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PubMedDate not supplied

Data reduction of multichannel fields: global field power and principal component analysis.

Electroencephalographic data recorded for topographical analysis constitute multidimensional observations, and the present paper illustrates methods of data analysis of multichannel recordings where components of evoked brain activity are identified quantitatively. The computation of potential field strength (Global Field Power, GFP) is used for component latency determination. Multivariate statistical methods like Principal Component Analysis (PCA) may be applied to the topographical distribution of potential values. The analysis of statistically defined components of visually elicited brain activity is illustrated with data sets stemming from different experiments. With spatial PCA the dimensionality of multichannel data is reduced to only three components that account for more than 90% of the variance. The results of spatial PCA relate to experimental conditions in a meaningful way, and this method may also be used for time segmentation of topographic potential maps series.

Action Potentials↗

PubMed1994

Achieving statistical power through research design sensitivity.

The challenge for nurse researchers is to design their intervention studies with sufficient sensitivity to detect the treatment effects they are investigating. In order to meet this challenge, researchers must understand the factors that influence statistical power. Underpowered studies can result in a majority of null results in a research area when, in fact, the interventions are effective. The sensitivity of a research design is not a function of just one element of the design but of the entire research design: its plan, implementation and statistical analysis. When discussing factors that can increase a research design's statistical power, attention is most often focused on increasing sample size. This paper addresses a variety of factors and techniques, other than increasing sample size, that nurse researchers can use to enhance the sensitivity of a research design so that it can attain adequate power.

Nursing Research↗

PubMed1993

Automated morphometric analysis of stallion spermatozoa.

Tissue variation in microscope slides made for spermatozoon analysis and variation introduced by the subjective techniques used to analyze these slides reduce the statistical power of studies that seek to use spermatozoon morphology to predict fertility. A simple specimen preparation method was developed to standardize stallion spermatozoon morphologic smears, and a new, automated spermatozoa morphometry instrument was used to objectively analyze the efficacy of the specimen preparation technique. The method achieved a standard spermatozoon concentration and reduced field-to-field variation in the number of spermatozoa analyzed. Metric measurements of spermatozoon head dimensions from clinically normal, fertile stallions revealed small, but highly significant, differences between stallions. The variation in metric measurements between replicate slides within stallions was small, indicating that replicate slide analysis probably is not necessary for clinically normal stallions. Coefficients of variation were generally < 11% for metric measurements between stallions, and were < 4% within stallions. This study revealed that a high degree of statistical power can be achieved when using these new, standardized specimen preparation and objective analysis techniques. Such power makes possible the detection of subtle differences between clinically normal stallions, and may facilitate accurate detection of abnormal fertility (ie, subfertility) in stallions.

Animals↗

PubMed1987

An alternative to interference indexes in neuropsychological time-sharing research.

Interference indexes are used as criterion measures in a significant proportion of time-sharing paradigms in order to control for the initial discrepancy between left- and right-handed tapping rates. Problems associated with these indexes include low reliability, low statistical power, and especially correlations with baseline tapping rates. An analysis of covariance procedure using raw-score concurrent tapping rates as criterion measures, and baseline tapping rates as covariates, can effectively address these problems as demonstrated through a reanalysis of data.

Functional Laterality↗

PubMed1987

Utility of molecular genetic analysis of bcr rearrangement in the diagnosis of chronic myeloid leukemia.

Two DNA probes for the breakpoint cluster region (bcr) of chromosome # 22 have been used to determine the proportion of Philadelphia chromosome (Ph)-positive chronic myeloid leukemia (CML) cases that can be diagnosed by Southern blot analysis. Studies on 17 normal individuals and 17 patients with lymphomas and leukemias (other than CML) indicated that for the restriction enzymes chosen, only expected germ line DNA bands were obtained. In contrast, novel DNA bands interpreted as being the product of translocation within the bcr region could be demonstrated in 31 of 31 cases of Ph-positive CML. One commercially available 1.2 kb bcr probe detected most cases of CML. Because of the frequent presence of deletion of part of the bcr region, however, a probe from the 5' end of bcr is essential to detect some cases. An analysis of the bcr breakpoints occurring in CML patients suggested a difference in the location of the breakpoints for the blast crisis patients versus chronic phase patients although the difference between these two groups was not statistically significant. It is concluded that bcr analysis provides a powerful aid in the diagnosis of CML. This technique is of particular merit in cases when cytogenetic analysis is inconclusive and has considerable potential for improved speed and sensitivity of diagnosis.

