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PubMed2001

[Comparison of performance of dairy herds that were or were not vaccinated with a bovine herpes virus 1 marker vaccine in 1998].

This study analysed the effects of the use of bovine herpesvirus 1 (BHV1) marker vaccine on the performance of dairy cattle. In Spring of 1999, vaccination of 12 herds with the BHV1 marker vaccine resulted in severe animal health problems and mortality. The vaccines used on these farms were all from a batch that appeared to be contaminated with bovine virus diarrhoea virus type 2. This led to a general call to farmers and veterinary practitioners to report side-effects of this vaccine. As a result, more than 7000 farmers reported symptoms. The information was obtained by means of a questionnaire; there was no control group. To determine the effects of the use of the marker vaccine, it was necessary to perform a study based on objectively acquired information. The information collected by the Royal Dutch Cattle Syndicate and the office of Identification and Registration was complied into herd indices on production, udder health, reproduction, and culling. Two groups of dairy farms that had used the BHV1 marker vaccine (attenuated and inactivated vaccine) were compared with farms that were certified BHV1-free. The analyses were performed based on intra-herd comparisons, meaning that per herd each index calculated over a certain period of time after the use of the marker vaccine was compared to a similar period of time prior to the use of the marker vaccine. A total of 144 comparisons were made. Seven comparisons were statistically significant. In two comparisons, the results were in favour of the BHV1-free farms and in five comparisons, the result were in favour of the vaccinated farms. Thus use of the BHV1 marker vaccine could not be proven to affect herd performance. The sensitivity of the tests was very high, so with a high level of probability even very small differences in indices between groups would have been detected.

Animals↗

PubMed2000

Comparison of bitemarks left in foodstuffs with models of the suspects' dentitions as a means of identifying a perpetrator.

In a recent court case, a comparison was made between an impression of marks left in cheese at a murder scene and a set of study models of one of the suspects. The court was reluctant to accept the validity of the pattern-associated comparison that was used in the identification. This study compared marks made in cheese, butter and cooked potato with study models taken from volunteers. Pattern-associated comparison was the method used. Eighty pair-wise comparisons were made by two odontologists. The examiners correctly identified all the true matches from among the eighty comparisons as well as selecting the dental models for which there were no corresponding silicone impressions. In the absence of identifiable fingerprints or DNA samples, the method can be employed for matching left in foodstuffs to the dentitions of suspects.

Adolescent↗

PubMed2001

Self-activation increases social comparison.

In a series of studies it was demonstrated that activating the self is sufficient to increase social comparison tendencies. Treating the relevant constructs as individual differences that can be measured as well as contextual variables that can be manipulated, the authors show that individual differences in self-activation are correlated with interest in social comparison information and that manipulations of self-activation cause changes in interest in social comparison. Self-certainty often has been portrayed as the primary determinant of social comparison interest. The present results suggest that self-activation affects interest in social comparison even when self-certainty is controlled.

Humans↗

PubMed2002

[First line endonasal dacryocystorhinostomy Technique and results. Comparison between diode laser and electrocautery instrument. Study based on 422 procedures].

