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PubMed2005

Using virtual environments to prototype auditory navigation displays.

There is a critical need for navigation and orientation aids for the visually impaired. Developing such displays is difficult and time consuming due to the lack of design tools and guidelines, the inefficiency of trial-and-error design, and experimental participant safety concerns. We discuss using a virtual environment (VE) to help in the design, evaluation, and iterative refinement of an auditory navigation system. We address questions about the (real) interface that the VE version allows us to study. Examples include sound design, system behavior, and user interface design. Improved designs should result from a more systematic and scientific method of assistive technology development. We also point out some of the ongoing caveats that researchers in this field need to consider, especially relating to external validity and over-reliance on VE for design solutions.

Auditory Perception↗

PubMed2002

Ranking of volatile organic compounds for tropospheric degradability by oxidants: a QSPR approach.

The limited availability and variability of data related to atmospheric degradation reaction is a very relevant issue in studies related to environmental fate and behavior of chemicals. For screening purposes, the experimental data of the oxidation rate constants for the reactions with the radicals OH, NO3 and with ozone of 65 heterogeneous organic compounds were explored by Principal Component Analysis: a ranking of volatile organic chemicals (VOC) according to their relative overall atmospheric degradability and an atmospheric persistence index (ATPIN) is proposed. This index has been modeled by theoretical molecular descriptors to obtain MLR models with high predictive power, both internally and externally validated, and the definition of chemical domain applicability. This procedure allows a fast ranking of VOCs according to their tendency to be degraded by atmospheric oxidants, starting only from the knowledge of their molecular structure.

Air Pollutants↗

PubMed2004

Using fragment chemistry data mining and probabilistic neural networks in screening chemicals for acute toxicity to the fathead minnow.

The paper is illustrating how the general data mining methodology may be adapted to provide solutions to the problem of high throughput virtual screening of organic chemicals for possible acute toxicity to the fathead minnow fish. The present approach involves mining fragment information from chemical structures and is using probabilistic neural networks to model the relationship between structure and toxicity. Probabilistic neural networks implement a special class of multivariate non-linear Bayesian statistical models. The mathematical principles supporting their use for value prediction purposes are clarified and their peculiarities discussed. As part of the research phase of the data mining process, a dataset consisting of 800 structures and associated fathead minnow (Pimephales promelas) 96-h LC50 acute toxicity endpoint information is used for both the purpose of identifying an advantageous combination of fragment descriptors and for training the neural networks. As a result, two powerful models are generated. Model 1 implements the basic PNN with Gaussian kernel (statistical corrections included) while Model 2 implements the PNN with Gaussian kernel and separated variables. External validation is performed using a separate dataset consisting of 86 structures and associated toxicity information. Both learning and generalization capabilities of the two models are investigated and their limitations discussed.

Animals↗

PubMed1995

On the use of backpropagation neural networks in modeling environmental degradation.

In this study a systematic analysis of the predictive capabilities of models built with backpropagation neural networks (BPNN) is made to corroborate the hypothesis that BPNN is capable of modeling the interaction terms in group contribution models, without explicitly adding these as descriptors. The data used for comparison are reactivities of 275 organic compounds towards the atomospheric OH-radical. This dataset was selected because of the internal consistency, reliability and relatively large size of this dataset. While training the network, the minimal Mean Squared Error (MSE) on a test set was used as the stop criterion. This avoids overfitting on the training data, and is most likely to give the best generalizing network. A network trained with a designed training and test set is compared with networks trained on randomly constructed training and test sets. The BPNN model based on designed training and test set not only gives the best model, but also the best predictability on an external validation set, compared both to linear models built with the same training and validation sets, and BPNN models based on randomly constructed training and test sets. The performance of the designed BPNN model is comparable to an existing model which includes interaction terms.

Environmental Pollutants↗

PubMed2000

Entertainment-education and HIV/AIDS prevention: a field experiment in Tanzania.

