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PubMed1998

A comparison of one-sided methods to identify significant individual outcomes in a multiple outcome setting: stepwise tests or global tests with closed testing.

We compare two approaches to the identification of individual significant outcomes when a comparison of two groups involves multiple outcome variables. The approaches are all designed to control the familywise error rate (FWE) with any subset of the null hypothesis being true (in the strong sense). The first approach is initially to use a global test of the overall hypothesis that the groups are equivalent for all variables, followed by an application of the closed testing algorithm of Marcus, Peritz and Gabriel. The global tests considered here are ordinary least squares (OLS), generalized least squares (GLS), an approximation to a likelihood ratio test (ALR), and a new test based on an approximation to the most powerful similar test for simple alternatives. The second approach is that of stepwise testing, which tests the univariate hypotheses in a specific order with appropriate adjustment to the univariate p-values for multiplicity. The stepwise tests considered include both step-down and step-up tests of a general type, and likewise permutation tests that incorporate the dependence structure of the data. We illustrate the tests with two examples of birth outcomes: a comparison of cocaine-exposed new-borns to control new-borns on neurobehavioural and physical growth variables, and, in a separate study, a comparison of babies born to diabetic mothers and babies born to non-diabetic mothers on minor malformations. After describing the methods and analysing the birth outcome data, we use simulations on Gaussian data to provide guidelines for the use of these procedures in terms of power and computation.

Adult↗

PubMed1999

Sample size determination for multiple comparison studies treating confidence interval width as random.

Methods for optimal sample size determination are developed using four popular multiple comparison procedures (Scheffe's, Bonferroni's, Tukey's and Dunnett's procedures), where random samples of the same size n are to be selected from k (>/=2) normal populations with common variance sigma2, and where primary interest concerns inferences about a family of L linear contrasts among the k population means. For a simultaneous coverage probability of (1-alpha), the optimal sample size is defined to be the smallest integer value n*m such that, simultaneously for all L confidence intervals, the width of the lth confidence interval will be no greater than tolerance 2deltal (l=1,2,...,L) with tolerance probability at least (1-gamma), treating the pooled sample variance S2p as a random variable. Using Scheffe's procedure as an illustration, comparisons are made to usual sample size methods that incorrectly ignore the stochastic nature of S2p. The latter approach can lead to serious underestimation of required sample sizes and hence to unacceptably low values of the actually tolerance probability (1-gamma'). Our approach guarantees a lower bound of [1-(alpha+gamma)] for the probability that the L confidence intervals will both cover the parametric functions of interest and also be sufficiently narrow. Recommendations are provided regarding the choices among the four multiple comparison procedures for sample size determination and inference-making.

Confidence Intervals↗

PubMed1997

Development of the multiple sequence approximation within the AGADIR model of alpha-helix formation: comparison with Zimm-Bragg and Lifson-Roig formalisms.

In this work we present the development of the multiple sequence approximation (AGADIRms) and the standard one-sequence approximation (AGADIRls) within the framework of AGADIR's alpha-helix formation model. The extensive comparison between these new formulations and the original one [AGADIR; V. Muñoz and L. Serrano (1994). Nat. Struct. Biol., Vol. 1, pp. 399-409] indicates that the standard one-sequence approximation is virtually identical to the multiple sequence approximation, while the previously used residue partition function approximation [Muñoz and Serrano (1994); (1995), J. Mol. Biol., Vol. 245, pp. 275-296] is less precise. The calculations of the average helical content performed with AGADIR are precise for peptides of less than 30 residues and progressively diverge from the multiple sequence formulation for longer peptides. The helicity distribution of heteropolypeptides with less than 50% average helical content is also well described, while those of quasi-homopolymers with high helical content tend to be-flattened. These inaccuracies lead to an underestimation of 0.017 kcal/mol for the mean-residue enthalpic contribution in AGADIR, as compared to AGADIRms and AGADIRls. The other energy contributions to alpha-helix stability are not affected by the original statistical approximation. We also discuss the particularities of the model for alpha-helix formation utilized in AGADIR and compare it with the classical Zimm-Bragg and Lifson-Roig theories. Moreover, we develop the mathematical relationships between the basic AGADIR energy contributions and helix nucleation and elongation, which permit the quantitative comparison between formalisms. Remarkably, the comparison between AGADIRms and the Lifson-Roig formalism shows that, despite the differences on treating helix/coil cooperativity, both theories give virtually identical results when an equivalent set of parameters is used. This indicates that the helix/coil transition is a solid theory independent of the particularities of the model for alpha-helix formation.

