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PubMed2001

Estimates of appropriate number of rats: interaction with housing environment.

An extensive list of physiological parameters from previous experiments was re-analysed in order to evaluate the effects of enrichment, cage type and group size on the within-group variation and hence on the number of animals needed in studies using Wistar rats. The independent factors studied in these experiments included the provision of aspen gnawing blocks for enrichment, solid bottom cages (SBCs) and grid floor cages (GFCs) and animal number per cage (varied from 1-4). SOLO power analysis was used to calculate the smallest number of animals (n) needed to detect an arbitrarily chosen 20% effect size, when significance was set at P = 0.05 and statistical power at 0.90. N ratios (nlarger/nsmaller) were calculated for the effect of enrichment, cage type and group size to compare the 'treatment group' with the 'control group'. The n values of adrenal gland, interscapular brown adipose tissue (BAT) and epididymal adipose tissue (EAT) weights seemed to vary most, whereas final body weight (FBWJ and growth seemed to be the least variable ones. According to one-sample t-test, the N ratios of most physiological parameters differed significantly from zero (except the ones of FBW) indicating that n values in 'treatment' and 'control' groups were unequal. The results indicate that some of the physiological parameters are susceptible to variability attributable to environmental modifications in general whereas some are not. Furthermore, they suggest that the variation of different parameters may vary from one experiment to another and between different environments thus hindering the estimations of appropriate number of animals.

Animal Husbandry↗
PubMed1999

Laboratory variables as additional staging parameters in patients with small-cell lung carcinoma. A systematic review.

We have reviewed the biomedical literature published over the last 25 years in order to try to establish which of four frequently evaluated laboratory parameters (i.e. serum, or plasma, NSE, LDH, sodium or albumin) might, alone or in combination, give the "best" pretreatment prognostic information in small-cell lung cancer (SCLC) patients, independent of the usual radiological and clinical parameters. From the 45 studies included in this review, the only clear conclusion that can be derived is that it has not yet been clearly demonstrated that the "new" tests (NSE or other tumor markers) are superior to the "old" tests (LDH, sodium, albumin etc.). From the only seven studies that used the same powerful statistical methodologies (Cox's models in association with recursive partitioning and amalgamation procedure (RECPAM) analysis) it could be concluded that LDH and albumin might have independent prognostic significance in SCLC and in advanced SCLC respectively. Provided that, in the future, both laboratory and statistical expertises are clearly guaranteed in the primary studies in this field, it might become possible to propose laboratory parameters as additional staging parameters in SCLC.

Carcinoma, Small Cell↗
PubMed1991

Female DUI offenders: a comparison to male counterparts and an examination of the effects of intervention on women's recidivism rates.

Female DUI offenders who participated in a controlled, random assignment DUI intervention study, the Mississippi DUI Probation Follow-Up Project, were compared to their male counterparts on demographic, drinker status and recidivism variables. In comparison to men, women in the project were less likely to be married, more likely to be between 30 and 50 years of age, less likely to have less than a 9th grade education, less likely to be screened as a high-problem-risk drinker, less likely to have prior DUI and public drunkenness arrests and less likely to recidivate. The effects of short-term rehabilitation, 1 year's probation and administration of the Life Activities Inventory-Current Status Questionnaire (LAI-CSQ) on the long-term recidivism rates of women were examined. The analysis for screened low-problem-risk women was inconclusive due to lack of statistical power. However, the repeated administration of the LAI-CSQ was detrimental for screened high-problem-risk women and tended to be detrimental for women with fewer than 12 years of education. Implications for intervening with female DUIs are discussed.

Accidents, Traffic↗
PubMed1999

Why the prone position is a risk factor for sudden infant death syndrome.

