Confidence intervals for an effect size measure based on the Mann–Whitney statistic. Part 1: general issues and tail-area-based methods

Systematic review and meta-analysis of the prognostic value of 18F-Fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) and/or computed tomography (CT)-based radiomics in head and neck cancer

AIM

Radiomics involves the extraction of quantitative data from medical images to facilitate the diagnosis, prognosis, and staging of tumors. This study provides a comprehensive overview of the efficacy of radiomics in prognostic applications for head and neck cancer (HNC) in recent years. It undertakes a systematic review of prognostic models specific to HNC and conducts a meta-analysis to evaluate their predictive performance.

MATERIALS AND METHODS

This study adhered rigorously to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for literature searches. The literature databases, including PubMed, Embase, Cochrane, and Scopus were systematically searched individually. The methodological quality of the incorporated studies underwent assessment utilizing the radiomics quality score (RQS) tool. A random-effects meta-analysis employing the Harrell concordance index (C-index) was conducted to evaluate the performance of all radiomics models.

RESULTS

Among the 388 studies retrieved, 24 studies encompassing a total of 6,978 cases were incorporated into the systematic review. Furthermore, eight studies, focusing on overall survival as an endpoint, were included in the meta-analysis. The meta-analysis revealed that the estimated random effect of the C-index for all studies utilizing radiomics alone was 0.77 (0.71-0.82), with a substantial degree of heterogeneity indicated by an I2 of 80.17%.

CONCLUSIONS

Based on this review, prognostic modeling utilizing radiomics has demonstrated enhanced efficacy for head and neck cancers; however, there remains room for improvement in this approach. In the future, advancements are warranted in the integration of clinical parameters and multimodal features, balancing multicenter data, as well as in feature screening and model construction within this field.

Murdering the person closest to you: Similarities and differences between intimate partner sexual homicide and non-intimate partner sexual homicide

Sexual homicides (SHs) demand nuanced research for effective prevention, treatment, risk assessment and theoretical insights. Intimate-partner sexual homicides (IPSHs), comprising approximately 20% of SHs, have received limited attention. This study compares IPSHs (n = 56) and non-intimate partner sexual homicides (NIPSHs) (n = 236) in Australia and New Zealand by investigating offender, victim, and crime-scene characteristics. While IPSH perpetrators were typically older, separated, and had prior domestic violence convictions, victims were more often non-white with histories of domestic violence and substance use. Although crime-scene locations and post-offence behaviours differed, similar crime scene behaviours were displayed across offender groups, which seemed to be routed in different underlying motives. Whereas drivers of IPSH commonly were grievance and anger, associated with offences occurring after arguments, drivers for NIPSH were more often sexual deviance and sadism. Overall, IPSH encompasses aspects of domestic violence, homicide, and sexual violence, distinguishing it from SH.

An Updated Guide to Robust Statistical Methods in Neuroscience

There is a vast array of new and improved methods for comparing groups and studying associations that offer the potential for substantially increasing power, providing improved control over the probability of false positives, and yielding a deeper and more nuanced understanding of data. These new techniques effectively deal with four insights into when and why conventional methods can be unsatisfactory. But for the non-statistician, this vast array of techniques for comparing groups and studying associations can seem daunting. This article briefly reviews when and why conventional methods can have relatively low power and yield misleading results. The main goal is to suggest guidelines regarding the use of modern techniques that improve upon classic approaches such as Pearson's correlation, ordinary linear regression, ANOVA, and ANCOVA. This updated version includes recent advances dealing with effect sizes, including situations where there is a covariate. The R code, figures, and accompanying notebooks have been updated as well. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC.

