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Background Missing data may seriously compromise inferences from randomised clinical trials, especially if missing data are not handled appropriately. The potential bias due to missing data depends on the mechanism causing the data to be missing, and the analytical methods applied to amend the missingness. Therefore, the analysis of trial data with missing values requires careful planning and attention. Methods The authors had several meetings and discussions considering optimal ways of handling missing data to minimise the bias potential. We also searched PubMed (key words: missing data; randomi*; statistical analysis) and reference lists of known studies for papers (theoretical papers; empirical studies; simulation studies; etc.) on how to deal with missing data when analysing randomised clinical trials. Results Handling missing data is an important, yet difficult and complex task when analysing results of randomised clinical trials. We consider how to optimise the handling of missing data during the planning stage of a randomised clinical trial and recommend analytical approaches which may prevent bias caused by unavoidable missing data. We consider the strengths and limitations of using of best-worst and worst-best sensitivity analyses, multiple imputation, and full information maximum likelihood. We also present practical flowcharts on how to deal with missing data and an overview of the steps that always need to be considered during the analysis stage of a trial. Conclusions We present a practical guide and flowcharts describing when and how multiple imputation should be used to handle missing data in randomised clinical.

Hydroxyethyl starch (HES) [corrected] is widely used for fluid resuscitation in intensive care units (ICUs), but its safety and efficacy have not been established in patients with severe sepsis. In this multicenter, parallel-group, blinded trial, we randomly assigned patients with severe sepsis to fluid resuscitation in the ICU with either 6% HES 130/0.42 (Tetraspan) or Ringer's acetate at a dose of up to 33 ml per kilogram of ideal body weight per day. The primary outcome measure was either death or end-stage kidney failure (dependence on dialysis) at 90 days after randomization. Of the 804 patients who underwent randomization, 798 were included in the modified intention-to-treat population. The two intervention groups had similar baseline characteristics. At 90 days after randomization, 201 of 398 patients (51%) assigned to HES 130/0.42 had died, as compared with 172 of 400 patients (43%) assigned to Ringer's acetate (relative risk, 1.17; 95% confidence interval [CI], 1.01 to 1.36; P=0.03); 1 patient in each group had end-stage kidney failure. In the 90-day period, 87 patients (22%) assigned to HES 130/0.42 were treated with renal-replacement therapy versus 65 patients (16%) assigned to Ringer's acetate (relative risk, 1.35; 95% CI, 1.01 to 1.80; P=0.04), and 38 patients (10%) and 25 patients (6%), respectively, had severe bleeding (relative risk, 1.52; 95% CI, 0.94 to 2.48; P=0.09). The results were supported by multivariate analyses, with adjustment for known risk factors for death or acute kidney injury at baseline. Patients with severe sepsis assigned to fluid resuscitation with HES 130/0.42 had an increased risk of death at day 90 and were more likely to require renal-replacement therapy, as compared with those receiving Ringer's acetate. (Funded by the Danish Research Council and others; 6S ClinicalTrials.gov number, NCT00962156.).

To assess the effects of comprehensive cardiac rehabilitation compared with usual care on physical activity and mental health for patients treated with catheter ablation for atrial fibrillation. The patients were randomized 1:1 stratified by paroxysmal or persistent atrial fibrillation and sex to cardiac rehabilitation consisting of 12 weeks physical exercise and four psycho-educational consultations plus usual care (cardiac rehabilitation group) versus usual care. The primary outcome was Vo2 peak. The secondary outcome was self-rated mental health measured by the Short Form-36 questionnaire. Exploratory outcomes were collected. 210 patients were included (mean age: 59 years, 74% men), 72% had paroxysmal atrial fibrillation prior to ablation. Compared with usual care, the cardiac rehabilitation group had a beneficial effect on Vo2 peak at four months (24.3mL kg−1 min−1 versus 20.7mL kg−1 min−1, p of main effect=0.003, p of interaction between time and intervention=0.020). No significant difference between groups on Short Form-36 was found (53.8 versus 51.9 points, P=.20). Two serious adverse events (atrial fibrillation in relation to physical exercise and death unrelated to rehabilitation) occurred in the cardiac rehabilitation group versus one in the usual care group (death unrelated to intervention) (P=.56). In the cardiac rehabilitation group 16 patients versus 7 in the usual care group reported non-serious adverse events (P=.047). Comprehensive cardiac rehabilitation had a positive effect on physical capacity compared with usual care, but not on mental health. Cardiac rehabilitation caused more non-serious adverse events.