Mathematics↗

PubMed2001

Probability binning comparison: a metric for quantitating multivariate distribution differences.

BACKGROUND: While several algorithms for the comparison of univariate distributions arising from flow cytometric analyses have been developed and studied for many years, algorithms for comparing multivariate distributions remain elusive. Such algorithms could be useful for comparing differences between samples based on several independent measurements, rather than differences based on any single measurement. It is conceivable that distributions could be completely distinct in multivariate space, but unresolvable in any combination of univariate histograms. Multivariate comparisons could also be useful for providing feedback about instrument stability, when only subtle changes in measurements are occurring. METHODS: We apply a variant of Probability Binning, described in the accompanying article, to multidimensional data. In this approach, hyper-rectangles of n dimensions (where n is the number of measurements being compared) comprise the bins used for the chi-squared statistic. These hyper-dimensional bins are constructed such that the control sample has the same number of events in each bin; the bins are then applied to the test samples for chi-squared calculations. RESULTS: Using a Monte-Carlo simulation, we determined the distribution of chi-squared values obtained by comparing sets of events from the same distribution; this distribution of chi-squared values was identical as for the univariate algorithm. Hence, the same formulae can be used to construct a metric, analogous to a t-score, that estimates the probability with which distributions are distinct. As for univariate comparisons, this metric scales with the difference between two distributions, and can be used to rank samples according to similarity to a control. We apply the algorithm to multivariate immunophenotyping data, and demonstrate that it can be used to discriminate distinct samples and to rank samples according to a biologically-meaningful difference. CONCLUSION: Probability binning, as shown here, provides a useful metric for determining the probability with which two or more multivariate distributions represent distinct sets of data. The metric can be used to identify the similarity or dissimilarity of samples. Finally, as demonstrated in the accompanying paper, the algorithm can be used to gate on events in one sample that are different from a control sample, even if those events cannot be distinguished on the basis of any combination of univariate or bivariate displays. Published 2001 Wiley-Liss, Inc.

Algorithms↗

PubMed2000

Parental intrusiveness in adolescence recalled by women with a history of bulimia nervosa and comparison women.

OBJECTIVE: To learn if women with a lifetime history of bulimia nervosa (BN) report more intrusive parental behavior during adolescence than their nonclinical peers, and to provide further validation of the Parental Intrusiveness Rating Scale (PIRS). METHOD: We administered the PIRS to 86 women with a lifetime history of BN and 573 comparison subjects and examined between-group differences. RESULTS: Relative to the comparison group, lifetime BN subjects reported higher levels of parental intrusiveness, specifically maternal invasion of privacy, maternal jealousy and competition, paternal seductiveness, and maternal and paternal overconcern with the daughter's eating, weight, and shape. There were no between-group differences in paternal invasion of privacy. In exploratory analyses with the comparison sample, Caucasian women reported greater maternal jealousy and competition than Asian American/Pacific Islander women, but there were no other differences. CONCLUSION: These results support clinical observations of high levels of parental intrusiveness in the adolescent experiences of women who develop BN. Nonclinical women of diverse ethnic backgrounds report largely equivalent experiences.

Adolescent↗

PubMedDate not supplied

Study of the distribution of trace elements in six species of marine organisms of the Ligurian Sea (north-western Mediterranean)--comparison with previous findings.

This paper presents the results of the determination of several trace elements (total and organic mercury, selenium, cadmium, lead, copper, manganese and zinc) in six species of marine organisms (Nephrops norvegicus, Engraulis encrasicolus, Mullus barbatus, Mullus surmuletus, Merluccius merluccius, and Sarda sarda), sampled in the Ligurian Sea (North-West Mediterranean) during a three-year period, from 1998 to 2000. The species analysed (388 samples) are the same studied in previous investigations in the same area (260 samples), so that a comparison with previous data measured in 1977-1986 was possible, in order to evaluate the variation of the marine environment in that area with respect to that period. Biological parameters of the specimens (length and weight of the individuals, and also sex for N. norvegicus) were taken into account in order to make possible the comparison between old and new data. No appreciable variation occurred in the levels of the trace elements analysed during the period 1998-2000, while the comparison with the data collected about 25 years ago showed a decrease of all the elements except for selenium.