Parametric and nonparametric methods for confidence intervals and sample size planning for win probability in parallel‐group randomized trials with Likert item and Likert scale data

Data on the Likert scale are ubiquitous in medical research, including randomized trials. Statistical analysis of such data may be conducted using the means of raw scores or the rank information of the scores. In the context of parallel-group randomized trials, we quantify treatment effects by the probability that a subject in the treatment group has a better score than (or a win over) a subject in the control group. Asymptotic parametric and nonparametric confidence intervals for this win probability and associated sample size formulas are derived for studies with only follow-up scores, and those with both baseline and follow-up measurements. We assessed the performance of both the parametric and nonparametric approaches using simulation studies based on real studies with Likert item and Likert scale data. The simulation results demonstrate that even without baseline adjustment, the parametric methods did not perform well, in terms of bias, interval coverage percentage, balance of tail error, and assurance of achieving a pre-specified precision. In contrast, the nonparametric approach performed very well for both the unadjusted and adjusted win probability. We illustrate the methods with two examples: one using Likert item data and the other using Like scale data. We conclude that non-parametric methods are preferable for two-group randomization trials with Likert data. Illustrative SAS code for the nonparametric approach using existing procedures is provided.

Pelvis and Trunk Energy Flow in Collegiate Softball Pitchers With and Without Upper Extremity Pain

BACKGROUND

The softball pitch is a full-body motion, where efficient proximal to distal energy flow through the kinetic chain is said to reduce stress at the upper extremity. Although altered trunk kinematic parameters are associated with upper extremity pain in softball pitchers, further research is needed to determine whether differences exist in proximal energy flow between softball pitchers with and without pain.

HYPOTHESIS/PURPOSE

To examine pelvis and trunk energy flow during the acceleration phase of the pitch in collegiate softball pitchers with and without upper extremity pain. It was hypothesized that those with upper extremity pain would have less energy flowing into the proximal ends of the pelvis and trunk as well as less energy flowing out of the distal ends of the pelvis and trunk during the acceleration phase when compared with pitchers who did not have upper extremity pain.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 54 female National Collegiate Athletic Association Division I softball pitchers (age, 20.2 ± 2.0 years; height, 173.5 ± 6.9 cm; weight, 78.5 ± 11.5 kg) were assigned to pain (n = 17) and pain-free (n = 38) groups. Participants pitched 3 maximal effort rise-balls for a strike, and the average of the 3 trials was used for analysis. Kinematic data were collected at 100 Hz using an electromagnetic tracking system. A segment power analysis was performed to quantify energy flow for the pelvis and trunk. The Mann-Whitney U test was used to compare pelvis and trunk energy flow during the acceleration phase of the pitch as well as pitch velocity between collegiate softball pitchers with and without upper extremity pain.

RESULTS

No significant differences were found between pelvis and trunk energy flow during the acceleration phase or pitch velocity between collegiate softball pitchers with and without upper extremity pain (all P values >.057).

CONCLUSION

Previous research determined that kinematic parameters differ between collegiate pitchers with and without upper extremity pain. However, the current study found no difference in pelvis and trunk energy flow or pitch velocity. Although altered kinematics in collegiate pitchers with upper extremity pain may serve as compensation patterns to maintain pitch velocity and proximal energy flow, future research is needed to confirm this postulation.

CLINICAL RELEVANCE

The lack of energy flow differences between upper extremity pain groups suggests that pitchers may adapt their biomechanics to maintain trunk and pelvis energy flow patterns. Coaches, athletes, and clinicians should know that movement adaptations can allow for maintained performance levels but may result in the presence of pain that may manifest in other deleterious and injury-susceptible biomechanics.

Association of Preexisting Mental Health Conditions With Increased Initial Symptom Count and Severity Score on SCAT5 When Assessing Concussion

Background:

Mental health conditions, such as depression, anxiety, and learning disabilities, are associated with symptoms that can overlap with those seen in persons with concussion. While concussion screening tools such as the Sport Concussion Assessment Tool–5th Edition (SCAT5) quantify the number of symptoms and symptom severity, it is not known whether these outcomes differ among individuals with concurrent mental health conditions compared with those without them.

Purpose:

To determine whether, during initial concussion assessment, individuals with a self-reported mental health condition have a significantly different number of self-reported concussion symptoms or symptom severity compared with those without a self-reported mental health condition (controls).

