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PubMed2006

Cognitive behavior therapy for fear of flying: sustainability of treatment gains after September 11.

This study examines the long-term efficacy of cognitive-behavioral therapy (CBT) for fear of flying (FOF) after a catastrophic fear-relevant event, the September 11, 2001, terrorist attacks. Participants (N = 115) were randomly assigned to and completed treatment for FOF using 8 sessions of either virtual reality exposure therapy (VRE) or standard exposure therapy (SE) prior to September 11, 2001. Individuals were reassessed in June, 2002, an average of 2.3 years after treatment, with a response rate of 48% (n = 55). Analyses were run on the original data and, using multiple imputation procedures, on imputed data for the full sample. Individuals maintained or improved upon gains made in treatment as measured by standardized FOF questionnaires and by number of flights taken. There were no differences between VRE and SE. Thus, results suggest that individuals previously treated for FOF with cognitive-behavioral therapy can maintain treatment gains in the face of a catastrophic fear-relevant event, even years after treatment is completed.

Adult↗

PubMed2005

The prevalence and correlates of nonaffective psychosis in the National Comorbidity Survey Replication (NCS-R).

BACKGROUND: To estimate the prevalence and correlates of clinician-diagnosed DSM-IV nonaffective psychosis (NAP) in a national household survey. METHODS: Data came from the United States National Comorbidity Survey Replication (NCS-R). A screen for NAP was followed by blinded sub-sample clinical reappraisal interviews. Logistic regression was used to impute clinical diagnoses to respondents who were not re-interviewed. The method of Multiple Imputation (MI) was used to estimate prevalence and correlates. RESULTS: Clinician-diagnosed NAP was well predicted by the screen (area under the curve [AUC] = .80). The MI prevalence estimate of NAP (standard error in parentheses) is 5.0 (2.6) per 1000 population lifetime and 3.0 (2.2) per 1000 past 12 months. The vast majority (79.4%) of lifetime and 12-month (63.7%) cases met criteria for other DSM-IV hierarchy-free disorders. Fifty-eight percent of 12-month cases were in treatment, most in the mental health specialty sector. CONCLUSIONS: The screen for NAP in the NCS-R greatly improved on previous epidemiological surveys in reducing false positives, but coding of open-ended screening scale responses was still needed to achieve accurate prediction. The lower prevalence estimate than in total-population incidence studies raises concerns that systematic nonresponse bias causes downward bias in survey prevalence estimates of NAP.

Adolescent↗

PubMed2005

Assessing missing data assumptions in longitudinal studies: an example using a smoking cessation trial.

Due to the chaotic nature of the clinical disorder, longitudinal data analysis in substance abuse research is plagued by missing values. To obtain an unbiased estimation on intervention effects, different longitudinal modeling strategies require various assumptions on the patterns and mechanisms of missing data. By defining missingness as intermittent missingness (occasional omission) and dropout (premature withdrawal), this article demonstrates statistical ways for assessing missing data assumptions using evidence from a clinical trial. Within the framework of multiple imputation, intermittent missing data are imputed first so that dropouts can be isolated and treated specifically. A computational tool called "pattern reduction resampling" is proposed to simplify missing data methods when the number of intra-subject repeated measures is large. To test whether missingness patterns are nondifferential across treatment conditions, a formal testing approach treats indicators of missingness as a special type of repeated measures (e.g., 0: intermittent missing, 1: observed, and 2: dropout missing). After reviewing the idea of ignorability for missing data and of classifying missingness mechanisms into subcategories, the article provides an example for assessing common assumptions on missingness mechanisms and how these assumptions affect model selection for significance testing. A carbon monoxide longitudinal data set in a smoking cessation study is used for illustration.

Bias↗

PubMed2005

Uncertainty method improved on best-worst case analysis in a binary meta-analysis.