PURPOSE OF THE STUDY: To assess the results of the first procedures of endoscopic endonasal dacryocystorhinostomy (ENL DCR). To study the efficiency of diode laser in this operation versus electrocautery instruments (ECI). DESIGN: Prospective study; comparative study. METHODS: Intraoperative comparison between ECI and diode laser is based on 422 ENL DCR achieved between June 1997 until June 2000. Three hundreds and sixty three procedures were diode laser assisted and 59 procedures were done with the use of an ECI. The diode laser was only used to vaporize nasal mucosa laying on the osteotomy site, to realize partial turbinectomy and to vaporize polyps and synechiae. Intraoperative comparison was based on the followings: frequency and extent of bleeding, quality of visibility, perception of pain during the use of the instrument and duration of the operation. Postoperative comparison is based on 318 procedures. Comparison was based on: frequency of granuloma formation in the nasal mucosa at the site of the osteotomy, frequency of acquired nasal synechiae, frequency of important crusting reaction of the nasal mucosa; success rates after a minimum follow up of 6 months. RESULTS: Intraoperative haemorrhages were fewer and smaller in the diode laser assisted procedures than in ECI assisted procedures; visibility was better with the diode laser; the use of the diode laser was painless versus 24% of patients complaining of pain during the use of electro-cautery. The duration of the procedure was shorter with the diode laser (29'30 vs 37'). In the postoperative follow-up frequency of granuloma formation was equal with the two instruments, synechiae were fewer with the diode laser (11% vs 22%) just like crusting reaction of the nasal mucosa (7% vs 36%). Success rates were similar (diode laser: 91.94% vs EC: 86.66%). CONCLUSION: Because of the effeciency of the vaporization and coagulation, the diode laser, in comparison with the ECI, allows to shorten mean operative time, to improve the visibility and to decrase bleeding. Contrary to EC it's use is painless. Fewer important crusting reactions and fewer synechiae after diode laser assisted procedures tend to prove than postoperative inflammation and surgical trauma are smaller than with ECI. There is no statiscally signifant difference between the success rates of ENL laser diode assisted procedures and ENL ECI assisted procedures.

Age Factors↗

PubMedDate not supplied

Graphic representation of data resulting from measurement comparison trials in cataract and refractive surgery.

BACKGROUND AND OBJECTIVES: The evaluation of new diagnostic measurement devices allows intraindividual comparison with an established standard method. However, reports in journal articles often omit the adequate incorporation of the intraindividual design into the graphic representation. PATIENTS AND METHODS: This article illustrates the drawbacks and the possible erroneous conclusions caused by this misleading practice in terms of recent method comparison data resulting from axial length measurement in 220 consecutive patients by both applanation ultrasound and partial coherence interferometry. RESULTS: Graphic representation of such method comparison data should be based on boxplots for intraindividual differences or on Bland-Altman plots. Otherwise, severe deviations between the measurement devices could be erroneously ignored and false-positive conclusions on the concordance of the instruments could result. CONCLUSION: Graphic representation of method comparison data should sensitively incorporate the underlying study design for intraindividual comparison.

Cataract↗

PubMed2004

Bristle end-rounding in toothbrushes: a comparison of different evaluation techniques, bristle position and viewing angle.

OBJECTIVE: Numerous studies using various evaluation techniques have shown substantial variations in the degree of bristle end-roundness of commercially available toothbrushes. The aim of the present study was to compare the effects of the examination angle, the bristle selection and two analyzing techniques assessing bristle end-rounding measurements. METHODOLOGY: The study was conducted in two parts. Part One used five randomly selected tufts from 20 brushes that were scanned with an electron micrograph (SEM; 45x) at two viewing angles (45 degrees and 90 degrees). Those bristle tips that were visible on both viewing angles were then judged by 1) a direct comparison to a grading scale, and 2) a shape factor (SF) analysis. In Part Two of the study, SEM images of five bristles from different tufts obtained from 40 brushes were taken at a viewing angle of 45 degrees, and five bristles from different locations within a tuft were also judged by both the direct comparison to a grading scale method, and the SF analysis, to assess bristle location. RESULTS: The SF values and the direct comparison percentage of rounded bristles did not differ because of the viewing angle (45 degrees or 90 degrees; p > 0.05; Mann-Whitney test), but differed significantly at various SF thresholds (percentage of bristles above or below a certain degree of end-roundness) when bristles from Part One were compared to Part Two (p < 0.01, adjusted chi-square-test). Location of the bristles from either the edge of a tuft or those located in the inner part had no effect on the assessments (p > 0.05). The results from the subjective direct comparison grading did not differ from those found with the SF analysis (p > 0.05). CONCLUSION: SF analysis is a time-consuming method for assessing bristle end-rounding, and can be as accurately done by direct comparison to a grading scale. One viewing angle (45 degrees) of bristles from different locations within a tuft can also be used to accurately assess a brush's level of end-roundness.