Entertainment-education is the process of designing and implementing an entertainment program to increase audience members' knowledge about a social issue, create more favorable attitudes, and change their overt behaviors regarding the social issue. The results of a field experiment in Tanzania to measure the effects of a long-running entertainment-education radio soap opera, Twende na Wakati (Let's Go with the Times), on knowledge, attitudes, and adoption of human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS) prevention behaviors are presented. Multiple independent measures of effects and the experimental design of this study confer strong internal and external validity regarding the results of this investigation. The effects of the radio program in Tanzania include (1) a reduction in the number of sexual partners by both men and women, and (2) increased condom adoption. The radio soap opera influenced these behavioral variables through certain intervening variables, including (1) self-perception of risk of contracting HIV/AIDS, (2) self-efficacy with respect to preventing HIV/AIDS, (3) interpersonal communication about HIV/AIDS, and (4) identification with, and role modeling of, the primary characters in the radio soap opera.

Adolescent↗

PubMed1999

Dependence of in vitro-in vivo correlation analysis acceptability on model selections.

The objectives of this study were to assess the influence of pharmacokinetic and dissolution model selection on the success of in vitro-in vivo correlation (IVIVC) analysis of fast-, medium-, and slow-dissolving metoprolol tartrate immediate-release tablet formulations. Several different compartmental models were fit to the fast formulation plasma data. Three candidate models with the best fits were ranked 1, 2, and 3 and used to predict AUC and Cmax of the medium and slow formulations. Acceptability of each model to predict the medium and slow formulations was determined using +/- 20% as the limit for acceptable relative prediction error. When the best dissolution models were used, models 1 and 2 each failed to adequately predict Cmax for slow formulation (-26.8% error for model 1 and -20.4% error for model 2). However, the less appropriate model 3 adequately predicted Cmax for slow formulation (-15.1% error). The selection of the dissolution model also determined the outcome of IVIVC analysis, again with a less appropriate model resulting in successful prediction. When the Weibull function was used to characterize dissolution, model 2 failed to adequately predict Cmax for slow formulation (-20.4% error); however, model 2 adequately predicted Cmax for slow formulation when dissolution was characterized using the poorer fitting first-order model (-14.4% error). These results indicate that the success or failure of external validation of these metoprolol tartrate tablets was dependent on the pharmacokinetic and the dissolution models employed. Considering the role of subjectivity in identifying pharmacokinetic and dissolution models, these findings suggest a need to develop objective criteria to identify models a priori to IVIVC analysis.

Biological Availability↗

PubMed2003

Including culturally diverse samples in health research: a case study of an urban trial of social support.

OBJECTIVES: To describe the recruitment procedures used in a study of Social Support and Family Health carried out in a disadvantaged urban area of the UK in 1999-2001; to consider the impact of using inclusive recruitment procedures on the final research sample and implications for the conduct of the research and data obtained. DESIGN: Face-to-face recruitment of eligible women, using interpreters where necessary, to a randomized controlled trial of two alternative strategies for providing support to women with infants. RESULTS: Of the 1,263 women eligible to enter the trial, 731 were successfully recruited. Forty-five languages other than English were spoken by eligible women; 14% needed an interpreter for the recruitment visit, and a further 30% spoke English as a second language. Inclusive recruitment practices added significant costs, resulted in a study sample with a different social profile from the sample that would have been achieved without these, and challenged some of the assumptions underlying the model of informed consent commonly used in much health services research. CONCLUSION: Procedures can be developed for recruiting people with diverse cultural backgrounds to take part in research. This helps to address the issue of possible bias in generalizing research findings by increasing external validity, and respects the ethic that everyone should have the right to be eligible for inclusion in research.

Cultural Diversity↗

PubMed2006

Representativity of a postal public health questionnaire survey in Sweden, with special reference to ethnic differences in participation.

