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PubMed1992

Analysis of beat-to-beat cardiovascular hemodynamic variables obtained from long-term biotelemetry.

Manual methods of large volume data storage, retrieval, and analysis are difficult, time consuming, and present numerous opportunities for calculation errors. We have designed and implemented a comprehensive computer-based system for performing these functions. Development of this system was necessary since left ventricular (LV) blood pressure and two regional LV wall thickness measurements were obtained during long-term extracorporeal biotelemetry of miniswine for 24-h periods. During a single recording period over 100,000 individual cardiac cycles were recorded on analog tape and later analysed for determination of global myocardial oxygen demand and regional myocardial function. In addition, custom designed software was developed to determine the extent and duration of myocardial dysfunction. Batch file commands enabled the customized software to operate without prompting by the user thus optimizing the time usage of the computer, and the computer based data acquisition and analysis system. Although this system was designed specifically for analysing cardiovascular hemodynamic variables, it is flexible and can be applied to other experimental applications.

Analog-Digital Conversion↗
PubMed1998

Low frontal electroencephalographic coherence in neuroleptic-free schizophrenic patients.

BACKGROUND: Electroencephalographic (EEG) coherence analysis is a noninvasive technique for studying corticocortical associations. As there is evidence for a dysfunction of the prefrontal dorsolateral cortex in schizophrenia, we hypothesized to find lower frontal EEG coherence in schizophrenia. METHODS: EEG amplitude and coherence analysis was performed in 16 antipsychotic-free schizophrenic patients and 16 healthy controls. EEG recordings were done with 19 gold-plated electrodes placed according to the International 10/20 system against averaged signals from both earlobes. Local coherence was computed for 22 adjacent electrode pairs within the hemispheres and interhemispheric coherence for eight corresponding electrode pairs of both hemispheres in the delta, theta, alpha, and beta-I band. RESULTS: Amplitude and interhemispheric coherence analysis revealed no differences. Local EEG coherence was significantly lower in schizophrenic patients for Fpl-F7 in the delta (p = .001) and the theta band (p = .002), and at F7-F3 in the alpha band (p = .002). In the delta band coherence of Fpl-F7 was inversely correlated to the Positive and Negative Syndrome Scale positive symptoms subscore (R = -.74, p = .014). CONCLUSIONS: Assuming that EEG coherence can be used to index functional coupling between brain areas under the electrodes, the low EEG coherence in Fpl-F7 and F7-F3 in schizophrenic patients might reflect impaired information processing in the left dorsolateral prefrontal cortex.

Adult↗
PubMed2003

Similarity between the C-terminal domain of the prion protein and chimpanzee cytomegalovirus glycoprotein UL9.

Prion diseases are a group of fatal neurodegenerative disorders associated with structural conversion of a normal, mostly alpha-helical cellular prion protein, PrP(C), into a pathogenic beta-sheet-rich conformation, PrP(Sc). The structure of PrP(C) is well studied, whereas the insolubility of PrP(Sc) makes the characterization of its structure problematic. No proteins similar to PrP, except for its paralog with the same fold, PrP-Doppel, are known. However, PrP-Doppel does not undergo a structural transition into a beta-sheet-rich conformation. Structural information from proteins that share a weak but significant sequence similarity with PrP may be used to gain additional insights into the conformation of PrP(Sc). We construct a sequence profile corresponding to the structured domain of PrP and use this profile to search the SWISS-PROT and TrEMBL databases. We identify a significant sequence similarity between PrP and chimpanzee cytomegalovirus glycoprotein UL9. This glycoprotein scores higher than all PrP-Doppel sequences. Fold recognition methods assign a mainly-beta fold to UL9. Owing to the observed sequence similarity with PrP and a putative mainly-beta fold, the UL9 glycoprotein may represent a potential target for experimental structure determination aimed at obtaining a structural template for PrP(Sc) modeling.

Amino Acid Sequence↗
PubMed2005

Determination of transmission patterns in multichannel data.

