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PubMed2000

Introduction to the special section on the use of computers for making judgments and decisions.

Computers have the potential to greatly increase the accuracy of judgments and decisions that are made in the area of psychological assessment. The validity of present-day computer programs are described in the first 2 articles of this Special Section. Both computer-based test interpretation programs and mechanical prediction rules (e.g., statistical prediction rules) are described. Limitations of present-day computer programs are described in the 3rd article along with methodological recommendations for building more powerful rules. In the 4th article, a statistical analysis (neural network modeling) is described that may allow us to build better rules.

Decision Making, Computer-Assisted↗

PubMedDate not supplied

[Reliability of electrophysiological measurements of motor control].

OBJECTIVES: The aim of the study was the short term test-retest-reliability of electrophyisiological correlates of simple processes of the motor control, i.e. the execution (go) and the inhibition (no go) of a prepared motor response, evoked during the Continuous Performance Test (CPT). Our interest was centered in the reliability of the topographical P300-parameters described in previous studies, i.e. the localizations of the go and no go centroids and the no go anteriorization (NGA), which is the difference between the two centroid locations. A sufficient reliability is a basic requirement for the application of these new topographical parameters for the investigation of different psychiatric illnesses with suspected dysfunctions of prefrontal motor control, e.g. schizophrenias and affective illnesses, obsessive-compulsive disorders, personality disorders with deficits in impulse control, and in children with attention deficit hyperactivity disorder. PATIENTS AND METHODS: We examined 23 healthy subjects who executed two versions of the CPT with an interval of 30 minutes. After averaging the obtained evoked potentials of each subject, we determined the latencies, amplitudes and positive centroids, at the moment of the peak of the Global Field Power in a P300 time window. RESULTS: Statistical analysis revealed sufficient test-retest-reliabilities in comparison to other electrophysiological paradigms, mainly for the localizations of the go (r = 0.93; p = 10(-10)) and no go centroid (r = 0.85; p = 10(-4)), as well as for the no go anteriorization (r = 0.63; p = 10(-3)). CONCLUSION: These results are a prerequisite for the application of these topographical parameters as measures of the prefrontal motor control in different healthy and psychiatric populations.

Adult↗

PubMed1977

Computerized EEG analysis for studying the effect of drugs on the central nervous system.

Samples of our experience in quantitative pharmaco-EEG are reviewed to discuss and define its applicability and limits. Simple processing systems, such as the computation of Hjorth's descriptors, are useful for on-line monitoring of drug-induced EEG modifications which are evident also at the visual visual analysis. Power spectral analysis is suitable to identify and quantify EEG effects not evident at the visual inspection. It demonstrated how the EEG effects of compounds in a long-acting formulation vary according to the sampling time and the explored cerebral area. EEG modifications not detected by power spectral analysis can be defined by comparing statistically (F test) the spectral values of the EEG from a single lead at the different samples (longitudinal comparison), or the spectral values from different leads at any sample (intrahemispheric comparison). The presently available procedures of quantitative pharmaco-EEG are effective when applied to the study of mutltilead EEG recordings in a statistically significant sample of population. They do not seem reliable in the monitoring of directing of neuropyschiatric therapies in single patients, due to individual variability of drug effects.

Alcoholic Intoxication↗

PubMed1995

Transabdominal chorionic villus sampling at 9.5-12 weeks' gestation. Placental vascular resistance and fetal cardiovascular responses.

