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 883 records · Page 49Linked to original sources

PubMed1991

Reproducibility of diurnal variation of heart rate.

Heart rate variation has been utilized as a parameter for validating autonomic nerve and sinus node function. However, few reports are available on the reproducibility of such data. In the present study, we studied the reproducibility of the diurnal variation of heart rate in 15 patients, and the effect of age differences on the variation in 30 normal men using a Holter ECG monitoring method. For investigating reproducibility, Holter ECG monitoring was performed twice, the two measurements being separated by a short interval. A moving average method applied on heart rate of every 3h exhibited essentially the same diurnal pattern of heart rate between two records in each patient. Excellent reproducibility of the pattern was also demonstrated by a lag correlation analysis. Variability of heart rate in normal men was independent of age. These results suggest that heart rate variation was essentially constant in each subject, at least within a short period.

Adult↗

PubMed1998

Long-term effects of pharmacological therapy for vasovagal syncope on the basis of reproducibility during head-up tilt testing.

The purpose of this study was to determine the efficacy of long-term pharmacological therapy selected on the basis of a head-up tilt test (HUT) in patients in whom reproducibility of the HUT response was demonstrable in the initial study. The HUT (80 degrees upright) was performed for 15 min with or without an infusion of isoproterenol (0.01-0.03 microgram/kg per min) in 54 patients with recurrent unexplained syncope. When vasovagal syncope was induced (positive response), the HUT was repeated to examine the test reproducibility. Vasovagal syncope was induced in 24 patients during HUT alone, and in 30 patients during the HUT with isoproterenol. Acute reproducibility was observed in 49/54 (91%) patients. In the tilt-positive patients, HUT was repeated after an intravenous administration of propranolol (0.1 mg/kg) or disopyramide (1 mg/kg) (acute test). Propranolol proved effective in 21 (80%) of 26 patients, and disopyramide in 13 (56%) of 23 patients. Thereafter, evaluation was done on the long-term clinical follow-up of the pharmacological intervention selected on the basis of the acute test in the 34 patients in whom the HUT could not induce vasovagal syncope after the oral administration of the pharmacological agent (propranolol 60 mg/day, disopyramide 300 mg/day). Thirty-two of 34 patients (94%) did not develop syncopal attacks during a 44 +/- 12-month period. Thus, in patients with unexplained syncope, HUT appears to have a high degree of acute reproducibility, and the acute drug response guided by HUT may be used to develop an effective long-term pharmacological therapy.

Administration, Oral↗

PubMed2005

Psychophysical estimates of the number of spectral-reflectance basis functions needed to reproduce natural scenes.

Theoretical analyses of spectral reflectances of natural surfaces suggest that their perceived colors can be well reproduced by approximations comprising combinations of three or four spectral basis functions. The aim of the present work was to assess psychophysically the number of basis functions necessary to reproduce entire natural outdoor scenes. Hyperspectral images of 20 such scenes were each subjected to a principal component analysis and then reproduced with a variable number of basis functions. The quality of the color approximation under daylight illumination was quantified theoretically in CIELAB space and psychophysically by spatial and temporal two-alternative forced-choice measurements in which the original and the approximated images were compared on a calibrated color monitor. Although five basis functions produced on average unit error in CIELAB space, original images were visually indistinguishable from their approximations only if there were at least eight basis functions. The combination of the spectral diversity of the natural world and the observed levels of color discrimination suggest that estimates of the minimum number of basis functions necessary to reproduce natural scenes may need to be revised upward.

Algorithms↗

PubMed1993

The Neer classification system for proximal humeral fractures. An assessment of interobserver reliability and intraobserver reproducibility.

