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PubMed2004

Image-based computational fluid dynamics: a new paradigm for monitoring hemodynamics and atherosclerosis.

Complex blood flow dynamics are thought to play a key role in the development and treatment of atherosclerosis; however, the exact nature of this role is incompletely understood owing to the practical difficulties associated with measuring important local hemodynamic factors, notably wall shear stresses, in vivo. Only recently has it become possible to consider mapping these hemodynamic factors in a prospective, patient-specific manner via the coupling of in vivo medical imaging and computational fluid dynamics (CFD) modelling. CFD models derived from intravascular ultrasound have already been used to elucidate the role that hemodynamic forces play in mechanical and pharmacological interventions for coronary atherosclerosis. CFD models derived from magnetic resonance imaging and three-dimensional ultrasound provide a less invasive window into more superficial vessels such as the carotid bifurcation, and thus are promising tools for clarifying the role of, and eventually exploiting, purported local geometric and hemodynamic risk factors for atherosclerosis and its response to therapeutic options. Efforts to improve the ease and robustness with which these models are constructed have led to concomitant improvements in accuracy and precision, data for which are presented to facilitate estimation of sample sizes for future studies. Current limitations and anticipated future directions for these powerful new tools are discussed.

Arteriosclerosis↗
PubMed2006

[Evaluation on methodological problems in reports concerning quantitative analysis of syndrome differentiation of diabetes mellitus].

OBJECTIVE: To evaluate the quality of reports published in recent 10 years in China about quantitative analysis of syndrome differentiation for diabetes mellitus (DM) in order to explore the methodological problems in these reports and find possible solutions. METHODS: The main medical literature databases in China were searched. Thirty-one articles were included and evaluated by the principles of clinical epidemiology. RESULTS: There were many mistakes and deficiencies in these articles, such as clinical trial designs, diagnosis criteria for DM, standards of syndrome differentiation of DM, case inclusive and exclusive criteria, sample size and estimation, data comparability and statistical methods. CONCLUSION: It is necessary and important to improve the quality of reports concerning quantitative analysis of syndrome differentiation of DM in light of the principles of clinical epidemiology.

Bibliometrics↗
PubMedDate not supplied

[Increased rate of spontaneous version in breech presentation by Indian bridge? A prospective, randomized study].

BACKGROUND: The effectiveness of Indian version to convert fetuses from breech to vertex presentation was evaluated. METHODS: One hundred and nine pregnant women presenting between 30 and 32 weeks of gestation with singleton breech infants were included in our prospective randomized open study making an interim analysis recruitment to estimate the sample sizes after one year. The spontaneous version rate of fetuses in breech presentation was compared with the version rate in women performing Indian version. Indian version is a maternal positioning exercise that consists of raising the pelvis, abduction of the thighs, and relaxed abdominal breathing. Clinical parameters that could influence the result were assessed. RESULTS: In primiparous women, the version rate was 70% in the Indian version group and 63% in the comparison group. In multiparous women, 89% Indian versions and 87% spontaneous versions were observed. Parity was the only clinical parameter found to be related to outcome. CONCLUSION: Indian version does not significantly improve the rate of spontaneous version of breech to vertex presentation.

Adult↗
PubMed1998

[Study on the power of O/E method].

This paper addresses the methodology of calculating the power of O/E method and introduces the relevant algorithm for estimating the sample size. Based on the principles of hyporthesis testing and Poisson distribution, the power can be worked out for given sample size, baseline rate(pi 0) and the factor of increasing (gamma). The power increases with the increase in sample size, pi 0 and gamma. In shape the power is not a continuous smooth line but a zigzag line. The method illustrated in this paper can be also used for estimaging the sample size of studies on the intervention of diseases.

Congenital Abnormalities↗
PubMed2001

Reliability of a questionnaire for evaluating the understanding of asthma.

The present study was designed to evaluate the repeatability of a questionnaire developed to assess the understanding that asthma patients have of their disease and, on the basis of its variability, estimate the sample size necessary for determining the efficacy of a future structured program on asthma knowledge. The repeatability of the Asthma Questionnaire (AQ) was evaluated by asking 89 patients to complete it twice within a period of 7-10 days without the subject being exposed to any programme on asthma knowledge between the two administrations. The AQ was demonstrated to have good content and face validity. Results showed that neither age nor sex had a significant influence on total scores, and that the degree of reliability was adequate (R = 0.769). The mean percentage of correct answers was observed to be approximately 70% in both sessions, suggesting a consistent area for possible improvement which could be targeted by means of an appropriately structured programme on asthma knowledge. For comparative purposes before and after the programme, or for measuring its efficacy, the AQ should be recommended. In conclusion the Asthma Questionnaire could provide a useful tool for the general practitioner, chest physician and other health professionals, to assess what the patient really does understand or does not, concerning asthma management, and hence be the starting point for a well-tailored educational intervention.