Animals↗

PubMed1987

Digital dermatoglyphics in the Basque population: univariate and multivariate comparison with other Spanish populations.

We have analyzed dermatoglyphic finger patterns in a Spanish Basque population (841 males and 911 females). Bimanual and sexual comparisons have been carried out by means of contingency analysis. The results in the Basque population are compared with those of other Spanish populations, based on univariate (chi 2 contingency test and Student's t-test) and multivariate (principal components analyses) statistical methods. Bilateral distribution asymmetry and sexual dimorphism were observed in the Basque sample. The results of the chi 2 test for pattern types in males and females show statistically significant differences between the Basques and other Spanish populations, with the exception of the males from El Bierzo. Comparing populations with regard to the Pattern Intensity Index, the differences observed are much lower; therefore, this confirms what other authors have suggested regarding the limited usefulness of indexes in populational comparisons. In the Caucasian variation range of pattern types, Basques are located in the high part with regard to arches, in the low part with regard to whorls and radial loops, and in an intermediate part in relation to ulnar loops and overall pattern intensity. Results of the multivariate comparisons show which populations are more or less distant from the Basque population and which variables are significant in contributing to these population relationships.

Dermatoglyphics↗

PubMed2002

A randomized comparison of care provided by a clinical nurse specialist, an inpatient team, and a day patient team in rheumatoid arthritis.

OBJECTIVES: To compare in a randomized, controlled trial the clinical effectiveness of care delivered by a clinical nurse specialist, inpatient team care, and day patient team care in patients with rheumatoid arthritis (RA) who have increasing functional limitations. METHODS: Between December 1996 and January 1999, 210 patients with RA were recruited in the outpatient clinic of the rheumatology department of 6 academic and nonacademic hospitals. Clinical assessments recorded on study entry and weeks 6, 12, 26, and 52 included the Health Assessment Questionnaire (HAQ) and the McMaster Toronto Arthritis Patient Preference Disability Questionnaire as primary outcome measures, and the RAND-36 Item Health Survey, the Rheumatoid Arthritis Quality of Life questionnaire, the Health Utility Rating Scale, and the Disease Activity Score as secondary outcome measures. Patient satisfaction with care was measured on a visual analog scale in week 6 in all 3 groups and again in week 12 in the nurse specialist group. RESULTS: Within all 3 groups, functional status, quality of life, health utility, and disease activity improved significantly over time (P < 0.05). However, a comparison of clinical outcome among the 3 groups and a comparison between the nurse specialist group and the inpatient and day patient care groups together did not show any sustained significant differences. Subgroup analysis showed that age had a significant impact on differences between the 3 treatment groups with respect to functional outcome as measured with the HAQ (P < 0.001). With increasing age, the most favorable outcome shifted from care provided by a clinical nurse specialist and inpatient care to day patient care. Patients' satisfaction with care was significantly lower in the nurse specialist group than in the inpatient and day patient care groups (P < 0.001). CONCLUSION: Care provided by a clinical nurse specialist appears to have a similar clinical outcome in comparison with inpatient and day patient team care. Although all patients were highly satisfied with multidisciplinary care, patients who received care provided by a clinical nurse specialist were slightly less satisfied than those who received inpatient or day patient team care. Age appeared to be the only factor related to differences in functional outcome between the 3 treatment groups. The choice of management strategy may, apart from age, further be dependent on the availability of facilities, the preferences of patients and health care providers, and economic considerations.

Adult↗

PubMed2005

Sirolimus- and paclitaxel-eluting stents in comparison with balloon angioplasty for treatment of in-stent restenosis.

