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Results for “Observer Variation”

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PubMed1989

Preferential looking in the mentally handicapped.

We have assessed the feasibility of Preferential Looking (PL), using Teller Acuity Cards, for the estimation of binocular and monocular visual acuities in a group of mentally handicapped adults. Our results show the comparison between grating and recognition acuities, inter-observer variation, success rate, time taken and the sensitivity of this method in identifying monocular visual deficit in this group of subjects. The reasons for success or failure with PL methods in relation to criteria for mental handicap are discussed.

Adult↗

PubMed1991

[The group study of diagnostic efficacy of cerebro-vascular disease by I-123 IMP SPECT images obtained with ring type SPECT scanner--the ROC analysis on the diagnosis of perfusion defect and redistribution].

We performed two image reading experiments in order to investigate the diagnostic capability of I-123 IMP SPECT obtained by the ring type SPECT scanner in cerebro-vascular disease. Fourteen physicians diagnosed SPECT images of 55 cases with reference to clinical neurological informations, first without brain XCT images and second with XCT images. Each physician detected perfusion defects and redistributions of I-123 IMP and assigned a confidence level of abnormality for these SPECT findings by means of five rating method. From results obtained by ROC analysis, we concluded as follows: (1) Generally, I-123 IMP SPECT is a stable diagnostic modality in the diagnosis of cerebro-vascular disease and the image reading of XCT had no effects on the diagnosis of SPECT on the whole of physician, (2) However, there were unnegligible differences among individuals in the detectability of findings and the effect of XCT image reading, (3) Detectability of redistribution of I-123 IMP was lower than that of perfusion defect and inter-observer variation in the diagnostic performance for redistribution was larger than that of perfusion defect. The results suggest that it is necessary to standardize diagnostic criteria among physicians for redistribution of I-123 IMP.

Amphetamines↗

PubMed2000

Pollen morphological survey of Pentas (Rubiaceae-Rubioideae) and its closest allies.

Pollen descriptions, based on LM and SEM observations, are provided for the Pentas complex, an African alliance within the Hedyotideae-Spermacoceae alliance, which includes the genera Pentas, Otomeria, Batopedina, Parapentas, and Chamaepentas. The close relationship among these genera is confirmed by pollen morphological data. The observed variation in pollen character states agrees well with the existing genera and subgenera. The combination of small spheroidal pollen grains with narrow, acute endocolpi, and a small apocolpium index distinguishes Batopedina from Otomeria and Pentas. Parapentas differs from Batopedina in having broad endocolpi with vague ends.Two of the three subgenera of Otomeria, Neotomeria and Volubilis, are supported by pollen data. Pollen of the subgenus Otomeria, however, is less differentiated and is similar to pollen of Pentas subgenus Pentas. The exact relationship between the genera Otomeria and Pentas remains unclear, and molecular data are needed to interpret the observed morphological variation. Chamaepentas has pollen that is nearly identical to that of the Pentas subgenus Chamaepentadoides and of the subgenus Megapentas, i.e. large spheroidal pollen grains with three, medium-length colpi and endocolpi with acute ends. Pollen morphology provides additional support for a close affinity between Pentas subgenus Phyllopentas and Pentas subgenus Vignaldiopsis.

Journal Article↗

PubMedDate not supplied

Scratch induction in the rat by intradermal serotonin: a model for pruritus.

Eight substances (histamine, compound 48/80, kallikrein, trypsin, papain, substance P, serotonin and platelet activating factor) were injected intradermally (volume 50 microl) into the rostral back (neck) of rats in order to establish an animal model for peripherally elicited pruritus. While serotonin induced excessive scratching at the site of injection, the other substances were weak or inactive. The dose-response relationship of serotonin was sigmoid, EC50=2.1 mg/ml (95% confidence interval: 1.0 to 4.3 mg/ml). Injections of serotonin 1 mg/ml into the caudal back elicited no scratching at all, i.e. neither at the site of injection nor elsewhere, so the experiment indicated no systemic effect of serotonin 1 mg/ml intradermally. Scratching was probably elicited histamine-independently, since histamine itself did not elicit scratching. The intra- and inter-observer variations were 3-4%. We conclude that serotonin is a reproducible local pruritogen eliciting scratching in the rat. The model may be useful in research and development of topical antipruritics of the nonhistaminic type as well as for various other purposes in pruritus research.