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A retrospective chart review was performed on consecutive patients aged ≥13 years who underwent post-concussion assessment at the Fowler Kennedy Sport Medicine Clinic between May 2018 and March 2020 (N = 765). Most participants did not self-report a mental health condition (n = 606; 79.2%). Participants with a self-reported mental health condition (n = 159) were classified as having a learning disability (n = 14; 8.8%), anxiety (n = 62; 39.0%), depression (n = 20; 12.6%), or multiple conditions (≥2 conditions: n = 63; 39.6%). Each participant with a mental health condition was matched with 2 control participants (overall pool, n = 318) based on age, sex, student status, and sport-related risk. Mann-Whitney U tests were used to determine the statistical significance of differences between each subgroup and their matched controls for the self-reported number of concussion symptoms and symptom severity as measured using the SCAT5.

Results:

The anxiety and multiple-conditions subgroups had a significantly greater number of reported symptoms than their corresponding control subgroups (median, 17 vs 15 [P = .004] and 18 vs 14.5 [P < .001], respectively). Additionally, the SCAT5 symptom severity score was significantly greater in the anxiety and multiple-conditions subgroups than their corresponding controls (median, 49 vs 34.5 [P = .018] and 62 vs 32 [P < .001], respectively).

Conclusion:

During initial concussion assessment, both the number of concussion-related symptoms and the symptom severity were greater in study participants with anxiety and multiple mental health conditions than participants without these conditions.

A Social-Cognitive Investigation of Young Adults Who Abuse Their Parents

Within the past decade, there has been an increase in research focusing on young people who abuse their parents. However, most research has narrowly focused on adolescent children, neglecting to investigate the nature, pattern, and factors related to child-to-parent abuse perpetrated by young adults. This article integrated two complementary social-cognitive theories of aggression to explore factors associated with perpetration of child-to-parent abuse among university students (N = 435, aged 18-25 years). Participants completed the Abusive Behavior by Children-Indices, a self-report measure that was designed to differentiate abusive and normative child-to-parent behavior. The results highlight that abuse is not limited to adolescent children, as one in seven young adults were categorized as abusive toward a parent over the previous 12 months. Sons were more likely than daughters to report abusing their parents. Specifically, sons disclosed greater rates of father abuse than daughters, but similar rates of mother abuse. Hierarchical logistic regression found that exposure to marital violence, parent-to-child aggression, trait anger, and aggressive scripts were significant predictors of both mother and father abuse. However, other factors related to abuse differed according to which parent was the target of abuse. For instance, male sex was a significant predictor of father abuse, whereas rumination and impulsive emotional regulation were significant predictors of mother abuse. Overall, father abuse was better explained by the model than mother abuse. The results suggest that although factors related to general aggressive behavior may be good predictors for father abuse, additional factors may be needed to explain mother abuse.

Food and alcohol disturbance by athlete status: the roles of drive for thinness, drive for muscularity, and sex

OBJECTIVE

This study investigated the association between self-identified athlete status and Food and Alcohol Disturbance (FAD) behaviors, and whether this association was moderated by drives for thinness or muscularity, and sex.

PARTICIPANTS

575 individuals (77.6% female, 40.0% identifying as athletes) recruited from a large southeastern university.

METHODS

Participants completed online measures of athletic identity, drives for muscularity and thinness, FAD behaviors, and demographic variables.

RESULTS

Compared to non-athletes, male athletes with higher drive for muscularity endorsed more alcohol effects behaviors; female athletes endorsed the inverse relationship. Higher drive for thinness was associated with more diet and exercise behaviors among all participants, and extreme weight control behaviors among athletes.

CONCLUSIONS

Athlete status moderated the associations between drives for thinness/muscularity and FAD Alcohol Effects and Extreme Weight Control Behaviors. Regardless of athlete status, college students with higher drive for thinness are at risk for engaging in more FAD Diet & Exercise behaviors.

