Use of days alive without life support and similar count outcomes in randomised clinical trials - an overview and comparison of methodological choices and analysis methods

The "Small" Clinical Trial: Methods, Analysis, and Interpretation in Acute Care Cardiology

Clinical trials in acute care settings, particularly those involving small populations or high mortality contexts, present unique challenges in design and analysis. In this review we explore novel statistical approaches and methodological considerations for such trials, with a focus on cardiovascular therapies. We discuss the concept of "small" sample sizes and their limitations and cover various analytical frameworks, including frequentist and Bayesian approaches, and emphasize their implications for result interpretation and reproducibility. We examine end points such as "days alive and free specific to disease state," which combines mortality and morbidity measures, the win ratio for hierarchical end points, and ordinal scales that capture detailed patient outcomes. These methods potentially increase statistical power and provide more clinically relevant measures compared with traditional binary outcomes; an extensive use of simulations is used to clarify this point. The use of longitudinal ordinal models is presented as a promising method to capture complex patient trajectories over time, offering insights into treatment effects at various disease stages. We also address the potential of adaptive platform trials for rare conditions, allowing for more efficient use of limited patient populations. In this overview we aim to guide researchers and clinicians in selecting optimal trial designs and analytical strategies, to ultimately improve the quality, efficiency, and interpretability of evidence in acute care cardiology.

Missing data and long-term outcomes from nutrition research in the critically ill

PURPOSE OF REVIEW

The use of functional outcomes in critical care nutrition research is increasingly advocated; however, this inevitably gives rise to missing data. Consequently there is a need to adopt modern approaches to the foreseeable problem of missing functional and survival outcomes in research trials.

RECENT FINDINGS

Analyses that ignore unobserved or missing data will often return biased effect estimates. An improved approach is to routinely anticipate the types and extent of missing data, and consider the likely mechanisms of that missingness. The researcher and their statistical advisor may then choose from a number of modern strategies to assess the sensitivity of the research conclusions to the patterns of missingness contained in these research data. Methods widely employed include multiple imputation of missing observations, mixed regression models, use of composite outcome variables with patients who die being attributed a value reflecting the lack of ability to function, and selected Bayesian methodology.

SUMMARY

Conclusions from clinical research in critical care nutrition will become more clinically interpretable and generalizable with the adoption of modern methods for the statistical handling of missing data.

Lower or Higher Oxygenation Targets in Patients With COVID-19 in the ICU: A Secondary Bayesian Analysis of the Handling Oxygenation Targets in COVID-19 Trial

BACKGROUND

In the Handling Oxygenation Targets in COVID-19 (HOT-COVID) trial, a Pao2 target of 60 mm Hg compared with 90 mm Hg resulted in more days alive without life support at 90 days in adults in the ICU with COVID-19 and hypoxemia. The trial was stopped after enrolling 726 of 780 planned patients because of slow recruitment. Herein, we present the preplanned Bayesian analysis of the HOT-COVID trial.

RESEARCH QUESTION

What are the probabilities of any benefits and of clinically relevant benefits resulting from a Pao2 target of 60 mm Hg vs 90 mm Hg in adult patients with COVID-19 and hypoxemia in the ICU and does heterogeneity of treatment effects (HTE) exist according to selected baseline characteristics?

STUDY DESIGN AND METHODS

We analyzed days alive without life support and 90-day mortality in the HOT-COVID intention-to-treat population (n = 697) using Bayesian general linear models to assess probabilities for benefit or harm, including clinically relevant benefits defined as > 1 day alive without life support and > 2 percentage points lower 90-day mortality. HTE was evaluated based on baseline Sequential Organ Failure Assessment scores, Pao2 to Fio2 ratio, norepinephrine doses, and lactate concentrations.

RESULTS

The mean difference in days alive without life support was 5.7 days (95% credible interval, 0.2-11.2), with a 95.2% probability of clinically relevant benefit and a 98.0% probability of any benefit from the lower Pao2 target. The risk difference in 90-day mortality was -4.6 percentage points (95% credible interval, -11.8 to 2.6 percentage points), with a 76.5% probability of a clinically relevant benefit from the lower target. HTE analyses revealed potential interaction with baseline norepinephrine dose and lactate concentrations for both outcomes.

INTERPRETATION

In patients with COVID-19 and hypoxemia in the ICU, we found a high probability for a clinically relevant benefit of targeting a Pao2 of 60 mm Hg vs 90 mm Hg on number of days alive without life support.

CLINICAL TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT04425031; URL: www.

