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1.
Stat Methods Med Res ; 33(5): 765-793, 2024 May.
Article En | MEDLINE | ID: mdl-38625756

Many non-fatal events can be considered recurrent in that they can occur repeatedly over time, and some researchers may be interested in the trajectory and relative risk of non-fatal events. With the competing risk of death, the treatment effect on the mean number of recurrent events is non-identifiable since the observed mean is a function of both the recurrent event and terminal event processes. In this paper, we assume independence between the non-fatal and the terminal event process, conditional on the shared frailty, to fit a parametric model that recovers the trajectory of, and identifies the effect of treatment on, the non-fatal event process in the presence of the competing risk of death. Simulation studies are conducted to verify the reliability of our estimators. We illustrate the method and perform model diagnostics using the Carvedilol Prospective Randomized Cumulative Survival trial which involves heart-failure events.


Carvedilol , Models, Statistical , Humans , Carvedilol/therapeutic use , Prospective Studies , Randomized Controlled Trials as Topic , Heart Failure/mortality , Heart Failure/drug therapy , Survival Analysis , Recurrence , Carbazoles/therapeutic use , Frailty , Propanolamines/therapeutic use , Computer Simulation
2.
JACC Heart Fail ; 2024 Mar 23.
Article En | MEDLINE | ID: mdl-38530701

Clinical trials are vital for assessing therapeutic interventions. The associated data monitoring committees (DMCs) safeguard patient interests and enhance trial integrity, thus promoting timely, reliable evaluations of those interventions. We face an urgent need to recruit and train new DMC members. The Heart Failure Collaboratory (HFC), a multidisciplinary public-private consortium of academics, trialists, patients, industry representatives, and government agencies, is working to improve the clinical trial ecosystem. The HFC aims to improve clinical trial efficiency and quality by standardizing concepts, and to help meet the demand for experienced individuals on DMCs by creating a standardized approach to training new members. This paper discusses the HFC's training workshop, and an apprenticeship model for new DMC members. It describes opportunities and challenges DMCs face, along with common myths and best practices learned through previous experiences, with an emphasis on data confidentiality and need for quality independent statistical reporting groups.

3.
Injury ; 54(11): 111053, 2023 Nov.
Article En | MEDLINE | ID: mdl-37741705

OBJECTIVE: Patients with blunt thoracic trauma requiring surgical stabilization of rib fractures (SSRF) frequently experience severe pain. Further, a rising prevalence of opioid-tolerant patients sustain traumatic injuries. The optimal pain management adjunct for concurrent use with SSRF remains uncertain. This study compared outcomes in patients undergoing SSRF with concomitant cryonerve block (CryoNB) or ropivacaine 0.2% elastomeric infusion pump (EIP). METHODS: A single-center retrospective comparative analysis was performed at a level II trauma center. A query of our institution's trauma registry of consecutive patients undergoing SSRF from October 2017 to November 2020 with either intercostal CryoNB or ropivacaine 0.2% EIP was conducted. Opioid consumption in oral morphine equivalents (OME), patient-reported pain scores by numerical rating scale, and pulmonary function measured by incentive spirometry effort (mL) were collected at baseline and on postoperative days 1-3. Results were analyzed using a linear-mixed-effects model. Length of stay (LOS), complications, and hospital charges were assessed as secondary outcomes. RESULTS: Twenty-six patients meeting inclusion criteria were evaluated. Patient demographics, injury, and surgical variables were similar between groups. The estimated effect for patients treated with CryoNB (n = 14) compared to EIP (n = 12) demonstrated a 25% (estimated -1.37 OME, 95% CI, -2.411 to -0.335, p = 0.01) reduction in hospital opioid requirements, fewer discharge opioids (41.3 mg (37.5-45) versus 175 mg (150- 200), p = 0.03), 22% (estimated -1.506, 95% CI, -2.722 to -0.290, p = 0.02) reduction in pain scores, and shorter postoperative LOS (4 days (4-5) versus 6 days (5-9.5), p = 0.04). Pulmonary function (estimated -48.8 mL, 95% CI, -312.74 to 215.05, p = 0.71), total hospital costs (CryoNB: $90,224 ± 34,633; EIP: $131,498 ± 73,072, p = 0.07), and complications were no different between cohorts. CONCLUSION: The addition of intercostal CryoNB as an adjunct to multimodal pain management in trauma patients undergoing surgical fixation of rib fractures may be of benefit. Based on our early data, this technique appears to be promising in reducing opioid requirements and providing an extended duration of pain control without increased costs or complications.