Adolescent↗
PubMed2001

Prostate specific antigen kinetics at tumor recurrence after radical prostatectomy do not suggest a worse disease prognosis in black men.

PURPOSE: It has been shown that black men with clinically localized prostate adenocarcinoma treated with radical prostatectomy have poorer disease-free and disease specific survival than white men with similar tumors. These findings suggest that a potentially more aggressive variant of prostate cancer exists in black men. Because prostate specific antigen (PSA) velocity at tumor recurrence is a good indicator of disease aggressiveness, we determine whether there was evidence that PSA velocity at biochemical recurrence after radical prostatectomy is faster in black men. MATERIALS AND METHODS: Our retrospective data search at 2 university centers resulted in 127 white and 37 black men with clinical stage cT1 to 2 prostate adenocarcinoma who underwent radical prostatectomy between 1990 and 1994 and had evidence of biochemical recurrence (PSA greater than 0.2 ng./ml.) on followup available for analysis. No neoadjuvant or adjuvant treatments were given before or after radical prostatectomy, and all PSA relapses and subsequent treatments were recorded. PSA velocity modeling was performed in patients before any form of treatment for PSA failure. Preoperative PSA, Gleason score and pathological stage were also included in the model to assess the impact on PSA velocity after recurrence. RESULTS: Our data suggested that PSA velocity at tumor recurrence was related to preoperative PSA on a continuous scale (p = 0.063). However, in our analysis there was little evidence that race had any effect on PSA velocity at tumor recurrence in our patient cohort (p = 0.58). Likewise, little difference in PSA velocity was seen in regard to Gleason score (p = 0.89) or pathological stage (p = 0.23) in these patients. With data on 37 black men available for analysis it was likely that only large or extreme trends could be detected. Results could be used to estimate required sample sizes for assessment of less extreme trends. CONCLUSIONS: Our data on tumor growth rate at recurrence, as reflected by PSA velocity kinetics, do not support the hypothesis that prostate tumors in black men are necessarily more aggressive due to enhanced growth. Further studies comparing the molecular and biological differences between prostate cancers in black and white males are needed to clarify reasons for the apparent differences in initial presentation, as compared to that at tumor recurrence in these 2 groups.

Adenocarcinoma↗
PubMed1975

Linkage data on MN and the Hb beta locus.

A sample of 28 informative families was studied for linkage between Hb beta and MN. Values of the neuterized recombination fraction from these and other families from the literature excluded a recombination fraction of less than .30 between these loci. Our results support different recombination values for males and females (theta equals .34 abd .50, respectively). A simple approach to estimate the sample size required as well as a study of the relationship between sibship size and sample size under conditions of loose linkage are also presented.

Brazil↗
PubMedDate not supplied

[Reproducibility of pediatric information collected with various methods: postal/telephone questionnaire and direct interview].

The paper reports on a research aimed to evaluate the repeatability of some paediatric data obtained from the parents by using different collection instruments: telephone interview, mail questionnaire, in-person interview. The study included 699 children consecutively born in the Policlinico Universitario "A. Gemelli" from September to November 1983. After 3 years a questionnaire containing questions about measles, anti measles immunization, age at which the baby started to walk, disease delaying the walking, and orthopaedic examinations was sent by mail to 149 families; the other 550 families were searched for by telephone and, if found, asked the same questions. All the contacted families were invited for a paediatric check-up, during which the same data were collected through direct interview. For each question crude agreement and K statistic (which controls for the agreement attributable to chance) were computed with respect to both the phone/direct and mail direct comparisons. 391 families (56%) were traced for the first interview, due to the high number of them which had moved home. Among these 289 (74%) attended the paediatric check-up. On the whole, rather high values of K statistic were observed, ranging from 0.59 (question on diseases delaying the walking, comparison phone/direct) to 0.93 (question on anti-measles immunization, comparison mail/direct). Due to the small sample size, the estimates concerning the comparison mail/direct are rather imprecise. Although its potential is limited by the low response rate, the study brings good evidence that the information considered is not sufficiently reliable when reported retrospectively by parents. However, the keeping of a prospective individual record containing data of medical interest should be encouraged.

Data Collection↗
PubMed2006

[Practical experiences of applying TCM intervention along principle of evidence-based medicine on restenosis after percutaneous coronary intervention].

As traditional Chinese medicine (TCM) attach importance to clinic, shortage of objective and quantitative criteria in evaluating therapeutic effect is one of the largest obstacles for TCM to move toward the world and win wide approval. The introduction of evidence-based medicine (EBM) concept brings favorable opportunity to research on TCM. The authors have conducted clinical studies on restenosis after percutaneous coronary intervention (PCI) intervened by TCM, in the period of Tenth Five-Year Project, and realized EBM was indeed a vital principle for clinical study on TCM. However, randomized controlled trial should be applied reasonably, attention should be paid to the standardized design of research, including estimation of sample size, concealment of randomized sequence, extension of blindness and selection of control, and stress should be put on the quality control in implementation, so as to provide objective evidence for effect evaluation of TCM treatment.

