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Analyzing small data sets using Bayesian estimation: the case of posttraumatic stress symptoms following mechanical ventilation in burn survivors.

ABSTRACT: Background : The analysis of small data sets in longitudinal studies can lead to power issues and often suffers from biased parameter values. These issues can be solved by using Bayesian estimation in conjunction with informative prior distributions. By means of a simulation study and an empirical example concerning posttraumatic stress symptoms (PTSS) following mechanical ventilation in burn survivors, we demonstrate the advantages and potential pitfalls of using Bayesian estimation. Methods : First, we show how to specify prior distributions and by means of a sensitivity analysis we demonstrate how to check the exact influence of the prior (mis-) specification. Thereafter, we show by means of a simulation the situations in which the Bayesian approach outperforms the default, maximum likelihood and approach. Finally, we re-analyze empirical data on burn survivors which provided preliminary evidence of an aversive influence of a period of mechanical ventilation on the course of PTSS following burns. Results : Not suprisingly, maximum likelihood estimation showed insufficient coverage as well as power with very small samples. Only when Bayesian analysis, in conjunction with informative priors, was used power increased to acceptable levels. As expected, we showed that the smaller the sample size the more the results rely on the prior specification. Conclusion : We show that two issues often encountered during analysis of small samples, power and biased parameters, can be solved by including prior information into Bayesian analysis. We argue that the use of informative priors should always be reported together with a sensitivity analysis.

SUBMITTER: van de Schoot R

PROVIDER: S-EPMC4357639 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Analyzing small data sets using Bayesian estimation: the case of posttraumatic stress symptoms following mechanical ventilation in burn survivors.

van de Schoot Rens R Broere Joris J JJ Perryck Koen H KH Zondervan-Zwijnenburg Mariëlle M van Loey Nancy E NE

European journal of psychotraumatology 20150311

Background : The analysis of small data sets in longitudinal studies can lead to power issues and often suffers from biased parameter values. These issues can be solved by using Bayesian estimation in conjunction with informative prior distributions. By means of a simulation study and an empirical example concerning posttraumatic stress symptoms (PTSS) following mechanical ventilation in burn survivors, we demonstrate the advantages and potential pitfalls of using Bayesian estimation. Methods : ...[more]

PMID: 25765534

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Project description:Background: A burn event can elicit symptoms of posttraumatic stress disorder (PTSD) in survivors and their partners and may impact the way these couple members interact with each other. They may try to protect each other from further emotional distress by avoiding talking about the burn event, but they may also show concern towards each other.Objective: The aim of this study was to investigate bidirectional relationships between survivor's and partner's PTSD symptoms and two interpersonal processes: partner-oriented 'self-regulation', which is avoidance-oriented, and 'expressed concern', which is approach-oriented.Method: In this longitudinal multi-centre study, 119 burn survivors and their partners participated. Measures of PTSD symptoms, self-regulation, and expressed concern were administered in the acute phase following the burns, and follow-ups took place up to 18 months postburn. Intra- and interpersonal effects were examined in a random intercept cross-lagged panel model. Exploratory effects of burn severity were also investigated.Results: Within individuals, survivor's expressed concern predicted later higher levels of survivor's PTSD symptoms. In their partners, self-regulation and PTSD symptoms reinforced each other in the early phase postburn. Between the two couple members, partner's expressed concern predicted later lower levels of survivor's PTSD symptoms. Exploratory regression analyses showed that burn severity moderated the effect of survivor's self-regulation on survivor's PTSD symptoms, indicating that self-regulation was continuously related to higher levels of PTSD symptoms over time within more severely burned survivors, but not in less severely burned survivors.Conclusion: PTSD symptoms and self-regulation reinforced each other in partners and possibly also in more severely burned survivors. Partner's expressed concern was related to lower levels of survivor's PTSD symptoms, whereas survivor's expressed concern was related to higher levels of survivor's PTSD symptoms. These findings emphasize the importance of screening for and monitoring PTSD symptoms in burn survivors and their partner and of encouraging couple's self-disclosure.

Project description:ImportanceKeeping a diary for patients while they are in the intensive care unit (ICU) might reduce their posttraumatic stress disorder (PTSD) symptoms.ObjectivesTo assess the effect of an ICU diary on the psychological consequences of an ICU hospitalization.Design, setting, and participantsAssessor-blinded, multicenter, randomized clinical trial in 35 French ICUs from October 2015 to January 2017, with follow-up until July 2017. Among 2631 approached patients, 709 adult patients (with 1 family member each) who received mechanical ventilation within 48 hours after ICU admission for at least 2 days were eligible, 657 were randomized, and 339 were assessed 3 months after ICU discharge.InterventionsPatients in the intervention group (n = 355) had an ICU diary filled in by clinicians and family members. Patients in the control group (n = 354) had usual ICU care without an ICU diary.Main outcomes and measuresThe primary outcome was significant PTSD symptoms, defined as an Impact Event Scale-Revised (IES-R) score greater than 22 (range, 0-88; a higher score indicates more severe symptoms), measured in patients 3 months after ICU discharge. Secondary outcomes, also measured at 3 months and compared between groups, included significant PTSD symptoms in family members; significant anxiety and depression symptoms in patients and family members, based on a Hospital Anxiety and Depression Scale score greater than 8 for each subscale (range, 0-42; higher scores indicate more severe symptoms; minimal clinically important difference, 2.5); and patient memories of the ICU stay, reported with the ICU memory tool.ResultsAmong 657 patients who were randomized (median [interquartile range] age, 62 [51-70] years; 126 women [37.2%]), 339 (51.6%) completed the trial. At 3 months, significant PTSD symptoms were reported by 49 of 164 patients (29.9%) in the intervention group vs 60 of 175 (34.3%) in the control group (risk difference, -4% [95% CI, -15% to 6%]; P = .39). The median (interquartile range) IES-R score was 12 (5-25) in the intervention group vs 13 (6-27) in the control group (difference, -1.47 [95% CI, -1.93 to 4.87]; P = .38). There were no significant differences in any of the 6 prespecified comparative secondary outcomes.Conclusions and relevanceAmong patients who received mechanical ventilation in the ICU, the use of an ICU diary filled in by clinicians and family members did not significantly reduce the number of patients who reported significant PTSD symptoms at 3 months. These findings do not support the use of ICU diaries for preventing PTSD symptoms.Trial registrationClinicalTrials.gov Identifier: NCT02519725.