CLINICALTRIALS

gov.

Advancing patient-centered metrics for heart transplantation: The role of days alive and outside the hospital

BACKGROUND

Heart transplantation (HT) survival and waitlist times are established outcome metrics. Patient-centered HT outcomes are insufficiently characterized. This study evaluates the role of days alive and outside the hospital (DAOH) as a candidate patient-centered HT performance measure.

METHODS

The study cohort included Medicare beneficiaries undergoing HT (July 2008-December 2017). The percent of days outside of hospital (%DOH) 6 months before (%DOH-BF) and percent of days alive outside of hospital 12 months after HT (%DAOH-AF) were evaluated along with adverse events (AEs, early: ≤3 months; late: 4-12 months). Patients were stratified by patient %DAOH-AF terciles. Risk-adjusted %DAOH was evaluated across hospitals.

RESULTS

A total of 5,104 beneficiaries underwent HT across 108 hospitals. Median [interquartile range (IQR)] age was 62 [53-67] years, 23.9% were female, and 21.4% were African-American. The overall median %DOAH-AF was 92.9% [83.8%, 95.9%], varying by tercile: low 71.8% [4.9%, 83.6%], intermediate 92.9% [91%, 94%]; high 96.4% [95.9%, 97.3%]. The lowest (vs highest) tercile %DAOH-AF had a lower median %DOH-BF (88% [73%-97%] vs 92% [81%-98%]) and longer post-HT inpatient stay (54 [36-81] vs 13 [10-15] days). After HT, the lowest versus highest tercile had greater AEs burden in the early (allograft failure [16.1% vs 1.6%], stroke [12.1% vs 2.3%]) and late (stroke [5.1% vs 1.9%], sternal wound infection [5.0% vs 0.8%]) phases post-HT. The mean hospital %DAOHadj was 80.5% (min:max 57.7%-96.7%).

CONCLUSIONS

Post-HT %DAOH varies across beneficiaries and hospitals and is associated with AEs. Further research is warranted to assess the role and validity of %DAOH as an HT quality metric.

TARGET Protein: the effect of augmented administration of enteral protein to critically ill adults on clinical outcomes-statistical analysis plan for a cluster randomized, cross-sectional, double cross-over, clinical trial

BACKGROUND

The TARGET Protein trial will evaluate the effect of greater enteral protein delivery (augmented protein) on clinical outcomes of critically ill adult patients when compared to usual care.

OBJECTIVE

To describe the statistical analysis plan for the TARGET Protein trial.

METHODS

TARGET Protein is a cluster randomized, cross-sectional, double cross-over, open-label, registry-embedded, pragmatic clinical trial conducted across Australia and New Zealand. The trial randomized eight intensive care units (ICU) to receive enteral formula containing either higher dose enteral protein (augmented protein) or usual dose protein in a 1:1 ratio. Each ICU received one trial formula for a 3-month period and then switched to the alternate formulae. This sequence was repeated, for a total trial length of 12 months. The primary outcome is the number of days free of the index hospital and alive at day 90. Secondary outcomes include proportion of patients alive at day 90, survivor-only analysis of days free of the index hospital at day 90, duration of invasive ventilation, ICU and hospital length of stay, incidence of tracheostomy insertion, renal replacement therapy, and discharge destination. The statistical methods and models which will be used to estimate the effects for the primary and secondary outcomes are described. All statistical models will account for the cluster-randomized cross-over design to ensure correct estimation of the 95% confidence intervals. Trial enrolment is complete with 3412 patients enrolled. Data linkage is ongoing.

CONCLUSION

This statistical analysis plan enables transparent reporting of the TARGET Protein trial. It will reduce the risk of potential selective reporting biases.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ACTRN12621001484831). Registered on November 1, 2021.

Statistical analysis plan for hemodynamic phenotype-based, capillary refill time-targeted resuscitation in early septic shock: the ANDROMEDA-SHOCK-2 randomized clinical trial

BACKGROUND

ANDROMEDA-SHOCK 2 is an international, multicenter, randomized controlled trial comparing hemodynamic phenotype-based, capillary refill time-targeted resuscitation in early septic shock to standard care resuscitation to test the hypothesis that the former is associated with lower morbidity and mortality in terms of hierarchal analysis of outcomes.

OBJECTIVE

To report the statistical plan for the ANDROMEDA--SHOCK 2 randomized clinical trial.

