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At least 433 records · Page 24Linked to original sources

PubMed2000

Evolutionary Model and Oscillation Frequencies for alpha Ursae Majoris: A Comparison with Observations.

Inspired by the observations of low-amplitude oscillations of alpha Ursae Majoris A by Buzasi et al. using the WIRE satellite, a grid of stellar evolutionary tracks has been constructed to derive physically consistent interior models for the nearby red giant. The pulsation properties of these models were then calculated and compared with the observations. It is found that, by adopting the correct metallicity and for a normal helium abundance, only models in the mass range of 4.0-4.5 M middle dot in circle fall within the observational error box for alpha UMa A. This mass range is compatible, within the uncertainties, with the mass derived from the astrometric mass function. Analysis of the pulsation spectra of the models indicates that the observed alpha UMa oscillations can be most simply interpreted as radial (i.e., l=0) p-mode oscillations of low radial order n. The lowest frequencies observed by Buzasi et al. are compatible, within the observational errors, with model frequencies of radial orders n=0, 1, and 2 for models in the mass range of 4.0-4.5 M middle dot in circle. The higher frequencies observed can also be tentatively interpreted as higher n-valued radial p-modes, if we allow that some n-values are not presently observed. The theoretical l=1, 2, and 3 modes in the observed frequency range are g-modes with a mixed mode character, that is, with p-mode-like characteristics near the surface and g-mode-like characteristics in the interior. The calculated radial p-mode frequencies are nearly equally spaced, separated by 2-3 µHz. The nonradial modes are very densely packed throughout the observed frequency range and, even if excited to significant amplitudes at the surface, are unlikely to be resolved by the present observations.

Journal Article↗

PubMed2005

Somatosensory activations during the observation of touch and a case of vision-touch synaesthesia.

In this study, we describe a new form of synaesthesia in which visual perception of touch elicits conscious tactile experiences in the perceiver. We describe a female subject (C) for whom the observation of another person being touched is experienced as tactile stimulation on the equivalent part of C's own body. Apart from this clearly abnormal synesthetic experience, C is healthy and normal in every other way. In this study, we investigate whether C's 'mirrored touch' synesthetic experience is caused by overactivity in the neural system that responds to the observation of touch. A functional MRI experiment was designed to investigate the neural system involved in the perception of touch in a group of 12 non-synesthetic control subjects and in C. We investigated neural activity to the observation of touch to a human face or neck compared with the observation of touch to equivalent regions on an object. Furthermore, to investigate the somatosensory topography of the activations during observation of touch, we compared activations when observing a human face or neck being touched with activations when the subjects themselves were touched on their own face or neck. The results demonstrated that the somatosensory cortex was activated in the non-synesthetic subjects by the mere observation of touch and that this activation was somatotopically organized such that observation of touch to the face activated the head area of primary somatosensory cortex, whereas observation of touch to the neck did not. Moreover, in non-synesthetic subjects, the brain's mirror system-comprising premotor cortex, superior temporal sulcus and parietal cortex-was activated by the observation of touch to another human more than to an object. C's activation patterns differed in three ways from those of the non-synesthetic controls. First, activations in the somatosensory cortex were significantly higher in C when she observed touch. Secondly, an area in left premotor cortex was activated in C to a greater extent than in the non-synesthetic group. Thirdly, the anterior insula cortex bilaterally was activated in C, but there was no evidence of such activation in the non-synesthetic group. The results suggest that, in C, the mirror system for touch is overactive, above the threshold for conscious tactile perception.

Adult↗

PubMed1990

[Experimental studies in the healing process of the rats tongue after Nd:YAG contact laser irradiation. Scanning electron microscopic observation].