INTRODUCTION: The laryngeal chemoreflex may explain why prone sleeping increases the risk of sudden infant death syndrome (SIDS). Swallowing and arousal are crucial to prevent laryngeal chemoreflex stimulation. Our aim was to examine these reflexes and breathing responses in healthy neonates after pharyngeal infusion of water in the supine versus the prone position, controlling for sleep state. METHODS: A total of 10 term infants were recruited after parental consent and ethics approval. Polygraphic recordings included sleep state (active and quiet sleep by electroencephalogram, eye movements, breathing, and behavior), cardiorespiratory measurements (nasal airflow, chest wall movements, heart rate, and oxygen saturation), swallowing, and esophageal activity (solid state pressure catheter). Initial sleeping position was assigned randomly. Measurements were made for 1 minute before and after 0.4 mL of water was instilled into the oropharynx. To detect a 30% decrease in swallowing, power analysis indicated that >/=10 babies were required. Analysis, blinded to position, was made using nonparametric statistics. RESULTS: Of the 164 infusions, the most commonly evoked airway protective responses to pharyngeal infusion were swallowing (95%) and arousal (54%). After infusion in active sleep, there was a significant reduction in swallowing and breathing when the prone position was compared with the supine position (prone: 21.3 [1.0] swallows/min and -9.6 [2.1] breaths/min; and supine: 32 (2.2) and -2. 9 (1.5), respectively). However, there was no difference in the occurrence of arousal after water infusion. CONCLUSION: These data suggest that airway protection is compromised in the prone sleeping position during active sleep, even in healthy infants exposed to minute pharyngeal fluid volumes of 0.4 mL. This is because swallowing rate is reduced significantly, and there is no compensatory increase in arousal. The reduction in airway protective reflexes when in the prone position and in active sleep may be the mechanism for the increased risk of SIDS in the prone position.

Arousal↗
PubMed2005

A pharmacokinetic comparison of three pharmaceutical formulations of nimesulide in healthy volunteers.

BACKGROUND/AIM: Switching the patient from one pharmaceutical formulation of the same drug to another, may lead to therapeutic inadequancy in some cases. To minimize the risk, careful pharmacokinetic studies are desired in the pre-registration period and afterwards. METHODS: A randomized, crossover design with one-week wash-out period between each dose was applied. Serum samples, obtained before dosing and at various appropriate time points up to 15 hours, were analyzed for nimesulide content by a high-performance liquid chromatographic method with ultraviolet (LU) detection. The pharmacokinetics and relative bioavailability of three different pharmaceutical formulations containing nimesulide, manufactured by the same pharmaceutical factory, were studied prospectively in 12 healthy subjects of both sexes. A single 100-mg oral dose of nimesulide was given to the volunteers in the form of conventional tablets, mouth dissolving tablets or as a suspension. Analysis of variance, power analysis, 90% confidence intervals, and two one-sided tests were used for the statistical analysis of pharmacokinetic parameters. RESULTS: The tolerability of all preparations was excellent. The respective confidence intervals of the ratios of geometric means of C(max) and AUC(0-infinity) of nimesulide were out of acceptable limits either for conventional tablets in comparison with suspension or for mouth dissolving tablets when compared with conventional tablets. A comparison of mouth dissolving tablets with suspension showed a statistically significant difference between C(max) values (suprabioavailability of mouth dissolving tablets), while the point estimate of the ratio of geometric means of AUC(0-infinity) was 0.945 with the corresponding 90% confidence interval of 0.902-0.991. At the 5% level of significance, there were no differences between the formulations under the study in times elapsed to peak serum concentrations, as revealed by the non-parametric Wilcoxon signed ranks test. CONCLUSION: Only a 90% confidence interval for the relative differences of log-transformed AUC(0-infinity) values of nimesulide absorbed from mouth dissolving tablets vs. suspension was included in the 80% to 125% interval proposed by the Food and Drug Administration (FDA). On that basis, mouth dissolving tablets (Nimulid-MD) were considered bioequivalent to Nimulid suspension according to the extent of drug absorption. Concerning the comparable amounts of nimesulide available in the systemic circulation after application of these formulations the one might not expect therapeutic failure after switching the patient from one to another.

Adult↗
PubMed2000

Measurement of cognitive performance in computer programming concept acquisition: interactive effects of visual metaphors and the cognitive style construct.

An innovative research program was devised to investigate the interactive effect of instructional strategies enhanced with text-plus-textual metaphors or text-plus-graphical metaphors, and cognitive style on the acquisition of programming concepts. The Cognitive Styles Analysis (CSA) program (Riding,1991) was used to establish the participants' cognitive style. The QUEST Interactive Test Analysis System (Adams and Khoo,1996) provided the cognitive performance measuring tool, which ensured an absence of error measurement in the programming knowledge testing instruments. Therefore, reliability of the instrumentation was assured through the calibration techniques utilized by the QUEST estimate; providing predictability of the research design. A means analysis of the QUEST data, using the Cohen (1977) approach to size effect and statistical power further quantified the significance of the findings. The experimental methodology adopted for this research links the disciplines of instructional science, cognitive psychology, and objective measurement to provide reliable mechanisms for beneficial use in the evaluation of cognitive performance by the education, training and development sectors. Furthermore, the research outcomes will be of interest to educators, cognitive psychologists, communications engineers, and computer scientists specializing in computer-human interactions.