Normative Reference of the Single Leg, Medial Countermovement Jump in Adolescent Youth Ice Hockey Players

Functional performance tests provide quantitative information on specialized sport movements and are important for documenting training and fatigue. The single leg, medial countermovement jump provides objective measures of frontal plane force, velocity and power, and is relevant for ice hockey players given the similar lateral movement to ice skating. This study measured normative single leg, medial countermovement jump parameters (i.e., vertical and lateral maximum force, average concentric power and average concentric power during the last 100 ms) amongst male youth ice hockey players and assessed interlimb asymmetry in these healthy athletes. Ninety-one elite youth players participated in the study. Participants completed three right and three left jumps. Non-parametric tests were performed to evaluate between-jump and between-group comparisons. Many differences in jump force and power parameters were observed between the 10U/11U and 12U/13U age groups, and the 12U/13U and 14U/15U age groups, but differences were not as consistent between older or younger players. The average asymmetry index for each age group was less than 15% for force parameters, while the power parameters had larger asymmetry indices (between 9% and 22%). Our results provide age-specific reference values and asymmetry indices for male elite youth ice hockey players aged 10-18 years performing the single leg, medial countermovement jump.

Glycinergic axonal inhibition subserves acute spatial sensitivity to sudden increases in sound intensity

Locomotion generates adventitious sounds which enable detection and localization of predators and prey. Such sounds contain brisk changes or transients in amplitude. We investigated the hypothesis that ill-understood temporal specializations in binaural circuits subserve lateralization of such sound transients, based on different time of arrival at the ears (interaural time differences, ITDs). We find that Lateral Superior Olive (LSO) neurons show exquisite ITD-sensitivity, reflecting extreme precision and reliability of excitatory and inhibitory postsynaptic potentials, in contrast to Medial Superior Olive neurons, traditionally viewed as the ultimate ITD-detectors. In vivo, inhibition blocks LSO excitation over an extremely short window, which, in vitro, required synaptically evoked inhibition. Light and electron microscopy revealed inhibitory synapses on the axon initial segment as the structural basis of this observation. These results reveal a neural vetoing mechanism with extreme temporal and spatial precision and establish the LSO as the primary nucleus for binaural processing of sound transients.

Confidence interval estimation for treatment effects in cluster randomization trials based on ranks

A cluster randomization trial is one in which clusters of individuals are randomly allocated to different intervention arms. This design has become the standard for the evaluation of health care and educational strategies. To assess treatment effect, many cluster randomization trials involve outcomes that are lack meaningful units, making interpretation difficult. This difficulty may be dealt with by estimating the Mann-Whitney probability, which quantifies the probability that a typical response from one treatment arm is larger (or smaller) than a typical response from the other arm. In this work, we propose procedures for estimating this probability in cluster randomization trials. Primary emphasis is given to confidence interval estimation in trials with a small number of large clusters. The essence of the procedures is to obtain placement values based on overall ranks and arm-specific ranks prior to application of the ratio estimator, cluster-size-weighted means and mixed models for adjusting clustering effects. Nine confidence intervals were developed by applying three interval methods each based on the three variance estimators. The proposed methods can be applied to studies with binary, ordinal or continuous outcomes without making parametric assumptions. Simulation results demonstrated that the three variance estimators performed equally well, with the confidence interval procedures based on logit and inverse hyperbolic sine transformations performing better in terms of coverage and average interval width, even when the numbers of clusters are as small as 3 to 5 clusters per arm. The methods are illustrated using data from three published cluster randomization trials with SAS code provided.

Assessing the Link Between Intimate Partner Violence and Postrelationship Stalking: A Gender-Inclusive Study

The link between intimate partner violence (IPV) during a relationship and postrelationship stalking (PRS) is poorly understood. The vast majority of relevant studies focus either on male perpetration or female victimization and use highly selective samples. The current study aimed to illuminate the link between IPV and PRS perpetration and victimization, respectively. To this end, heterosexual male and female university students (n = 422) retrospectively self-reported on IPV during their most conflicted relationship and a wide range of pursuit behavior after the dissolution of this romantic relationship. Using empirical criteria, participants were classified as stalkers or nonstalkers based on their responses. A relationship between male-perpetrated IPV and PRS perpetration was detected. There was no systematic relationship between IPV and PRS perpetration in women. In contrast, there was a link between IPV and stalking victimization that followed a similar, linear trend in both male and female victims. A larger proportion of participants were classified as stalking victims as IPV severity increased. Implications for research (e.g., the importance of gender-inclusive studies), clinical practice (e.g., how to prevent stalking after an abusive relationship), and future directions (e.g., the need for prospective studies using more diverse samples) are discussed.