The Nd:YAG laser is useful in clinical oral surgery because of its superior hemostatic and coagulating effects. The purpose of this study was to examine the healing process of the tongue wounds caused by the Nd:YAG contact laser. A scanning electron microscope (SEM) was used, focusing mainly on the papillae filiformes of the tongue, and the results were compared with the pathological findings. The laser's effect on the microcirculatory network and the healing process were observed using the injection replica scanning electron microscope method. One hundred and eighty nine male Wistar rats were used in the experiment. Irradiation condition were 3, 6, 9 and 12-W for 1.0 second. The rats were sacrificed immediately after irradiation and on the 1st, 4th, 7th, 10th, 14th, 21st, 28th and 56th days after irradiation. The results were as follows. Pathological observations; Immediately after irradiation, the 3-W wound was observed below the lamina propria. The 6-W and 9-W wounds were observed from the upper musculi transversus linguae to the near center. The 12-W wound was observed to the center of the musculi transversus linguae. SEM observations; In the case of the 3-W wound, on the 7th day, normal epithelization was largely complete and there was a mucosal bulge which appeared to be regenerating papillae filiformes at the edge of the wound. On the 28th day, regenerated papillae filiformes were observed over the entire surface of the wound. The similar healing process was observed for the 6, 9 and 12-W wounds. However, in the cases of the 6-W and 9-W wounds the regenerated papillae filiformes were morphologically different from the original ones. In the case of the 12-W wound, on the 56th day regenerated papillae filiformes were observed around the edge of the wound but not in the center. Injection replica SEM observations; Concerning the effect of contact laser irradiation (6-W) on the tongue's microcirculatory network, the blood vessels at the edge of the wound were cut straight off, which suggested that they had been cauterized. Observations of the network during the healing of the wound showed that capillary loops had been restored and were related to the papillae filiformes.

Animals↗

PubMed1999

Observation levels in acute psychiatric admissions.

It was our objective to compare the influence of patients' variables and circumstances of admission on the use of observation levels in acute psychiatric admissions in a British mental health unit. We performed a prospective case note survey of all acute psychiatric admissions during 28 consecutive days in June and July 1991 within a large teaching hospital and a traditional psychiatric hospital in Nottingham, England. We compared, the demographic characteristics of 88 consecutive admissions, admission procedures, clinical data, initial observation levels and changes in observation levels. As for the results, most patients were admitted outside of regular working hours (weekends or after 5 p.m.). Most patients were placed on intermediate (close) observation. The most important factor associated with the choice of observation level was the legal status of the patient (chi2 = 14.79, df = 2, p < 0.001, Fisher's exact test p < 0.0001). There were significantly fewer incidents (chi2 = 7.72, df= 2, p < 0.05, Fisher's exact test p < 0.01) on the highest (special) category of observation. The observation policy of the unit was not followed consistently. The number of factors contributing to the choice of observation levels reflects the complexity of the task facing the staff. Special observation is an effective method of managing acutely disturbed patients. The time of admission of most patients implies that more trained staff should be provided outside of regular hours. Clinical staff should be regularly trained in the use of observation procedures. It should be a regular topic in clinical audit.

Adult↗

PubMed2000

Pain behavior observation: current status and future directions.

Individuals who have pain engage in certain pain-related behaviors that tend to communicate their pain to others. There is growing recognition that the careful observation of such pain behaviors is an important component of a comprehensive pain assessment. This article provides an overview of the current status of behavioral observation methods used to assess pain behavior. The first half of this article describes and evaluates the most commonly used pain behavior observation methods. These include self-observation methods such as activity diaries, and direct observation methods such as the use of standard behavior sampling methods and naturalistic observation methods. The second half of the article discusses several important future clinical and research applications of pain behavior observation methods. The need to develop practical, clinical methods for incorporating pain behavior observation methods into practice settings is emphasized. Important future research topics include studying the social context of pain behavior (eg, by examining how spouses respond to displays of pain behavior), examining the predictive validity of pain behavior (ie, how observed pain behaviors predict future disability and impairment), and identifying pain behavior subgroups within heterogeneous chronic pain populations. Further development and refinement of pain behavior observation methods is likely to increase our understanding of the varied ways that patients adapt to persistent pain.

Adaptation, Psychological↗

PubMed1992

Inter-observer variance in ultrasonographical assessment of Schistosoma mansoni-related morbidity in young schoolchildren.