Analysis of Variance↗

PubMed2004

Body-image evaluation and body-image investment among adolescents: a test of sociocultural and social comparison theories.

Sociocultural theory and social comparison theory were used to account for variations in body-image evaluation and body-image investment among male and female adolescents (N = 1,543). Exposure to magazines and television programs containing idealistic body imagery as well as frequency of self-comparison to universalistic targets (e.g., fashion models) were measured. Results provided minimal support for sociocultural theory, but fairly strong support for social comparison theory. Specifically, the extent to which males engaged in universalistic social comparison predicted appearance self-esteem, number of diets to gain weight, use of pathogenic weight control practices, and use of steroids to increase muscle mass. For females, universalistic social comparison predicted appearance self-esteem, body dissatisfaction, number of diets to lose weight, and use of pathogenic weight control practices. The possibility that the null effects for sociocultural theory were an artifact of dummy coding for missing data or theoretical interdependence were explored, but did not appear to be valid. Limitations of the present study and directions for future research are outlined.

Adolescent↗

PubMed2005

Evaluation of alkaline phosphatase activity assay for the Reflotron system after substitution of the comparison method.

The alkaline phosphatase (ALP) assay for the Reflotron system is a dry chemistry method applicable for decentralized testing. The ALP diethanolamine method has been applied as the comparison method, which is now replaced by the more widely distributed aminomethylpropanol method. The new comparison method measures ALP activities by approximately 59% lower compared to the former method. The analytical performance of the newly calibrated ALP Reflotron method was evaluated at three clinical laboratories. The study of the imprecision showed coefficients of variation ranging from 1.6-3.0% (intraassay) and 2.7-5.7% (interassay). Blood samples from liver disease patients (n=192), adolescents (n=40) and pregnant women in the third trimester (n=34) were collected in order to evaluate the impact of different ALP isoenzymes. The comparison between ALP Reflotron and the new comparison method revealed an excellent agreement in Passing-Bablok regression analysis (slope: 1.004; intercept: 0.14 U/l; median difference: 0.5%) for samples with prevailing liver ALP. However, in plasma samples with predominantly elevated bone or placental isoenzyme the Reflotron method measured lower or higher activities, respectively (slope: 0.912, 1.394; intercept: -4.16, -17.26 U/l; median difference: -10.58, 26.33%). The ALP Reflotron assay is an adequate method for decentralized testing. It shows a good precision and agreement with the comparison method, although the systematic differences for placental and bone ALP isoenzymes have to be considered.

Adolescent↗

PubMed2005

[Alignment-free biomolecular sequence comparison method].

Biosequence analysis is the primary research field of bioinformatics. In this field, useful information can be extracted by comparison analysis methods. Among them, sequence alignment is the most common comparison method. However the sequence comparison by alignment, which assumes conservation of contiguity between homologous segments, is at odds with genetic recombination. Especially for the multisequence alignment, there exists the difficulty in the complexity of calculation. Therefore, alignment-free sequence comparison methods are required. In this paper, two main categories of alignment-free sequence comparison methods are reviewed. The first one is based on the word (oligomer) frequency and its distribution. The sequences are compared using the distances defined in a Cartesian space by the frequency vectors. In the second category, sequences are compared using Kolmogorov complexity and chaos theory.

Algorithms↗

PubMedDate not supplied

Compared to whom? An investigation of the relative health comparisons of well people.