Aptitude Tests↗
PubMed1979

Classification and bioavailability studies with WE 941 by quantitative pharmaco-EEG and clinical analyses.

Psychoactivity, pharmacodynamic properties and drug tolerance of 2-bromo-4-(2-chlorophenyl)-9-methyl-6H-thieno[3,2-f]1,2-(4-triazolo)[4,3-a][1,4]diazepine (WE 941), a new triazolodiazepine, were studied in 10 normal subjects utilizing quantitative pharmaco-EEG and clinical evaluation methods. In the double-blind, placebo-controlled trial, the subjects received randomized at weekly intervals oral single doses of 0.1 mg, 0.3 mg and 0.5 mg WE 941, placebo, and 30 mg flurazepam as reference substance. Measurements were obtained before and at the 2nd, 4th, 6th h post drug. EEG power spectral density analysis demonstrated no changes after placebo, while WE 941 and flurazepam induced statistically significant alterations characterized by an increase in beta-activity, a decrease in alpha-activity and increase in average frequency ("anxiolytic pharmaco-EEG profile"). In addition, 0.3 mg and 0.5 mg WE 941 and 30 mg flurazepam produced a significant augmentation of delta-activity indicating hypnotic qualities. Considering spontaneous and placebo-induced alterations, evaluation of the time- and dose-effect relationship indicated that all active substances exerted a tranquilizing effect throughout 8 h, while the hypnotic properties of 0.1 mg WE 941 were minimal (up to the 4th h), those of 0.3 mg WE 941 were moderate (up to 6 h) and those of 0.5 mg WE 941 were marked (up to 8 h). The dosage equipotent to 30 mg flurazepam is 0.3 mg WE 941. Heart rate and blood pressure exhibited no relevant changes, while side effects including fatigue, drowsiness and dizziness were mostly observed after the highest dosage of WE 941.

Adult↗
PubMedDate not supplied

Study of prognosis in acute myeloid leukemias (AML) by cluster analysis.

BACKGROUND: Cluster analysis is particularly effective in detecting homogeneous subgroups among large series of observations. We applied this relatively uncommon approach to the study of prognosis in 137 patients affected by acute myeloid leukemia (AML). METHODS AND RESULTS: Employing simple presentation parameters (age, WBC, splenomegaly, hepatomegaly) we used cluster analysis to define 3 groups with different overall survival (p = 0.0019). This classification was obtained following a rescaling of the variables and principal component analysis. Validation was performed through random definition of a control group. With the same variables, univariate analysis demonstrated age was the only prognostic factor, while Cox's model was not significant. CONCLUSIONS: In our series cluster analysis allowed a better definition of prognosis than Cox's analysis. Since the 3 groups are well identifiable, each patient can be rapidly classified and his allocation confirmed by discriminant functions. For cluster 2 we were able to project a possible myelodysplastic evolution, while cluster 3 was more frequently associated with a monocytic blastic component. We think that cluster analysis deserves consideration as an alternative statistical approach in the analysis of large series of data; its usefulness lies in its power to define homogeneous prognostic or biologic subgroups and to elaborate further hypotheses for new studies.

Acute Disease↗
PubMed1993

Meta-analysis as a guide to clinical practice.

BACKGROUND: Meta-analysis is now widely used in order to increase the power of individual clinical studies. Important far-reaching conclusions have been derived by pooling the results of studies which in isolation would not be large enough to reach definitive conclusions. While the statistical power is thereby amplified, so is the potential for error. OBJECTIVE: To assess the potential and the pitfalls of meta-analysis as a guide to clinical practice. CONCLUSIONS: Conclusions derived from meta-analysis may be influenced by unrecognized selection bias and heterogeneity of studies included. Publication of the results may be in a form which does not lend itself readily to critical analysis and misleading results may therefore be accepted.

Antihypertensive Agents↗
PubMedDate not supplied

[The psychological status of workers subjected to noise exposure].