49 Sudanese schoolchildren aged 6-9 years with Schistosoma mansoni infection were ultrasonographically examined by two independent observers in a double-blind fashion. The first observer recorded normal appearance of the liver in 23 cases, whereas the second observer recorded the appearance as normal in 33 cases. There were 23 concordant observations. For Grade I periportal fibrosis (PF), 13 observations were concordant. PF Grade II was rarely observed (2 versus 3 cases), and Grade III was not recorded at all. In total, 38 out of 49 observations were concordant (77.5%). These preliminary data from two ultrasound observers, from observations on a limited number of patients, can be seen as an indication of a potential inter-observer variation of around 20% for the distinction between the absence of PF and a low level of PF.

Child↗

PubMed1991

Measurement of intima-media thickness of common carotid arteries with high-resolution B-mode ultrasonography: inter- and intra-observer variability.

High-resolution B-mode ultrasonography enables quantitative measurement of the thickness of the intima-media layer of superficial large arteries noninvasively. We investigated the inter- and intra-observer variability of this measurement in the common carotid arteries in 10 randomly selected men. The maximal right and left carotid intima-media thickness (IMT) was measured with calipers during the scanning from frozen images by four observers in a blinded fashion. Three observers also repeated the scanning and the measurements twice with a week's intervals, with no knowledge of the previous readings. The inter-observer coefficient of variation (CV) was 10.5%. The intra-observer CV (mean of right and left CCA) was 5.4-5.8% for the three observers who carried out the measurements three times. The mean absolute difference between the first and third measurement was 0.087 mm. The intra-observer variation accounted for only 4% of the total measurement variability, 96% being attributable to inter-observer variation. These data show that most of the measurement variability in ultrasonographic B-mode IMT measurements is due to differences between observers, whereas the within-observer variability over time appears proportionately very small.

Analysis of Variance↗

PubMed1994

Observer variation in pattern type and extent of disease in fibrosing alveolitis on thin section computed tomography and chest radiography.

In fibrosing alveolitis the pattern type on thin section computed tomography (CT) predicts histological appearances at open lung biopsy and the likelihood of response to treatment. To test the level of inter- and intra-observer variability on CT and chest radiography (CXR), the pattern type and extent of disease were assessed by four observers (two experienced, two inexperienced). A total of 126 CT examinations and 108 concurrent postero-anterior chest radiographs were scored on two occasions, at least 8 weeks apart. A confidence rating was assigned to each observation. Three out of four observers agreed on pattern type in 81% of cases on CT compared with 54% on CXR (kappa coefficient 0.48 and 0.16 for CT and CXR, respectively). Inter-observer variability in categorizing pattern type on CT was lowest in patients with the highest confidence scores (kappa = 0.63). Confident observations were associated with extensive or moderately extensive disease (P < 0.001), and with a predominantly reticular pattern (P < 0.0001). Intra-observer variability for pattern type on CT was less for the experienced observers (kappa = 0.78 and 0.70) than for the inexperienced group (kappa = 0.50 and 0.37). Inter-observer variability for extent of disease was significantly less on CT than on CXR (standard deviations 7.8% and 9.2% respectively, P < 0.001). This study shows that observer variability using a clinical grading system is lower with CT than with chest radiography in fibrosing alveolitis.

Attitude of Health Personnel↗

PubMed1999

Monocular horizontal OKN in observers with early- and late-onset strabismus.

Several reports on monocular optokinetic nystagmus (OKN) in observers with strabismus have found that asymmetry of OKN tends to occur in both eyes of observers with an early onset of strabismus but only in the deviating eye of those with a later onset of strabismus. Our objective was to quantify and compare the magnitude of the OKN asymmetry in each eye as a function of observer's age at onset of strabismus. We studied monocular OKN in ten observers with early-onset (up to 24 months of age), seven observers with late-onset (after 24 months of age) unilateral strabismus, and 12 normally sighted control observers. In the deviating eye, observers with early-onset strabismus showed large OKN asymmetries in favour of nasalward motion while observers with late-onset strabismus showed smaller OKN asymmetries in that eye. The majority of early- and late-onset observers showed near normal OKN in the non-deviating eye although the early-onset observers showed bilateral asymmetries more often. These findings may be due to both age at onset of strabismus and chronological age and are discussed in terms of the issue of plasticity or recovery of function.