METHODS

We briefly describe the trial design, patients, methods of randomization, interventions, outcomes, and sample size. We portray our planned statistical analysis for the hierarchical primary outcome using the stratified win ratio method, as well as the planned analysis for the secondary and tertiary outcomes. We also describe the subgroup and sensitivity analyses. Finally, we provide details for presenting our results, including mock tables, baseline characteristics, and the effects of treatments on outcomes.

CONCLUSION

According to best trial practices, we report our statistical analysis plan and data management plan prior to locking the database and initiating the analyses. We anticipate that this practice will prevent analysis bias and improve the utility of the study's reported results.

Rocking Motion Therapy for Delirious Patients in the ICU: A Multicenter Randomized Clinical Trial

OBJECTIVES

Rocking motion therapy has been shown to calm people with dementia but has never been investigated in delirious patients in the ICU. The aim of this clinical trial was to investigate the efficacy and safety of a rocking motion vs. nonrocking motion chair on the duration of delirium and intensity of agitation in ICU patients with delirium. We hypothesized that rocking motion therapy would increase the number of days alive without coma or delirium at 2 weeks of follow-up.

DESIGN

This was a multicenter, investigator initiated, parallel-group randomized controlled trial.

SETTING/PATIENTS

ICU patients 18 years or older with a positive delirium assessment.

INTERVENTIONS

Participants were assigned to either a minimum of 20 minutes rocking motion therapy or a minimum of 20 minutes in the same chair without rocking motion therapy turned on daily.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was days alive without coma or delirium 2 weeks after randomization. We enrolled 149 patients; 73 were randomly assigned to rocking motion therapy and 76 to nonrocking motion therapy. Primary outcome data were available in 141 patients.

CONCLUSIONS

Among patients with delirium in the ICU, the use of rocking motion therapy did not lead to a statistically significantly greater number of days alive without coma or delirium at the 2 weeks of follow-up than nonrocking motion therapy.

Prokinetic agents in adult intensive care unit patients (PATIENCE)-An international inception cohort study protocol

BACKGROUND

Feeding intolerance is common in critically ill patients and can lead to malnutrition. Prokinetic agents may be used to enhance the uptake of nutrition. However, the evidence on the effectiveness and safety of prokinetic agents is sparse, and there is a lack of data on their use in intensive care units (ICU).

METHODS

We will conduct an international 14-day inception cohort study of 1000 acutely admitted adult ICU patients. Data will be collected from ICU admission and daily during ICU stay for up to 90 days. The primary outcome will be the proportion of ICU patients who receive prokinetic agents. Secondary outcomes include mortality, days alive without life support, days alive out of ICU, days alive out of hospital (all within 90 days) and the number of patients with one or more serious adverse events.

RESULTS

We will present data on the use of prokinetic agents descriptively and use Cox regressions with death and ICU discharge as competing events to evaluate the association between patient characteristics and the use of prokinetic agents. We will use extended Cox models with time-varying covariates and linear regression models to assess the associations between the use of prokinetic agents and the secondary outcomes.

CONCLUSION

The outlined international cohort study will provide valuable epidemiological data on the use of prokinetic agents in adult, acutely admitted ICU patients.

Statistical Power and Performance of Strategies to Analyze Composites of Survival and Duration of Ventilation in Clinical Trials

BACKGROUND

Patients with acute hypoxemic respiratory failure are at high risk of death and prolonged time on the ventilator. Interventions often aim to reduce both mortality and time on the ventilator. Many methods have been proposed for analyzing these endpoints as a single composite outcome (days alive and free of ventilation), but it is unclear which analytical method provides the best performance. Thus, we aimed to determine the analysis method with the highest statistical power for use in clinical trials.

METHODS

Using statistical simulation, we compared multiple methods for analyzing days alive and free of ventilation: the t, Wilcoxon rank-sum, and Kryger Jensen and Lange tests, as well as the proportional odds, hurdle-Poisson, and competing risk models. We compared 14 scenarios relating to: 1) varying baseline distributions of mortality and duration of ventilation, which were based on data from a registry of patients with acute hypoxemic respiratory failure and 2) the varying effects of treatment on mortality and duration of ventilation.

RESULTS AND CONCLUSIONS

All methods have good control of type 1 error rates (i.e., avoid false positive findings). When data are simulated using a proportional odds model, the t test and ordinal models have the highest relative power (92% and 90%, respectively), followed by competing risk models. When the data are simulated using survival models, the competing risk models have the highest power (100% and 92%), followed by the t test and a ten-category ordinal model. All models struggled to detect the effect of the intervention when the treatment only affected one of mortality and duration of ventilation. Overall, the best performing analytical strategy depends on the respective effects of treatment on survival and duration of ventilation and the underlying distribution of the outcomes. The evaluated models each provide a different interpretation for the treatment effect, which must be considered alongside the statistical power when selecting analysis models.