ROC curves for clinical prediction models part 1. ROC plots showed no added value above the AUC when evaluating the performance of clinical prediction models

OBJECTIVES

Receiver operating characteristic (ROC) curves show how well a risk prediction model discriminates between patients with and without a condition. We aim to investigate how ROC curves are presented in the literature and discuss and illustrate their potential limitations.

STUDY DESIGN AND SETTING

We conducted a pragmatic literature review of contemporary publications that externally validated clinical prediction models. We illustrated limitations of ROC curves using a testicular cancer case study and simulated data.

RESULTS

Of 86 identified prediction modeling studies, 52 (60%) presented ROC curves without thresholds and one (1%) presented an ROC curve with only a few thresholds. We illustrate that ROC curves in their standard form withhold threshold information have an unstable shape even for the same area under the curve (AUC) and are problematic for comparing model performance conditional on threshold. We compare ROC curves with classification plots, which show sensitivity and specificity conditional on risk thresholds.

CONCLUSION

ROC curves do not offer more information than the AUC to indicate discriminative ability. To assess the model's performance for decision-making, results should be provided conditional on risk thresholds. Therefore, if discriminatory ability must be visualized, classification plots are attractive.

Sharp bounds on the relative treatment effect for ordinal outcomes

For ordinal outcomes, the average treatment effect is often ill-defined and hard to interpret. Echoing Agresti and Kateri, we argue that the relative treatment effect can be a useful measure, especially for ordinal outcomes, which is defined as γ = pr { Y i ( 1 ) > Y i ( 0 ) } - pr { Y i ( 1 ) < Y i ( 0 ) } , with Y i ( 1 ) and Y i ( 0 ) being the potential outcomes of unit i under treatment and control, respectively. Given the marginal distributions of the potential outcomes, we derive the sharp bounds on γ , which are identifiable parameters based on the observed data. Agresti and Kateri focused on modeling strategies under the assumption of independent potential outcomes, but we allow for arbitrary dependence.

Relative difference among 27 functional measures in patients with knee osteoarthritis: an exploratory cross-sectional case-control study

Background

To raise the effectiveness of interventions, clinicians should evaluate important biopsychosocial aspects of the patient’s situation. There is limited knowledge of which factors according to the International Classification of Function, Disability, and Health (ICF) are most deviant between patients with knee osteoarthritis (KOA) and healthy individuals. To assist in measures’ selection, we aimed to quantify the differences between patients with KOA and healthy controls on various measures across the ICF dimensions of body function, activity, and participation.

Methods

We performed an exploratory cross-sectional case-control study. In total, 28 patients with mild-to-moderate KOA (mean age 61 years, 64% women) referred by general physicians to a hospital’s osteoarthritis-school, and 31 healthy participants (mean age 55 years, 52% women), volunteered. We compared between-group differences on 27 physical and self-reported measures derived from treatment guidelines, trial recommendations, and trial/outcome reviews. Independent t-test, Chi-square, and Mann-Whitney U test evaluated the significance for continuous parametric, dichotomous, and ordinal data, respectively. For parametric data, effect sizes were calculated as Cohen’s d. For non-parametric data, ds were estimated by p-values and sample sizes according to statistical formulas. Finally, all ds were ranked and interpreted after Hopkins’ scale. An age-adjusted sensitivity-analysis on parametric data validated those conclusions.

Results

Very large differences between patients and controls were found on the Pain numeric rating scale¹, the Knee Injury and Osteoarthritis Scale (KOOS, all subscales)², as well as the Örebro Musculoskeletal psychosocial scale³ (P < 0.0001). Large differences were found on the Timed 10-steps-up-and-down stair climb test⁴ and Accelerometer registered vigorous-intensity physical activity in daily life⁵ (P < 0.001). Respectively, these measures clustered on ICF as follows: ¹body function, ²all three ICF-dimensions, ³body function and participation, ⁴activity, and ⁵participation.