BACKGROUND: Most systematic reviewers aim to perform an intention-to-treat meta-analysis, including all randomized participants from each trial. This is not straightforward in practice: reviewers must decide how to handle missing outcome data in the contributing trials. OBJECTIVE: To investigate methods of allowing for uncertainty due to missing data in a meta-analysis. STUDY DESIGN AND SETTING: The Cochrane Library was surveyed to assess current use of imputation methods. We developed a methodology for incorporating uncertainty, with weights assigned to trials based on uncertainty interval widths. The uncertainty interval for a trial incorporates both sampling error and the potential impact of missing data. We evaluated the performance of this method using simulated data. RESULTS: The survey showed that complete-case analysis is commonly considered alongside best-worst case analysis. Best-worst case analysis gives an interval for the treatment effect that includes all of the uncertainty due to missing data. Unless there are few missing data, this interval is very wide. Simulations show that the uncertainty method consistently has better power and narrower interval widths than best-worst case analysis. CONCLUSION: The uncertainty method performs consistently better than best-worst case imputation and should be considered along with complete-case analysis whenever missing data are a concern.

Antimalarials↗

PubMed2006

Bias arising from missing data in predictive models.

OBJECTIVE: The purpose of this study is to determine the effect of three common approaches to handling missing data on the results of a predictive model. STUDY DESIGN AND SETTING: Monte Carlo simulation study using simulated data was used. A baseline logistic regression using complete data was performed to predict hospital admission, based on the white blood cell count (WBC) (dichotomized as normal or high), presence of fever, or procedures performed (PROC). A series of simulations was then performed in which WBC data were deleted for varying proportions (15-85%) of patients under various patterns of missingness. Three analytic approaches were used: analysis restricted to cases with complete data, missing data assumed to be normal (MAN), and use of imputed values. RESULTS: In the baseline analysis, all three predictors were all significantly associated with admission. Using either the MAN approach or imputation, the odds ratio (OR) for WBC was substantially over- or underestimated depending on the missingness pattern, and there was considerable bias toward the null in the OR estimates for fever. In the CC analyses, OR for WBC was consistently biased toward the null, OR for PROC was biased away from the null, and the OR for fever was biased toward or away from the null. Estimates for overall model discrimination were substantially biased using all analytic approaches. CONCLUSIONS: All three methods of handling large amounts of missing data can lead to biased estimates of the OR and of model performance in predictive models. Predictor variables that are measured inconsistently can affect the validity of such models.

Adolescent↗

PubMed2026

A novel reusable transcriptome-wide association study workflow used to map key genes linked to important cattle traits.

Transcriptome-wide association studies (TWAS) are a powerful approach for studying the genes underlying complex traits by directly integrating GWAS and gene expression datasets. In cattle, they have been previously applied to identify genes driving fertility, milk production, and health. However, these studies have also highlighted several challenges, from difficulties in reproducing these complex analyses to limitations from poor genotype calls, especially when called directly from RNA sequencing data. To address these and other challenges, for the H2020 BovReg Project, we have developed a streamlined, species-agnostic, and reusable Nextflow TWAS workflow to integrate transcriptomic and GWAS summary statistic datasets. Our workflow first generates accurate genotype calls and gene expression prediction models from transcriptomic datasets and then applies these tools to impute gene expression levels into GWAS cohorts, enabling the association of genes with traits of interest. We explore optimal strategies for calling genetic variants directly from transcriptomic data and illustrate that using imputation approaches specifically designed for low-pass sequencing data can improve variant calling over previously adopted methods. We demonstrate the utility of our TWAS workflow by applying it to both novel and publicly available GWAS cohorts for cattle, detecting novel gene-trait associations for complex traits. Using a new transcriptome annotation of the cattle genome generated for the BovReg project we also illustrate how previously un-assayable associations can be detected. The results and the workflow we present, provide a new resource for the community and contribute to a better understanding of the molecular drivers of complex traits in cattle with the goal of eventually leveraging this information in future breeding decisions.

Animals↗

PubMed2001

Use of a toxicokinetic model in the analysis of cancer mortality in relation to the estimated absorbed dose of dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD).

