across all manufacturers' electrospray instruments. Two different experimental protocols were attempted. The first used a tuning compound to establish standard ESI source conditions, with fixed fragmentation potentials. The second involved the attenuation of the [M + H](+) ion to a known degree. A diverse range of compounds (pharmaceutical, photographic, pesticides) was tested to establish the reproducibility of the spectra on the six instruments. Both protocols produced spectra on the various instruments that in many cases were very similar. In other examples, the spectra differed not only in their relative ion abundances, but also in terms of the spectral content. Important observations regarding the effect of ion source design are also reported. The degree of spectral reproducibility was calculated off-line by comparing the five most abundant ions (20% for each ion that matches) from each spectrum on each instrument. This approach was adopted, as we do not possess a software package that met our requirements for spectral comparison. Match factors (% fit) were calculated by comparing each spectrum against the spectra recorded for the same compound and then for all other compounds, on each instrument. The % fit values derived by the off-line approach gave a clear view of the spectral reproducibility from instrument to instrument and also discriminated the spectra of the various compounds from each other. The applicability of this approach was tested using a blind trial in which several compounds were presented as unknowns, their in-source CID spectra recorded and the five-ion approach used for identification.

Chromatography, Liquid↗

PubMed2007

PET imaging of neurokinin-1 receptors with [(18)F]SPA-RQ in human subjects: assessment of reference tissue models and their test-retest reproducibility.

[(18)F]SPA-RQ (substance P antagonist receptor quantifier) labels the substance P-preferring (NK(1)) receptor in human brain. A prior study showed that [(18)F]SPA-RQ brain uptake can be quantified with a reference tissue method and thereby avoid invasive blood sampling. The purposes of this study were to compare three different reference tissue methods and to assess test-retest reproducibility. Eight healthy subjects underwent two [(18)F]SPA-RQ scans. We calculated the binding potential (BP), which is proportional to receptor density, from both regional volume of interest and voxel-wise data. We compared three reference tissue methods: simplified reference tissue model, multilinear reference tissue model (MRTM), and its two-parameter version (MRTM2). The three methods generated equivalent values of regional BP, but MRTM2 was the most resistant to noise. Temporally stable values of BP were obtained with 240 min of imaging data. MRTM2 had excellent test-retest reproducibility, with high reliability (intraclass correlation > 0.9) and low variability (< 10%). In addition to regional volume of interest analysis, we also created parametric images of BP, variability, and reliability based on voxel-wise time-activity data. The reproducibility of parametric BP was also good, with variability < 20% and reliability > 0.7 in gray matter regions. In conclusion, a two-parameter reference tissue method (MRTM2) provided reproducible and reliable measurements of [(18)F]SPA-RQ brain uptake using 240 min of both regional and voxel-wise data.

Adult↗