Adolescent↗

PubMed2002

Definition of gross tumor volume in lung cancer: inter-observer variability.

BACKGROUND AND PURPOSE: To determine the inter-observer variation in gross tumor volume (GTV) definition in lung cancer, and its clinical relevance. MATERIALS AND METHODS: Five clinicians involved in lung cancer were asked to define GTV on the planning CT scan of eight patients. Resulting GTVs were compared on the base of geometric volume, dimensions and extensions. Judgement of invasion of lymph node (LN) regions was evaluated using the ATS/LCSG classification of LN. Clinical relevance of the variation was studied through 3D-dosimetry of standard conformal plans: volume of critical organs (heart, lungs, esophagus, spinal cord) irradiated at toxic doses, 95% isodose volumes of GTVs, normal tissue complication probabilities (NTCP) and tumor control probabilities (TCP) were compared for evaluation of observer variability. RESULTS: Before evaluation of observer variability, critical review of planning CT scan led to up- (two cases) and downstaging (one case) of patients as compared to the respective diagnostic scans. The defined GTVs showed an inter-observer variation with a ratio up to more than 7 between maximum and minimum geometric content. The dimensions of the primary tumor had inter-observer ranges of 4.2 (transversal), 7.9 (cranio-caudal) and 5.4 (antero-posterior) cm. Extreme extensions of the GTVs (left, right, cranial, caudal, anterior and posterior) varied with ranges of 2.8-7.3 cm due to inter-observer variation. After common review, only 63% of involved lymph node regions were delineated by the clinicians (i.e. 37% are false negative). Twenty-two percent of drawn in lymph node regions were accepted to be false positive after review. In the conformal plans, inter-observer ranges of irradiated normal tissue volume were on average 12%, with a maximum of 66%. The probability (in the population of all conformal plans) of irradiating at least 95% of the GTV with at least 95% of the nominal treatment dose decreased from 96 to 88% when swapping the matched GTV with an unmatched one. The average (over all patients) inter-observer range in NTCP varied from 5% (spinal cord) to 20% (ipsilateral lung), whereas the maximal ranges amounted 16% (spinal cord) to 45% (heart). The average TCP amounted 51% with an average range of 2% (maximally 5%) in case of matched GTVs. These values shifted to 42% (average TCP) with an average range of 14% (maximally 31%) when defining unmatched GTVs. Four groups of causes are suggested for the large inter-observer variation: (1) problems of methodology; (2) impossible differentiation between pathologic structures and tumor; or (3) between normal structures and tumor, and (4); lack of knowledge. Only the minority of these can be resolved objectively. For most of the causal factors agreements have to be made between clinicians, intra- and inter-departmentally. Some of the factors will never be unequivocally solved. CONCLUSIONS: GTV definition in lung cancer is one of the cornerstones in quality assurance of radiotherapy. The large inter-observer variation in GTV definition jeopardizes comparison between clinicians, institutes and treatments.

Carcinoma, Non-Small-Cell Lung↗

PubMed2003

Observer agreement in recording the clinical signs of nail disease and the accuracy of a clinical diagnosis of fungal and non-fungal nail disease.

BACKGROUND: Onychomycosis is increasing in incidence. To date, no studies have examined the detection of abnormalities of the nail apparatus, nor the accuracy of a clinical diagnosis of onychomycosis and non-fungal nail disease. OBJECTIVES: To assess the agreement between and within different groups of observers in detecting signs of nail disease, and to obtain information regarding clinical diagnostic skills. METHODS: An observational study was performed. Nine observers, including dermatologists, mycologists, general practitioners and a dermatology clinical assistant, completed a questionnaire containing 21 clinical signs of nail disease during examination of nine patients, five with onychomycosis and four with non-fungal nail disease. Observers were additionally requested to suggest the most likely underlying diagnosis for the nail dystrophy. Mean pair observer agreement values were calculated for each of the clinical signs, between all observers and within groups of observers. The chance-corrected agreement index, kappa, was determined. From the clinical diagnoses given, the positive predictive value of a diagnosis of fungal and non-fungal nail disease was calculated. RESULTS: There was substantial between-observer agreement on only three clinical signs: abnormal nails on both hands, abnormal toenails and abnormal fingernails. More specific signs of nail disease such as onycholysis elicited weaker agreement. All observers showed accuracy in making a clinical diagnosis of fungal nail disease, with a mean positive predictive value of 0.91, compared with 0.77 for non-fungal nail disease. CONCLUSIONS: Our results showed that agreement between observers, in recording signs of nail disease, was generally poor. The clinical diagnosis of onychomycosis was highly likely to be correct, suggesting that other criteria are being employed by individuals in reaching the diagnosis.