Chromosome Banding↗

PubMed2004

Topiramate: effect on EEG interictal abnormalities and background activity in patients affected by focal epilepsy.

PURPOSE: To evaluate the effects of topiramate (TPM) on interictal epileptiform abnormalities (IEA) and background activity by means of a computerized EEG analysis, in adult patients affected by focal epilepsy, with or without secondarily generalization, treated with TPM as adjunctive therapy or monotherapy. METHODS: Twenty-four patients affected by symptomatic or cryptogenic focal epilepsy underwent long-term video-EEG recording before and after TPM addition (mean dose 175+/-25 mg per day). RESULTS: TPM addition induced a significant reduction of both partial and secondarily generalized tonic-clonic (SGTC) seizures; treatment responder patients (seizure reduction > or = 50%) were 19 out of 24 patients (79.1%), of whom 5 were seizure-free. Quantitative analysis of IEA showed a significant decrease in the mean number of spikes/10 min during TPM therapy ( 4.2+/-4.2 versus 2.2+/-4.4; P<0.003 ). The analysis of spatial distribution of interictal spikes showed that such reduction was more evident at the level of the epileptogenic area rather than on the spreading component. Statistical analysis revealed only a significant decrease of mean relative power of alpha band in the EEG spectral content, recorded at rest in a group of 18 out of 24 epileptic patients during TPM therapy. In addition, during TPM treatment we observed a significant reduction in alpha reactivity without any important changes of alpha indexes (peak frequency and median frequency). CONCLUSION: These findings suggest that TPM has a strong inhibitory effect on IEA, probably acting on the generating processes, and, if used at low dosage and gradually titrated, seems to have only mild interferences with EEG background activity.

Adolescent↗

PubMed2005

Recipes for the linear analysis of EEG.

In this paper, we describe a simple set of "recipes" for the analysis of high spatial density EEG. We focus on a linear integration of multiple channels for extracting individual components without making any spatial or anatomical modeling assumptions, instead requiring particular statistical properties such as maximum difference, maximum power, or statistical independence. We demonstrate how corresponding algorithms, for example, linear discriminant analysis, principal component analysis and independent component analysis, can be used to remove eye-motion artifacts, extract strong evoked responses, and decompose temporally overlapping components. The general approach is shown to be consistent with the underlying physics of EEG, which specifies a linear mixing model of the underlying neural and non-neural current sources.

Algorithms↗

PubMed1997

Oligodendrogliomas. Part II: A new grading system based on morphological and imaging criteria.

This second part of our study of 'pure' oligodendrogliomas focuses on survival data analysis. In order to identify potentially useful prognostic factors and to assess the effectiveness of a new grading system, the 79 patients in the previously analyzed series for whom adequate follow-up could be obtained (52%) were entered in the present analysis. Statistical analysis demonstrated that contrast enhancement and endothelial hyperplasia had powerful and similar influence on survival. Median survival with and without contrast enhancement were: 3 versus 11 years, and with or without endothelial hyperplasia were: 3.5 versus 11 years. Conversely, the degree of nuclear atypia and presence or absence of mitosis or necrosis were not correlated with survival. These findings allowed us to devise a simple grading system which discriminates two malignancy grades as follows: absence of endothelial hyperplasia and of contrast enhancement = Grade A, presence of endothelial hyperplasia and/or of contrast enhancement = Grade B. Of the 79 oligodendrogliomas in this study, 59 tumors were categorized as grade A and 20 as grade B. Median survival were: 11 years in grade A and 3.5 years in grade B. Five-year and 8-year survival rates were: 89% and 60% in grade A and: 33% and 15% in grade B. Double blind grading between two independent observers was concordant in 96% of the cases. Application of this simple efficient and reproducible grading scheme should permit reliable comparison of retrospective or prospective therapeutic data emanating from various institutions.