OBJECTIVES: Responses to the self-reported health (SRH) question, "In general how would you rate your health? Excellent, very good, good, fair or poor", have been repeatedly demonstrated to predict mortality. Survival curves plotted for each response category show that the likelihood of death increases in a stepped fashion with each progressively negative response category and the relationship persists for up to 12 years following initial measurement. To whom do people compare themselves when answering the self-reported health question? METHODS: Twenty-one interviews with people who selected the better-health response choices (i.e., good, very good, or excellent) were conducted in a Canadian city. Qualitative content analysis was undertaken and the interviews were approached with no pre-conceived ideas about what the participants would say. RESULTS: Analysis of the interviews suggested that there are three key features in making a health comparison: the type (i.e., with whom), direction (i.e., upward or downward), and magnitude of the comparison (i.e., with a few people or an ideal person vs. many other people). These key features varied in a systematic way with the chosen response. DISCUSSION: The findings related to the direction of comparison contradict, somewhat, the theories of social psychologists but these differences may have occurred because the participants were well. Healthy people may use different factors than ill people when making social comparisons as they select a self-reported health question response category. The nature of the comparisons are complex and the responses indicate that they are affected by age, gender, and life experience.

Adult↗

PubMed1991

Nosocomial infection rates for interhospital comparison: limitations and possible solutions. A Report from the National Nosocomial Infections Surveillance (NNIS) System.

Improvement in quality of patient care has received increasing attention in the last decade, with emphasis in infection control and interhospital comparison of infection rates. One of the main objectives of the National Nosocomial Infections Surveillance (NNIS) system is to provide hospitals with comparative nosocomial infection data that at least partially adjust for patients' intrinsic and extrinsic risks for infection. This article summarizes the methods and results of analyses from the NNIS system and describes their application to future surveillance in US hospitals. We emphasize the importance of nosocomial infection surveillance data that adjust for specific infection risks in order to provide better interhospital comparison of infection rates. Traditional rates that do not provide such adjustment include the crude overall nosocomial infection rate of a hospital or service and site-specific infection rates by service. Because these inadequately adjusted rates are potentially misleading, they should not be used for interhospital comparison. This article describes several new infection rates, including device-associated, device-day infection rates for intensive care units and high-risk nurseries, and an NNIS surgical wound infection risk index. These rates appear to be better for interhospital comparison. NNIS data also suggest the importance of examining interventions (devices and operative procedures) that increase patient risk for infection. Failure to use appropriately adjusted rates and to examine the intervention experience may make interhospital comparisons meaningless or even misleading.

Centers for Disease Control and Prevention, U.S.↗

PubMed2006

The comparison of clinical imaging devices with respect to parallel readings in both devices.

OBJECTIVE: Many proposals for the comparison of diagnostic devices refer to the computation of ROC curves or sensitivity / specificity-based parameters, thereby strictly assuming the presence of a reliably parameterized clinical reference method. When none of the devices under consideration can be regarded as a reference, Cohen's kappa coefficient for assessing the methods' relative agreement becomes increasingly popular. If, however, not only the agreement between two diagnostic devices, but also the devices' reliability must be taken into account (for example, if multiple parallel readings are obtained from one or both of the devices), no corresponding coefficients can be obtained from standard software. Bearing the recent modifications in the German Medicinal Devices Law (Medizinproduktegesetz) in mind, such methods will soon become necessary and strongly demanded for the sake of immediate re-evaluation of previously certified medicinal devices. METHODS: Generalizations of Cohen's kappa (kappa) for complex multi reader designs can be found by estimating weighted averages of the observed and expected agreement among subsets of parallel readings. A flexible, although instructive, strategy for designing kappa coefficients in the context of method comparison trials is proposed, which measures the two methods' overall agreement while correcting for each method's underlying inter / intra observer reliability. Cluster algorithms will be outlined, which allow to identify (in)compatible clusters of readings. Their application will be illustrated by means of the intraindividual comparison of two different strategies in radiographical imaging, where none of the underlying imaging methods can be regarded as a reference. RESULTS: The algorithms are illustrated by the comparison of two radiological imaging devices R and F, where none of these imaging methods could be considered as a valid reference, i.e. replicate readings by three independent radiologists were taken from each device, respectively. The setting allowed for intraindividual comparison of the imaging methods, since each of the three involved radiologists took one reading from both devices on each of 120 individuals. The algorithm identifies a subset of compatible reading patterns with an overall agreement of kappa = 0.83 (95% confidence interval 0.78 - 0.88) despite the fact, that the underlying readings arose from two different imaging devices. An obvious interpretation suggests, that the gradient in experience between the readers was more relevant to their reading patterns' outcome than any difference between the imaging devices. CONCLUSIONS: The generalized kappa coefficients can be modified according to the study design at hand to instructively identify (in)compatible clusters of multiple parallel reading patterns; the relative agreement of imaging methods can be estimated as well as each imaging method's internal reliability as assessed by parallel readings from the respective methods.