Adult↗

PubMed2005

Reliable and feasible evaluation of linear scars by the Patient and Observer Scar Assessment Scale.

BACKGROUND: Although scar evaluation tools are necessary for an evidence-based approach to scar management, there is as yet no generally accepted tool. The Patient and Observer Scar Assessment Scale was developed recently and found to be a useful subjective evaluation tool for burn scars. The authors tested the Patient and Observer Scar Assessment Scale on linear scars, the largest category of surgical scars. METHODS: One hundred linear surgical scars were assessed by three independent observers using the observer scale to evaluate vascularity, pigmentation, thickness, relief, pliability, and surface area. The patients evaluated their scars simultaneously and 2 weeks later using the patient scale for the following parameters: pain, itching, color, stiffness, thickness, and relief. RESULTS: The internal consistency of the observer and patient scales was good (Cronbach's alpha = 0.86 and 0.90, respectively). The reliability of the observer scale was good for the total score (r = 0.96, p < 0.001) and separate items (r > 0.86, p < 0.001) for three observers. Even a single observer evaluated scars reliably with respect to the total score (r = 0.88, p < 0.001) and the items vascularity, pigmentation, thickness, and surface area (r > 0.70, p < 0.001). The patient's intraobserver reliability was good for the total score (r = 0.94, p < 0.001) and separate items (r > 0.89, p < 0.001). The coefficient of variation of the total score was 10.4 percent for the observer scale and 15.8 percent for the patient scale, indicating good agreement. CONCLUSIONS: The Patient and Observer Scar Assessment Scale is an appropriate subjective tool for the evaluation of linear scars.

Adolescent↗

PubMed1999

Emergency department observation of poisoned patients: how long is necessary?

OBJECTIVE: To compare the emergency physician disposition decisions after observation periods of two, four, and six hours in a single cohort of ED patients with acute intentional ingestion to determine the accuracy of disposition decisions at two and four hours relative to the six-hour period of observation. METHODS: This was a prospective observational study at two university hospital EDs. Study participants were patients with potentially toxic oral ingestions occurring less than six hours prior to ED presentation. Patients with isolated recreational drug or ethanol use were excluded. Structured data forms were completed at presentation, and two, four, and six hours later. Data included signs and symptoms consistent with toxic ingestion, physical examination, laboratory determinations, medications ingested, treatment, and suicide risk. At two and four hours, physicians were asked to determine whether they thought the patient was safe for medical clearance. These patients continued to be observed for six hours. The main outcome was whether patients initially thought to be appropriate for early medical clearance were ultimately cleared at six hours. RESULTS: There were 260 patients enrolled: 28 were immediately admitted to the hospital and 17 were immediately discharged; 215 entered ED observation. Patients had a mean age of 24 years; 55% were female; 50% were suicidal; 17% had toxidromes. Of the 215 observed patients, 106 (49%) were deemed safe for early medical clearance at two hours. All 106 were ultimately cleared at six hours (100%, 95% CI = 97% to 100%). Of the 109 not safe for early medical clearance at two hours, 61 (56%) were deemed safe for early medical clearance at four hours; all 61 were subsequently discharged at six hours (100%; 95% CI = 95% to 100%). Overall, 167 of 215 (77%) observed overdose patients were deemed safe for early medical clearance after two or four hours of observation. All 167 were ultimately cleared at six hours (100%; 95% CI = 98.2% to 100%). CONCLUSIONS: A large subset of overdose patients who are medically cleared after six hours of observation can be identified within two to four hours of presentation. No patient who was believed to be safe for medical clearance at either two or four hours had a complication within the six-hour time period (95% CI = 0% to 1.8%). These data suggest that asymptomatic patients with selected acute intentional ingestions can be released from medical observation in less than six hours.