Mental health was examined in workers from a reinforced concrete plant and a thermal electric power station who were exposed to intensive noise at work. Noise was shown to have an adverse effect on their body's function. Higher occupational doses were found to result in the asthenic syndrome, to impair psychic processes along with the most profound emotional and volitional changes.

Adolescent↗
PubMed1991

Unraveling the mystique of power analysis.

Power analysis provides one method for assessing the efficacy of alternative research designs. The purpose of this article is to simplify the methods for calculating power analysis to determine an adequate sample size. Although attention to type I errors (alpha error) is prevalent among nurse researchers, there is less appreciation for research problems resulting from a type II error. Without the a priori examination of the power of the test of significance, there is no assurance that the sample is sufficient to discern significant differences. Formulas for calculating effect size are provided for t tests, correlations, chi-square, analysis of variance, and regression. Examples of calculating the effect size by using four different statistical tests based on research studies are presented: t tests with unequal variance between groups, chi-square, an analysis of variance, and regression. Power analysis is an additional procedure to ensure that the sample size is adequate for the research project about to be undertaken.

Nursing Research↗
PubMed2002

Identification of the sources of error in allele frequency estimations from pooled DNA indicates an optimal experimental design.

Genotyping costs still preclude analysis of a comprehensive SNP map in thousands of individual subjects in the search for disease susceptibility loci. Allele frequency estimation in DNA pools from cases and controls offers a partial solution, but variance in these estimates will result in some loss of statistical power. However, there has been no systematic attempt to quantify the several sources of error in previous studies. We report an analysis of the magnitude of variance components of each experimental stage in DNA pooling studies, and find that a design based on the formation of numerous small pools of approximately 50 individuals is superior to the formation of fewer, larger pools and the replication of any of the experimental stages. We conclude that this approach may retain an effective sample size greater than 68% of the true sample size, whilst offering a 60-fold reduction in DNA usage and a greater than 30-fold saving in cost, compared to individual genotyping. The possibility of combining pooling with informed selection of haplotype tag SNPs is also considered. In this way further savings in efficiency may be possible by using pooled allele frequency estimates to infer haplotype frequencies and hence, allele frequencies at untyped markers.

Alleles↗
PubMed2002

On the advantage of haplotype analysis in the presence of multiple disease susceptibility alleles.

We investigated the effect of multiple susceptibility alleles at a single disease locus on the statistical power of a likelihood ratio test to detect association between alleles at a marker locus and a disease phenotype in a case-control design. Using simplifying assumptions to obtain the joint frequency distribution of marker and disease locus alleles, we present numerical results that illustrate the impact of historical variation of initial associations between marker alleles and susceptibility alleles on the power of a likelihood ratio test for association. Our results show that an increase in the number of susceptibility alleles produces a decrease in power of the likelihood ratio test. The decrease in power in the presence of multiple susceptibility alleles, however, is less for markers with multiple alleles than for markers with two alleles. We investigate the implications of this observation for tests of association based on haplotypes made up of tightly linked single-nucleotide polymorphisms (SNPs). Our results suggest that an analysis based on haplotypes can be advantageous over an analysis based on individual SNPs in the presence of multiple susceptibility alleles, particularly when linkage disequilibria between SNPs is weak. The results provide motivation for further development of statistical methods based on haplotypes for assessing the potential for association methods to identify and locate complex disease genes.

Alleles↗
PubMed2003

Gaussian distributions on Lie groups and their application to statistical shape analysis.

The Gaussian distribution is the basis for many methods used in the statistical analysis of shape. One such method is principal component analysis, which has proven to be a powerful technique for describing the geometric variability of a population of objects. The Gaussian framework is well understood when the data being studied are elements of a Euclidean vector space. This is the case for geometric objects that are described by landmarks or dense collections of boundary points. We have been using medial representations, or m-reps, for modelling the geometry of anatomical objects. The medial parameters are not elements of a Euclidean space, and thus standard PCA is not applicable. In our previous work we have shown that the m-rep model parameters are instead elements of a Lie group. In this paper we develop the notion of a Gaussian distribution on this Lie group. We then derive the maximum likelihood estimates of the mean and the covariance of this distribution. Analogous to principal component analysis of covariance in Euclidean spaces, we define principal geodesic analysis on Lie groups for the study of anatomical variability in medially-defined objects. Results of applying this framework on a population of hippocampi in a schizophrenia study are presented.

Algorithms↗
PubMed1996

Changes in aerobic power of women, ages 20-64 yr.