This study evaluated the acute and follow-up effectiveness of sirolimus-eluting stents (SESs) and nonpolymer-based paclitaxel-eluting stents (PESs) in comparison will balloon angioplasty for treatment of complex in-stent restenosis (ISR) lesions. Drug-eluting stents have been demonstrated to be highly effective for treatment of de novo lesions. The use of drug-eluting stents for treatment of complex ISR is less well defined. Eighty one lesions with in-stent restenosis (lesion length < 30 mm in a native coronary artery) were treated with either PTCA alone (n = 26 lesions in 25 patients), PES (n = 27 lesions in 24 patients; Achieve, Cook; 3,1 mug paclitaxel/mm(2) nonpolymer-based coating), SES (n = 28 lesions in 28 patients; Cypher, Cordis; 140 mug sirolimus/cm(2) metal surface area). Nine-month MACE rates were 32%, 8%, and 14% (all due to repeated revascularization procedures, except one death in the SES group) in the PTCA, PES, and SES group, respectively. Postintervention minimal lumen diameter in stent was significantly greater in the SES and the PES group in comparison with the PTCA group (2.37 +/- 0.26, 2.54 +/- 0.42, 1.78 +/- 0.23 mm; P < 0.001). At 6-month angiographic follow-up, late loss in stent was 0.77 +/- 0.45, 0.43 +/- 0.53, and 0.29 +/- 0.52 mm for the PTCA, PES, and SES group, respectively (P = 0.005). In-lesion restenosis rate was 61% for the PTCA group, 20% for the PES group, and 13% for the SES group (P = 0.042). The implantation of SES as well as nonpolymer PES proved to be effective for treatment of ISR. The combination of improved acute gain and reduced late loss results in a significantly improved angiographic follow-up result in comparison with PTCA.

Aged↗

PubMed1995

Tilt table evaluation for control pediatric patients: comparison with symptomatic patients.

This study was designed to evaluate pediatric control patients during head-up tilt in comparison with symptomatic neurocardiogenic syncope patient head-up tilt responses. Twenty-three pediatric control (c) patients (13 females, 10 males; 11.9 +/- 3.1 years) were tested with head-up tilt (HUT) and compared with 66 symptomatic (s) patients. Baseline drug-free HUT (cHUT-1), a second drug-free HUT (cHUT-2), and a final HUT with isoproterenol infusion (cHUT-3) were each performed at 80 degrees tilt angle for 30 min or until positive. For comparison, 66 symptomatic patients (41 females, 25 males; 13.6 +/- 2.5 years) underwent drug-free HUT (sHUT-1); negative responders during sHUT-1 underwent follow-up HUT with isoproterenol (sHUT-2). HUT data were compared for both groups at both 30 and 20 min tilt duration. Twelve control patients (52%) had a symptomatic response during cHUT-1 at 18 +/- 8 min. During cHUT-2, 5 of 23 patients were positive at 13 +/- 5 min; each had previously tested positive during cHUT-1. Two patients, each positive in cHUT-1 and cHUT-2, refused cHUT-3. The only patient testing positive during cHUT-3 was test positive in cHUT-1 but negative for cHUT-2. In comparison, 43 of 66 (65%) symptomatic patients tested positive during drug-free sHUT-1 at 11 +/- 6 min. Subsequently, 20 of the 23 negative patients underwent HUT with isoproterenol (sHUT-2), with 8 of 20 testing positive. Thus, 51 of 66 symptomatic patients (77%) were called "true positives."(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1987

Comparison of met-enkephalin-, dynorphin A-, and neurotensin-immunoreactive neurons in the cat and rat spinal cords: I. Lumbar cord.