Recommendations for clinical trial design in acute kidney injury from the 31st acute disease quality initiative consensus conference. A consensus statement

PURPOSE

Novel interventions for the prevention or treatment of acute kidney injury (AKI) are currently lacking. To facilitate the evaluation and adoption of new treatments, the use of the most appropriate design and endpoints for clinical trials in AKI is critical and yet there is little consensus regarding these issues. We aimed to develop recommendations on endpoints and trial design for studies of AKI prevention and treatment interventions based on existing data and expert consensus.

METHODS

At the 31st Acute Disease Quality Initiative (ADQI) meeting, international experts in critical care, nephrology, involving adults and pediatrics, biostatistics and people with lived experience (PWLE) were assembled. We focused on four main areas: (1) patient enrichment strategies, (2) prevention and attenuation studies, (3) treatment studies, and (4) innovative trial designs of studies other than traditional (parallel arm or cluster) randomized controlled trials. Using a modified Delphi process, recommendations and consensus statements were developed based on existing data, with > 90% agreement among panel members required for final adoption.

RESULTS

The panel developed 12 consensus statements for clinical trial endpoints, application of enrichment strategies where appropriate, and inclusion of PWLE to inform trial designs. Innovative trial designs were also considered.

CONCLUSION

The current lack of specific therapy for prevention or treatment of AKI demands refinement of future clinical trial design. Here we report the consensus findings of the 31st ADQI group meeting which has attempted to address these issues including the use of predictive and prognostic enrichment strategies to enable appropriate patient selection.

Empirical meropenem versus piperacillin/tazobactam for adult patients with sepsis (EMPRESS) trial: Protocol

BACKGROUND

Piperacillin/tazobactam may be associated with less favourable outcomes than carbapenems in patients with severe bacterial infections, but the certainty of evidence is low.

METHODS

The Empirical Meropenem versus Piperacillin/Tazobactam for Adult Patients with Sepsis (EMPRESS) trial is an investigator-initiated, international, parallel-group, randomised, open-label, adaptive clinical trial with an integrated feasibility phase. We will randomise adult, critically ill patients with sepsis to empirical treatment with meropenem or piperacillin/tazobactam for up to 30 days. The primary outcome is 30-day all-cause mortality. The secondary outcomes are serious adverse reactions within 30 days; isolation precautions due to resistant bacteria within 30 days; days alive without life support and days alive and out of hospital within 30 and 90 days; 90- and 180-day all-cause mortality and 180-day health-related quality of life. EMPRESS will use Bayesian statistical models with weak to somewhat sceptical neutral priors. Adaptive analyses will be conducted after follow-up of the primary outcome for the first 400 participants concludes and after every 300 subsequent participants, with adaptive stopping for superiority/inferiority and practical equivalence (absolute risk difference <2.5%-points) and response-adaptive randomisation. The expected sample sizes in scenarios with no, small or large differences are 5189, 5859 and 2570 participants, with maximum 14,000 participants and ≥99% probability of conclusiveness across all scenarios.

CONCLUSIONS

EMPRESS will compare the effects of empirical meropenem against piperacillin/tazobactam in adult, critically ill patients with sepsis. Due to the pragmatic, adaptive design with high probability of conclusiveness, the trial results are expected to directly inform clinical practice.

Empirical carbapenems or piperacillin/tazobactam for infections in intensive care: An international retrospective cohort study

BACKGROUND

Critically ill patients in intensive care units (ICU) are frequently administered broad-spectrum antibiotics (e.g., carbapenems or piperacillin/tazobactam) for suspected or confirmed infections. This retrospective cohort study aimed to describe the use of carbapenems and piperacillin/tazobactam in two international, prospectively collected datasets.

METHODS

We conducted a post hoc analysis of data from the "Adjunctive Glucocorticoid Therapy in Patients with Septic Shock" (ADRENAL) trial (n = 3713) and the "Antimicrobial de-escalation in the critically ill patient and assessment of clinical cure" (DIANA) study (n = 1488). The primary outcome was the proportion of patients receiving initial antibiotic treatment with carbapenems and piperacillin/tazobactam. Secondary outcomes included mortality, days alive and out of ICU and ICU length of stay at 28 days.