Algorithms↗

PubMed1989

[Social comparison processes in health psychology and psychotherapy].

Recently, Festinger's (1954) theory of social comparison processes has been "detected" for application in clinical psychology. Patients' social as well as physical comparisons evidently are of high relevance for their starting, participating in, and breaking-off of a (psycho)-therapy. As to our analysis, the availability of physical comparisons, on the one hand, and social comparisons with patients (participating in a group therapy) high in similarity, on the other hand, are of high importance for patients' motivation to successfully end a therapy. Suggesting these results, empirical research supports Festinger's (1954) theory. In the final part of the paper we speculatively apply these results to health counseling. As a consequence of these applications, we expect a growing relevance of the theory of social comparison processes for psychotherapy and health psychology as well.

Humans↗

PubMed1986

Comparison and message-formulation skills in the referential communication of severely mentally retarded children.

The importance of comparison and message-formulation skills in referential communication was studied with severely mentally retarded children. A store game task was used that required the child to communicate a choice of one or two objects on a shelf. Comparison training taught the children to select the appropriate object when paired with a similar but inappropriate object. Message training taught the children to communicate by pointing and/or gesturing. Results indicated that combined comparison and message training produced higher communication accuracy than did comparison training alone. Comparison training, however, increased subjects' accuracy of communicating as compared to an untrained control group. A parallel pattern of results was found for communication frequency. The training groups either maintained or improved their communicative performance in a near-generalization task, suggesting that they learned communicative behavior and not merely task-specific behavior.

Activities of Daily Living↗

PubMed1981

Cardiovascular effects of amezinium in humans during passive upright tilt in comparison with norfenefrine and dihydroergotamine.

20 min after single i.v. administration of 10 mg 4-amino-6-methoxy-1-phenyl-pyridazinium methyl sulfate (ameziniummetilsulfate, LU 1631, Regulton), in the following briefly called amezinium, a new antihypotensive agent, was studied in comparison with 10 mg norfenefrine i.m. and 1 mg dihydroergotamine i.m. during orthostatic stress on a tilt table in a total group of 29 healthy volunteers with stable cardiovascular conditions. The study of each substance was preceded by a control tilting test. After amezinium a higher systolic blood pressure of 10 to 15 mmHg in comparison with the control test was maintained during 5 min upright tilt with both a smaller increase in the rise of heart rate and decrease in stroke volume. In comparison with control, pulse pressure was also clearly increased whereas cardiac output and total peripheral resistance were not significantly different. The increase in stroke volume in comparison with control was a result of the positive inotropic effect on the one hand, which could be seen in both a diminished prolongation of the preejection period and increase in the PEP/LVET ratio, and an increased venous return to the heart on the other hand. Systolic blood pressure and heart rate after norfenefrine were principally similar to those after amezinium, whereas the effect on stroke volume was of minor magnitude because of the absence of a positive inotropic action. Moreover, cardiac output decreased more with higher total peripheral resistance in comparison to control. Besides a slight reduction in heart rate, dihydroergotamine did not reveal any significant differences from control during orthostatic stress. At the dose studied, amezinium seemed to produce a better adaptation to passive upright tilt than the reference substances.