Adolescent↗

PubMed2003

The role of structured observational research in health care.

Structured observational research involves monitoring of healthcare domains by experts to collect data on errors, adverse events, near misses, team performance, and organisational culture. This paper describes some of the results of structured observational studies carried out in health care. It evaluates the strengths, weaknesses, and future challenges facing observational researchers by drawing lessons from the human factors and neonatal arterial switch operation (ASO) study in which two human factors specialists observed paediatric cardiac surgical procedures in 16 UK centres. Lessons learned from the ASO study are germane to other research teams embarking on studies that involve observational data collection. Future research needs robust observer training, clear measurable criteria to assess each researcher's domain knowledge, and observational competence. Measures of inter-rater reliability are needed where two or more observers participate in data collection. While it is important to understand the factors that lead to error and excellence among healthcare teams, it is also necessary to understand the characteristics of a good observer and the key types of error that can occur during structured observational studies like the human factors and ASO project.

Cardiac Surgical Procedures↗

PubMed2003

Influence of socioeconomic status on the effectiveness of bicycle helmet legislation for children: a prospective observational study.

OBJECTIVE: To evaluate the influence of average family income in a geographic area on the effectiveness of helmet legislation on observed helmet use by children (5-14 years). METHODS: The study was conducted in East York, a health district of Metropolitan Toronto, in collaboration with the East York Health Unit. In 1996, the total population was 107 822, 11 340 of which were children 5 to 14 years. Census data were used to group the 21 census tracts in East York into 7 geographically distinct areas. The boundaries of these areas are natural barriers to travel, such as expressways, ravines, railway tracks, and hydroelectric power lines. The areas were also ranked according to average family income (based on Statistics Canada data). For analytical purposes, areas were defined as low-, mid-, and high-income areas. Census data profiles of the areas have been previously described. For each consecutive year from 1990 to 1997 inclusive, direct observations of children riding bicycles in East York during the months of April through October were made. In 1995, observations were completed before the introduction of the law on October 1, 1995. Only children who were between 5 and 14 years of age and riding a 2-wheeled bicycle were included in the study. In total, 111 sites across all 7 areas were selected for observation. Observational sites included school yards of all elementary and middle schools (kindergarten to grade 8) and all parks in East York. In addition, 5 major intersections and 5 residential streets from each area were randomly selected. Observers were trained and used a standardized data collection form. A pilot study showed that the data collected by observers were reliable and valid. Observers remained at each site for 1 hour and collected data on helmet use and sex. Ethical approval for the study was obtained from the Hospital for Sick Children Research Ethics Board, the East York Board of Education, and the Metropolitan Separate School Board. The proportion of children who were wearing a bicycle helmet was estimated by year (1990-1997, inclusive), sex (male, female), location (school, park, major intersection, residential street), and income area (low, mid, high). For estimating the effect of legislation on helmet use, data from the year immediately after legislation (1996) were compared with data from the year preceding legislation (1995). The relative risk (RR) of helmet use (after vs before legislation) was calculated along with a 95% confidence interval (CI). Logistic regression analysis was used to adjust for potential confounding variables (sex and location). RESULTS: During the 8-year study period, 9768 observations were made (range: 914-1879 observations per year). The proportion of child cyclists who wore a bicycle helmet increased steadily during the first 4 years of the study period, from 4% in 1990 (34 of 914), to 16% in 1991 (303 of 1879), to 25% in 1992 (383 of 1563), and to 45% in 1993 (438 of 984). During 1994 (460 of 1083) and 1995 (568 of 1227), helmet use remained relatively stable at approximately 44%. Helmet use rose markedly in 1996 (the first year after helmet legislation was introduced) to 68% (818 of 1202) and remained stable at 66% (609 of 916) in 1997. Throughout the study period, girls were consistently more likely to wear helmets than were boys. In total, 47% (1420 of 3047) of girls wore helmets, compared with 33% (2193 of 6721) of boys (RR: 1.43; 95% CI: 1.36-1.50). In addition, children who were riding to school were more likely to use helmets, compared with children who were riding on residential streets, major intersections, and parks. Overall, 48% (1497 of 3129) of children who were riding to school wore bicycle helmets, compared with 32% (2116 of 6639) of children who were riding at other locations (RR: 1.50; 95% CI: 1.43-1.58). Children in the high-income areas were consistently more likely to wear helmets, compared with children in the mid- and low-income areas. Helmet legislation was associated with a significant increase in helmet use by children in East York. In 1995, 46% (ast York. In 1995, 46% (568 of 1227) of children wore bicycle helmets, compared with 68% (818 of 1202) of children in 1996 (RR: 1.47; 95% CI: 1.37-1.58). The effect of legislation, however, varied by income area. In low-income areas, helmet use increased by 28% after legislation, from 33% (213 of 646) in 1995 to 61% (442 of 721) in 1996 (RR: 1.86; 95% CI: 1.64-2.11). In mid-income areas, helmet use increased by 29% after legislation, from 50% (150 of 300) in 1995 to 79% (185 of 234) in 1996 (RR: 1.58; 95% CI: 1.39-1.80). In high-income areas, helmet use increased by only 4%, from 73% (205 of 281) in 1995 to 77% (191 of 247) in 1996 (RR: 1.06; 95% CI: 0.96-1.17). This finding of a significant increase in helmet use after legislation in low- and mid-income areas but not in high-income areas remained even after logistic regression analysis adjusted for sex and location. CONCLUSIONS: This study showed that bicycle helmet use by children increased significantly after helmet legislation. In this urban area with socioeconomic diversity and in the context of prelegislation promotion and educational activities, the legislative effect was most powerful among children who resided in low-income areas.