We performed an analysis of All cancer and Lung cancer mortality in relation to estimated absorbed dose of dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD) in the cohort of chemical workers at 12 US plants assembled by the US National Institute for Occupational Safety and Health (NIOSH) (n = 5172). Estimates of cumulative exposure to TCDD were based on a minimal physiologic toxicokinetic model (MPTK) that accounts for inter- and intra-individual variations in body mass index (BMI) over time. Population-level parameters related to liver elimination and background (input or concentration) of TCDD were estimated from separate data with repeated measures of serum TCDD (US Air Force Health Study). An occupational TCDD input parameter was estimated based on one-point-in-time TCDD data available for a subset (n = 253) of the NIOSH cohort. Model-based time-dependent cumulative dose estimates (area under the curve (AUC) of the lipid-adjusted serum TCDD concentration over time) were obtained for members of the full cohort with recorded body height and weight (n = 4049), as this information is required by the MPTK model to compute dose. Missing-value problems arose in the estimation of the occupational input parameter (n = 42) and in TCDD-dose calculation in the full cohort (n = 886) and they were handled with multiple imputation methods. Risk-regression analyses were based on Cox log-linear models including age at entry, year of entry and duration of employment as categorical covariates in addition to the logarithm of cumulative TCDD dose in ppt-years. Risk sets were stratified on birth cohort. Estimates of the unlagged exposure coefficient in these models were 0.1249 [95% confidence interval (CI) 0.0144, 0.2354] for All cancer and 0.2158 (95% CI 0.02376, 0.4078) for lung cancer. A 10-year lag produced an increase in the estimate for all cancer (0.1539, 95% CI 0.0387, 0.2691), whereas, the estimate for lung cancer was not affected much (0.2125, 95% CI 0.0138, 0.4112). At a dose level of 100 times the background the estimates obtained with a 10-year lag translate into a relative risk of 2.03 (95% CI 1.19-3.45) for all cancer and of 2.66 (95% CI 1.07-6.64) for lung cancer. Higher estimates of the exposure coefficients were obtained after imputation of missing values. This increase in risk seemed due to the inclusion of short-term workers, who may exhibit a higher mortality for reasons other than dioxin exposure.

Body Mass Index↗

PubMed2003

The economic burden of gynecologic cancers in California, 1998.

OBJECTIVE: Our aim was to estimate the direct and indirect costs of gynecologic cancers including cervical, ovarian, and uterine cancer in California in 1998. METHODS: Hospitalization costs, including costs of primary and secondary diagnoses of each of the gynecologic cancers, are derived from the California Patient Discharge dataset. Charges are converted to costs using hospital-specific cost-to-charge ratios and an imputed cost for HMO hospitalizations. Other direct medical costs are derived from the 1997 Medical Expenditure Panel Survey. Indirect mortality costs are the product of the number of deaths and the expected value of a female's future earnings, including an imputed value of housekeeping services. RESULTS: The total cost of the three gynecologic cancers in California is estimated at $624 million for 1998. Indirect costs or losses in productivity due to premature death are twice the direct medical care costs. Hospitalization inpatient costs account for more than half of total direct costs for each of these cancers. Total costs for ovarian cancer are highest among the three cancers. CONCLUSIONS: The estimates presented here highlight the need for studies that identify cost-effective screening methods and the relationship between treatment protocols and outcomes. The methods presented here could be used to develop stage- or treatment-specific costs that would be useful for such analyses. Only through early detection and more effective management of gynecologic cancers can there be a reduction in the morbidity, premature death, and high costs of cervical, ovarian, and uterine cancers.

Adolescent↗

PubMed2004

[Study of the clonality of cutaneous and blood lymphocytes during drug-induced hypersensitivity in 6 patients].

INTRODUCTION: The drug-induced hypersensitivity syndrome or DRESS (drug reaction with eosinophilia and systemic symptoms) is a severe toxiderma because it is accompanied by lethal visceral involvement in 6 to 10% cases. Its physiopathology remains unclear. In order to specify the immunological characteristics of this toxiderma we analyzed, prospectively, the rearrangement of the blood and cutaneous T-cell lymphocyte receptor (TCR) genes of patients exhibiting a drug-induced hypersensitivity syndrome between April 1998 and April 2000. PATIENTS AND METHODS: The inclusion criteria were: age over 18 years, occurrence of a drug-induced generalized eruption, existence of associated systemic involvement (lymph node or visceral), and presence of hypereosinophilia greater than 0.5 G/l and/or circulating atypical lymphocytes. Six patients (3 men and 3 women), with a mean age of 54 years were included. The imputable drug was an anti-seizure in 3 cases, allopurinol in 2 and oxazepam in one. Remission occurred within a delay of 10 to 30 days after the acute phase. Two patients presented several flares. RESULTS: No clonal rearrangement in TCR genes was detected in the cutaneous samples. A clonal rearrangement of TCR genes was initially detected in the blood lymphocytes of 3 out of the 6 patients (allopurinol: n=2 and oxazepam: n=1). The latter remained detectable during the evolution, during the second or third flare of the drug-induced hypersensitivity in 2 patients (allopurinol: n=1 and oxazepam: n=1). DISCUSSION: The presence of circulating T-cell clones detectable for several months after the occurrence of a drug-induced hypersensitivity shows the mono or oligoclonal expansion of activated T-cells, induced by the drug imputed. Their persistence over several months corresponds to a remnant activation of the immune system that can explain the prolonged and/or recurrent evolution of the drug-induced hypersensitivity syndrome in some patients.