The power of today's laboratory equipment allows more and more data channels to be easily recorded. However, some misunderstandings about processing such multivariate data may still be found in the literature. The typical mistake is to treat a multichannel system as comprising pairs of channels; this approach does not use all the collected information about the investigated system, and may lead to erroneous conclusions. In this paper, the differences between single- and multichannel approaches will be briefly summarized and some examples of problems will be described.

Computer Simulation↗
PubMed2003

Intravenous angiotensin II does not affect dynamic baroreflex characteristics of the neural or peripheral arc.

Although the elevation of angiotensin II (Ang II) associated with cardiovascular diseases has been considered to suppress the arterial baroreflex function, how Ang II affects dynamic arterial pressure (AP) regulation remains unknown. The aim of the present study was to elucidate the acute effects of Ang II on dynamic AP regulation by the arterial baroreflex. In seven anesthetized Japanese white rabbits, we randomly perturbed intra-carotid sinus pressure (CSP) according to a binary white noise sequence while recording renal sympathetic nerve activity (RSNA) and AP. We estimated the neural arc transfer function from CSP to RSNA and the peripheral arc transfer function from RSNA to AP before and after 30-min intravenous administration of Ang II (100 ng/kg/min). Ang II increased mean AP from 75.7 +/- 3.1 to 95.5 +/- 5.1 mmHg (p < 0.01), while it did not affect mean RSNA (from 5.9 +/- 1.3 to 5.7 +/- 1.2 a.u.). The neural arc transfer functions did not differ before or after Ang II administration (dynamic gain: -0.94 +/- 0.04 vs. -0.94 +/- 0.13, corner frequency: 0.06 +/- 0.01 vs.0.06 +/- 0.01 Hz, pure delay: 0.16 +/- 0.01 vs. 0.17 +/- 0.02 s). The peripheral arc transfer function did not differ before or after Ang II administration (dynamic gain: 1.18 +/- 0.05 vs. 1.06 +/- 0.11, natural frequency: 0.07 +/- 0.01 vs. 0.08 +/- 0.01 Hz, damping ratio: 1.19 +/- 0.06 vs. 1.24 +/- 0.19, pure delay: 0.83 +/- 0.06 vs. 0.78 +/- 0.05 s). Intravenous Ang II hardly affects the dynamic characteristics of neural and peripheral arc around the physiological operating pressure.

Algorithms↗
PubMed2001

[Tracing algorithms of ECG tracks from scanned image].

This paper presents a discussion on the tracing algorithms of the extraction of Electrocardiogram (ECG) data from scanned image of hardcopy ECG. We have advanced a new algorithm integrated by seek-and-predict method and polygon model method, which can tolerate crossing of two leads, fault-line and disturbing of grid lines. Two practical situations that may be encountered while processing hardcopy ECG are discussed in detail. Furthermore, the after-treatment of extraction-filtering is considered and an SVD-based filter designed to smooth ECG signal is analyzed.

Algorithms↗
PubMed1997

[Qualitative methods in empirical health research. V. Analyzing data and coding procedures].

The fifth article in this series outlines a general working procedure for the analysis of qualitative data. Some theoretical constructs relating to the interpretation of qualitative data are presented first, followed by discussion of data processing procedures, including coding. Examples of coding and interpretation are given, and finally guidelines regarding data presentation.

Data Interpretation, Statistical↗
PubMed1998

Automated key process monitors for patient care documentation.

Complete, accurate and timely patient care documentation is an essential part of the practice of medicine. As with any other process in medicine or industry, continuous quality improvement (CQI) is essential to assure the highest quality at the lowest cost. CQI requires objective key process measures that can be assessed routinely. A set of key process monitors designed to assess completeness, accuracy and timeliness were created based on local, regional and national standards. Feasibility was assessed in the LDS Hospital Emergency Department using 31,429 patient visits in the 18 months from June 1995 to November 1996. The logic of the score was programmed into SQL scripts and run against an Oracle database containing the patient care documentation. The results indicate that the chosen key process monitors can be used to provide real time assessment of the patient care documentation process. The general concepts of the key process measures of completeness, accuracy and timeliness are generalizable to many areas of medicine. The overall score provides one method of easily tracking departmental performance while the overall process monitoring database allows powerful, in-depth analysis of individual components of the process. It is recommended that such automated process monitoring tools be integrated into future clinical information systems.