Pregnancies subjected to chorionic villus sampling (CVS) have been associated with transverse limb reduction defects. This study was designed to examine the possible fetal cardiovascular responses to transabdominal CVS. We examined 42 patients referred for CVS between 9.5 and 12 weeks' gestation. CVS was performed transabdominally under ultrasonic guidance with a 20-gauge needle. Placental vascular resistance was evaluated by means of the umbilical artery pulsatility index. Fetal heart rate was ascertained automatically from two successive flow velocity waveforms. Paired t test, regression analysis, power analysis and normal distribution analysis were performed, and statistical significance was set at P < or = .05. Fetal heart rate increased with increasing amounts of tissue, but placental vascular resistance did not change. The earlier the gestation, the larger the amount of tissue obtained. Multiple regression analysis demonstrated that the fetal heart rate change was influenced by neither gestation nor placental vascular resistance after CVS. Analysis of the change (difference before and after CVS) in placental resistance and fetal heart rate according to gestational age and amount of tissue did not change the above findings. Although statistically significant fetal cardiovascular responses can be elicited in relation to the amount of chorionic villi obtained during transabdominal CVS, the clinical significance of these findings remains unclear, given the fact that all the fetuses in this group of patients were normal. These responses may be secondary to various degrees of placental hemorrhage and may represent part of or the total fetal response to various degrees of fetal blood loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

[Follow-up of infra-inguinal bypass operations: value of the peak systolic velocity and arm-ankle index for evaluation of femorodistal reconstructions].

In a prospective study, the efficacy of noninvasive surveillance techniques including measurement of ABI and duplex-derived velocity parameters was studied after 74 infrainguinal arterial reconstructions. A decrease of ABI > or = 0.2 compared with prior examinations was considered abnormal. Results of the duplex scan were interpreted as abnormal when PSV was less than 45 cm/sec or greater than 200 cm/sec or when an interval decrease of greater than 30 cm/sec occurred. All patients meeting any of these criteria during the follow-up examinations were subjected to i.a. DSA. The combination of all duplex velocity criteria was significantly more sensitive to identify a failing graft than was measurement of ABI (90% vs. 18%; p = 0.00004). When independent variables (ABI- and PSV criteria, monophasic curve configuration) were entered into a logistic regression multivariate analysis, the model proved to be effective (F-value 5.551; df 4.8; R2 = 0.735; significance 98.03%; p < 0.02) in predicting angiogram findings (dependent variable). ABI measurements (significance 4.75%; p > 0.95) and the presence of a monophasic curve configuration (significance 89.58%; p > 0.1) failed to reach significance in the multivariate analysis. By excluding these latter parameters, the statistical power for the model could be improved (F-value 1036.57; df 2.1; R2 = 0.999; significance 97.69%; p = 0.0231): As a result normal PSV criteria indicated normal and abnormal angiographic findings in 83 and 17%, respectively. A PSV less than 45 cm/sec or greater than 200 cm/sec was suggestive of an abnormal angiogram in 80% and of a normal angiogram in 20%. The corresponding figures for a PSV interval decrease > 30 cm/sec were 71% and 29%. In conclusion, PSV parameters were found to be measurably more accurate to identify a failing graft than was measurement of ABI.

Aged↗

PubMedDate not supplied

Perinatal outcomes: a comparison between family physicians and obstetricians.

BACKGROUND: This retrospective study compared obstetrician and family physician patient population demographics, obstetric outcomes, delivery methods, and medical risk factors. METHODS: Obstetricians and family practice faculty and residents provided delivery services at an urban community hospital. A retrospective case study of all deliveries by obstetrician-gynecologists and family physicians in a 20-month period was analyzed with descriptive statistics, chi-square analysis, logistic regression, and power analysis. A modified risk score analysis was completed on all patients to assess comparability between the obstetrician and family physician patients. RESULTS: Risk score analysis of the two patient populations demonstrated no difference in high-risk patients (P = 0.102). Family physicians' patients had a lower incidence of Cesarean section, use of forceps, diagnosis of cephalopelvic disproportion, and low-birth-weight babies. They had a higher incidence of spontaneous vaginal delivery, vaginal birth after previous Cesarean section, and vacuum extraction use. The overall Cesarean section rate for family physicians was 15.4 percent, compared with 26.5 percent for obstetricians. CONCLUSIONS: These findings support the high-quality outcomes of perinatal care provided by family physicians. They also provide evidence for training and privileging family physicians to perform their own Cesarean sections.