RESULTS

In the ADRENAL trial, carbapenems were used in 648 out of 3713 (17%), whereas piperacillin/tazobactam was used in 1804 out of 3713 (49%) participants. In the DIANA study, carbapenems were used in 380 out of 1480 (26%), while piperacillin/tazobactam was used in 433 out of 1488 (29%) participants. Mortality at 28 days was 23% for patients receiving carbapenems and 24% for those receiving piperacillin/tazobactam in ADRENAL and 23% and 19%, respectively, in DIANA. We noted variations in secondary outcomes; in DIANA, patients receiving carbapenems had a median of 13 days alive and out of ICU compared with 18 days among those receiving piperacillin/tazobactam. In ADRENAL, the median hospital length of stay was 27 days for patients receiving carbapenems and 21 days for those receiving piperacillin/tazobactam.

CONCLUSIONS

In this post hoc analysis of ICU patients with infections, we found widespread initial use of carbapenems and piperacillin/tazobactam in international ICUs, with the latter being more frequently used. Randomized clinical trials are needed to assess if the observed variations in outcomes may be drug-related effects or due to confounders.

Position Paper on the Reporting of Norepinephrine Formulations in Critical Care from the Society of Critical Care Medicine and European Society of Intensive Care Medicine Joint Task Force

OBJECTIVES

To provide guidance on the reporting of norepinephrine formulation labeling, reporting in publications, and use in clinical practice.

DESIGN

Review and task force position statements with necessary guidance.

SETTING

A series of group conference calls were conducted from August 2023 to October 2023, along with a review of the available evidence and scope of the problem.

SUBJECTS

A task force of multinational and multidisciplinary critical care experts assembled by the Society of Critical Care Medicine and the European Society of Intensive Care Medicine.

INTERVENTIONS

The implications of a variation in norepinephrine labeled as conjugated salt (i.e., bitartrate or tartrate) or base drug in terms of effective concentration of norepinephrine were examined, and guidance was provided.

MEASUREMENTS AND MAIN RESULTS

There were significant implications for clinical care, dose calculations for enrollment in clinical trials, and results of datasets reporting maximal norepinephrine equivalents. These differences were especially important in the setting of collaborative efforts across countries with reported differences.

CONCLUSIONS

A joint task force position statement was created outlining the scope of norepinephrine-dose formulation variations, and implications for research, patient safety, and clinical care. The task force advocated for a uniform norepinephrine-base formulation for global use, and offered advice aimed at appropriate stakeholders.

Sample size estimation in clinical trials using ventilator-free days as the primary outcome: a systematic review

BACKGROUND

Ventilator-free days (VFDs) are a composite endpoint increasingly used as the primary outcome in critical care trials. However, because of the skewed distribution and competitive risk between components, sample size estimation remains challenging. This systematic review was conducted to systematically assess whether the sample size was congruent, as calculated to evaluate VFDs in trials, with VFDs' distribution and the impact of alternative methods on sample size estimation.

METHODS

A systematic literature search was conducted within the PubMed and Embase databases for randomized clinical trials in adults with VFDs as the primary outcome until December 2021. We focused on peer-reviewed journals with 2021 impact factors greater than five. After reviewing definitions of VFDs, we extracted the sample size and methods used for its estimation. The data were collected by two independent investigators and recorded in a standardized, pilot-tested forms tool. Sample sizes were calculated using alternative statistical approaches, and risks of bias were assessed with the Cochrane risk-of-bias tool.

RESULTS

Of the 26 clinical trials included, 19 (73%) raised "some concerns" when assessing risks of bias. Twenty-four (92%) trials were two-arm superiority trials, and 23 (89%) were conducted at multiple sites. Almost all the trials (96%) were unable to consider the unique distribution of VFDs and death as a competitive risk. Moreover, significant heterogeneity was found in the definitions of VFDs, especially regarding varying start time and type of respiratory support. Methods for sample size estimation were also heterogeneous, and simple models, such as the Mann-Whitney-Wilcoxon rank-sum test, were used in 14 (54%) trials. Finally, the sample sizes calculated varied by a factor of 1.6 to 17.4.

CONCLUSIONS

A standardized definition and methodology for VFDs, including the use of a core outcome set, seems to be required. Indeed, this could facilitate the interpretation of findings in clinical trials, as well as their construction, especially the sample size estimation which is a trade-off between cost, ethics, and statistical power. Systematic review registration PROSPERO ID: CRD42021282304. Registered 15 December 2021 ( https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021282304 ).