Animals↗

PubMed1991

Reliability of the acetabular teardrop as a landmark.

This study investigated the effect of tilt and observer reliability on radiographic measurements of the position of a prosthetic acetabular cup in seven dry bone pelves using the teardrop as a landmark. Coronal or sagittal tilt of more than five degrees was easily recognisable and there was effectively no observer variation in the measurements up to this limit. In addition, 90 out of 100 randomly selected antero-posterior pelvic radiographs from an outpatient department were not significantly rotated and 93 demonstrated a clearly defined teardrop. Measurements about the teardrop on routine radiographs are therefore sufficiently accurate to allow assessment of prosthetic position.

Acetabulum↗

PubMed1995

Observer reliability in assessing placental maturity by histology.

AIMS: To evaluate the ability of five experienced perinatal pathologists to assess placental maturity reliably by histology. METHODS: Twenty four haematoxylin and eosin slides, six each from placentas of 27, 31, 35, and 39 weeks' gestation, were circulated to five pathologists on three separate occasions. The slides were labelled with the correct or incorrect gestational ages. RESULTS: The mean absolute error over all 360 readings was 2.72 weeks. Only 54% of the slides were assessed within two weeks of the correct gestation. Pathologist tended to overestimate younger gestations and underestimate older gestations. Two, and possibly three, pathologist were influenced by the gestational age state on the label. One pathologist, who did not appear to be influenced by the label, was more accurate in diagnosing gestation of the placentas than other colleagues. CONCLUSIONS: Experienced pathologists can have difficulty in assessing the villous maturity of placentas by histology. They can also be influenced by clinical information provided, such as gestational age. Other observer reliability studies must address the issue of the influence of labelled information on observer variation. A difference in maturation would have to be of a six week magnitude to have a chance of being detected by current methods. This may limit the value of the histological diagnosis of placental dysmaturity as a surrogate marker for uteroplacental ischaemia.

Analysis of Variance↗

PubMed1990

Clinical assessment of osteoarthritis of the knee.

The repeatability of physical signs used to assess osteoarthritis of the knee has not been systematically examined. The within and between observer variation of 10 commonly used physical signs to determine osteoarthritis of the knee has been assessed here. The results obtained show variation in the repeatability of these signs. For those examining the tibiofemoral joints the repeatability was greater than for those examining the patellofemoral joint. It would therefore seem vital to take note of the repeatability of physical signs in determining the number of subjects to be studied in epidemiological studies and therapeutic studies in osteoarthritis.

Female↗

PubMed1991

System 8000: computerized antenatal FHR analysis.

SYSTEM 8000 is a computerized system for antenatal fetal heart rate (FHR) analysis, with interaction online to ensure good quality recording and to minimize the time required to obtain the necessary information (based on fetal movements and tocodynamometer readings as well as FHR). The equipment consists of a Personal Computer with hard disk, interfaced to a fetal monitor. Software is written in C. An extensive definition is given on most of the functions and parameters as calculated by the system, e.g. record quality, uterine contraction peaks, basal heart rate, variation, decelerations and accelerations. System 8000 is designed to take account of the episodic changes in FHR and fetal movements characteristic of sleep states. Their presence naturally affects the mean FHR variation calculated over, say 20-30 mins. But, as the amplitude of these episodes is attenuated in association with growth retardation and hypoxaemia, the measurements of variation decline. In practice inter- and intra-observer variation is greatest in assessing FHR variation. Yet a decrease in variation is the most reliable index of fetal deterioration. The system measures FHR variation accurately and reproducibly, as well as fetal movements. In the synoptic display these two equally important fetal variables are given their rightful prominence. It has been interesting to observe how rarely the basal FHR changes in fetuses suffering progressive respiratory insufficiency, and how extreme tachycardia (a basal rate greater than 170/min) tends to reflect other fetal problems such as infection or maternal pyrexia.

Cardiotocography↗

PubMed1992

Reliability of first-pass radionuclide determination of cardiac output in the upright position at rest and during exercise.