Adolescent↗

PubMed1993

Analytical methods to differentiate similar electroencephalographic spectra: neural network and discriminant analysis.

Differences in electroencephalographic (EEG) power spectra obtained under similar, but not identical, conditions may be difficult to discern using standard techniques. Statistical analysis may not be useful because of the large number of comparisons necessary. Visual recognition of differences also may be difficult. A new technique, neural network analysis, has been used successfully in other problems of pattern recognition and classification. We examined a number of methods of classifying similar EEG data: standard statistical analysis (analysis of variance), visual recognition, discriminant analysis, and neural network analysis. Twenty-nine volunteers received either thiopental (n = 9), midazolam (n = 10), or propofol (n = 10) in sedative doses in 3 different studies. These drugs produced very similar changes in the EEG power spectra. Except for beta 2 power during thiopental infusion, differences between drugs could not be detected using analysis of variance. Visual categorization was correct in 72% of the baseline EEGs, 70% of thiopental EEGs, 27% of propofol EEGs, and 46% of midazolam EEGs. A classification neural network (Learning Vector Quantization network) containing a Kohonen hidden layer was able to successfully classify 57 of 58 EEG samples (of 4 minutes' duration). Discriminant analysis had a similar rate of success. This level of performance was achieved by dividing the EEG power spectrum from 1 to 30 Hz into 15 2-Hz bandwidths. When the EEG power spectrum was divided into the "classical" frequency bandwidths (alpha, beta 1, beta 2, theta, delta), both neural network and discriminant analysis performance deteriorated. By training the network using only certain inputs we were able to identify drug-specific bandwidths that seemed to be important in correct classification. We conclude that propofol, thiopental, and midazolam produce different effects on the EEG and that both neural network and discriminant analysis are useful in identifying these differences. We also conclude that EEG spectra should be analyzed without using classical EEG bands (alpha, beta, etc.). Additionally, neural networks can be used to identify frequency bands that are "important" in specific drug effects on the EEG. Once a classification algorithm is obtained using either a neural network or discriminant analysis, it could be used as an on-line monitor to recognize drug-specific EEG patterns.

Adult↗

PubMed1999

Using pooled exposure assessment to improve efficiency in case-control studies.

Assays can be so expensive that interesting hypotheses become impractical to study epidemiologically. One need not, however, perform an assay for everyone providing a biological specimen. We propose pooling equal-volume aliquots from randomly grouped sets of cases and randomly grouped sets of controls, and then assaying the smaller number of pooled samples. If an effect modifier is of concern, the pooling can be done within strata defined by that variable. For covariates assessed on individuals (e.g., questionnaire data), set-based counterparts are calculated by adding the values for the individuals in each set. The pooling set then becomes the unit of statistical analysis. We show that, with appropriate specification of a set-based logistic model, standard software yields a valid estimated exposure odds ratio, provided the multiplicative formulation is correct. Pooling minimizes the depletion of irreplaceable biological specimens and can enable additional exposures to be studied economically. Statistical power suffers very little compared with the usual, individual-based analysis. In settings where high assay costs constrain the number of people an investigator can afford to study, specimen pooling can make it possible to study more people and hence improve the study's statistical power with no increase in cost.

Animals↗

PubMed2003

A wealth index to screen high-risk families: application to Morocco.

This study defined a wealth index that was strongly correlated with a health indicator: the survival of children aged less than five years. This index allowed the most vulnerable social groups for health outcomes to be identified. These groups could become the target for focused interventions and in particular for health-insurance schemes. The study was based on a thorough analysis of data collected in Morocco in the 1992 Demographic and Health Survey (DHS). Results of the analysis showed that a simple score based on 15 socioeconomic indicators provided a proper discriminatory tool for screening families at higher risk of infant and child mortality. The score was based on characteristics of housing and household goods which are easy to collect in the field. The scoring system was shown to be as powerful as more complex statistical techniques, such as discriminant analysis. It could be used for determining who could be eligible for free health insurance.