The randomized clinical trial, SafeBoosC II, examined the effect of monitoring of cerebral oxygenation by near-infrared spectroscopy combined with a guideline on treatment when cerebral oxygenation was out of the target range. Data on cerebral oxygenation was collected in both the intervention and the control group. The primary outcome was the reduction in the burden of cerebral hypo- and hyperoxia between the two groups. In this study we describe the associations between the burden of cerebral hypo- and hyperoxia, regardless of allocation to intervention or control group, and the biomarkers of brain injury from birth till term equivalent age that was collected as secondary and explorative outcomes in the SafeBoosC II trial. Cerebral oxygenation was continuously monitored during the first 72h of life in 166 extremely preterm infants. Cranial ultrasound was performed at day 1,4,7,14, and 35 and at term. Electroencephalogram (EEG) was recorded at 64h. Blood-samples taken at 6 and 64 hours were analysed for the brain injury biomarkers; S100beta, brain-fatty-acid-binding-protein, and neuroketal. All analyses were conducted post hoc. Significantly more infants with a cerebral burden of hypoxia within the 4th quartile versus infants within quartile 1-3 were diagnosed with severe intracranial haemorrhage (11/39 versus 11/117, p = 0.003), had low burst rate on EEG (12/28 versus 21/103, p = 0.015), or died (14/41 versus 18/123, p = 0.006), whereas none of these events were significantly associated with cerebral hyperoxia. The blood biomarkers were not significantly associated with the burden of cerebral hypo- or hyperoxia. The explorative analysis showed that early burden of cerebral hypoxia, but not hyperoxia was significantly associated with low brain electrical activity and severe intracranial haemorrhage while none of the three blood biomarkers were associated with the burden of either cerebral hypo- or hyperoxia.

Objective and methods: It is rare that trialists report power estimations of non-primary outcomes. In the present article, we will describe how to define a valid hierarchy of outcomes in a randomised clinical trial, to limit problems with Type I and Type II errors, using considerations on the clinical relevance of the outcomes and power estimations. Conclusion: Power estimations of non-primary outcomes may guide trialists in classifying non-primary outcomes as secondary or exploratory. The power estimations are simple and if they are used systematically, more appropriate outcome hierarchies can be defined, and trial results will become more interpretable.

Prospective parents widely use education to gain information about, e.g., labour and parenting skills. It is unknown if antenatal education in small classes is more beneficial for parenting stress and parenting alliance compared with other types of antenatal education. In the present randomised trial, we examined the effect of antenatal education in small classes versus auditorium-based lectures on perceived stress, parenting stress, and parenting alliance. A total of 1,766 pregnant women were randomised to receive: antenatal education in small classes three times in pregnancy and one time after delivery, each session lasted 2.5 hours, versus standard care consisting of two times two hours auditorium-based lectures. Previous analysis of the primary outcome showed no difference between intervention and control group. Here we conduct an exploratory analysis of three secondary outcomes. Effects of the interventions on parents' global feelings of stress at 37 weeks gestation and nine weeks and six months postpartum and parenting stress nine weeks and six months postpartum were examined using linear regression analyses and mixed models with repeated measurements. The effect on parenting alliance six months postpartum was examined using the non-parametric Wilcoxon rank-sum test. Antenatal education in small classes had a small beneficial main effect on global feelings of stress six months postpartum and a statistically significant interaction between time and group favoring antenatal education in small classes. The P values of intervention effects on parenting stress and parenting alliance were all larger than the threshold value (0.05).