This study compared the distribution of methionine enkephalin-, dynorphin A 1-8-, and neurotensin-immunoreactive (IR) perikarya in laminae I and IV-VII of selected segments of lumbar spinal cord of cat(L5) and rat(4). Immunoreactive neurons for each peptide were found throughout the dorsal horn and dorsal lamina VII but were quantified only within laminae I and IV-VII. In lamina I, both large (greater than 20 micron) and small (less than 20 micron) IR neurons were identified. Large IR neurons for each peptide in both species resembled Waldeyer neurons studied by Golgi stain and were outnumbered by small IR neurons. Comparison among the laminae of the distribution of met-enkephalin IR neurons showed a similar pattern in the two species with the majority of IR neurons (greater than 65%) in laminae V and VI. Differences in laminar distribution occurred between species for the other peptides. Dynorphin IR neurons were greatest in number in lamina V in rat but greatest in number in laminae I and V in cat. Neurotensin IR neurons occurred predominantly in cat lamina I but were nearly equal in density in rat laminae I and VI. The topographic distribution of each peptide in laminae V and VI was similar between the two species with IR neurons occurring laterally in lamina V and more medially in lamina VI. Comparisons between species of the numbers of IR neurons/segment indicated distinct relationships for each peptide. The number of met-enkephalin IR neurons in laminae of cat L5 was generally two times greater than the number of IR neurons in the same laminae of rat L4, except in laminae I and IV, where the numbers were nearly equal. In contrast, the number of dynorphin IR neurons in cat laminae was generally one-half the number in rat, except in lamina I, where the number in cat was two times greater than rat. A high degree of variability occurred in laminar comparisons of neurotensin IR neurons. Neurotensin IR neurons in lamina I of cat outnumbered those of rat 2:1, but in laminae IV-VII, the ratio of cat to rat IR neurons varied from 1:1 to 1:20. The met-enkephalin, dynorphin, and neurotensin IR neurons quantified in this study may be interneurons or may serve as projection neurons to brainstem and/or thalamic nuclei. The observed differences in distribution may be relevant to differences in spinal cord physiology in the two species.

Animals↗

PubMed2004

Multiplex bead array assays for detection of soluble cytokines: comparisons of sensitivity and quantitative values among kits from multiple manufacturers.

BACKGROUND: Multiplex bead array assays permit simultaneous cytometric quantitation of multiple cytokines in solution by capturing these to spectrally distinct beads. Because several manufacturers offer reagents to quantitate the same cytokines on a single instrument, a comparison should be made to determine whether these kits yield similar data and whether these data are comparable to enzyme-linked immunosorbent assay (ELISA). METHODS: This study compared cytokine detection kits by using Luminex 100. Twenty-six serum samples from seven subjects were analyzed for interferon-gamma, interleukins 1beta, 6, and 8, and tumor necrosis factor-alpha by using multiplex kits from LINCO Research, Bio-Rad Laboratories, R&D Systems, and BioSource International. Each assay was performed according to the manufacturers' specifications. Standard curves were generated by using reference concentrations supplied by each manufacturer. ELISAs for interleukin-8 were performed by using kits from R&D and BioSource. RESULTS: Cytokine levels followed similar patterns, although absolute concentrations differed among kits. ELISA and Luminex values for interleukin-8 were similar in kits from the same manufacturer. CONCLUSIONS: Because relative cytokine measurements are often valuable when performed serially, it may be possible to make interlaboratory comparisons by using different kits. When comparison of absolute values is crucial, kits from the same supplier should be used. Within-vendor, bead array, and ELISA values appear comparable.

Cytokines↗

PubMed1993

Specimen adequacy evaluation in gynecologic cytopathology: current laboratory practice in the College of American Pathologists Interlaboratory Comparison Program and tentative guidelines for future practice.

Routine specimen adequacy evaluation, as advocated by The Bethesda System (TBS), can play an important role in improving the sensitivity and accuracy of cervical cytopathology screening. The effectiveness of this measure, however, has been limited by the lack of uniform criteria for adequacy. Practice parameters are now emerging, through TBS development of tentative criteria and interlaboratory comparison of adequacy practices. This study reviews 1) nationwide responses to surveys of laboratory practices in the College of American Pathologists Interlaboratory Comparison Program in Cervicovaginal Cytology (CAP PAP); 2) the definitions of adequacy based on TBS; and 3) the results of implementation of these criteria in a private independent laboratory, university hospital laboratory, and private nonprofit hospital laboratory. In the initial CAP PAP survey in 1990, 35% of responding laboratories routinely reported specimen adequacy, increasing to 66% in 1991 and 85% in 1992. Interlaboratory variations in adequacy practices were observed, however, underscoring the need for consensus criteria. The experience in the authors' laboratories indicates that TBS criteria can serve as a sound guideline. Effective implementation of adequacy assessment in the individual laboratory requires careful attention to ensuring the quality of adequacy ratings, correlating clinical and prior laboratory information, issuing clear and concise reports, and giving recommendations judiciously. Through interlaboratory comparison and consistent intralaboratory emphasis on specimen adequacy, greater uniformity of adequacy assessment can be achieved, and adequacy evaluation can achieve its promise of improving the quality of cervical cytopathology.