Brain Neoplasms↗

PubMed2001

Problems in the definition, interpretation, and evaluation of genetic heterogeneity.

Suppose that we wish to classify families with multiple cases of disease into one of three categories: those that segregate mutations of a gene of interest, those which segregate mutations of other genes, and those whose disease is due to nonhereditary factors or chance. Among families in the first two categories (the hereditary families), we wish to estimate the proportion, p, of families that segregate mutations of the gene of interest. Although this proportion is a commonly accepted concept, it is well defined only with an unambiguous definition of "family." Even then, extraneous factors such as family sizes and structures can cause p to vary across different populations and, within a population, to be estimated differently by different studies. Restrictive assumptions about the disease are needed, in order to avoid this undesirable variation. The assumptions require that mutations of all disease-causing genes (i) have no effect on family size, (ii) have very low frequencies, and (iii) have penetrances that satisfy certain constraints. Despite the unverifiability of these assumptions, linkage studies often invoke them to estimate p, using the admixture likelihood introduced by Smith and discussed by Ott. We argue against this common practice, because (1) it also requires the stronger assumption of equal penetrances for all etiologically relevant genes; (2) even if all assumptions are met, estimates of p are sensitive to misspecification of the unknown phenocopy rate; (3) even if all the necessary assumptions are met and the phenocopy rate is correctly specified, estimates of p that are obtained by linkage programs such as HOMOG and GENEHUNTER are based on the wrong likelihood and therefore are biased in the presence of phenocopies. We show how to correct these estimates; but, nevertheless, we do not recommend the use of parametric heterogeneity models in linkage analysis, even merely as a tool for increasing the statistical power to detect linkage. This is because the assumptions required by these models cannot be verified, and their violation could actually decrease power. Instead, we suggest that estimation of p be postponed until the relevant genes have been identified. Then their frequencies and penetrances can be estimated on the basis of population-based samples and can be used to obtain more-robust estimates of p for specific populations.

Family Health↗

PubMed1992

The multi-site tumour transplantation model for human endometrial carcinoma: a statistical evaluation.

We studied the effect of multi-site tumour transplantation on tumour growth by implanting varying numbers of EnCa 101 human endometrial tumours in athymic mice. One treatment group received a single tumour per mouse, another group received two tumours per mouse and a third group received four tumours per mouse. Tumour growth was sustained in all animals by implantation of oestradiol-17 beta pellets. We observed positive correlation between tumours within the same mouse, which implies that individual tumours are not statistically independent. The correlation is sufficiently large that failure to account for it in statistical design and analysis could result in studies with insufficient power and in spurious assertions of significance. Regression modelling of tumour growth curves showed that mean tumour volume per animal is not affected by the number of tumours growing on the animal; that is, the data are consistent with the null hypothesis that mean tumour volume is the same regardless of the number of tumours present. Our results therefore suggest that the use of multiple tumours per animal can increase the precision of experiments without loss of validity and at relatively little cost. However, correct and efficient analysis of the data so obtained requires more sophisticated techniques than those--such as fixed-effects analysis of variance and the two sample t-test--that assume independence of tumours.

Animals↗

PubMedDate not supplied

Processes and methodologies for research validation of nursing diagnoses.

