Beyond randomized, controlled trials

Causal pathways in preeclampsia: a Mendelian randomization study in European populations

Purpose

Our study utilizes Mendelian Randomization (MR) to explore the causal relationships between a range of risk factors and preeclampsia, a major contributor to maternal and perinatal morbidity and mortality.

Methods

Employing the Inverse Variance Weighting (IVW) approach, we conducted a comprehensive multi-exposure MR study analyzing genetic variants linked to 25 risk factors including metabolic disorders, circulating lipid levels, immune and inflammatory responses, lifestyle choices, and bone metabolism. We applied rigorous statistical techniques such as sensitivity analyses, Cochran's Q test, MR Egger regression, funnel plots, and leave-one-out sensitivity analysis to address potential biases like pleiotropy and population stratification.

Results

Our analysis included 267,242 individuals, focusing on European ancestries and involving 2,355 patients with preeclampsia. We identified strong genetic associations linking increased preeclampsia risk with factors such as hyperthyroidism, BMI, type 2 diabetes, and elevated serum uric acid levels. Conversely, no significant causal links were found with gestational diabetes, total cholesterol, sleep duration, and bone mineral density, suggesting areas for further investigation. A notable finding was the causal relationship between systemic lupus erythematosus and increased preeclampsia risk, highlighting the significant role of immune and inflammatory responses.

Conclusion

This extensive MR study sheds light on the complex etiology of preeclampsia, underscoring the causal impact of specific metabolic, lipid, immune, lifestyle, and bone metabolism factors. Our findings advocate for a multidimensional approach to better understand and manage preeclampsia, paving the way for future research to develop targeted preventive and therapeutic strategies.

Did studies on HFOV fail to improve ARDS survival because they did not decrease VILI? On the potential validity of a physiological concept enounced several decades ago

High frequency oscillatory ventilation (HFOV) has been the subject of extensive physiological research for 30 years and even more so of an intense debate on its potential usefulness in the treatment of acute respiratory distress syndrome (ARDS). This technique has been enthusiastically promoted by some teams until two high-quality randomized clinical trials in adults with ARDS showed that HFOV did not decrease and might have even increased mortality. As a consequence of these results, physiological concepts such as atelectrauma and biotrauma on which ARDS management with HFOV were based should be reexamined. In contrast, the concept of volutrauma, i.e., end-inspiratory overdistension, as the cause for ventilator-induced lung injury might help explain excess mortality during mechanical ventilation of ARDS when inspiratory volumes are too high. This is what might have happened during one of the recent studies on HFOV. Failure of this complex technique must be put in perspective with the dramatic improvement of ARDS prognosis with very simple interventions such as tidal volume reduction, early pharmacological paralysis, and prone positioning which all limited end-inspiratory volume.

When do confounding by indication and inadequate risk adjustment bias critical care studies? A simulation study

Introduction

In critical care observational studies, when clinicians administer different treatments to sicker patients, any treatment comparisons will be confounded by differences in severity of illness between patients. We sought to investigate the extent that observational studies assessing treatments are at risk of incorrectly concluding such treatments are ineffective or even harmful due to inadequate risk adjustment.

Methods

We performed Monte Carlo simulations of observational studies evaluating the effect of a hypothetical treatment on mortality in critically ill patients. We set the treatment to have either no association with mortality or to have a truly beneficial effect, but more often administered to sicker patients. We varied the strength of the treatment’s true effect, strength of confounding, study size, patient population, and accuracy of the severity of illness risk-adjustment (area under the receiver operator characteristics curve, AUROC). We measured rates in which studies made inaccurate conclusions about the treatment’s true effect due to confounding, and the measured odds ratios for mortality for such false associations.

Results

Simulated observational studies employing adequate risk-adjustment were generally able to measure a treatment’s true effect. As risk-adjustment worsened, rates of studies incorrectly concluding the treatment provided no benefit or harm increased, especially when sample size was large (n = 10,000). Even in scenarios of only low confounding, studies using the lower accuracy risk-adjustors (AUROC < 0.66) falsely concluded that a beneficial treatment was harmful. Measured odds ratios for mortality of 1.4 or higher were possible when the treatment’s true beneficial effect was an odds ratio for mortality of 0.6 or 0.8.

Conclusions

Large observational studies confounded by severity of illness have a high likelihood of obtaining incorrect results even after employing conventionally “acceptable” levels of risk-adjustment, with large effect sizes that may be construed as true associations. Reporting the AUROC of the risk-adjustment used in the analysis may facilitate an evaluation of a study’s risk for confounding.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0923-8) contains supplementary material, which is available to authorized users.

Outcomes and statistical power in adult critical care randomized trials

RATIONALE

Intensive care unit (ICU)-based randomized clinical trials (RCTs) among adult critically ill patients commonly fail to detect treatment benefits.

OBJECTIVES

Appraise the rates of success, outcomes used, statistical power, and design characteristics of published trials.

METHODS

One hundred forty-six ICU-based RCTs of diagnostic, therapeutic, or process/systems interventions published from January 2007 to May 2013 in 16 high-impact general or critical care journals were studied.