Adult↗

PubMed2001

A case-control study on scrapie in Norwegian sheep flocks.

Scrapie first was detected in indigenous sheep in Norway in 1981, and from 1995 to 1997 an increase in the number of flocks with scrapie cases was recorded. These flocks were mainly in one geographical region. A study to identify risk factors for scrapie was conducted. The study had three frequency-matched controls selected for every case within the same Veterinary District. A questionnaire was submitted to 176 sheep flocks (42 had been scrapie flocks). The data obtained by the questionnaire were linked to data collected from governmental and industry registers. After imputing missing data using single random imputation, the statistical analysis was performed using multivariable conditional logistic regression. Purchase of female sheep from scrapie flocks, sharing of rams, or sharing of pastures between different flocks were the risk factors associated with the occurrence of scrapie. Of factors potentially sustaining and promoting the infection in the flock, number of winter-fed sheep, number of buildings for housing sheep, rams and ewes shared room during mating period and increase in the flock size were associated with scrapie. We interpret these findings to show that factors involving transfer of sheep between flocks or direct contact between sheep of different flocks are important for the spread of scrapie. Management factors are important for the development of scrapie. However, it was not possible to discriminate between the different management factors in this study at the flock level. Also, factors indicating awareness and interest of the farmer (as well as willingness to contact a veterinarian for diseased sheep) were related to the detection of scrapie in the flock.

Animal Husbandry↗

PubMed1998

A search for serologic correlates of immunity to Bordetella pertussis cough illnesses.

In a pertussis vaccine efficacy trial in Germany we collected sera from vaccinees (DTaP or DTP) after the third and fourth doses of vaccine or at comparable time periods in DT vaccine recipients. In addition, sera were collected from a randomized sample of subjects in each vaccine group at approximately 3-month intervals from which antibody kinetic curves were constructed, which allowed us to estimate specific antibody values to pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin and fimbriae-2 at the time of exposure in the household setting. The imputed geometric mean antibody values to PT, pertactin and fimbriae-2 at the time of household exposure to Bordetella pertussis infection were higher (p < 0.07 or lower) in non-cases compared with cases. A multivariate (classification tree) analysis found that only pertactin and PT were significant in protection. Subjects with an imputed pertactin value of < 7 EU ml-1 had a 67% (18/27) chance of infection regardless of the PT value. If the pertactin value was > or = 7 EU ml-1 and the PT value > or = 66 EU ml-1 all subjects were non-cases. If the pertactin value was > or = 7 and the PT value was < 66 EU ml-1 the predicted probability of being a case was 31% (15/49). Logistic regression analysis also found that high versus low pertactin values were associated with illness prevention following household exposure. In the presence of antibody to pertactin, PT and fimbriae-2, the additional presence of antibody to FHA did not contribute to protection. Our data support historical data indicating that agglutinating antibodies are associated with protection and also recent serologic correlates data and clinical efficacy data which indicate that multicomponent vaccines containing pertactin and fimbriae have better efficacy than PT or PT/FHA vaccines.

Adhesins, Bacterial↗

PubMed1998

Migration, remittances, and inequality: estimating the net effects of migration on income distribution.

"This paper examines the net effects of migration and remittances on income distribution. Potential home earnings of migrants are imputed, as are the earnings of non-migrants in migrant households, in order to construct no-migration counterfactuals to compare with the observed income distribution including remittances. The earnings functions used to impute migrant home earnings are estimated from observations on non-migrants in a selection-corrected estimation framework which incorporates migration choice and labor-force participation decisions. For a sample of households in Bluefields, Nicaragua, migration and remittances increase income inequality when compared with the no-migration counterfactual."