Accidents, Traffic↗

PubMed1999

Approaches to missing data inference results from CaPSURE: an observational study of patients with prostate cancer.

OBJECTIVE: There are multiple reasons for missing data in observational studies; excluding patients with missing data can lead to significant bias. In this study, we evaluated several methods for assigning missing values to health service utilisation. DESIGN AND SETTING: Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) is a US national database of men with prostate cancer. Physician visits and diagnostic tests for 342 patients newly diagnosed with prostate cancer were evaluated. PATIENTS AND PARTICIPANTS: Patients were followed for a full year (observed data, n = 228) and patients with incomplete data (predicted data, n = 114) were included. INTERVENTIONS: We used the following approaches for imputing missing data: assigning the group mean, a time-specific mean, a patient-specific mean, a stratified mean (by age, localised disease and insurance status) and carrying the last observation forward and/or backward. MAIN OUTCOME MEASURES AND RESULTS: All prediction strategies resulted in higher estimates (19.3 to 23.1) for annual physician visits than was observed (17.1 +/- 15.5), and differences were statistically significant for both the last observation carried forward (23.1 +/- 15.5) and the patient's individual mean (22.7 +/- 36.1) when predicting physician visits. The same strategies had higher predicted values for x-rays (1.8 +/- 5.1 and 1.8 +/- 4.4 vs 1.1 +/- 1.9 for the observed group), although the last observation carried forward was not statistically different from the observed value. CONCLUSIONS: We were unable to identify a single optimal strategy. However, imputation from individual means and the last observation carried forward methods did not perform as well as the other strategies. While the differences observed in this study were small, we anticipate that with increased length of follow-up and more dropouts, there would be greater differences among strategies.

Adult↗

PubMed1992

Ventilation-perfusion lung scanning and the diagnosis of pulmonary embolism: improvement of observer agreement by the use of a lung segment reference chart.