AIM: Non-participation in health surveys is a common phenomenon. When differences between participants and non-participants are considerable, the external validity of the sample survey may decrease and false conclusions might be drawn about the health status of the population. For this reason, the authors aimed to investigate the representativity of a postal questionnaire survey performed in the county of Scania, Sweden, in 1999-2000. The survey, which was based on an 18- to 80-year-old population sample, had a 58% response rate (n = 13 604). METHODS: For some variables, the information obtained using the questionnaire was compared with information obtained from a population register that covers all the population in the county (for the 18- to 80-year-old group, n = 850 476). The population register includes, among other data, information on age, gender, educational level, country of birth, and healthcare expenditure. RESULTS: Men, individuals with a low level of education, and immigrants were under-represented in the survey. However, except for immigrants, the under-representation was not large. Among immigrants, particularly those born in former Yugoslavia, the Arabic-speaking countries, and Poland were very significantly under-represented in the study. By contrast, immigrants born in other Nordic countries had responded to almost the same extent as respondents born in Sweden. The survey sample had about the same healthcare utilization costs as did the general population. CONCLUSIONS: In summary, the "Health Survey for Scania, 2000" seems largely representative of the total Scanian population. A major concern, however, is the under-representation of the immigrant population.

Adolescent↗

PubMed2004

The nicotine dependence syndrome scale: a multidimensional measure of nicotine dependence.

We report the development of a new multidimensional questionnaire to measure nicotine dependence, based on Edwards's syndromal conceptualization of dependence. We present three studies. In study 1, we administered the Nicotine Dependence Syndrome Scale (NDSS) to 317 smokers in a smoking cessation study. Factor analysis of the NDSS revealed five factors: Drive (craving and withdrawal, and subjective compulsion to smoke), priority (preference for smoking over other reinforcers), tolerance (reduced sensitivity to the effects of smoking), continuity (regularity of smoking rate), and stereotypy (invariance of smoking). A single overall score based on the first principal component, NDSS-T, was retained as a single core measure of dependence. The NDSS showed promising psychometric properties: NDSS-T and factor scores showed strong associations with dependence-relevant measures, even when we controlled for scores on the Fagerström Tolerance Questionnaire (FTQ); and the NDSS predicted urges when smoking, withdrawal in acute abstinence, and outcome in cessation. The five factor scores showed differential patterns of correlations with external validators, supporting the multidimensionality of the measure. In study 2, we revised the NDSS to expand some subscales and administered it to 802 smokers in a cessation study. The same five factors were extracted, the internal reliability of some subscales was improved, and the factor scores again showed associations with dependence-relevant validators, which were largely maintained when we controlled for FTQ scores. In study 3, with 91 smokers in a cessation trial, we established that the test-retest reliability of the subscales was adequate. Thus, the NDSS presents a valid multidimensional assessment of nicotine dependence that may expand on current measures.

Adult↗

PubMed2005

The types of regular cigarette smokers: a latent class analysis.

The present study sought to refine cigarette smoking exposure by examining whether individuals with a history of regular cigarette smoking could be classified into meaningful subgroups based on their smoking habits, nicotine dependence, and quit attempts. Data were obtained from 3,025 male and female twins aged 22-59 years who participated in two longitudinal studies based on the Virginia Twin Registry. Latent class analysis was used to identify the number and nature of subgroups of smokers reporting similar smoking habits based on 18 characteristics. Estimates of prevalence for different classes of smoking were obtained along with expected frequencies of endorsements for each smoking behavior by class. Distributions of demographic characteristics, psychopathology, and personality were examined as external validators. The results demonstrated considerable heterogeneity and revealed eight classes of smokers who differed in their degree of nicotine dependence, cessation attempts, and ability to quit smoking. Smoking classes ranged from individuals who were all former smokers with low nicotine dependence who attempted to quit once and were successful, to individuals who were all current smokers with little desire to quit, to individuals with high nicotine dependence with multiple quit attempts, only a subset of which were successful. Estimates of prevalence for each class were 9%-20%. Our findings support the idea that regular cigarette smokers are highly heterogeneous and highlight the need for smoking exposure refinement in future studies. Acknowledging the complexity of cigarette smoking and classifying smokers into more specific subgroups based on their smoking behavior in future studies will enable more accurate evaluation of disease etiology and risk and could lead to more appropriate smoking cessation interventions.