Angioplasty, Balloon, Coronary↗
PubMed1988

The dexamethasone suppression test and depression. Approaches to the use of a laboratory test in psychiatry.

The dexamethasone suppression test has undergone unprecedented study among the biologic tests proposed for clinical use in psychiatry. Since the 1970s, its study has involved hundreds of reports and thousands of patients. Although important technical aspects of the test appear to be well accepted and validated, additional information is needed regarding the pharmacokinetics of dexamethasone. Marked interindividual differences in plasma dexamethasone suggest that performance of the test might be improved by factoring dexamethasone levels into test interpretations. There also may be advantages to the development of a modified test involving other exogenous and index steroids, such as monitoring corticosterone levels. Although it is too early to determine how ROC analysis will alter the clinical application of the test, some implications for methodology and data presentation are already clear. First, because the test is a diagnostic system with nonbinary outcomes, ROC analysis can augment traditional performance indices such as sensitivity, specificity, and positive predictive power. Second, ROC analysis will improve comparisons between the studies of different research groups and will help assess innovations in the application of the test. Third, ROC analytic techniques permit appropriate planning of sample size given estimates of the expected values of AUC that would be obtained from the studies. ROC theory thus promises to play an increasingly important role in the evaluation and future improvement of the dexamethasone suppression test and other biologic markers in clinical psychiatry. In conclusion, neither uncritical enthusiasm nor excessive skepticism is warranted about the use of the dexamethasone suppression test in clinical psychiatry. Evidence to date should encourage investigators to pursue refinement of the test or other tests of hypothalemic-pituitary-adrenal functioning to increase their accuracy and clinical utility.

Adrenocorticotropic Hormone↗
PubMed1988

The dexamethasone suppression test and depression. Approaches to the use of a laboratory test in psychiatry.

The dexamethasone suppression test has undergone unprecedented study among the biologic tests proposed for clinical use in psychiatry. Since the 1970s, its study has involved hundreds of reports and thousands of patients. Although important technical aspects of the test appear to be well accepted and validated, additional information is needed regarding the pharmacokinetics of dexamethasone. Marked interindividual differences in plasma dexamethasone suggest that performance of the test might be improved by factoring dexamethasone levels into test interpretations. There also may be advantages to the development of a modified test involving other exogenous and index steroids, such as monitoring corticosterone levels. Although it is too early to determine how ROC analysis will alter the clinical application of the test, some implications for methodology and data presentation are already clear. First, because the test is a diagnostic system with nonbinary outcomes, ROC analysis can augment traditional performance indices such as sensitivity, specificity, and positive predictive power. Second, ROC analysis will improve comparisons between the studies of different research groups and will help assess innovations in the application of the test. Third, ROC analytic techniques permit appropriate planning of sample size given estimates of the expected values of AUC that would be obtained from the studies. ROC theory thus promises to play an increasingly important role in the evaluation and future improvement of the dexamethasone suppression test and other biologic markers in clinical psychiatry. In conclusion, neither uncritical enthusiasm nor excessive skepticism is warranted about the use of the dexamethasone suppression test in clinical psychiatry. Evidence to date should encourage investigators to pursue refinement of the test or other tests of hypothalamic-pituitary-adrenal functioning to increase their accuracy and clinical utility.

Adrenocorticotropic Hormone↗
PubMed1988

General statistical design considerations of randomized clinical trials.

Randomized clinical trials are the most objective method for evaluating new therapies, but they are subject to the same biases as nonrandomized studies unless the principles of statistical design are observed at the planning stage. Estimation of sample size also requires early careful consideration, since studies of inadequate size will not have sufficient statistical power to detect meaningful treatment differences. For ethical reasons, interim data monitoring procedures should be used to detect early treatment responses that may lead to alteration or interruption of the planned study to give patients early benefit from a superior treatment or diminish their risk from ineffective or harmful treatment. Additional important aspects of clinical trial design that were not addressed in this report include: definition of study objectives and endpoints, description of data to be collected, details of the treatment regimens, informed consent and plans for data analysis. The science of clinical trial design is complex; only some of the key statistical issues have been addressed briefly in this report.

Clinical Trials as Topic↗
PubMed1995

Outcome measurement in osteoarthritis clinical trials.