OBJECTIVE: To test the hypothesis that the systematic use of a lung segment reference chart can improve the inter- and intra-observer agreement for the interpretation of ventilation-perfusion lung scans. DESIGN: A randomized trial. STUDY POPULATION: Ventilation-perfusion lung scans were obtained in a series of 220 consecutive patients with clinically suspected pulmonary embolism. INTERVENTION: Ventilation-perfusion scans were randomly allocated to one of two series each consisting of 110 ventilation-perfusion lung scans. The first series of lung scans was interpreted according to the routine diagnostic approach, and the second series was interpreted with the mandatory use of a lung segment reference chart on which observed ventilation and perfusion defects were drawn. The two nuclear medicine physicians agreed a priori on the diagnostic criteria of the classification scheme. MEASUREMENTS: Lung scans were classified as normal, non-high probability, or high probability for pulmonary embolism. The extent of disagreement between the nuclear medicine physicians (inter-observer disagreement) and the lack of internal consistency of each nuclear medicine physician (intra-observer disagreement) was assessed by the percentage disagreement and by kappa statistic. RESULTS: Inter-observer disagreement which was 20% in the first series, decreased significantly in the second series to 7%; P = 0.003. Intra-observer disagreement for the first series was 10% and 22% for the nuclear medicine physicians, respectively. Intra-observer disagreement for the second series of lung scans decreased significantly for one nuclear medicine physician (intra-observer disagreement, 0%; P less than 0.01), whereas intra-observer disagreement was reduced to 10% for the other nuclear medicine physician (P = 0.09). CONCLUSION: Inter- and intra-observer disagreement were significantly reduced when two nuclear medicine specialists interpreted ventilation-perfusion lung scans according to the routine diagnostic approach plus the use of a lung segment reference chart. The use of the lung segment reference chart for the interpretation of lung scans is likely to improve the management of patients with clinically suspected pulmonary embolism.

Humans↗

PubMed2005

Inter- and Intra-Observer Variability Assessment of in Vivo Carotid Plaque Burden Quantification Using Multi-Contrast Dark Blood MR Images.

UNLABELLED: The chapter presents the research to test the hypotheses that (1) vessel wall volume measurements from dark blood MR images with multiple contrast-weightings (T1W, T2W and PDW) are highly reproducible, and that (2) the intra-observer and inter-observer variability of carotid wall volume measurements will be less than those obtained with maximum wall area (MaxWA) measurements. METHODS: Sixteen patients (aged 72 +/- 7years) with carotid stenosis documented by duplex ultrasound were recruited for the study. Dark blood T1W, PDW and T2W MR images were used to measure carotid wall volume and MaxWA by two independent observers for inter-observer and intra-observer variability assessment. RESULTS: The intra-observer absolute difference of carotid wall volume for T1W, T2W and PDW images were 67.3 +/- 47.5 mm(3) (2.3 +/- 1.8%), 63.2 +/- 52.2 mm(3) (2.0 +/- 1.3%), and 69.8 +/- 45.2 mm(3) (2.4 +/- 1.7%) respectively. The inter-observer absolute difference of carotid wall volume for T1W, T2W and PDW images were 103.5 +/- 141.8 mm(3) (3.0 +/- 3.1%), 95.9 +/- 102.1 mm(3) (3.1 +/- 2.6%), and 132.1 +/- 87.8 mm(3) (4.3 +/- 2.7%) respectively. The intra-observer absolute difference of carotid MaxWA for T1W, T2W and PDW images were 6.9 +/- 5.0 mm(2) (4.2 +/- 2.9%), 5.1 +/- 4.2 mm(2) (3.1 +/- 2.3%) and 7.5 +/- 4.7 mm(2) (4.2 +/- 2.7%) respectively. The inter-observer absolute difference of carotid MaxWA for T1W, T2W and PDW images were 9.5 +/- 4.2 mm(2) (5.8 +/- 2.3%), 6.4 +/- 6.1 mm(2) (3.8 +/- 3.1%) and 10.8 +/- 7.3 mm(2) (6.1 +/- 3.7%) respectively. Both intra- and inter-observer variability in carotid volume measurement tend to be smaller than that in carotid MaxWA measurement with intraclass correlation coefficients ranged 0.932 to 0.987 for volume measurement and 0.822 to 0.946 for MaxWA measurement.

Carotid Artery Diseases↗