Clinical Laboratory Techniques↗

PubMedDate not supplied

Cardioprotection with pioglitazone is abolished by nitric oxide synthase inhibitor in ischemic rabbit hearts--comparison of the effects of pioglitazone and metformin.

BACKGROUND: The effects of two drugs representing different classes of antidiabetic pharmacology (pioglitazone, a thiazolidinedione; and metformin, a biguanide) on the myocardial metabolism in the ischemia are poorly understood. METHODS: To test the hypothesis that cardioprotection of pioglitazone and metformin is associated with nitric oxide (NO), we studied the high energy phosphate metabolism by 31P-nuclear magnetic resonance (NMR) in isolated rabbit hearts. Forty-five minutes of continuous normothermic global ischemia was carried out. Pioglitazone or metformin was administered at the beginning, 60 min prior to the global ischemia, with or without the nitric oxide synthase inhibitor, L-NAME, administered 5 min or 60 min prior to the ischemia. In the first experiment, whether NO was produced or not by administration of pioglitazone, for the prevention of myocardial ischemic injury, was investigated. Hearts of male Japanese white rabbits were divided into 4 experimental groups: the control (C) group, the P group consisting of pioglitazone treatment, the P + L5 group consisting of pioglitazone treatment with L-NAME (5 min before ischemia), and the P + L60 group consisting of pioglitazone treatment with L-NAME (60 min before ischemia). In the next experiment, a comparison between the effects of pioglitazone and metformin in preventing ischemic injury were studied. The hearts were divided into 4 experimental groups: the control (C) group, the P group consisting of pioglitazone treatment, the P + L5 group consisting of pioglitazone treatment with L-NAME (5 min before ischemia), the M group consisting of metformin treatment, and the M + L5 group consisting of metformin treatment with L-NAME (5 min before ischemia). RESULTS: In the first experiment, the decrease in adenosine triphosphate (ATP) during ischemia was significantly inhibited in the P group in comparison with the C group (P < 0.01). However, the decrease in ATP was not inhibited in the P + L5 group during ischemia. In contrast, in the P + L60 group, the decrease in ATP was not inhibited during a part of ischemia. In the next experiment, a comparison between the effects of pioglitazone and metformin in preventing ischemic injury was studied. As a result of administration of either pioglitazone or metformin, there was no difference between groups with and without L-NAME. CONCLUSION: These results suggest that pioglitazone has a significant beneficial effect on improving the myocardial energy metabolism during ischemia. This cardioprotection may be dependent on nitric oxide (NO) synthase during ischemia more than preischemia. Furthermore, the present findings suggest that both pioglitazone and metformin have equal cardioprotective effects mediated by NO on myocardial ischemic injury in rabbits.

Adenosine Triphosphate↗

PubMed2007

Understanding the recent evolution of the human genome: insights from human-chimpanzee genome comparisons.

The sequencing of the chimpanzee genome and the comparison with its human counterpart have begun to reveal the spectrum of genetic changes that has accompanied human evolution. In addition to gross karyotypic rearrangements such as the fusion that formed human chromosome 2 and the human-specific pericentric inversions of chromosomes 1 and 18, there is considerable submicroscopic structural variation involving deletions, duplications, and inversions. Lineage-specific segmental duplications, detected by array comparative genomic hybridization and direct sequence comparison, have made a very significant contribution to this structural divergence, which is at least three-fold greater than that due to nucleotide substitutions. Since structural genomic changes may have given rise to irreversible functional differences between the diverging species, their detailed analysis could help to identify the biological processes that have accompanied speciation. To this end, interspecies comparisons have revealed numerous human-specific gains and losses of genes as well as changes in gene expression. The very considerable structural diversity (polymorphism) evident within both lineages has, however, hampered the analysis of the structural divergence between the human and chimpanzee genomes. The concomitant evaluation of genetic divergence and diversity at the nucleotide level has nevertheless served to identify many genes that have evolved under positive selection and may thus have been involved in the development of human lineage-specific traits. Genes that display signs of weak negative selection have also been identified and could represent candidate loci for complex genomic disorders. Here, we review recent progress in comparing the human and chimpanzee genomes and discuss how the differences detected have improved our understanding of the evolution of the human genome.