Data Interpretation, Statistical↗
PubMed1994

Accuracy of statistical methods in TRANSFUSION: a review of articles from July/August 1992 through June 1993.

BACKGROUND: Statistical errors have been noted in a large percentage of articles appearing in medical journals. Their incidence in a blood banking journal, however, has not been studied. STUDY DESIGN AND METHODS: Original articles appearing in the journal TRANSFUSION from July 1992 through June 1993 were analyzed for correctness of statistical methods. Each article was reviewed by both a transfusion medicine physician and a statistician. RESULTS: There were 122 original articles, of which 59 contained statistical methods and were reviewed. Of these, 23 (39%) contained an error in the statistical description of their data, 47 (80%) failed to describe clearly the statistical tests performed, and 44 (75%) involved an incorrect statistical test or contained an error in test calculation or interpretation. As a result of these errors, 13 (22%) of the 55 articles analyzed reported conclusions not supported by the data. CONCLUSION: Misuse of statistical methodology may not be uncommon in transfusion medicine research, and it would be prudent to give more attention to statistical methodology in such research.

Blood Transfusion↗
PubMedDate not supplied

Can patients interpret health information? An assessment of the medical data interpretation test.

OBJECTIVE: To establish the reliability/validity of an 18-item test of patients' medical data interpretation skills. DESIGN: Survey with retest after 2 weeks. Subjects. 178 people recruited from advertisements in local newspapers, an outpatient clinic, and a hospital open house. RESULTS: The percentage of correct answers to individual items ranged from 20% to 87%, and medical data interpretation test scores (on a 0- 100 scale) were normally distributed (median 61.1, mean 61.0, range 6-94). Reliability was good (test-retest correlation=0.67, Cronbach's alpha=0.71). Construct validity was supported in several ways. Higher scores were found among people with highest versus lowest numeracy (71 v. 36, P<0.001), highest quantitative literacy (65 v. 28, P<0.001), and highest education (69 v. 42, P=0.004). Scores for 15 physician experts also completing the survey were significantly higher than participants with other postgraduate degrees (mean score 89 v. 69, P<0.001). CONCLUSION: The medical data interpretation test is a reliable and valid measure of the ability to interpret medical statistics.

Adult↗
PubMed2003

[Maternal mortality in developing countries: statistical data and improvement in obstetrical care].

Since launching of the safe motherhood initiative in 1987, much work has been undertaken, understanding of the situation in developing countries has improved, and numerous health programs have been designed. However the end result of action has been considered disappointing more often than encouraging especially in Sub Saharan Africa. What is the true picture? The purpose of this article is to review the means available for studying all facets of maternal mortality and methodological precautions that must be applied in the interpretation of statistical data. Perusal of recent reports on maternal mortality reveals that estimated incidences in different populations vary widely from 85 to 1000 per 100,000 live births, that rural zones are more affected than urban areas, that reductions have been achieved in the major cities, that the most common direct obstetrical causes are postpartum hemorrhage, dystocia with uterine rupture, eclampsia, and sepsis, and that 70% of deaths are avoidable, i.e., due to absent or insufficient care. Although currently underused, qualitative study methods are gradually being implemented and will identify the health care sectors requiring priority improvement. Based on previous experience, it is unlikely that technical or obstetrical measures and action on the part of medical professionals alone will achieve any reduction in maternal mortality without the commitment of political authorities.

Adult↗
PubMed1996

A human friendly reporting and database system for brain PET analysis.