Analgesia , Rib Fractures , Wounds, Nonpenetrating , Humans , Rib Fractures/complications , Retrospective Studies , Ropivacaine , Analgesics, Opioid , Pain , Wounds, Nonpenetrating/complications , Infusion Pumps , Length of Stay
4.
Proc Biol Sci ; 290(2005): 20231108, 2023 08 30.
Article En | MEDLINE | ID: mdl-37583325

Ecological interactions influence evolutionary dynamics by selecting upon fitness variation within species. Antagonistic interactions often promote genetic and species diversity, despite the inherently suppressive effect they can have on the species experiencing them. A central aim of evolutionary ecology is to understand how diversity is maintained in systems experiencing antagonism. In this review, we address how certain single-celled and dimorphic fungi have evolved allelopathic killer phenotypes that engage in antagonistic interactions. We discuss the evolutionary pathways to the production of lethal toxins, the functions of killer phenotypes and the consequences of competition for toxin producers, their competitors and toxin-encoding endosymbionts. Killer phenotypes are powerful models because many appear to have evolved independently, enabling across-phylogeny comparisons of the origins, functions and consequences of allelopathic antagonism. Killer phenotypes can eliminate host competitors and influence evolutionary dynamics, yet the evolutionary ecology of killer phenotypes remains largely unknown. We discuss what is known and what remains to be ascertained about killer phenotype ecology and evolution, while bringing their model system properties to the reader's attention.


Fungi , Models, Biological , Phylogeny , Phenotype , Ecology , Biological Evolution
5.
Langmuir ; 38(45): 13814-13821, 2022 Nov 15.
Article En | MEDLINE | ID: mdl-36326209

A rapid procedure for the functionalization of glassy carbon surfaces (GCSs) is disclosed. A three-step sequence of bromomethylation, azide displacement, and copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) allows ethynylated molecules to be attached covalently to the carbon surface through a methylene functional group. Redox-active ethynyl ferrocene and [RuII(Cl)(DMSO)(ethynyl-TPA)]1+ (DMSO = dimethylsulfoxide; TPA = tris(2-pyridylmethyl)amine) are attached with high coverages as assessed by cyclic voltammetry, and the elemental composition of the surface is confirmed by X-ray photoelectron spectroscopy. In less than 1 h, surface coverages of 1 × 1014 molecules/cm2 are possible that exhibit good durability in both acidic and basic media. Attached [RuII(Cl)(DMSO)(ethynyl-TPA)]1+ catalytically oxidizes alcohols, yet the currents and potentials are less impressive compared to an attachment without the intervening methylene group. The advantages of this covalent attachment procedure for GCSs are its short reaction times, mild reaction conditions, and the use of standard laboratory reagents and glassware, allowing for many types of ethynylated molecules to be attached rapidly to the surface.

6.
Prev Sci ; 23(8): 1343-1358, 2022 11.
Article En | MEDLINE | ID: mdl-36040619

Clearinghouses develop scientific criteria that they then use to vet existing research studies on a program to reach a verdict about how evidence-based it is. This verdict is then recorded on a website in hopes that stakeholders in science, public policy, the media, and even the general public, will consult it. This paper (1) compares the causal design and analysis preferences of 13 clearinghouses that assess the effectiveness of social and behavioral development programs, (2) estimates how consistently these clearinghouses rank the same program, and then (3) uses case studies to probe why their conclusions differ. Most clearinghouses place their highest value on randomized control trials, but they differ in how they treat program implementation, quasi-experiments, and whether their highest program ratings require effects of a given size that independently replicate or that temporally persist. Of the 2525 social and behavioral development programs sampled over clearinghouses, 82% (n = 2069) were rated by a single clearinghouse. Of the 297 programs rated by two clearinghouses, agreement about program effectiveness was obtained for about 55% (n = 164), but the clearinghouses agreed much more on program ineffectiveness than effectiveness. Most of the inconsistency is due to clearinghouses' differences in requiring independently replicated and/or temporally sustained effects. Without scientific consensus about matters like these, "evidence-based" will remain more of an aspiration than achievement in the social and behavioral sciences.