Objective Occupational hand eczema has adverse health and socioeconomic impacts for the afflicted individuals and society. Prevention and treatment strategies are needed. This study aimed to assess the effectiveness of an educational intervention on sickness absence, quality of life and severity of hand eczema. Methods PREVEX (Prevention of EXema) is an individually randomized, parallel-group superiority trial investigating the pros and cons of one-time, 2-hour, group-based education in skin-protective behavior versus treatment as usual among patients with newly notified occupational hand eczema, with follow-up after one year. Co-primary outcomes were total sickness absence, health-related quality of life (HR-QoL), and self-reported severity of hand eczema. Results Patients (N=1668) with notified occupational skin diseases from July 2012 to November 2014 were invited to participate in the trial. Of these, 756 were randomized to the intervention (N= 376) versus control (N=380) group. The intervention group had 21% fewer sickness absence days compared with the control group [95% confidence interval (CI) -55-40%, P=0.43]. We found no significant difference in the change of HR-QoL for the intervention compared with the control group (4% lower in the intervention group, 95% CI -18-13%, P=0.67). The ordinal odds of scoring worse on self-reported hand eczema severity was 15% lower in the intervention compared with the control group (95% CI -39-18%, P=0.34). Post-hoc sub-group analyses indicated that the effect of the intervention on severity differed between occupations, being detrimental to healthcare workers and beneficial in all other occupations. Conclusion The educational skincare program had no marked effect on the primary outcomes sickness absence, HR-QoL, and severity of hand eczema when compared with treatment as usual.

To investigate the effects of social-skills training and parental training programme for children with attention deficit hyperactivity disorder (ADHD). We conducted a randomized two-armed, parallel group, assessor-blinded superiority trial consisting of social-skills training plus parental training and standard treatment versus standard treatment alone. A sample size calculation showed at least 52 children should be included for the trial with follow up three and six months after randomization. The primary outcome measure was ADHD symptoms and secondary outcomes were social skills and emotional competences. RESULTS 56: children (39 boys, 17 girls, mean age 10.4 years, SD 1.31) with ADHD were randomized, 28 to the experimental group and 27 to the control group. Mixed-model analyses with repeated measures showed that the time course (y  =  a + bt + ct(2)) of ADHD symptoms (p = 0.40), social skills (p = 0.80), and emotional competences (p = 0.14) were not significantly influenced by the intervention. Social skills training plus parental training did not show any significant benefit for children with attention deficit hyperactivity disorder when compared with standard treatment. More and larger randomized trials are needed. ClinicalTrials.gov NCT00937469.

ObjectiveTo evaluate off-pump versus on-pump coronary artery bypass grafting (CABG) in patients with three-vessel disease and a high-risk operative profile.DesignA randomised clinical trial.SettingRigshospitalet, University Hospital, Copenhagen, Denmark.Participants341 patients with three-vessel disease and a EuroSCORE of 5 or greater. Main exclusion criteria were previous heart surgery, poor left ventricular function (ejection fraction <30%), or unstable preoperative condition.InterventionCABG performed with versus without cardiopulmonary bypass.Main outcome measureThe primary outcome was a composite of major adverse cardiac and cerebrovascular events (MACCE) including all-cause mortality, acute myocardial infarction, cardiac arrest with successful resuscitation, low cardiac output syndrome/cardiogenic shock, stroke and coronary reintervention.ResultsMACCE occurred in 69 (40%) patients allocated to off-pump versus 54 (33%) patients allocated to on-pump CABG during the median 3.7 years of follow-up (HR 1.22; 95% CI 0.86 to 1.75; p=0.26). All-cause mortality was significantly increased in the off-pump group (24% vs 15%; HR 1.66, 95% CI 1.02 to 2.73; p=0.04), but cardiac-related death was not significantly different (10% vs 7%; HR 1.30, 95% CI 0.64 to 2.66; p=0.47). An insignificant trend towards a reduction in myocardial infarction after off-pump CABG was observed (7% vs 14%; HR 0.53, 95% CI: 0.27 to 1.04; p=0.06).ConclusionsNo significant difference in the primary outcome of MACCE was found between off-pump and on-pump CABG. However, mortality seemed higher after off-pump CABG.Trial registrationhttp://clinicaltrials.gov/ number, NCT00120991.