Adult↗

PubMed2006

Adolescent smokers screened for a nicotine replacement treatment trial: correlates of eligibility and enrollment.

The enrollment process determines the study sample and external validity of clinical trial results; however, few reports describe the process and outcome of screening efforts for smoking cessation studies among adolescents. We describe and evaluate a screening protocol to enroll adolescent smokers for a randomized clinical trial of nicotine replacement therapy. Adolescent smokers obtained the recruitment call-in number (1-800-NO-SMOKE) via media and other advertisements. Trained recruitment staff collected information using an internally developed, targeted telephone screening interview, which was used to determine pre-eligibility for the clinical trial. Correlates of qualification and of study enrollment were determined. Among 1,347 adolescents screened, 329 (24.4%) were eligible to participate in the trial. Light smoking (39.1%) and lack of parental support (14.8%) were the biggest contributors to ineligibility. Eligible adolescents were more likely to be female (66.9% vs. 58.2%, p = .0052) and more likely to be European American (63.5% vs. 52.2%, p = .0003). The higher rates of ineligibility for African Americans and boys were partly explained by lower scores on the Fagerström Test for Nicotine Dependence. Of those eligible to participate in the trial, 159 (48.3%) enrolled. Results underscore the need for screening instruments that are measurement-invariant across ethnicities and gender, and for enrollment strategies that maximize inclusion of eligible participants.

Adolescent↗

PubMed2026

A pragmatic adaptation of the RANO clinical risk score for IDH-Wildtype glioblastoma in the absence of MGMT promoter methylation testing.

BACKGROUND: The novel RANO risk score provides prognostic stratification for patients with IDH-wildtype glioblastoma(GBM) and includes age, Karnofsky Performance Scale(KPS), RANO resection class(RRC), and MGMT promoter methylation(MGMTm). However, MGMTm testing is unavailable in many countries. We aimed to explore the prognostic performance of a RANO-adapted clinical score excluding MGMTm. METHODS: We applied the same scoring system established by original RANO score, excluding MGMTm. Three risk classes were defined as numerical scores derived through tertiles. The primary endpoint was overall survival(OS), and the secondary exploratory endpoint was progression-free survival(PFS). RESULTS: One-hundred twenty patients were included. Three risk classes were identified:low-risk(0-1 points,n:47, 39.2%), intermediate-risk(2-3 points,n:27, 22.5%), and high-risk(≥4 points,n:46, 38.3%). The median OS was 35.5 months(95% CI:21.1-49.9) for the low-risk group, 16 months(95% CI:9.9-22.1) for the intermediate-risk group, and 5 months(95% CI:3.6-6.3) for the high-risk group(p < 0.001). Similarly, the median PFS was 16.3 months(95% CI:12.3-20.3) for the low-risk group, 9.9 months(95% CI:7.2-12.6) for the intermediate-risk group, and 4.1 months(95% CI:3.5-4.7) for the high-risk group(p < 0.001). CONCLUSION: This simplified RANO-adapted score demonstrated promising prognostic stratification using basic clinical parameters. As a pragmatic adaptation study, external validation is required before clinical application, particularly in settings where MGMTm testing is unavailable.

Humans↗

PubMed2002

Diagnostic data in clinical toxicology--should we use a Bayesian approach?