The clinical assessment of outcome in osteoarthritis (OA) clinical trials is highly dependent on the use of valid, reliable, and responsive measurement techniques. Despite several decades of clinical studies, and a half-century of development in clinical metrology, we still lack international standards of measurement for OA trials. There have, nevertheless, been several very encouraging developments. In particular, the Osteoarthritis Research Society and the 5th WHO/ILAR Task Force have discussed issues of standardization. The Western Ontario and McMaster Universities Osteoarthritis Index and Lequesne Index have been proposed as important outcome measures. Finally, data have recently been published on observer variability, variance estimation, and sample size determination for OA trials.

Canada↗
PubMed1997

The Hong Kong vision study: a pilot assessment of visual impairment in adults.

PURPOSE: The Hong Kong Adult Vision Pilot Study is a population based study of the distribution and determinants of eye disease in a random sample of the Chinese population age 40 and over. The present pilot study identifies the extent and causes of visual loss using methods developed in the United States and Australia. The pilot study uses the prevalence data to estimate the sample size necessary to predict the size of an effect a larger study may detect and the confidence with which that effect may be considered and the standard deviation of the Hong Kong population. The smallest detectable odds ratios were calculated based on known risk factor prevalence rates of the pilot study. METHODS: Hong Kong Chinese residents aged 40 and over in 2 random cluster sites were identified by private household census. The examinations were performed at one location and included, health history and habits, presenting and best corrected LogMar vision, Humphrey visual field and IOP measurement, dilated slit lamp, fundus examination, fundus photography and echography. RESULTS: In the two test sites, 355 people were examined of the 441 eligible residents (81% response). 76.6% of the population reported a change in vision in the last 10 years; 45% had not sought examination. 4.54% had vision less than 20/60. This was caused by: myopic choroidal degeneration (31%), cataract (19%), cataract + ARM (19%), ARMD (19%), glaucoma (6%), and corneal disease (6%). Vision loss increased significantly with age. Vision loss was more common in older women than in older men. The prevalence rates calculated from the pilot study data were used, requiring a relative precision of 95% and +/- 20% confidence interval of the prevalence rates, indicate that a sample size of 2500 would be a good number for a larger study. CONCLUSIONS: The methods developed in the United States and Australia for completing eye disease prevalence studies are applicable in Hong Kong. Vision loss is increasingly common in older people and the percent of visual impairment in Hong Kong is higher than studies in the US and Australia. As the population ages demands on the health care systems will increase. The results from this pilot warrant continuation of the study. Efforts must be directed toward prevention of visual loss.

Adult↗
PubMed1989

[Random sample planning in morphometry].

This report tries to explain principles and presuppositions of planning sample sizes. The aim is estimation of the optimal, that means minimally necessary sample size, justifying an investigation ethically and economically. The problems are complicated because of the necessity of nested sampling or samples within samples. We describe the most important presuppositions using an example of mean value estimation. These are: establishing of demands for exactness, of error probability, and knowledge of variance of the parameters. It is explained in detail by means of binomially distributed variables as we find them in the point counting method.

Humans↗
PubMed2006

Estimating population size with noninvasive capture-mark-recapture data.

Estimating population size of elusive and rare species is challenging. The difficulties in catching such species has triggered the use of samples collected noninvasively, such as feces or hair; from which genetic analysis yields data similar to capture-mark-recapture (CMR) data. There are, however two differences between classical CMR and noninvasive CMR. First, capture and recapture data are gathered over multiple sampling sessions in classical CMR, whereas in noninvasive CMR they can be obtained from a single sampling session. Second, because of genotyping errors and unlike classical CMR, there is no simple relationship between (genetic) marks and individuals in noninvasive CMR. We evaluated, through simulations, the reliability of population size estimates based on noninvasive CMR. For equal sampling efforts, we compared estimates of population size N obtained from accumulation curves, a maximum likelihood, and a Bayesian estimator. For a closed population and without sampling heterogeneity, estimates obtained from noninvasive CMR were as reliable as estimates from classical CMR. The sampling structure (single or multiple session) did not alter the results, the Bayesian estimator in the case of a single sampling session presented the best compromise between low mean squared error and a 95% confidence interval encompassing the parametric value of N in most simulations. Finally, when suitable field and lab protocols were used, genotyping errors did not substantially bias population size estimates (bias < 3.5% in all simulations). The ability to reliably estimate population size from noninvasive samples taken during a single session offers a new and useful technique for the management and conservation of elusive and rare species.

Animals↗
PubMed1993

[Optimum sample size in the crossing experiments].

Crossing experiments are time-consuming and costly, hence, it is very essential to make a through plan and provide the necessary and sufficient sample size in advance. The common formula of the sample size in statistics is not suitable for the crossing experiments. This paper discussed two cases and put forward a corresponding estimate formula of sample size for crossing experiments, by utilizing the sample size derived from the estimate formula to arrange the crossing experiments; thus the total experimentation cost could be reduced to the lowest, or the total number of tested livestocks may be the fewest under the precondition of satisfying the requirements of the experiment designer.

Costs and Cost Analysis↗