TOPIC: Research validation of nursing diagnoses. PURPOSE: To provide a historical review of processes and methodologies for research validation of nursing diagnoses and suggested directions for future nursing diagnosis research. SOURCES: Nursing diagnosis research methodologies and processes from the Invitational Conference on Research Methods for Validating Nursing Diagnoses, Nursing Diagnosis: The Journal of Nursing Language and Classification, and the North American Nursing Diagnosis Association (NANDA) conference proceedings for the first through the 12th conference. CONCLUSIONS: Future nursing diagnosis research should include concept analysis, expert validation, clinical validation, instrument development, larger studies, powerful statistical analyses, replication and comparison of studies, and concerted efforts to support group research activities that target priority areas of research.

Data Interpretation, Statistical↗

PubMed1987

Entrainment of respiratory frequency to exercise rhythm during hypoxia.

Breathing frequency (f) is often reported as having an integer-multiple relationship to limb movement (entrainment) during rhythmic exercise. To investigate the strength of this coupling while running under hypoxic conditions, two male Caucasians and four male Nepalese porters were tested in the Annapurna region of the Himalayas at altitudes of 915, 2,135, 3,200, 4,420, and 5,030 m. In an additional study in a laboratory at sea level, three male and four female subjects inspired various O2-N2 mixtures [fraction of inspired O2 (FIO2) = 20.93, 17.39, 14.40, 11.81%] that were administered in a single-blind randomized fashion during a treadmill run (40% FIO2 maximum O2 consumption). Breathing and gait signals were stored on FM tape and later processed on a PDP 11/73 computer. The subharmonic relationships between these signals were determined from Fourier analysis (power spectrum), and the coincidence of coupling occurrence was statistically modeled. Entrainment decreased linearly during increasing hypoxia (P less than 0.01). Moreover, a significant linear increase in f occurred during hypoxia (P less than 0.05), whereas stride frequency and metabolic rate remained constant, suggesting that hypoxic-induced increases in f decreased the degree of entrainment.

Adult↗

PubMed1990

An analysis of methodology in follow-up studies of adult inpatient psychiatric treatment.

A review of 70 follow-up studies of adult inpatient psychiatric treatment published since 1975 reveals substantial methodological shortcomings. Recurring problems include lack of descriptive information about the patient population studied, inadequate depiction of the psychiatric treatment provided before or during hospitalization, weak research design, lack of blind analysis, unsystematic approaches to data collection, and avoidance of powerful statistical techniques. Eight specific recommendations are offered to aid future researchers in designing outcome studies.

Adult↗

PubMed2026

Quizartinib for patients with newly diagnosed FLT3-ITD-positive AML who received maintenance therapy in QuANTUM-First.

QuANTUM-First demonstrated improved overall survival (OS) in patients with newly diagnosed acute myeloid leukemia with FMS-like receptor tyrosine kinase 3-internal tandem duplication (FLT3-ITD) treated with quizartinib + standard chemotherapy. Herein, we evaluated the impact of postconsolidation/posttransplant single-agent maintenance therapy on clinical outcomes in patients receiving maintenance, focusing on measurable residual disease (MRD) status at maintenance onset. OS, event-free survival, and relapse-free survival were prespecified exploratory analyses. Cumulative incidence of relapse, analyses by allogeneic hematopoietic cell transplant (allo-HCT), and analyses by MRD status were post hoc and not powered for statistical significance. Samples for FLT3-ITD MRD analysis were collected from patients with composite complete remission ≤30 days before receiving maintenance and assessed using an ultrasensitive amplicon-based assay. More patients who had received an allo-HCT and quizartinib treatment received maintenance (71%) vs placebo (55%); OS benefit was not demonstrated among these patients. In patients who did not undergo allo-HCT, quizartinib maintenance was associated with a significant OS benefit (hazard ratio [HR], 0.401; 95% confidence interval [CI], 0.192-0.838), including a benefit in patients who were MRD negative at the start of maintenance (OS HR, 0.194; 95% CI, 0.056-0.676). Patients who were MRD negative at the completion of consolidation achieved 89.1% (95% CI, 70.0-96.4) survival at 3 years with quizartinib maintenance in the absence of allo-HCT. These data suggest that for patients who achieve FLT3-ITD MRD negativity after induction and consolidation with quizartinib, maintenance with quizartinib provides a significant survival benefit and, in some patients, may eliminate the need for allo-HCT. This trial was registered at www.clinicaltrials.gov as NCT02668653.