Achievement , Public Policy , Humans , Program Evaluation
7.
J Inorg Biochem ; 231: 111784, 2022 06.
Article En | MEDLINE | ID: mdl-35298933

A dearth of discrete immobilized metal complexes exist that electrocatalytically oxidize methanol. Reported here is the covalent immobilization of a tris(2-pyridylmethyl)amine ruthenium complex [RuII(Cl)(DMSO)(ethynyl-TPA)]+ (ethynyl-TPA = (5-ethynyl-2-pyridylmethyl)bis(2-pyridylmethyl)amine) to a glassy carbon (GC) electrode through a CuI catalyzed azide-alkyne cycloaddition (click) reaction between the ethynyl-TPA ligand and an azide derivatized carbon surface forming [RuII(Cl)(DMSO)(GC-click-TPA)]+. Following water substitution for DMSO and proton coupled electron transfer, [RuIV(O)(Cl)(GC-click-TPA)]+ electrooxidizes alcohols, including methanol, efficiently relative to other immobilized metal complexes. A primary kinetic isotope effect suggests rate-limiting Cα-H bond cleavage of benzyl alcohol. Approximately 40% of the [RuII(Cl)(DMSO)(GC-click-TPA)]+ undergoes the DMSO for water exchange to form an active oxidant, consistent with the 40% distribution of the more labile Cl-cis-amine isomer before immobilization. Using the benchmark of benzyl alcohol electrocatalytic oxidation, [RuIV(O)(Cl)(GC-click-TPA)]+ operates at ca. 250 mV lower overpotential, with a 15% increase in faradaic efficiency, and at least an order of magnitude increase in average turnover frequency (0.7 s-1 TOFavg) compared to the previously best immobilized discrete ruthenium complexes.


Coordination Complexes , Ruthenium , Amines , Azides , Benzyl Alcohols , Carbon , Coordination Complexes/chemistry , Dimethyl Sulfoxide , Methanol , Protons , Pyridines/chemistry , Ruthenium/chemistry , Water/chemistry
8.
Ecol Evol ; 12(1): e8558, 2022 Jan.
Article En | MEDLINE | ID: mdl-35127053

Upon starvation diploid cells of the facultative sexual yeast Saccharomyces cerevisiae undergo sporulation, forming four metabolically quiescent and robust haploid spores encased in a degradable ascus. All endosymbionts, whether they provide net benefits or costs, utilize host resources; in yeast, this should induce an earlier onset of sporulation. Here, we tested whether the presence of endosymbiotic dsRNA viruses (M satellite and L-A helper) correspond with higher sporulation rate of their host, S. cerevisiae. We find that S. cerevisiae hosting both the M and L-A viruses (so-called "killer yeasts") have significantly higher sporulation efficiency than those without. We also found that the removal of the M virus did not reduce sporulation frequency, possibly because the L-A virus still utilizes host resources with and without the M virus. Our findings indicate that either virulent resource use by endosymbionts induces sporulation, or that viruses are spread more frequently to sporulating strains. Further exploration is required to distinguish cause from effect.

9.
NEJM Evid ; 1(5): EVIDctw2100026, 2022 May.
Article En | MEDLINE | ID: mdl-38319224

Stopping Trials Early Due to HarmDSMBs protect clinical trial participants from harm. We describe two trials stopped for potential harm to enrollees: a DSMB recommended termination soon after enrollment began when data showed higher mortality in the experimental versus the control arm, and a trial with completed enrollment was stopped while participants were being followed and treated.

10.
Article En | MEDLINE | ID: mdl-34952844

Recent guidelines restricted aspirin (ASA) in primary prevention of cardiovascular disease (CVD) to patients <70 years old and more recent guidance to <60.In the most comprehensive prior meta-analysis, the Antithrombotic Trialists Collaboration reported a significant 12% reduction in CVD with similar benefit-risk ratios at older ages. Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, four trials were added to an updated meta-analysis.ASA produced a statistically significant 13% reduction in CVD with 95% confidence limits (0.83 to 0.92) with similar benefits at older ages in each of the trials.Primary care providers should make individual decisions whether to prescribe ASA based on benefit-risk ratio, not simply age. When the absolute risk of CVD is >10%, benefits of ASA will generally outweigh risks of significant bleeding. ASA should be considered only after implementation of therapeutic lifestyle changes and other drugs of proven benefit such as statins, which are, at the very least, additive to ASA. Our perspective is that individual clinical judgements by primary care providers about prescription of ASA in primary prevention of CVD should be based on our evidence-based solution of weighing all the absolute benefits and risks rather than age. This strategy would do far more good for far more patients as well as far more good than harm in both developed and developing countries. This new and novel strategy for primary care providers to consider in prescribing ASA in primary prevention of CVD is the same as the general approach suggested by Professor Geoffrey Rose decades ago.