We have developed a human friendly reporting and database system for clinical brain PET (Positron Emission Tomography) scans, which enables statistical data analysis on qualitative information obtained from image interpretation. Our system consists of a Brain PET Data (Input) Tool and Report Writing Tool. In the Brain PET Data Tool, findings and interpretations are input by selecting menu icons in a window panel instead of writing a free text. This method of input enables on-line data entry into and update of the database by means of pre-defined consistent words, which facilitates statistical data analysis. The Report Writing Tool generates a one page report of natural English sentences semi-automatically by using the above input information and the patient information obtained from our PET center's main database. It also has a keyword selection function from the report text so that we can save a set of keywords on the database for further analysis. By means of this system, we can store the data related to patient information and visual interpretation of the PET examination while writing clinical reports in daily work. The database files in our system can be accessed by means of commercially available databases. We have used the 4th Dimension database that runs on a Macintosh computer and analyzed 95 cases of 18F-FDG brain PET studies. The results showed high specificity of parietal hypometabolism for Alzheimer's patients.

Alzheimer Disease↗
PubMed2006

Simulated data sets for single molecule kinetics: some limitations and complications of data analysis.

When the fluorescence intensity of a chromophore attached to or bound in an enzyme relates to a specific reactive step in the enzymatic reaction, a single molecule fluorescence study of the process reveals a time sequence in the fluorescence emission that can be analyzed to derive kinetic and mechanistic information. Reports of various experimental results and corresponding theoretical studies have provided a basis for interpreting these data and understanding the methodology. We have found it useful to parallel experiments with Monte Carlo simulations of potential models hypothesized to describe the reaction kinetics. The simulations can be adapted to include experimental limitations, such as limited data sets, and complexities such as dynamic disorder, where reaction rates appear to change over time. By using models that are known a priori, the simulations reveal some of the challenges of interpreting finite single-molecule data sets by employing various statistical signatures that have been identified.

Data Interpretation, Statistical↗
PubMed2005

Tracing selection effects in three non-probability samples.

Snowball sampling and targeted sampling are widely applied techniques to recruit samples from hidden populations, such as problematic drug users. The disadvantage is that they yield non-probability samples which cannot be generalised to the population. Despite thorough preparatory mapping procedures, selection effects continue to occur. This paper proposes an interpretation frame that allows estimating the direction of selection bias after data collection. Critical examination of the recruitment procedure and comparison with statistical and non-statistical external data sources are the core features of the interpretation frame. Applying the interpretation frame increases insight into the reliability of the results and allows to estimate where selection bias may have occurred.

Adult↗
PubMedDate not supplied

Issues in the statistical analysis of sperm motion data derived from computer-assisted systems.

Computer-assisted sperm motion measurements present certain features that must be accounted for in statistical analyses. Some are specific to this type of data, whereas others are standard considerations. For example, the measurement of multiple sperm from individuals creates correlations that must be accounted for if each sperm's measurement is used, and unequal variances may arise that need to be addressed if an average measurement from the individual is used. Also, the limitations on the ranges of some measurements create discrepancies between observed and actual means and may make treatment-related effects more difficult to detect--a circumstance that has an impact on study design. When variables that are truly continuous are measured in a discrete fashion, odd effects may arise and care is needed. Other considerations, such as the shapes of distributions and correlations among various measurements, should also be examined. Attention to these details of statistical analysis are vital to proper interpretation of data.

Animals↗
PubMed2003

Adjusting for population heterogeneity: a framework for characterizing statistical information and developing efficient test statistics.

The focus of this work is the TDT-type and family-based test statistics used for adjusting for potential confounding due to population heterogeneity or misspecified allele frequencies. A variety of heuristics have been used to motivate and derive these statistics, and the statistics have been developed for a variety of analytic goals. There appears to be no general theoretical framework, however, that may be used to evaluate competing approaches. Furthermore, there is no framework to guide the development of efficient TDT-type and family-based methods for analytic goals for which methods have not yet been proposed. The purpose of this paper is to present a theoretical framework that serves both to identify the information which is available to methods that are immune to confounding due to population heterogeneity or misspecified allele frequencies, and to inform the construction of efficient unbiased tests in novel settings. The development relies on the existence of a characterization of the null hypothesis in terms of a completely specified conditional distribution of transmitted genotypes. An important observation is that, with such a characterization, when the conditioning event is unobserved or incomplete, there is statistical information that cannot be exploited by any exact conditional test. The main technical result of this work is an approach to computing test statistics for local alternatives that exploit all of the available statistical information.

Data Interpretation, Statistical↗