MEASUREMENT AND MAIN RESULTS

Of 146 RCTs, 54 (37%) were positive (i.e., the a priori hypothesis was found to be statistically significant). The most common primary outcomes were mortality (n = 40 trials), infection-related outcomes (n = 33), and ventilation-related outcomes (n = 30), with positive results found in 10, 58, and 43%, respectively. Statistical power was discussed in 135 RCTs (92%); 92 cited a rationale for their power parameters. Twenty trials failed to achieve at least 95% of their reported target sample size, including 11 that were stopped early due to insufficient accrual/logistical issues. Of 34 superiority RCTs comparing mortality between treatment arms, 13 (38%) accrued a sample size large enough to find an absolute mortality reduction of 10% or less. In 22 of these trials the observed control-arm mortality rate differed from the predicted rate by at least 7.5%.

CONCLUSIONS

ICU-based RCTs are commonly negative and powered to identify what appear to be unrealistic treatment effects, particularly when using mortality as the primary outcome. Additional concerns include a lack of standardized methods for assessing common outcomes, unclear justifications for statistical power calculations, insufficient patient accrual, and incorrect predictions of baseline event rates.

Early revascularization is beneficial across all ages and a wide spectrum of cardiogenic shock severity: A pooled analysis of trials

BACKGROUND

A pooled analysis in cardiogenic shock due to acute coronary syndromes is desirable to assess the effect of early revascularization (ERV) across all ages and a wide spectrum of disease severity.

METHODS

Only two randomized controlled trials (RCT), i.e. SMASH and SHOCK, met the inclusion criteria and were combined for a pooled analysis using individual patient data (n = 348).

RESULTS

SMASH patients (n = 54, 16%) had more severe disease than SHOCK patients (n = 294, 84%). After adjustment for age, anoxic brain damage, non-inferior myocardial infarction, prior coronary artery bypass graft surgery, renal failure, systolic blood pressure, and selection for coronary angiography, one-year mortality was similar (relative risk SHOCK versus SMASH 0.87, 95% CI: 0.61-1.25). Relative risk of one-year death for ERV versus initial medical stabilization was 0.82 (95% CI: 0.70-0.96). There was no significant difference in the treatment effect by age (≤75 years relative risk at one year 0.79, 95% CI: 0.63-0.99; > 75 years relative risk at one year 0.93, 95% CI: 0.56-1.53; interaction P = 0.10).

CONCLUSIONS

Only two RCT have been published emphasizing the difficulty of enrolling critically ill patients. Despite large differences in shock severity, ERV benefit is similar across all ages and not significantly different for the elderly.

Positive pressure therapy: a perspective on evidence-based outcomes and methods of application

The sleep medicine community has increasingly recognized the necessity that clinical care be based on high-quality levels of evidence. Although research supports a favorable influence of positive airway pressure (PAP) therapy on risk for significant adverse outcomes in patients with severe obstructive sleep apnea-hypopnea (OSAH), well-designed trials are still required to elucidate the effect of PAP on health, quality of life, and economic risks in patients with milder OSAH. Similarly, although there is strong evidence supporting various PAP titration strategies and PAP modalities in patients with severe OSAH without significant medical and psychiatric comorbidities, there is insufficient high-level evidence assessing and comparing the clinical efficacy and health care cost implications of various titration paradigms and various PAP modalities in individuals with milder OSAH and those with comorbid conditions. For ethical and other reasons, it may not be possible to apply a randomized controlled design to address all questions. However, whichever design is employed, it must be rigorously developed with attention to all potential confounders with adequate power to provide compelling, high-quality evidence.

Have changes in ventilation practice improved outcome in children with acute lung injury?

OBJECTIVES

To describe the changes that have occurred in mechanical ventilation in children with acute lung injury in our institution over the last 10-15 yrs and to examine the impact of these changes, in particular of the delivered tidal volume on mortality.

DESIGN

Retrospective study.

SETTING

University-affiliated children's hospital.

PATIENTS

The management of mechanical ventilation between 1988 and 1992 (past group, n = 79) was compared with the management between 2000 and 2004 (recent group, n = 85).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The past group patients were ventilated with a significantly higher mean tidal volume (10.2 +/- 1.7 vs. 8.1 +/- 1.4 mL.kg actual body weight, p < .001), lower levels of positive end-expiratory pressure (6.1 +/- 2.7 vs. 7.1 +/- 2.4 cm H2O, p = .007), and higher mean peak inspiratory pressure (31.5 +/- 7.3 vs. 27.8 +/- 4.2 cm H2O, p < .001) than the recent group patients. The recent group had a lower mortality (21% vs. 35%, p = .04) and a greater number of ventilator-free days (16.0 +/- 9.0 vs. 12.6 +/- 9.9 days, p = .03) than the past group. A higher tidal volume was independently associated with increased mortality (odds ratio 1.59; 95% confidence interval 1.20, 2.10, p < .001) and reduction in ventilation-free days (95% confidence interval -1.24, -0.77, p < .001).

CONCLUSIONS

The changes in the clinical practice of mechanical ventilation in children in our institution reflect those reported for adults. In our experience, mortality among children with acute lung injury was reduced by 40%, and tidal volume was independently associated with reduced mortality and an increase in ventilation-free days.