The reliability of non-invasive determination of cardiac output using first-pass radionuclide cardiography at rest and during exercise in the upright position was evaluated in 20 patients with coronary artery disease. Cardiac output values ranged from 2.97 to 5.99 l/min at rest and from 5.08 to 10.82 l/min during exercise. Cardiac output results obtained by the radionuclide method were compared with those derived from the thermodilution technique performed simultaneously. The mean difference between the two techniques was 0.02 l/min at rest and -0.34 l/min during exercise; the limits of agreement (mean +/- 1.96 SD) were -1.29 to 1.33 l/min and -1.97 to 1.29 l/min, respectively, indicating an acceptable level of agreement. A high reproducibility of the radionuclide technique was found, with a mean difference between determinations by two observers of 0.03 l/min at rest and 0.21 l/min during exercise, the corresponding limits of agreement being -0.75 to 0.81 l/min and -0.79 to 1.21 l/min, respectively. With the aid of a variance component analysis of two determinations by each of four observers, 95% confidence intervals of +/- 10% at rest and +/- 12% during exercise were computed for the radionuclide cardiac output measurements. The observer variation was most pronounced for the part of the cardiac output determination related to measurement of left ventricular equilibrium activity during exercise. First-pass radionuclide cardiography is a reliable method for determination of cardiac output in cardiac patients at rest and during exercise in the upright position.

Aged↗

PubMed1996

A critical appraisal of six modern classifications of ductal carcinoma in situ of the breast (DCIS): correlation with grade of associated invasive carcinoma.

The in-situ component of 180 cases of screen detected infiltrating duct carcinoma of the breast was classified according to six published classifications for ductal carcinoma in situ based on architecture, necrosis and cytology. All cases were assessed independently by two experienced observers to assess inter-observer variation. The differentiation of ductal carcinoma in situ as assessed by all the classification systems correlated with the grade of the associated invasive carcinoma (chi-squared between 50 and 107: P < 0.0001). Disagreements were commonest in the assessment of architecture and least common in the assessment of necrosis. For cytonuclear grade most disagreements (62.2%) involved the distinction between low and intermediate as against 33.9% disagreements for intermediate vs. high. Nuclear grade alone and necrosis alone were correlated with the grade of invasive carcinoma associated with the ductal carcinoma in situ and the Nottingham prognostic index of the patient. The Van Nuys classification of ductal carcinoma in situ is commended because it has a low inter-observer disagreement, is significantly correlated with the grade of the infiltrating carcinoma, uses simple well-defined criteria (with no requirement for percentage estimations), is applicable to small numbers of ducts and, most importantly, appears to correlate with disease-free survival.

Breast Neoplasms↗

PubMed2001

Three-dimensional echocardiography with tissue harmonic imaging shows excellent reproducibility in assessment of left ventricular volumes.

We studied the reproducibility of repeated measurements of left ventricular (LV) volumes by 2-dimensional (biplane method of disks) and 3-dimensional echocardiography (coaxial scanning) with tissue harmonic imaging. Ten healthy subjects underwent estimation of LV volumes by transthoracic echocardiography twice within 1 week by 2 different operators to investigate interexamination and operator variance. In addition, the analysis of LV volume was done manually by 2 observers to assess both interobserver and intraobserver variances. With 3D echocardiography, observer variation had the greatest impact on variance. Operator variability showed important contributions to total variance with the use of 2D echocardiography. The reproducibility of 3D echocardiography and tissue harmonic imaging is excellent and comparable to magnetic resonance imaging techniques; 3D echocardiography therefore should provide a powerful tool for noninvasive LV volume estimation.

Adult↗

PubMed1997

Two-dimensional gray-scale clustering for texture analysis.

OBJECTIVES: To develop a new quantitative method for the visual discrimination of image texture. METHODS: Two kinds of image phantoms were prepared, one for evaluating the effects of change in size and gray values of individual pixels (primitives) on perceived coarseness and the other for evaluating changes in groups of pixels (clusters) on perceived heterogeneity. The phantom images were displayed on a CRT and presented to 11 observers who assessed heterogeneity and coarseness on a 10-point scale between -5 and +5. On the basis of the observers' results, a new texture analysis method termed two-dimensional gray-scale clustering analysis was developed and applied to measure quantitatively the texture of the phantoms. The results obtained were then compared with those of the visual evaluation. RESULTS: The size of the primitives and the clusters greatly affected the visual evaluation of heterogeneity and coarseness. Changes in the gray value had only a slight effect. The intra-observer variation for heterogeneity was significantly larger than that for coarseness. Two-dimensional gray-scale clustering analysis could differentiate heterogeneity from coarseness. A high correlation was obtained between the visual evaluation and the quantitative data. CONCLUSION: Quantitative two-dimensional gray-scale clustering analysis appears to be a useful means of texture analysis.