Animals↗

PubMed2002

The application accuracy of the NeuroMate robot--A quantitative comparison with frameless and frame-based surgical localization systems.

The NeuroMatetrade mark robot system (Integrated Surgical Systems, Davis, CA) is a commercially available, image-guided, robotic-assisted system used for stereotactic procedures in neurosurgery. In this article, we present a quantitative comparison of the application accuracy of the NeuroMate with that of standard frame-based and frameless stereotactic techniques. The article discusses a five-way application accuracy comparison study. The variables of our comparison and their mean errors are as follows: (1) with the robot in a frame-based configuration, the RMS was 0.86 +/- 0.32 mm; (2) with the robot in the frameless configuration, the RMS was 1.95 +/- 0.44 mm; (3) in a standard stereotactic (ZD) frame-based approach, the RMS was 1.17 +/- 0.25 mm; (4) with an infrared tracking system using the frame for fiducial registration, the RMS was 1.47 +/- 0.45 mm; (5) with an infrared tracking system using screw markers for registration, the RMS was 0.68 +/- 0.26 mm. The study was performed with 2-mm sections of CT scans. These results show that the application accuracy of the frame-based NeuroMate robot is comparable to that of standard localizing systems, whether they are frame-based or infrared tracked.

Equipment Design↗

PubMed2006

Methodological issues in international comparison of interval breast cancers.

International comparisons of interval cancers (IC) are important to better understand the relationship between programmes' performance and screening practices. In this respect, differences in (i) definition, (ii) identification and (iii) quantification of IC have received little attention. To examine these 3 comparability issues and activities involving IC, an assessment was conducted among member countries of the International Breast Cancer Screening Network, and the impact of accuracy of identification and quantification practices was estimated using 1996-98 data from the Dutch breast cancer screening programme. Information was obtained from 19 screening programmes in 18 countries, 16 of which acknowledged the coexistence of opportunistic screening. IC data were collected to evaluate performance of the screening programme (100% of programmes) and the radiologists (89%); 53% of programmes had a designated review process for IC. Most programmes (84%) agreed with the European Guidelines definition of IC, but a case situation exercise evidenced substantial discrepancy in classification of cancers that occurred after a positive screen. Completeness of identification of IC appears to contribute most to international variation, and cannot be easily controlled for in methodologically rigorous comparisons. Statistically significant differences of about 4% were measured between quantification methods for IC. An operational definition of IC is proposed to enhance international comparability. Valid comparisons of IC are possible with careful attention to the definition but true differences in IC frequency across screening programmes should exceed 10% to be possibly indicative of real differences between programmes.

Adult↗

PubMed2003

Ion release in stable hip arthroplasties using metal-on-metal articulating surfaces: a comparison between short- and medium-term results.

The use of metallic heads articulating with metallic cups could solve the problem of polyethylene (PE) wear in total hip replacement (THR) with metal-on-PE bearings. A conspicuous release of metal ions from new models of metal-on-metal bearings has been found in the short-term, but it is yet unclear whether the medium-term corrosion rate is high or, on the contrary, it becomes negligible, because of the continuous surface finishing. Our purpose was to compare the serum ion values (nanograms per milliliter) in 15 patients with metal-on-metal stable prosthesis (Group A), in the short-term (subgroup A(1); mean follow-up: 24 mo) and medium-term (subgroup A(2); mean follow-up: 52 mo), in order to determine whether the ion release decreased with time of implant. Chromium (Cr), cobalt (Co), molybdenum (Mo) and aluminum (Al) were analyzed. Twenty-two presurgical patients were used for comparison (Group B). The reference range was obtained from a population of 27 healthy subjects (Group C). Co and Cr levels in the medium-term (subgroup A(2)) were not decreased in comparison with the short-term values (subgroup A(1)) and were significantly higher (p < 0.001) than presurgical and reference values. Otherwise, Mo and Al concentrations were not significantly increased in comparison with reference values. In conclusion, despite the apparent advantage of metal-on-metal coupling, especially in younger patient populations, there is a major concern about the extent and duration of the relevant "internal" exposure to Cr and Co ions. This exposure should be carefully monitored, in order to clarify the biologic effects of ion dissemination and, consequently, to identify risks concerning long-term toxicity of metals.

Adult↗