Aspirin , Cardiovascular Diseases , Aged , Aspirin/adverse effects , Cardiovascular Diseases/prevention & control , Humans , Middle Aged , Odds Ratio , Primary Health Care , Risk Assessment
11.
Int J Cardiol ; 326: 131-138, 2021 03 01.
Article En | MEDLINE | ID: mdl-33091520

AIM: Heart failure following myocardial infarction (MI) is a potentially lethal problem with a staggering incidence. The CardiAMP Heart Failure trial represents the first attempt to personalize marrow-derived cell-based therapy to individuals with cell characteristics associated with beneficial responses in prior trials. Before the initiation of the randomized pivotal trial, an open-label "roll-in cohort" was completed to ensure the feasibility of the protocol's procedures. METHODS: Patients with chronic post-MI heart failure (NYHA class II-III) receiving stable, guideline-directed medical therapy with a left ventricular ejection fraction between 20 and 40% were eligible. Two weeks prior to treatment, a ~ 5 mL bone marrow aspiration was performed to examine "cell potency". On treatment day, a 60 mL bone marrow aspiration, bone marrow mononuclear cell (BM MNC) enrichment and transendocardial injection of 200 million BM MNC's was performed in a single, point of care encounter. Patients were then followed to assess clinical outcomes. RESULTS: The cell potency small volume bone marrow aspirate, the 60 mL bone marrow aspirate, and transendocardial injections were well tolerated in 10 patients enrolled. There were no serious adverse events related to bone marrow aspiration or cell delivery. Improvement in 6-min walk distance was observed at 6 months (+47.8 m, P = 0.01) and trended to improvement at 12 months (+46.4, P = 0.06). Similarly, trends to improved NYHA heart failure functional class, quality of life, left ventricular ejection fraction and recruitment of previously akinetic left ventricular wall segments were observed. CONCLUSION: All CardiAMP HF protocol procedures were feasible and well tolerated. Favorable functional, echo and quality of life trends suggest this approach may offer promise for patients with post MI heart failure. The randomized CardiAMP Heart Failure pivotal trial is underway to confirm the efficacy of this approach. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT02438306.


Heart Failure , Myocardial Ischemia , Bone Marrow , Bone Marrow Transplantation , Cell- and Tissue-Based Therapy , Feasibility Studies , Heart Failure/diagnosis , Heart Failure/therapy , Humans , Point-of-Care Systems , Quality of Life , Stroke Volume , Treatment Outcome , Ventricular Function, Left
12.
New Dir Child Adolesc Dev ; 2020(172): 135-149, 2020 Jul.
Article En | MEDLINE | ID: mdl-32960503

Although developmental science has always been evolving, these times of fast-paced and profound social and scientific changes easily lead to disorienting fragmentation rather than coherent scientific advances. What directions should developmental science pursue to meaningfully address real-world problems that impact human development throughout the lifespan? What conceptual or policy shifts are needed to steer the field in these directions? The present manifesto is proposed by a group of scholars from various disciplines and perspectives within developmental science to spark conversations and action plans in response to these questions. After highlighting four critical content domains that merit concentrated and often urgent research efforts, two issues regarding "how" we do developmental science and "what for" are outlined. This manifesto concludes with five proposals, calling for integrative, inclusive, transdisciplinary, transparent, and actionable developmental science. Specific recommendations, prospects, pitfalls, and challenges to reach this goal are discussed.


Biobehavioral Sciences , Psychology, Developmental , Biobehavioral Sciences/methods , Biobehavioral Sciences/standards , Biobehavioral Sciences/trends , Humans , Psychology, Developmental/methods , Psychology, Developmental/standards , Psychology, Developmental/trends
13.
J Ultrasound Med ; 39(10): 2033-2042, 2020 Oct.
Article En | MEDLINE | ID: mdl-32395885