Algorithms↗

PubMed2006

Quantifying esophageal peristalsis with high-resolution manometry: a study of 75 asymptomatic volunteers.

The vastly enhanced spatial resolution of high-resolution manometry (HRM) makes it possible to simultaneous monitor contractile activity over the entire length of the esophagus. The aim of this investigation was to define the essential features of esophageal peristalsis in novel HRM paradigms and establish their normative values. Ten 5-ml water swallows were recorded in each of 75 asymptomatic controls with a solid-state manometric assembly incorporating 36 circumferential sensors spaced at 1-cm intervals positioned to record from the hypopharynx to the stomach. The data set was then subjected to intensive computational analysis to distill out the essential characteristics of normal peristalsis. Esophageal peristalsis was conceptualized in terms of a proximal contraction, a distal contraction, and a transition zone separating the two. Each contractile segment was quantified in length and then normalized among subjects to summarize focal fluctuation of contractile amplitude and propagation velocity. Furthermore, the temporal and spatial characteristics of the transition zone separating the proximal and distal contraction were quantified. For each paradigm, graphics were developed, establishing median values along with the 5th to 95th percentile range of observed variation. In addition, the synchronization between peristalsis and esophagogastric junction relaxation was analyzed using a novel concept of the outflow permissive pressure gradient. We performed a detailed analysis of esophageal peristalsis aimed at quantifying its essential features and, in so doing, devised new paradigms for the quantification of peristaltic function that will hopefully optimize the utility of HRM in clinical and investigative studies.

Adult↗

PubMed2002

Digital imaging versus conventional contact tracing for the objective measurement of venous leg ulcers.

OBJECTIVE: This study aimed to compare the accuracy and inter-observer reproducibility of leg ulcer measurements made using digital images and conventional contact tracing. METHOD: The accuracy of measurements made with these two methods by four observers of 11 shapes with a known area was assessed. The time taken to do this was also measured. Following this, the accuracy and inter-observer reproducibility of the two methods was measured for patients with leg ulcers presenting to the vascular clinic, with contact tracing as the reference. RESULTS: For the reference shapes, both methods had a mean error of less than 5%. Contact tracing significantly underestimated the area by 3.9% (p < 0.05), while digital tracing showed no significant error. Digital tracing was quicker than contact tracing, especially for larger shapes (p < 0.05). For leg ulcers, there was no significant difference between area measurements made by the two methods. Inter-observer variation of digital tracing was greater for the ulcers than the reference shapes. This was due to differences in subjective interpretation and technical problems in recording some images. CONCLUSION: Measurement of leg ulcer area using computer-aided tracing of digital camera images is more accurate and quicker than contact tracing provided that appropriate care is taken when taking the pictures. Digital images offer considerable advantages in the shared hospital-community care of patients with leg ulcers.

Humans↗

PubMed2000

Perinatal deaths in a Norwegian county 1986-96 classified by the Nordic-Baltic perinatal classification: geographical contrasts as a basis for quality assessment.

BACKGROUND: Quality assessment of perinatal care can be carried out by classifying perinatal deaths. In the following we have analyzed the geographical contrasts in perinatal deaths according to the Nordic-Baltic perinatal death classification in a sparsely populated Norwegian county. MATERIAL AND METHODS: All stillbirths (> or =28 weeks of gestation) and neonatal deaths (gestational age > or =22 weeks; death < or =28 days) in 1986-96 from Nordland county (240,000 inhabitants) were classified. For comparison the county was geographically divided into six general local hospital areas and one central hospital area. RESULTS: The classification showed a well acceptable inter and intra observer variation. One hundred and seventy-one stillbirths and 155 neonatal deaths were analyzed. The death rate (pr 1,000 births) for single, non-malformed, antenatal stillbirths was higher in the central hospital area than in the local hospital areas (3.22 vs. 2.02). The death rate for extreme preterm infants (22-27 weeks of gestation) was on the other hand higher in the local hospital areas (2.45 vs. 1.05). One of the general local hospital areas was singled out with an especially high neonatal death rate among extreme preterm infants. This was to some extent explained by the death of extreme preterm twins and triplets. CONCLUSION: The Nordic-Baltic perinatal death classification system is a consistent and reproducible tool also for studying perinatal death in restricted geographical areas. The observed contrasts in perinatal deaths were used as basis for programs aimed at improving perinatal care. The observation of an unexplained increased number of antenatal stillbirths in the central hospital area resulted in a program for prospective recording and better characterization of the placenta and umbilical cord. Proposals for a better antenatal program preventing extreme preterm birth of twins for the whole county has been launched. In utero transfer to a hospital with a neonatal intensive care unit seems crucial in improving the prognosis for these infants.