The radiographs of fifty fractures of the proximal part of the humerus were used to assess the interobserver reliability and intraobserver reproducibility of the Neer classification system. A trauma series consisting of scapular anteroposterior, scapular lateral, and axillary radiographs was available for each fracture. The radiographs were reviewed by an orthopaedic shoulder specialist, an orthopaedic traumatologist, a skeletal radiologist, and two orthopaedic residents, in their fifth and second years of postgraduate training. The radiographs were reviewed on two different occasions, six months apart. Interobserver reliability was assessed by comparison of the fracture classifications determined by the five observers. Intraobserver reproducibility was evaluated by comparison of the classifications determined by each observer on the first and second viewings. Kappa (kappa) reliability coefficients were used. All five observers agreed on the final classification for 32 and 30 per cent of the fractures on the first and second viewings, respectively. Paired comparisons between the five observers showed a mean reliability coefficient of 0.48 (range, 0.43 to 0.58) for the first viewing and 0.52 (range, 0.37 to 0.62) for the second viewing. The attending physicians obtained a slightly higher kappa value than the orthopaedic residents (0.52 compared with 0.48). Reproducibility ranged from 0.83 (the shoulder specialist) to 0.50 (the skeletal radiologist), with a mean of 0.66. Simplification of the Neer classification system, from sixteen categories to six more general categories based on fracture type, did not significantly improve either interobserver reliability or intraobserver reproducibility.

Evaluation Studies as Topic↗

PubMed2004

Fast response temperature measurement and highly reproducible heating methods for 96-well plates.

Hyperthermia, the procedure of exposing cells to a temperature between 42 degrees and 49 degrees C, has been shown to be a promising approach for cancer treatment. To understand the underlying mechanisms of hyperthermic killing of cancer cells, it is critical to have an accurate temperature measurement technique and a heating method with high reproducibility. To this end, we have developed a method using fine thermocouples with fast response time to measure the temperatures in multiple wells of a 96-well plate. The accuracy of temperature measurement was +/- 0.2 degree C. Such a capability allows a complete record of the time and temperature of the treatment procedure and helps define an accurate thermal dose. We have also compared several methods for heating 96-well plates and found that use of copper blocks in contact with the lower surface of the 96-well plate in an incubator provides a highly reproducible heating method. The common method of using water bath to heat cells in vitro resulted in a decrease of cell viability even at the control temperature of 37 degrees C and a decrease in the reproducibility of certain biological assays. In summary, using these improved techniques, proposed thermal dose can be defined more precisely, and highly reproducible heating in vitro can be achieved.

Cell Culture Techniques↗

PubMed1985

Reproducibility of relaxation times and spin density calculated from routine MR imaging sequences: clinical study of the CNS.

This study was undertaken to determine if routine clinical magnetic resonance imaging sequences using only two different repetition times (TRs) and with only two sequential spin echoes (SEs) can be used to calculate reproducible relaxation time and spin density values for normal central nervous system tissue using a 0.35 T production-model instrument. In 43 patients 650 regions of interest of 11 different anatomic sites were measured. T1 and T2 relaxation times and spin density were measured. For each anatomic location, the mean and standard deviation of these values were determined. In most solid regions of brain, the standard deviation of both T1 and T2 was 4%-8%. Relaxation times of cortical gray matter varied more, with a standard deviation of 10%, probably because of volume-averaging with adjacent cerebrospinal fluid (CSF). CSF and ocular vitreous humor were neither reproducibly nor accurately measured because of the short TR and TE settings of the imaging sequences relative to the long T1 and T2 relaxation times of these substances. Significant and reproducible differences were found between the spin densities of gray matter and white matter, as well as between different regions of white matter. These differences are of major importance in contrast discrimination of gray and white matter on the long TR images. Knowing that relaxation values and spin densities calculated from routine imaging sequences are in fact reproducible, these normal ranges can now be used to investigate changes occurring in disease states.

Adolescent↗

PubMed1978

Reproducibility and comparative analysis of repeated intravenous and oral glucose tolerance tests.

We have developed a methodology for measuring the reproducibility of the oral glucose tolerance test (OGTT) and the intravenous glucose tolerance test (IVGTT) in normal subjects and in offspring of conjugal diabetic parents. Both groups of subjects revealed more striking correlations of several parameters of blood glucose and insulin secretion between two IVGTTs than between two OGTTs. Employing arbitrary criteria, we calculated a "reproducibility index" as a quantitative measure of blood glucose variability in each subject. No significant difference was found in the reproducibility of OGTT versus IVGTT, nor in normals versus the offspring. Only about 50 per cent of the tests in normals and in the offspring could be considered to be "reproducible." The offspring revealed greater correlations of several parameters, particularly insulin secretion, between the two IVGTTs and between the two OGTTs as compared with the normal group. However, the blood glucose variations tended to be considerably greater in the offspring from one to the other test.