OBJECTIVES: Traditional Doppler measures have been used to predict cognitive performance in patients with carotid atherosclerosis. Novel measures, such as carotid plaque strain indices (CPSIs), have shown associations with cognitive performance. We hypothesized that lower mean middle cerebral artery (MCA) velocities, higher bulb-internal carotid artery (ICA) velocities, the MCA pulsatility index (PI), and CPSIs would be associated with poorer cognitive performance in individuals with advanced atherosclerosis. METHODS: Neurocognitive testing, carotid ultrasound imaging, transcranial Doppler imaging, and carotid strain imaging were performed on 40 patients scheduled for carotid endarterectomy. Kendall tau correlations were used to examine relationships between cognitive tests and the surgical-side maximum peak systolic velocity (PSV; from the bulb, proximal, mid, or distal ICA), mean MCA velocity and PI, and maximum CPSIs (axial, lateral, and shear strain indices used to characterize plaque deformations with arterial pulsation). Cognitive measures included age-adjusted indices of verbal fluency, verbal and visual learning/memory, psychomotor speed, auditory attention/working memory, visuospatial construction, and mental flexibility. RESULTS: Participants had a median age of 71.0 (interquartile range, 9.75) years; 26 were male (65%), and 14 were female (35%). Traditional Doppler parameters, PSV, mean MCA velocity, and MCA PI did not predict cognitive performance (all P > .05). Maximum CPSIs were significantly associated with cognitive performance (P < .05). CONCLUSIONS: Traditional velocity measurements of the maximum bulb-ICA PSV, mean MCA velocity, and PI were not associated with cognitive performance in patients with advanced atherosclerotic disease; however, maximum CPSIs were associated with cognitive performance. These findings suggest that cognition may be associated with unstable plaque rather than blood flow.


Atherosclerosis , Carotid Stenosis , Blood Flow Velocity , Carotid Arteries/diagnostic imaging , Carotid Stenosis/complications , Carotid Stenosis/diagnostic imaging , Child , Cognition , Female , Humans , Male , Middle Cerebral Artery/diagnostic imaging , Ultrasonography, Doppler, Transcranial
14.
Ultrasound Med Biol ; 46(6): 1513-1532, 2020 06.
Article En | MEDLINE | ID: mdl-32291105

Quantitative ultrasound has been used to assess carotid plaque tissue composition. Here, we compute the attenuation coefficient (AC) in vivo with the optimum power spectral shift estimator (OPSSE) and reference phantom method (RPM), extract AC parameters and form parametric maps. Differences between OPSSE and RPM AC parameters are computed. Relationships between AC parameters, surgical scores and histopathology assessments are examined. Kendall's τ correlations between OPSSE AC and surgical scores are significant, including those between cholesterol and Standard Deviation (adjusted p = 0.038); thrombus and Minimum (adjusted p = 0.002), Maximum (adjusted p = 0.021) and Standard Deviation (adjusted p = 0.001); ulceration and Average (adjusted p = 0.033), Median (unadjusted p = 0.013), Maximum (unadjusted p = 0.039) and Mode (adjusted p = 0.009). The strongest correlations with histopathology are percentage cholesterol and Median OPSSE (unadjusted p = 0.007); percentage hemorrhage and Minimum OPSSE (adjusted p < 0.001); hemosiderin score and Median OPSSE (adjusted p = 0.010); and percentage calcium and Percentage Non-physical RPM Pixels (unadjusted p = 0.014). Kruskal-Wallis H and Dunn's post hoc tests have the ability to distinguish between groups (p < 0.05). Results suggest AC parameters may assist in vivo evaluation of carotid plaque vulnerability.


Carotid Artery Diseases/diagnostic imaging , Plaque, Atherosclerotic/diagnostic imaging , Ultrasonography , Aged , Calcium/analysis , Carotid Artery Diseases/pathology , Cholesterol/analysis , Female , Hemorrhage/pathology , Hemosiderin/analysis , Humans , Image Interpretation, Computer-Assisted , Male , Plaque, Atherosclerotic/chemistry , Plaque, Atherosclerotic/pathology , Thrombosis/pathology , Ulcer/pathology
15.
Psychol Methods ; 25(6): 726-746, 2020 Dec.
Article En | MEDLINE | ID: mdl-32162946

This study uses a within study comparison design (WSC) to conduct a novel test of how much causal bias results when researchers use a nonequivalent comparison group design type (NECGD) that combines: (a) a comparison group local to the treatment group; (b) a pretest measure of the study outcome; and (c) a rich set of 19 other multidimensional covariates. Most prior WSCs have dealt with the bias consequences of only 1 of these, revealing that each routinely reduces bias but does not necessarily eliminate it. Thus, a need exists to identify NECGDs that more robustly eliminate bias. This study is the first to examine how combining the 3 bias-control mechanisms above affects bias. The intervention we examine is a prekindergarten mathematics curriculum, for which a randomized control trial (RCT) produces a positive 1-year math effect. Final bias in the NECGD is assessed as the difference between its impact and that of the RCT when each design has the same intervention, outcome, and estimand. Over the many specifications we explore, NECGD bias is less than .10 standard deviations, indicating that minimal bias results when an NECGD combines all 3 design elements. The factorial design we use in this study also tests the bias associated with seven other NECGD types. Comparing the total pattern of results shows that the minimal bias when all 3 elements are combined is uniquely attributable to the locally chosen comparison group and not the availability of a pretest or other covariates. In actual research practice, it is impossible to predict in advance which design elements will affect bias by how much in any given application. So further research is needed to probe whether the simultaneous use of all three design elements achieves minimal bias dependably across diverse applications and not just in the preschool math context examined here. (PsycInfo Database Record (c) 2020 APA, all rights reserved).