Child, Preschool↗

PubMed1994

Bispectral analysis of the electroencephalogram during induction of anesthesia may predict hemodynamic responses to laryngoscopy and intubation.

The use of electroencephalography as a measure of adequacy of anesthesia has achieved limited success. Our purpose was to determine whether the non-linear properties of the electroencephalogram (EEG) as defined by the bispectral index was a better predictor of autonomic responses to endotracheal intubation during opioid-based anesthesia than the linear statistical properties of the EEG formulated by power spectral analysis. Thirty-nine adults scheduled for elective non-cranial surgery had a continuous EEG recorded during induction of anesthesia and endotracheal intubation. Anesthesia consisted of thiopental and nitrous oxide in oxygen, followed by 1 of 5 randomized opioid dose regimens. The EEG was continuously recorded and blood pressure was measured every minute. All electroencephalographic parameters were derived for the 3 min before and after intubation and were compared to the blood pressure and heart rate responses. Responders were defined by 2 analyses: patients who had a 20% or greater increase (1) in blood pressure or (2) in heart rate to laryngoscopy. Responders and non-responders were compared using Student's unpaired t test, and differences due to dose regimens were examined with logistic regression. Based on the criterion for blood pressure change, there were 27 responders and 12 non-responders. Heart rate changes did not differentiate between the two groups. There was a significant difference between response groups as measured by the bispectral index which distinguished responders from non-responders independently of the amount of drug given. None of the variables of power spectral analysis accurately distinguished responder from non-responder.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1997

Comparison of the Injury Severity Score and ICD-9 diagnosis codes as predictors of outcome in injury: analysis of 44,032 patients.

INTRODUCTION: Appropriate stratification of injury severity is a critical tool in the assessment of the treatment and the prevention of injury. Since its inception, the Injury Severity Score (ISS) has been the generally recognized "gold standard" for anatomic injury severity assessment. However, there is considerable time and expense involved in the collection of the information required to calculate an accurate ISS. In addition, the predictive power of the ISS has been shown to be limited. Previous work has demonstrated that the anatomic information about injury contained in the International Classification of Diseases Version 9 (ICD-9) can be a significant predictor of survival in trauma patients. The goal of this study was to utilize the San Diego County Trauma Registry (SDTR), one of the nation's leading trauma registries, to compare the predictive power of the ISS with the predictive power of the information contained in the injured patients' ICD-9 diagnoses codes. It was our primary hypothesis that survival risk ratios derived from patients' ICD-9 diagnoses codes would be equal or better predictors of survival than the Injury Severity Score. The implications of such a finding would have the potential for significant cost savings in the care of injured patients. METHODS: Data for the test population were obtained from the SDTR, which contains data from 1985 through 1993 from five participating hospitals. Four data sources were utilized to estimate the expected survival rate/mortality rate for each ICD-9 code in the SDTR. These were (1) the SDTR patients themselves, (2) the North Carolina State Hospital Discharge Database, (3) the North Carolina Trauma Registry Database, and (4) the Agency for Health Care Policy Research's Health Care Utilization Project Database. Each of these data sources was separately utilized to develop a survival risk ratio (SRR) for each ICD-9 diagnoses code. The SRR was calculated by dividing the number of survivors for patients with each ICD-9 code by the total number of all patients with the particular ICD-9 diagnoses code. The four groups of SRRs derived from our four data sources were used as predictors of survival and the ability of the SRRs to predict survival was compared with the predictive power of the ISS using measures of accuracy, sensitivity, specificity, and receiver operator characteristic curves. RESULTS: During the years 1985 through 1993, complete data were available for analysis on 44,032 patients. Of these, 2,848 patients died during their hospitalization (6%). Survival risk ratios were calculated for each of the diagnoses in the data base. Logistic regression, using the SAS System for statistical analysis, was used to assess the relative predictive power of the ISS and the survival risk ratios derived from the ICD-9 diagnoses codes from each of the four data bases. The analyses demonstrated that the regression models using the SRRs were generally as good or better than ISS as predictors of survival. The predictive power of the SRRs derived from the SDTR data, the North Carolina Trauma Registry data and the Health Care Utilization Report data were the best. In a subsequent analysis, the SRR values and the ISS were added to the patient's age and the revised Trauma Scores to create new predictive models in the mode of TRISS methodology. The analyses again indicated that the models using SRRs had as good or better predictive power than the model using the ISS. CONCLUSIONS: The present study confirms previous work showing that survival risk ratios derived from injured patients' ICD-9 diagnoses codes are as good as or better than ISS as predictors of survival.