Americas↗

PubMed2005

[Ulcerating haemorrhagic colitis induced by celecoxib].

INTRODUCTION: Selectivity of cyclooxygenase-2 inhibitors (Cox2 inhibitors) decreased gastroduodenal toxicity of nonsteroidal anti-inflammatory drugs. Effects on colic mucosa are little known. OBSERVATION: A case history is described of a 38-year-old women, without digestive past, who presented with hemorrhagic ulcerated acute colitis beginning 2 days after starting celecoxib (200 mg/d) prescribed for sciatica. DISCUSSION: Intrinsic imputability of celecoxib is very probable in this case report by combination of chronological and semiological criteria. Extrinsic imputability is discussed, starting from the available bibliographical data which relate primarily to rofecoxib. CONCLUSION: This observation, which constitutes, as far as we know, the first case report of hemorrhagic ulcerated colitis related to celecoxib, confirms the colic toxicity of anti-Cox2 and identify a new cause of acute colitis. Report of colic side effects with Cox2 inhibitors is required because of their new marketing.

Acute Disease↗

PubMed2003

Effects of coaching by community pharmacists on psychological symptoms of antidepressant users; a randomised controlled trial.

BACKGROUND: Community pharmacists strive to deliver pharmaceutical care to patients. At the moment, coaching of depressive primary care patients on taking their antidepressants (ADs) is not yet part of their standard care package. AIMS: To investigate the effects of coaching by community pharmacists on psychological symptoms. METHOD: A randomised controlled trial with a 6-month follow-up. OUTCOMES: psychological symptoms with the Hopkins Symptom Checklist (SCL). Intention-to-treat (ITT) was performed with (1) last observation carried forward and (2) with group mean imputation (GMI). RESULTS: Analyses with LOCF and GMI resulted in different findings. The LOCF method revealed that at the 6-month follow-up, the intervention patients were less depressed and less anxious than the controls. The intervention was particularly effective in patients with lower levels of education who received pharmacist's coaching. However, ITT with the GMI method showed no differences in psychological symptoms. Differences between LOCF and GMI were explained by the selective attrition in the intervention arm (attrition intervention patients had lower initial SCL-item scores on depression and anxiety than the completers) and by the higher attrition rate in controls. CONCLUSIONS: Our study indicates that the interpretation of the effects of an intervention on psychological symptoms can differ substantially by the way missing values are imputed. If both LOCF and GMI produce significant differences, efficacy can be concluded. If not, the effects based on ITT analyses with LOCF are based on artefacts. We recommend that positive intervention effects should only be reported when findings with LOCF and GMI are in accordance.

Adult↗

PubMed1997

The correction of risk estimates for measurement error.

PURPOSE: The methods available for the correction of risk estimates for measurement errors are reviewed. The assumptions and design implications of each of the following six methods are noted: linear imputation, absolute limits, maximum likelihood, latent class, discriminant analysis and Gibbs sampling. METHODS: All methods, with the exception of the absolute limits approach, require either repeated determinations on the same subjects with use of the methods that are prone to error or a validation study, in which the measurement is performed for a number of persons with use of both the error-prone method and a more accurate method regarded as a "gold standard". RESULTS: The maximum likelihood, latent class and absolute limits methods are most suitable for purely discrete risk factors. The linear imputation methods and the closely related discrimination analysis method are suitable for continuous risk factors which, together with the errors of measurement, are usually assumed to be normally distributed. CONCLUSIONS: The Gibbs sampling approach is, in principle, useful for both discrete and continuous risk factors and measurement errors, although its use does mandate that the user specify models and dependencies that may be very complex. Also, the Bayesian approach implicit in the use of Gibbs sampling is difficult to apply to the design of the case-control study.

Bayes Theorem↗

PubMed2004

Beyond classical meta-analysis: can inadequately reported studies be included?