Project description:PURPOSE:A systematic review and meta-analysis was conducted to answer the question 'In adults with respiratory failure requiring invasive ventilation for more than 24 h, does a weaning strategy with early extubation to non-invasive ventilation (NIV) compared to invasive ventilation weaning reduce all-cause hospital mortality?' METHODS:We included randomised and quasi-randomised controlled trials that evaluated the use of non-invasive ventilation, compared to invasive ventilation, as a weaning strategy in adults mechanically ventilated for at least 24 h. The EMBASE, MEDLINE and Cochrane Central Register of Controlled Trials (CENTRAL) bibliographic databases were searched from inception to February 2018. Bayesian hierarchical models were used to perform the meta-analysis. The primary outcome was mortality at hospital discharge. Secondary outcomes included mortality (30, 60, 90 and 180 days), quality of life, duration of invasive ventilation, weaning failure, length of stay [intensive care unit (ICU) and hospital] and adverse events. RESULTS:Twenty-five relevant studies involving 1609 patients were included in the quantitative analysis. Studies had moderate to high risk of bias due to risk of performance and detection bias. Mortality at hospital discharge was lower in the NIV weaning group compared to the invasive weaning group [pooled odds ratio (OR) 0.58, 95% highest density interval (HDI) 0.29-0.89]. Subgroup analyses showed lower pooled mortality at hospital discharge rates in NIV weaning than those in the control group in chronic obstructive pulmonary disease (COPD) patients (pooled OR 0.43, 95% HDI 0.13-0.81) and the effect is less certain in the mixed ICU population (pooled OR 0.88, 95% HDI 0.25-1.48). NIV weaning reduced the duration of invasive ventilation in patients [standardised mean difference (SMD) -?1.34, 95% HDI -?1.92 to -?0.77] and ICU length of stay (SMD -?0.70, 95% HDI -?0.94 to -?0.46). Reported rates of ventilator associated pneumonia (VAP) were lower in the NIV group. NIV weaning did not reduce overall hospital length of stay or long-term mortality. There were insufficient data to compare other adverse events and health-related quality of life. CONCLUSIONS:The use of NIV in weaning from mechanical ventilation decreases hospital mortality, the incidence of VAP and ICU length of stay. NIV as a weaning strategy appears to be most beneficial in patients with COPD.

Project description:Background: Rape is a common traumatic event which may result in the development of posttraumatic stress disorder (PTSD), yet few studies have investigated risk biomarkers in sexually traumatised individuals. Adiponectin is a novel cytokine within inflammatory and cardiometabolic pathways with evidence of involvement in PTSD. Objective: This prospective exploratory study in a sample of female rape survivors investigated the association of single nucleotide polymorphisms (SNPs) in the adiponectin gene (ADIPOQ) and posttraumatic stress symptom (PTSS) severity, and the interaction of these SNPs of interest with childhood trauma in modifying the association with PTSS severity. Method: The study involved 455 rape-exposed black South African women (mean age (SD), 25.3 years (±5.5)) recruited within 20 days of being raped. PTSS was assessed using the Davidson Trauma Scale (DTS) and childhood trauma was assessed using a modified version of the Childhood Trauma Scale-Short Form Questionnaire. Eight ADIPOQ SNPs (rs17300539, rs16861194, rs16861205, rs2241766, rs6444174, rs822395, rs1501299, rs1403697) were genotyped using KASP. Mixed linear regression models were used to test additive associations of ADIPOQ SNPs and PTSS severity at baseline, 3 and 6 months following rape. Results: The mean DTS score post-sexual assault was high (71.3 ± 31.5), with a decrease in PTSS severity shown over time for all genotypes. rs6444174TT genotype was inversely associated with baseline PTSS in the unadjusted model (β = -13.6, 95% CI [-25.1; -2.1], p = .021). However, no genotype was shown to be significantly associated with change in PTSS severity over time and therefore ADIPOQ SNP x childhood trauma interaction was not further investigated. Conclusion: None of the ADIPOQ SNPs selected for investigation in this population were shown to be associated with change in PTSS severity over a 6-month period and therefore their clinical utility as risk biomarkers for rape-related PTSD appears limited. These SNPs should be further investigated in possible gene-gene and gene-environment interactions.

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Analyzing small data sets using Bayesian estimation: the case of posttraumatic stress symptoms following mechanical ventilation in burn survivors.

Publications

Analyzing small data sets using Bayesian estimation: the case of posttraumatic stress symptoms following mechanical ventilation in burn survivors.

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