Humans↗

PubMed1988

An N of 1 service: applying the scientific method in clinical practice.

The N of 1 service at our institution acts as a full referral service for clinicians who want a definitive answer to a difficult management question, and an instructional environment for clinicians who have more time and want to learn to run their own N of 1 RCT. The trial design is a double blind, randomized pair, multiple crossover. A number of methodologic issues are discussed, such as appropriateness of the patients problem to N of 1 trials, feasibility, types of measurement, such as clinical objective measurement and quality of life measurement, as well as timing of these measurements. The analysis issues include developing a reporting method which is statistically powerful and understandable to clinicians with little research background. Some of these issues have been well investigated and some have not.

Clinical Trials as Topic↗

PubMed2000

Evaluating group distributional characteristics: why psychophysiologists should be interested in qualitative departures from the normal distribution.

Real data often do not approximate the normal distribution. Under nonnormal conditions, psycho-physiologists who use parametric statistics may be testing with inadequate power and/or testing a measure of location (i.e., the mean) that does not represent the desired portion of the distribution for statistical comparison. The purpose of this paper is: first, to provide psycho-physiologists with a method to investigate group distributional characteristics; second, to evaluate the distributional characteristics of heart period and respiratory sinus arrhythmia in human adults and newborns; third, to demonstrate the increased statistical power that can accompany the selection of an alternative statistical analysis for nonnormal data. Suggestions are provided on how to analyze nonnormal data.

Adult↗

PubMed2001

Treating postoperative pain improves outcome.

Recent surveys show that many patients still receive inadequate post-surgical analgesia, this problem is international in character. Analgesia techniques like patient-controlled analgesia (PCA) and spinal opioids alone or in combination with local anaesthetics provide superior pain relief compared to intermittent i.m. injections of opioids. Patient satisfaction with these techniques is high; however, reduced pain and suffering or high patient satisfaction is not considered sufficient in this age of diminished health care budgets. There is no overwhelming evidence that effective postoperative pain relief assures good postoperative outcome. Most studies lack sufficient statistical power to detect clinically significant differences. A meta-analysis showed higher patient satisfaction with i.v. PCA compared to i.m. opioid injection. Although PCA still is the standard of care there's little rational or scientific evidence that i.v. PCA improves outcome. A meta-analysis of randomized, controlled trials to assess the effects of seven analgesic therapies on postoperative pulmonary function after various procedures has shown that postoperative epidural pain control can significantly decrease the incidence of pulmonary morbidity. None of the other analgesic techniques had a significant impact on pulmonary outcome. There are few outcome studies with peripheral nerve blocks. Evidence that peripheral nerve blocks are better than PCA and safer than epidural increases. One reason why improved outcome is difficult to demonstrate is that pain management strategies are not integrated with overall perioperative care and postoperative rehabilitation of the patient. The importance of a good APS in developing cost-effective, evidence-based pain treatment strategies for different surgical procedures should not be underestimated.

Analgesia↗

PubMed1991

[Topographic selective mapping in patients with disorders of thermoregulation of cerebral origin].

The paper privides the data on topographic selective mapping of electric activity in a state of relaxed consciousness in 11 patients with derangement of thermoregulation of the central genesis compared to a group of patients with vegetative crises. 10 healthy volunteers served as control. On the whole the patients' group was characterized by diffuse augmentation of percentile presentation of the power of slow and regress of rapid ranges. The statistical analysis revealed varying electrophysiological organization in patients with paroxysmal and permanent character of hyperthermia. In the group of patients with paroxysmal temperature rises and vegetative crises, the electrophysiological parameters were identical. In patients with permanent ++sub-febrility, the pattern of spatial electric activity was characterized by qualitative and quantitative differences from the control group.

Action Potentials↗