A number of toxidromes (toxicology syndromes) have been described for various poisonings and are promoted as a means of reaching a diagnosis in patients presenting with unknown poisonings. Many are based entirely on deductive reasoning from the known pharmacological effects of these drugs rather than on documented clinical experience. In this paper, we used our database, where we have recorded clinical signs on presentation in unselected poisonings to explore how clinical signs actually alter the odds of ingestion of different poisons. Many signs substantially altered the list of drugs likely to have been ingested. We found that the most important factor determining whether an unconscious patient had ingested a particular drug was how frequently that drug was taken generally (i.e., the a priori probability), rather than the presence of any particular physical sign. It also follows that our (or anyone else's) intuitive or deductive approach to diagnosis, derived from experience, will not necessarily be very useful at another place where predominantly different drugs are involved in poisoning. Our data were used to derive odds ratios as a measure of the strength of association of physical signs or investigations with ingested poisons. These can be used to develop simple diagnostic algorithms orflow charts to identify the most likely drugs ingested, or using more complicated programming, could also be used to calculate the precise probability of different drug-ingestion using Bayes' Theorem. The usefulness (i.e., external validity) of clinical research from other centers can also be determined.

Adolescent↗

PubMed2004

An Internet survey of asthma treatment.

The aim of this investigation was to study pharmacological treatment in relation to asthma severity among patients visiting an asthma web site on the Internet. The study comprised 650 subjects from 30 countries with self-reported asthma that participated in an Internet based patient survey. The survey was posted on the web site Asthma Information Centre (www.mdnet.de). Moderate or severe night cough or wheezing was reported by 43% and activity limitation by 55% of the asthmatics. Short-acting beta-agonists were used by 67% and inhaled steroids by 59%. The use of short-acting beta-agonists decreased with age, whereas the use of inhaled steroids, long-acting beta-agonists and antileukotrienes was lowest in the youngest (0-20 years) and highest age groups (> 60 years). The use of short-acting beta-agonists increased, and the use of inhaled steroids decreased with the severity of nocturnal symptoms (p < 0.01). Side effects were most often reported for oral beta-agonists (42%) and least often for antileukotrienes (9%). We conclude that despite problems with selection and external validity, an online asthma survey produces results that agree highly with more resource-demanding surveys. We find that many asthmatics have a low level of asthma control, and the survey indicates that underuse of inhaled steroids is one of the reasons why the goals set up in asthma guidelines so far have not been reached.

Anti-Asthmatic Agents↗

PubMed2002

Cost effectiveness of treatment for benign prostatic hyperplasia: an economic model for comparison of medical, minimally invasive, and surgical therapy.

PURPOSE: To evaluate the cost effectiveness of minimally invasive therapy relative to medical (alpha-blocker) therapy and transurethral resection (TURP) for patients with moderate to severe symptoms of benign prostatic hyperplasia (BPH). METHODS: We constructed a decision-analytic Markov model for a hypothetical cohort of 65-year-old men with moderate to severe BPH symptoms. Microwave thermotherapy was selected to represent minimally invasive treatment. Cost-effectiveness analysis was performed with 25 health states using the 3 treatments, 5 short-term clinical events, and 17 possible long-term outcomes. Each health state had an associated cost and utility. Quality of life (QoL) and utility estimates were obtained by interviewing 13 men with BPH symptoms using the standard gamble reference methods. Patients were classified as risk averse (RA) or non-risk averse (NRA) on the basis of their attitudes to risk. We calculated the incremental cost effectiveness of microwave thermotherapy relative to medical therapy and TURP over 5 years after treatment initiation. Event probabilities were obtained from the literature, a consensus panel, and published randomized clinical trials. RESULTS AND CONCLUSIONS: The utility values generated were internally consistent and externally valid for a hypothetical cohort of 10,000 RA patients. Microwave thermotherapy was preferred by the NRA group, while medical therapy was preferred by the RA group. Surgery was least preferred by both groups. Microwave thermotherapy had a small incremental cost but improved QoL in comparison with medical therapy. Microwave thermotherapy had a higher utility and lower cost than TURP and thus was dominant over TURP. This analytical method can be applied to evaluate the cost effectiveness of any BPH therapy.

Aged↗

PubMed2006

Designing an acupuncture study: the nationwide, randomized, controlled, German acupuncture trials on migraine and tension-type headache.