Bias , Data Interpretation, Statistical , Outcome Assessment, Health Care , Psychology/methods , Research Design , Child, Preschool , Humans , Mathematics/education , Randomized Controlled Trials as Topic
17.
Mol Neurobiol ; 57(4): 2048-2071, 2020 Apr.
Article En | MEDLINE | ID: mdl-31919777

Folate supplementation in F0 mating rodents increases regeneration of injured spinal axons in vivo in 4 or more generations of progeny (F1-F4) in the absence of interval folate administration to the progeny. Transmission of the enhanced regeneration phenotype to untreated progeny parallels axonal growth in neuron culture after in vivo folate administration to the F0 ancestors alone, in correlation with differential patterns of genomic DNA methylation and RNA transcription in treated lineages. Enhanced axonal regeneration phenotypes are observed with diverse folate preparations and routes of administration, in outbred and inbred rodent strains, and in two rodent genera comprising rats and mice, and are reversed in F4-F5 progeny by pretreatment with DNA demethylating agents prior to phenotyping. Uniform transmission of the enhanced regeneration phenotype to progeny together with differential patterns of DNA methylation and RNA expression is consistent with a non-Mendelian mechanism. The capacity of an essential nutritional co-factor to induce a beneficial transgenerational phenotype in untreated offspring carries broad implications for the diagnosis, prevention, and treatment of inborn and acquired disorders.


Folic Acid/pharmacology , Nerve Regeneration/drug effects , Neurons/physiology , Administration, Oral , Animals , Axons/drug effects , Axons/pathology , Azacitidine/pharmacology , DNA Methylation/genetics , Female , Folic Acid/administration & dosage , Genome , Histone Deacetylase Inhibitors/pharmacology , Hydroxamic Acids/pharmacology , Injections, Intraperitoneal , Male , Neurons/drug effects , Phenotype , Rats, Sprague-Dawley , Transcription, Genetic/drug effects
18.
Stat Med ; 39(2): 192-204, 2020 01 30.
Article En | MEDLINE | ID: mdl-31726480

Despite our best efforts, missing outcomes are common in randomized controlled clinical trials. The National Research Council's Committee on National Statistics panel report titled The Prevention and Treatment of Missing Data in Clinical Trials noted that further research is required to assess the impact of missing data on the power of clinical trials and how to set useful target rates and acceptable rates of missing data in clinical trials. In this article, using binary responses for illustration, we establish that conclusions based on statistical analyses that include only complete cases can be seriously misleading, and that the adverse impact of missing data grows not only with increasing rates of missingness but also with increasing sample size. We illustrate how principled sensitivity analysis can be used to assess the robustness of the conclusions. Finally, we illustrate how sample sizes can be adjusted to account for expected rates of missingness. We find that when sensitivity analyses are considered as part of the primary analysis, the required adjustments to the sample size are dramatically larger than those that are traditionally used. Furthermore, in some cases, especially in large trials with small target effect sizes, it is impossible to achieve the desired power.


Randomized Controlled Trials as Topic/methods , Sample Size , Bias , Computer Simulation , Data Interpretation, Statistical , Humans , Likelihood Functions , Models, Statistical
19.
New Dir Child Adolesc Dev ; 2019(167): 17-37, 2019 Sep.
Article En | MEDLINE | ID: mdl-31507056

This chapter highlights the key assumptions underlying Randomized Control Trials (RCTs) and illustrates them with regard to the practice of RCTs in the realm of child and adolescent development. Given the prominence of RCTs in policy research, we analyze the possible ways in which these assumptions might not be met by single randomized experiments, thereby making it difficult to draw valid causal inference from single studies. We frame this discussion within the categories of internal validity, statistical conclusion validity, construct validity, and external validity and address the debate about the "gold standard" status accorded to RCTs.


Adolescent Development , Child Development , Randomized Controlled Trials as Topic/standards , Research Design/standards , Adolescent , Child , Humans , Reproducibility of Results
20.
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