2-Hydroxyphenethylamine↗

PubMed1980

[Myocardial scintigraphy (thallium-201) and electrocardiography at rest and during exercise in angina pectoris. A comparison with coronary angiography (author's transl)].

Ecg (at rest and during exercise) was compared to Thallium-201 myocardial perfusion imaging (at rest and after exercise) in 65 patients with coronary heart disease (myocardial infarction in 53 patients) and angina pectoris. These results were compared to coronary angiography and left ventricular angiography. Group I: (48 patients, comparison of Ecg at rest and Thallium-201 imaging at rest): 33 patients showed agreement of results. In comparison to angiography the 201-Thallium imaging showed less false-negative results than the Ecg as rest. Group II: (23 patients, comparison of Ecg during exercise with Thallium-201 imaging after exercise): 8 patients showed agreement, 15 patients did not. In comparison to angiography the imaging showed better agreement in 20 of 23 patients, the exercise Ecg in 14 of 23 patients. Exercise-Ecg showed false-negative results in 7 patients, Thallium-201 imaging in none. Especially in 1-vessel-disease imaging was superior. Group III: (24 patients, comparison of Ecg at rest and during exercise to 201-Thallium at rest and after exercise): In 19 patients results agreed almost. Because of background-correction imaging is inferior to the Ecg in the apical region. Imaging is superior to the Ecg in the septal and inferior-myocardial regions. Combination of both methods gives best correlations. Sensitivity of Ecg-results is 77% and in imaging 93%.

Adult↗

PubMed1996

[Examples of pitfalls in statistical analysis--3: Why do we need to use multiple comparison procedures?].

When comparing the means of more than three groups, we first have to carry out an analysis of variance (ANOVA) to confirm whether all of the means of each group are equal, and we then have to evaluate all possible pairwise comparisons with multiple comparison procedures. If we use only the unpaired t-test for all pairwise comparisons without ANOVA and multiple comparison procedures, we are more likely not only to erroneously conclude that two means in a pair are significantly different when actually they are not, but also to create a contradiction between pairs of means with large differences which are not considered significant, and pairs of means with small differences which are considered significant. In this article, I discuss two problems in comparing the means of multiple groups by presenting an example in which I apply unpaired t-test on data that should be analyzed by ANOVA and multiple comparison procedures.

Analysis of Variance↗

PubMed1998

Validity of linear regression in method comparison studies: is it limited by the statistical model or the quality of the analytical input data?

We compared the application of ordinary linear regression, Deming regression, standardized principal component analysis, and Passing-Bablok regression to real-life method comparison studies to investigate whether the statistical model of regression or the analytical input data have more influence on the validity of the regression estimates. We took measurements of serum potassium as an example for comparisons that cover a narrow data range and measurements of serum estradiol-17beta as an example for comparisons that cover a wide data range. We demonstrate that, in practice, it is not the statistical model but the quality of the analytical input data that is crucial for interpretation of method comparison studies. We show the usefulness of ordinary linear regression, in particular, because it gives a better estimate of the standard deviation of the residuals than the other procedures. The latter is important for distinguishing whether the observed spread across the regression line is caused by the analytical imprecision alone or whether sample-related effects also contribute. We further demonstrate the usefulness of linear correlation analysis as a first screening test for the validity of linear regression data. When ordinary linear regression (in combination with correlation analysis) gives poor estimates, we recommend investigating the analytical reason for the poor performance instead of assuming that other linear regression procedures add substantial value to the interpretation of the study. This investigation should address whether (a) the x and y data are linearly related; (b) the total analytical imprecision (s(a,tot)) is responsible for the poor correlation; (c) sample-related effects are present (standard deviation of the residuals >> s(a,tot)); (d) the samples are adequately distributed over the investigated range; and (e) the number of samples used for the comparison is adequate.

Chromatography, Ion Exchange↗