Abbreviated Injury Scale↗

PubMed2001

Structural asymmetries in the human brain: a voxel-based statistical analysis of 142 MRI scans.

The use of computational approaches in the analysis of high resolution magnetic resonance images (MRI) of the human brain provides a powerful tool for in vivo studies of brain anatomy. Here, we report results obtained with a voxel-wise statistical analysis of hemispheric asymmetries in regional 'amounts' of gray matter, based on MRI scans obtained in 142 healthy young adults. Firstly, the voxel-wise analysis detected the well-known frontal (right > left) and occipital (left > right) petalias. Secondly, our analysis confirmed the presence of left-greater-than-right asymmetries in several posterior language areas, including the planum temporale and the angular gyrus; no significant asymmetry was detected in the anterior language regions. We also found previously described asymmetries in the cingulate sulcus (right > left) and the caudate nucleus (right > left). Finally, in some brain regions we observed highly significant asymmetries that were not reported before, such as in the anterior insular cortex (right > left). The above asymmetries were observed in men and women. Our results thus provide confirmation of the known structural asymmetries in the human brain as well as new findings that may stimulate further research of hemispheric specialization.

Adolescent↗

PubMed2001

To type or not to type: the use of unaffected siblings in nonparametric linkage analysis.

Unaffected individuals are often disregarded in nonparametric linkage analysis. Because of the presumed high complexity of genetic interactions and the resulting low penetrance of any single genetic effect, the statistical contribution of unaffected sib pairs is thought to be considerably lower than that of the affected. However, in cases where a large number of unaffected family members are available for genotyping--as is the case in the simulated Genetic Analysis Workshop 12 data set--the relatively low value of the unaffected sibs may be offset by their number. In this paper, I demonstrate that unaffected siblings do contain a significant amount of statistical information, and show that the most powerful method of nonparametric analysis utilizes both affected and unaffected individuals. I also show that selecting the unaffected individuals based on their age is the most cost effective and usually the most powerful strategy.

Adult↗

PubMed2004

BAPS 2: enhanced possibilities for the analysis of genetic population structure.

UNLABELLED: Bayesian statistical methods based on simulation techniques have recently been shown to provide powerful tools for the analysis of genetic population structure. We have previously developed a Markov chain Monte Carlo (MCMC) algorithm for characterizing genetically divergent groups based on molecular markers and geographical sampling design of the dataset. However, for large-scale datasets such algorithms may get stuck to local maxima in the parameter space. Therefore, we have modified our earlier algorithm to support multiple parallel MCMC chains, with enhanced features that enable considerably faster and more reliable estimation compared to the earlier version of the algorithm. We consider also a hierarchical tree representation, from which a Bayesian model-averaged structure estimate can be extracted. The algorithm is implemented in a computer program that features a user-friendly interface and built-in graphics. The enhanced features are illustrated by analyses of simulated data and an extensive human molecular dataset. AVAILABILITY: Freely available at http://www.rni.helsinki.fi/~jic/bapspage.html.

Algorithms↗

PubMed2003

Increased predictive value of parameters by fuzzy logic-based multiparameter analysis.