Administration, Oral↗

PubMed1978

Reproducibility of regional cerebral blood flow measurements in acute severe head injury.

In order to evaluate the reproducibility of regional cerebral blood flow (rCBF) measurements in pathological brain tissue, serial measurements were carried out in 13 determinations performed in patients who were comatose after severe head injuries within the first 2 weeks after the head trauma. The xenon-133 intra-arterial method was used for the flow measurements, and the flow was studied separately in 16 areas of the brain, producing 197 regional double determinations. The patients were maintained in a steady state during and between the measurements, and only differences of less than 2 mm Hg in the arterial CO2 pressure and less than 5 mm Hg in the perfusion pressure were tolerated. The reproducibility was found to be reasonably good as regards initial slope-flow indices and height/area flow indices and height/area flow values, whereas that of the compartmentally calculated flow parameters was poorer. On dividing the series into severely and moderately pathological areas, it could be shown that the reproducibility of the flor values in the moderately pathological brain areas was acceptable and similar to the results reported by others, whereas the reproducibility in the most severely pathological areas of the brain was rather poor, as regards the flow in the fast compartments. The correlation between the various flow parameters was found to be fairly good.

Brain Injuries↗

PubMed2003

Comparison Tests of BioRID II and RID 2 with Regard to Repeatability, Reproducibility and Sensitivity for Assessment of Car Seat Protection Potential in Rear-End Impacts.

The objective of our study was to investigate the properties of the BioRID II and RID2 dummies regarding repeatability and reproducibility as well as their suitability to identify the protection potential of different car seats. For repeatability and reproducibility tests, three BioRID II and three RID 2 dummies at current build levels were seated on a rigid bench seat equipped with a head restraint, and mounted on a HyGe-type sled. The test velocity was prescribed by the proposed ISO-Pulse. For testing the interaction of the dummies with varying car seat geometries and mechanical properties and their ability to assess the protection potential of the seats, three seat types with passive and one seat with an active head restraint system from different car manufacturers were used. The seats were chosen due to their injury protection potential, indicated by accident field data and results of seat evaluation tests. One BioRID II equipped with a T1-load cell and one RID2 were positioned side-by-side on identical seats for each test. The tests were performed at velocities prescribed by the ISO-Pulse (deltav 16km/h / 8 g max.)and a more severe pulse (deltav 24km/h / 13 g max.). The dummy responses were interpreted by applying all currently proposed whiplash injury criteria (e.g. NIC, N(km), NDC, LNL). A comparison of these criteria shows their sensitivity for identification of the respective seat protection potential. This study examines the repeatability, reproducibility, kinematics and sensitivity of these two dummies in sled tests as well as their suitability with regard to the different injury criteria. The RID2 exhibited better repeatability and reproducibility than the BioRID II, because of its simpler mechanical design. The dummies did not give a consistent ranking of the low-speed, rear-end impact protection potentials of the four seat evaluated. More experience is needed to decide which dummy, injury criteria and limits should be used to assess the whiplash protection potential of seat designs.

Journal Article↗

PubMed1996

Reproducibility of blood pressure measurements.

Clinic blood pressure readings are less reproducible than 24 h and daytime average ambulatory blood pressures. This may depend on (1) the continuous and spontaneous variability which characterizes daily life blood pressure, (2) the well-known 'white-coat' effect and (3) other methodological problems affecting traditional sphygmomanometric readings, such as the observer's bias and digit preference. The higher reproducibility of average 24 h and daytime blood pressures is also, at least in part, a function of the greater number of blood pressure readings available. On the other hand, the various components of the 24 h blood pressure profile appear, in general, to be less reproducible than the 24 h average value. This is the case for hourly values, for the day-night blood pressure difference and for a number of statistical parameters employed for modelling the 24 h blood pressure curve. An alternative and simple way to obtain reproducible blood pressure values, without making use of ambulatory blood pressure monitoring techniques, may be offered by the average of 20-25 blood pressure readings obtained automatically or semi-automatically under standardized conditions in outpatient clinics. The implications of these findings for clinical trials aimed at evaluating the features of the effects of antihypertensive drugs on 24 h blood pressure are discussed.