Classical meta-analysis requires the same data from each clinical trial, thus data-reporting must be of a high-quality. Imputation methods are used to include studies that provide incomplete information on variability and the fixed and random effects of a drug. Regression models can be used to include studies other than randomized placebo-controlled studies. In the example outlined here, the use of non-randomized single-arm studies and studies against comparator treatments has little influence on the estimation of the treatment effect in comparison with placebo, an effect that is based on the randomized placebo-controlled studies. The inclusion of other studies serves to increase the precision of the effect of the treatment compared with baseline. Although multiple imputation techniques enable a larger number of studies to be included, which will typically increase the precision of the estimated effect, a careful sensitivity analysis is also required.

Clinical Trials as Topic↗

PubMed2026

Efficacy and safety of once-weekly semaglutide 2·4 mg in Chinese adults with overweight or obesity (STEP 12): a randomised, double-blind, placebo-controlled, multicentre, phase 3b trial.

BACKGROUND: Semaglutide 2·4 mg is a GLP-1 receptor agonist that reduces bodyweight, and provides other cardiometabolic benefits, among people with a BMI at least 30 kg/m2 or at least 27 kg/m2 and with weight-related comorbidities. This trial aimed to evaluate the efficacy, tolerability, and safety of semaglutide 2·4 mg in adults from mainland China and Taiwan with overweight or obesity according to locally defined, BMI thresholds. METHODS: This completed randomised, double-blind, placebo-controlled, multicentre, two-armed, parallel-group, phase 3b trial (STEP 12) was conducted at 19 sites across mainland China and Taiwan. Adults with a BMI of 24-<28 kg/m2 and at least one weight-related comorbidity, or a BMI of 28-<30 kg/m2, with or without type 2 diabetes, were randomly assigned (2:1) to once-weekly subcutaneous semaglutide 2·4 mg or placebo, plus lifestyle intervention, for 44 weeks. Randomisation was performed by the study sponsor using the Randomisation Trial Supplies Management System. Coprimary endpoints were percentage change in bodyweight and the proportion of participants achieving at least 5% bodyweight reduction. Safety was analysed descriptively in all participants who received the trial intervention. Missing data at week 44 were imputed with washout multiple imputation. This study is registered with ClinicalTrials.gov, NCT06041217, and is completed. FINDINGS: Between Sept 15, 2023, and May 7, 2025, of 254 screened participants, 161 (66·5%) of 242 participants were randomly assigned to semaglutide 2·4 mg and 81 (33·5%) to placebo; 121 (50·0%) participants were female, and 47 (19·4%) participants had type 2 diabetes. Bodyweight reduction was greater with semaglutide versus placebo (-12·1% [SE 0·6] vs -2·2% [0·8]; estimated treatment difference -9·9 percentage points [95% CI -11·8 to -8·0]; p<0·0001), with a greater proportion of participants achieving at least 5% bodyweight reduction (80·5% vs 24·4%; odds ratio [OR] 14·8 [95% CI 7·4 to 29·6]; p<0·0001). Adverse events were reported in 141 (87·6%) of 161 participants in the semaglutide 2·4 mg group and 61 (75·3%) of 81 participants in the placebo group, with gastrointestinal disorders being the most common. INTERPRETATION: Semaglutide 2·4 mg provided a superior reduction in bodyweight versus placebo in Chinese adults with overweight or obesity. The safety profile was consistent with the known profile of semaglutide. FUNDING: Novo Nordisk A/S. TRANSLATION: For the Mandarin translation of the abstract see Supplementary Materials section.

Adult↗

PubMed1976

Effect of vestibular deafferentation upon positional nystagmus in the squirrel monkey.

Seventeen of eighteen squirrel monkeys, under a restrained condition, showed positional nystagmus in different body positions. Good repeatability and consistency of the nystagmus were found, especially at the left-lateral, right-lateral, and head-hanging positions. Positional nystagmus was not observed after the subject underwent bilateral labyrinthectomy. However, one subject in which part of the crista ampullaris posterior remained, continuously showed a positional nystagmus. Therefore, the existence of a minimal vestibular imput from the crista ampullaris could provoke the nystagmus. Some changes occurred in positional nystagmus after bilateral macular ablation; however, the nystagmus did not completely disappear. Even though imput from the crista ampullaris is essential to provoke positional nystagmus in squirrel monkeys, the positional nystagmus probably results from a central dyscoordination between vestibulo-oculomotor function, spino-oculomotor function, vestibular and brain circulation, and psychological condition.

Animals↗