This study quantified and compared the cross-sectional and longitudinal influence of age, self-report physical activity (SR-PA), and body composition (%fat) on the decline of maximal aerobic power (VO2peak) of women. The cross-sectional sample consisted of 409 healthy women, ages 20-64 yr. The 43 women of the longitudinal sample were from the same population and examined twice, the mean time between tests was 3.7 (+/-2.2) yr. Peak oxygen uptake was determined by indirect calorimetry during a maximal treadmill test. The zero-order correlation of -0.742 between VO2peak and %fat was significantly (P < 0.05) higher then the SR-PA (r = 0.626) and age correlations (r = -0.633). Linear regression defined the cross-sectional age-related decline in VO2peak at 0.537 ml.kg-1.min-1.yr-1. Multiple regression analysis (R = 0.851) showed that adding %fat and SR-PA and their interaction to the regression model reduced the age regression weight of -0.537, to -0.265 ml.kg-1.min-1.yr-1. Statistically controlling for time differences between tests, general linear models analysis showed that longitudinal changes in aerobic power were due to independent changes in %fat and SR-PA, confirming the cross-sectional results. These findings are consistent with men's data from the same lab showing that about 50% of the cross-sectional age-related decline in VO2peak was due to %fat and SR-PA.

Adult↗
PubMed1994

Efficacy of new generation antidepressants: meta-analysis of imipramine-controlled studies.

When assessing the efficacy of a new antidepressant in comparison with a standard treatment, most clinical trials have come to the conclusion that the nullhypothesis (equal efficacy) cannot be rejected, and have not been reformulated with respect to (at least) equivalent studies. However, it cannot be concluded from this that the compared treatments have the same (or similar) efficacy, because in many of the studies the statistical power is not sufficient. Using the effect-size formula described by Glass et al. (1981), a meta-analysis were performed combining the results of comparative trials of maprotiline, mianserin, viloxazine, trazodone, nomifensine, fluvoxamine, and fluoxetine, performed according to similar objectives and designs (similar patient selection, double-blind, randomized, etc.) and with imipramine as reference compound. Together with the results of a former meta-analysis of amitriptyline-controlled studies (Möller and Haug, 1988) the present investigation indicates differences in efficacy, which in the case of most of the new generation antidepressants is similar to the reference compounds imipramine and amitriptyline.

Adolescent↗
PubMed2004

Phacoemulsification parameters: series 20000 Legacy Versus Legacy with AdvanTec software and NeoSoniX handpiece.

PURPOSE: To examine the differences in average phaco power and effective phaco time (EPT) and evaluate the clinical results with the standard Series 20000 Legacy system (Alcon) and the Legacy with AdvanTec software and the NeoSoniX handpiece (Alcon). SETTING: Department of Ophthalmology, University Hospital, Hradec Králové, Czech Republic. METHODS: The mean phaco power and EPT in 240 eyes of 240 consecutive patients having cataract surgery by a single surgeon using the standard Legacy 20000 system were retrospectively compared with results in 240 eyes of 240 consecutive patients operated on by the same surgeon using the Legacy with AdvanTec software and the NeoSoniX handpiece. Statistical analysis was performed using the Kruskal-Wallis 1-way analysis of variance. All chi-square (chi(2)) values are approximations. RESULTS: The EPT and mean phaco power were less in the AdvanTec-NeoSoniX group than in the standard Legacy 20000 group in all cases. The mean EPT was 56.9 seconds +/- 29.5 (SD) in the standard Legacy 20000 group and 4.2 +/- 3.8 seconds in the AdvanTec-NeoSoniX group. The mean phaco power was 19.2% +/- 6.2% and 5.1% +/- 2.5%, respectively. The difference between groups was statistically significant in EPT (age > or =90 years, chi(2) = 4.5, P =.034; age <90 years, chi(2)>57, P<.00005) and in mean phaco power (chi(2) = 4.58 and P =.032 and chi(2)>44 and P<.00005, respectively). No trace of corneal striae or edema was observed in 92% eyes on the first postoperative day. The best corrected visual acuity was 20/25 or better in 60% of cases. CONCLUSIONS: The Legacy system with AdvanTec software and the NeoSoniX handpiece significantly reduced the mean EPT and phaco power. This low-power technology minimizes intraoperative damage to ocular structures and maximizes the level and rapidity of visual rehabilitation.

Aged↗