BACKGROUND: In the nationwide German Acupuncture Trials (GERAC) verum acupuncture, based on Traditional Chinese Medicine (TCM), was to be tested against sham acupuncture for the entities classified in the West as "migraine" (MIG) and "tension-type headache" (TTH). However, there were no generally accepted guidelines on how to perform a consistent verum or sham treatment. OBJECTIVE: To design broadly consensual verum and sham acupuncture treatment protocols for MIG and TTH for the GERAC. METHODOLOGY: Extensive literature study and consultation with acupuncture experts. Personal interviews, both free and structured, e-mail discussions, and phone conferences were used. RESULTS: Broadly consensual acupuncture protocols for MIG and TTH for verum and sham acupuncture were developed. They included semi-standardized point combinations with clearly described point selection rules based on TCM acupuncture diagnoses. A procedure was developed to help ensure homogenous treatment quality in a large multicenter trial. CONCLUSIONS: The GERAC study design allowed acupuncture to be tested in a naturalistic environment. The rigorous study design and the large number of physician investigators guaranteed a high external validity for the results. The results will help determine the significance of Chinese acupuncture in the context of Western medicine for the treatment of MIG and TTH.

Female↗

PubMed2006

Designing an acupuncture study: II. The nationwide, randomized, controlled German acupuncture trials on low-back pain and gonarthrosis.

BACKGROUND: In the nationwide German Acupuncture Trials (GERAC), verum acupuncture, mirroring the Traditional Chinese Medicine (TCM) acupuncture style, was tested against sham acupuncture and guideline standard therapy for the entities classified in the West as chronic low back pain (LBP) and gonarthrosis (GON). OBJECTIVE: The objective was to develop broadly consensual acupuncture and control protocols for the treatment of LBP and GON in the GERAC trials. METHODOLOGY: Extensive literature study and consultation with acupuncture experts were consulted. Personal interviews, both free and structured, e-mail discussions, and phone conferences were used as well. RESULTS: Broadly consensual acupuncture protocols for LBP and GON for verum and invasive sham acupuncture were developed. They included semistandardized point combinations with clearly described point selection rules based on TCM acupuncture diagnosis. A procedure was developed to help ensure homogenous treatment quality in a large multicenter trial. CONCLUSIONS: With 1162 randomized patients for LBP and 1039 patients for GON, the GERAC study design allowed acupuncture to be tested in a naturalistic environment. The rigorous study design and large number of physician investigators guaranteed a high external validity for the results. The results will help determine the significance of Chinese acupuncture in the context of Western medicine for the treatment of LBP and GON.

Acupuncture Points↗

PubMed2006

Real-time PCR quantitation of subtype C HIV DNA in a Zambian discordant couple cohort.

To study the viral sequence diversity that is characteristic of HIV infection, PCR amplification and sequencing of viral genes is an essential step. However, a limitation of traditional PCR methods is that one viral target may be preferentially amplified over another when multiple sequences are present. This presents a particular problem when conclusions about diversity are made from one or only a few PCRs. One way to avoid resampling is to perform a large number of PCR amplifications on a single template; however, this requires that extensive dilution series be carried out on each patient sample to identify the appropriate concentration of input DNA. Here we describe the development and implementation of a quantitative real-time PCR (qPCR) method that detects a short sequence in gag and is optimized to detect subtype C HIV sequences. The standard curve was externally validated using two chronically infected cell lines carrying a known number of HIV copies per genome, and this assay yielded reproducible and accurate measurements on patient DNA samples over a wide range of input targets. The qPCR assay results were consistent with those obtained by the traditional limiting dilution method yet entailed only a fraction of the time and reagents required for the latter. This robust and quantitative real-time assay can be used to ensure that each viral sequence obtained through PCR represents a single template for studies in which the diversity of the entire population must be accurately portrayed, and can readily be applied to other research settings and viral subtypes.

Cohort Studies↗