Journal Article↗

PubMed1975

Inter-examiner and intra-examiner reproducibility in clinical and radiographic diagnosis.

The first technical report to be published by the FDI considered the principal requirements for controlled clinical trials of caries preventive agents and procedures. This document advocated the use of a simple reproducibility ratio as a measure of variability in caries diagnosis. In accordance with the FDI recommendations available figures from published work on duplicated examinations are presented in terms of this reproducibility ratio. The data refers to intra- and inter-examiner variability with respect to both clinical and radiographic examinations. Reproducibility studies carried out as a pre-calibration investigation and during the baseline examinations of a current clinical trial are also included. Considerable diversity is apparent, the intra- and inter-examiner variation for clinical examinations ranging from 0-13 to 0-61, and for radio-graphic assessments from 0-06 to 0-60. If an acceptable range of reproducibility ratios is to be formulated then this wide variation will have to be taken into account. Ultimately, if examiner variability cannot be maintained within reasonable limits, then the choice of an examiner could be just as important as the choice of the test substance.

Child↗

PubMed2002

[Reproducibility of CT scan evaluation of muscular fatty degeneration. Intra- and interobserver analysis of 56 shoulders presenting with a ruptured rotator cuff muscles].

PURPOSE OF THE STUDY: This study was undertaken to determine the reproducibility of measurements of fatty degeneration of the rotator cuff using computed tomography (CT). MATERIAL AND METHODS: Fifty-six patients who had undergone surgery for rotator cuff tear were included in this retrospective study. The extent of fatty infiltration was evaluated on CT scans with soft tissue windows in all 56 shoulders using a five-stage scoring system described by Goutallier. Five independent observers made the assessments. The same operation was repeated one month later to test intraobserver agreement. Four parameters were recorded: fatty infiltration of three muscles (supraspinatus, infraspinatus, subscapularis), and overall fatty infiltration grading. Interobserver variability was determined for each parameter using the intercorrelation coefficient (a test of reproducibility of quantitative measurements). RESULTS: The most reproducible measurement was the overall fatty infiltration grade. For this parameter, interobserver agreement was good with an intercorrelation coefficient of 0.75. The interval of confidence was +/- 0.5. Intraobserver agreement depended on the observer's level of experience. It was good for overall fatty infiltration grade assess by three senior observers (r=0.78) and moderate for two junior observers. CONCLUSION: The overall fatty infiltration grade is a reproducible parameter that should be used to evaluate the degree of fatty infiltration as the safety margin of this value (graded 0 to 4) is about 0.5. Fatty infiltration of a torn cuff would not be the only criterion to improve indications for treatment of rotator cuff tears.

Adipose Tissue↗

PubMedDate not supplied

[The role of the lateral and medial hypothalamus in reproducing a motor reaction as the signal during the acquisition of classical conditioned reflexes].

In experiments on three dogs there was shown that testing electrostimulation of the lateral hypothalamus reproduced the motor reaction which is a signal stimulus at elaboration of classic alimentary conditioned reflexes (CRs) and did not reproduce it at elaboration of classic defensive CR. Testing electrostimulation of medial parts of the hypothalamus reproduced, as LH electrostimulation the "signal" motor reaction, but in less percentage of cases, during elaboration of classic alimentary CRs and did not reproduce it at elaboration of classic defensive CRs. The reproduction of the signal motor reaction at LH electrostimulation is connected with activation of backward conditioned connection from motivation structures of the hypothalamus to representation of the signal stimulus in the motor cortex.

Animals↗

PubMedDate not supplied

Reliability of repeatability and reproducibility measures in collaborative trials.