Age Factors↗

PubMed1990

The reproducibility of continuous wave Doppler measurements in the assessment of mitral stenosis or mitral prosthetic function: the relative contributions of heart rate, respiration, observer variability and their clinical relevance.

The reproducibility of continuous wave Doppler echocardiographic measurements of transmitral diastolic flow velocity were studied in terms of bias and random error in 40 patients with either mitral stenosis or a Björk-Shiley mitral valve prosthesis. Twenty-seven patients were in sinus rhythm; 13 patients had atrial fibrillation. Intra- and interobserver differences in bias were small for the Doppler parameters studied i.e. early peak velocity (0.6% vs 3.6%), mean diastolic velocity (1.1% vs 8.6%), mean temporal velocity (2.3% vs 14.5%) and pressure half-time (2.7% vs 4.8%). The overall random error of the measurements (in terms of twice the standard deviation) was estimated separately in patients in sinus rhythm and atrial fibrillation: early peak velocity 5.6% and 9.2%, respectively, mean diastolic velocity 9.4% and 22%, mean temporal velocity 8.6% and 19% and pressure half-time 34% and 46%. The relative contributions to the overall random error of observer variation, heart rate dependency and respiratory variation were also studied. Heart rate dependency was demonstrated for both the mean diastolic velocity and the pressure half-time. Respiratory variation was found in the early peak velocity. From the results of this study the number of measurements to reduce the random error of the final average could be determined. Our results indicate that for the measurements in which a respiratory effect is present it is advisable to average the measurements taken over complete respiratory cycles.

Blood Flow Velocity↗

PubMed2004

Accuracy of digital panoramic images displayed on monitor, glossy paper, and film for assessment of mandibular third molars.

OBJECTIVE: The aim of this study was to compare the accuracy of 3 modalities of digital panoramic radiographs-monitor-displayed images and printed copies on glossy paper and on blue transparent film-for assessment of position and morphology of mandibular third molars. STUDY DESIGN: 164 third molars were recorded with one of 2 digital panoramic systems (Digora and Orthophos Plus) and assessed by 4 observers on 3 radiographic modalities: monitor display, glossy paper, and transparent film. The assessments were compared with surgeons' findings at the time of the operation ("gold standard"). RESULTS: Overall, the observer variation was larger than the variation between methods. A detailed paired analysis revealed some differences between the modalities for some diagnostic categories, but these were few and inconsistent. CONCLUSION: Printed images from the Kodak 1200 ink-jet printer on glossy paper and blue transparent film may be as accurate as the original monitor-displayed digital panoramic images from the Digora and Orthophos Plus systems for assessment of position and morphology of mandibular third molars.

Adolescent↗

PubMed2005

Is there a way for pathologists to decrease interobserver variability in the diagnosis of dysplasia?

Many obstacles interfere with our efforts to screen patients with Barrett esophagus. Probably the largest is choosing the appropriate patient group for screening. Beyond this problem, sampling error on the part of endoscopists is probably more serious a problem than observer variation among pathologists reviewing patient samples. Pathologists agree well on lesions that merit close follow-up or other intervention (high-grade dysplasia and invasive carcinoma), although interobserver agreement between pathologists interpreting lesser lesions is not good. This lack of agreement is not likely to improve substantially, and many adjunct markers are being sought in an attempt to identify patients with lesions of lower grades that are most likely to progress, allowing doctors to identify patients who would benefit from upgraded surveillance.

Barrett Esophagus↗