BACKGROUND: A recent study on postoperative effusions and edema was used to demonstrate the potential of fuzzy techniques in multiparameter data analysis. In this study, more than 50 parameters of 75 patients were collected and examined for correlations between some of the parameters and the later development of complications. METHODS: We employed a rule-based fuzzy-logic system in order to combine the diagnostic values of single parameters. The advantage of fuzzy sets is that they substitute sharp cut-off values with a smooth transition from one property to another. Therefore, there is no decision of "either-or" but rather a graded assessment of "more or less", which is often more suitable for a problem. RESULTS: The fuzzy combination of parameters led to a large increase of sensitivity and specificity when compared with the best single parameter. This increase was achieved by taking a close look at the parameters. A newly created parameter, relative weight, turned out to be very powerful. CONCLUSIONS: Fuzzy techniques can increase the discriminating power of classical statistical tools. In addition, results obtained by fuzzy analysis are highly interpretable. A combination of the CLASSIF1 algorithm for the identification of the most relevant parameters, followed by fuzzy analysis, represents a powerful tool for the handling of large amounts of multiparameter data.

Adolescent↗

PubMed1984

Comparison between the central effects of camazepam and temazepam. Computerized analysis of sleep recordings.

The effects of acute administration per os of 30 mg camazepam and the same dose of temazepam, were compared with placebo in 8 young male volunteers, fully adapted to the laboratory environment by 6 nights of adaptation. The study was double-blind, in a random order, 10 days separating each session. Spectral analysis was performed on the all-night records (1-min epochs), and the relative power of six frequency bands calculated. Concerning sleep parameters, temazepam induces a statistically significant reduction of: phase shifts; number of awakenings; percent duration of sleep stages I and IV. A significant increase of the percent duration of stage II and sleep efficiency was also found. Camazepam shows modification, with the same trend, but not reaching statistical significance. Concerning spectral analysis, temazepam induces a light increase of the relative power of the slowest frequencies, paralleled by an increase of the fast bands, while major effects are found on the characteristic periodicity of delta activities, which appear disrupted by the drug. These effects are not evident with camazepam, which does not seem to distort the normal sleep pattern.

Adult↗

PubMed2003

Using the noninformative families in family-based association tests: a powerful new testing strategy.

For genetic association studies with multiple phenotypes, we propose a new strategy for multiple testing with family-based association tests (FBATs). The strategy increases the power by both using all available family data and reducing the number of hypotheses tested while being robust against population admixture and stratification. By use of conditional power calculations, the approach screens all possible null hypotheses without biasing the nominal significance level, and it identifies the subset of phenotypes that has optimal power when tested for association by either univariate or multivariate FBATs. An application of our strategy to an asthma study shows the practical relevance of the proposed methodology. In simulation studies, we compare our testing strategy with standard methodology for family studies. Furthermore, the proposed principle of using all data without biasing the nominal significance in an analysis prior to the computation of the test statistic has broad and powerful applications in many areas of family-based association studies.

Analysis of Variance↗

PubMed2005

Enhancing dynamic graphical analysis with the Lisp-Stat language and the ViSta statistical program.

Presented is a sample of computerized methods aimed at multidimensional scaling and psychometric item analysis that offer a dynamic graphical interface to execute analyses and help visualize the results. These methods show how the Lisp-Stat programming language and the ViSta statistical program can be jointly applied to develop powerful computer applications that enhance dynamic graphical analysis methods. The feasibility of this combined strategy relies on two main features: (1) The programming architecture of ViSta enables users to add new statistical methods as plug-ins, which are integrated into the program environment and can make use of all the functions already available in ViSta (e.g., data manipulation, editing, printing); and (2) the set of powerful statistical and graphical functions integrated into the Lisp-Stat programming language provides the means for developing statistical methods with dynamic graphical visualizations, which can be implemented as ViSta plug-ins.

Computer Graphics↗