The acceptability of a new analytical method is generally assessed in terms of repeatability and reproducibility estimates derived from a collaborative study. Procedures are presented for calculating confidence intervals and operating characteristic curves for acceptance criteria based on the repeatability and reproducibility estimates. Comparisons of the reliability of estimates are provided for various numbers of collaborators. With a small number of collaborators, the estimates of reproducibility are not reliable and decisions regarding acceptability of a method will be heavily based on the method's repeatability rather than the property of most interest, namely, the reproducibility of the method.

Analysis of Variance↗

PubMed1977

[The reproducibility of occlusal contacts in the Dentatus and Stuart articulators].

The reproducibility of occlusal contacts of 30 subjects was tested in the Dentatus and Stuart articulators. Primary contacts in the terminal hinge axis position were reliably reproducible in both articulators. Contacts in habitual intercuspidation were reproduced only approximately by both devices. Contacts in eccentric occlusion were satisfactorily reproduced in the Stuart articulator only. The findings show that doubts are indicated about the simulating capacity of semi-adjustable articulators which is frequently rated too high.

Dental Articulators↗

PubMed1986

Dual asthmatic reactions to inhaled Dermatophagoides pteronyssinus: reproducibility and antagonism by cromolyn sodium.

Twenty-four asthmatic patients sensitized to Dermatophagoides pteronyssinus were challenged with a standardized extract of this allergen. All the patients selected on the basis of skin tests and RAST, had an early asthmatic reaction (EAR). Seventeen of them also had a late asthmatic reaction (LAR). Eleven patients were rechallenged in order to study the reproducibility of both EAR and LAR. Six patients were also challenged after cromolyn sodium premedication Results show that (1) reproducibility of both EAR and LAR is satisfactory (coefficient of variation = 14%), (2) patients with reproducible EAR also have reproducible LAR, and (3) a single dose of cromolyn given before challenge can prevent EAR and markedly attenuate LAR.

Adolescent↗

PubMed1988

Reproducibility of mitotic counts and identification of mitotic figures in malignant glial tumors.

Quantitative pathology is a rapidly growing field of pathology. This field is developing methods allowing greater objectivity and better reproducibility in diagnostic decisions. The introduction of quantitative pathology as a teaching subject in medical education will help this field to become more widely and more correctly applied. Courses on quantitative pathology are organized yearly by the Department of Pathology at the University of Ancona. The 1986 course emphasized training of students in understanding basic problems such as variation caused by tissue processing, instrumentation, data handling and interpretation, and variation between observers. In this paper we describe experiments performed during the course on identification and quantitation of mitoses in malignant glial tumors. The participants, i.e. students of the postgraduate Pathology School, could identify mitoses with a 'substantial' reproducibility. However, when the observers were allowed freely to choose the fields to count, the reproducibility was 'slight'. The study suggests that sampling rules should be applied which secure reproducible application of morphometric method also on condition of free selection of fields. Because the application of such rules needs expertise in histopathology, it seems that morphometric method can best be applied by histopathologists themselves.

Glioma↗

PubMed1988

Reproducibility of counting immunoglobulin-containing cells in colonic mucosal biopsies.

Counting immunoglobulin (Ig)-containing cells in colonic mucosal biopsies can help to objectively support the differential diagnosis of ulcerative colitis and Crohn's disease. Before a method for counting Ig-containing cells can be applied in a clinical setting, however, its reproducibility must be determined. This study investigated the reproducibility of two different methods for counting such cells. The use of a light microscope with an ocular grid resulted in a slightly better reproducibility than did the use of a projection microscope with a graphics tablet. Moreover, the ocular grid method had a higher efficiency. The counting of IgM- and IgG-containing cells had a considerably higher reproducibility than did the counting of IgA-containing cells. To determine the minimal number of cells to be counted in order to ascertain a stabilized mean number of Ig-containing cells, the running means of counts of Ig-containing cells were calculated for two observers. When at least 600 Ig-containing cells (i.e., two to four fields) were counted, the interobserver variation of the running means was less than 10% for IgA and IgG counts and less than 5% for IgM counts. Since earlier studies showed differences in the counts of IgA-, IgG- and IgM-containing cells between ulcerative colitis and Crohn's disease to be, respectively, 3%, 25% and 28%, the results of the present study suggest that the proposed counting method can be useful in the differentiation between these entities.

Cell Count↗