Limitations

The limited sample excluded elderly patients with severe obesity.

Conclusions

Very large differences across all ICF dimensions were indicated for the KOOS and Örebro questionnaires together for patients aged 45–70 with KOA. Clinicians are suggested to use them as means of selecting supplementary measures with appropriate discriminative characteristics and clear links to effective therapy. Confirmative studies are needed to further validate these explorative and partly age-unadjusted conclusions.

Exploratory comparison of auditory verbal hallucinations and other psychotic symptoms among youth with borderline personality disorder or schizophrenia spectrum disorder

OBJECTIVE

This study explored phenomenological aspects of auditory verbal hallucinations (AVH) and other psychotic symptoms among youth with borderline personality disorder (BPD).

METHODS

Sixty-eight outpatients, aged 15 to 25 years, were categorized into three groups according to their primary Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) diagnosis and AVH symptom profile; BPD + AVH (n = 23), schizophrenia spectrum disorder (SZ) + AVH (n = 22) and BPD with no AVH (n = 23).

RESULTS

No differences in AVH were found between BPD + AVH and SZ + AVH. Compared with SZ + AVH, BPD + AVH scored lower on delusions and difficulty in abstract thinking and higher on hostility. BPD + AVH reported more severe self-harm, paranoid ideation, dissociation, anxiety and stress than BPD no AVH.

CONCLUSIONS

This study replicates, in a sample of youth, the finding from studies of adults that AVH in BPD are indistinguishable from those in SZ, when assessed with the Psychotic Symptom Rating Scales (PSYRATS). Clinicians should specifically enquire about AVH among youth with BPD. When present, AVH appear to be an indicator of a more severe form of BPD.

Effect size measures and their benchmark values for quantifying benefit or risk of medicinal products

The standardized mean difference is a well-known effect size measure for continuous, normally distributed data. In this paper we present a general basis for important other distribution families. As a general concept, usable for every distribution family, we introduce the relative effect, also called Mann-Whitney effect size measure of stochastic superiority. This measure is a truly robust measure, needing no assumptions about a distribution family. It is thus the preferred tool for assumption-free, confirmatory studies. For normal distribution shift, proportional odds, and proportional hazards, we show how to derive many global values such as risk difference average, risk difference extremum, and odds ratio extremum. We demonstrate that the well-known benchmark values of Cohen with respect to group differences-small, medium, large-can be translated easily into corresponding Mann-Whitney values. From these, we get benchmarks for parameters of other distribution families. Furthermore, it is shown that local measures based on binary data (2 × 2 tables) can be associated with the Mann-Whitney measure: The concept of stochastic superiority can always be used. It is a general statistical value in every distribution family. It therefore yields a procedure for standardizing the assessment of effect size measures. We look at the aspect of relevance of an effect size and-introducing confidence intervals-present some examples for use in statistical practice.

A Robust Nonparametric Measure of Effect Size Based on an Analog of Cohen's d, Plus Inferences About the Median of the Typical Difference

The paper describes a nonparametric analog of Cohen's d, Q. It is established that a confidence interval for Q can be computed via a method for computing a confidence interval for the median of D = X1 − X2, which in turn is related to making inferences about P(X1 < X2).

Preliminary Evidence for the Cognitive Model of Auditory Verbal Hallucinations in Youth With Borderline Personality Disorder

Objectives: This is the first study to explore cognitive, emotional, and behavioral responses to voices in youth with borderline personality disorder (BPD) compared with those with schizophrenia spectrum disorder (SZ), and to examine if negative appraisals of voices predict depression and anxiety across the groups. Methods: The sample comprised 43 outpatients, aged 15-25 years, who reported auditory verbal hallucinations (AVH) and were diagnosed with either Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) BPD or SZ. Data were collected using the Psychotic Symptom Rating Scales, the revised Beliefs About Voices Questionnaire, the Voice Rank Scale, and the Depression Anxiety Stress Scale. Results: Youth with BPD did not differ from youth with SZ in beliefs about the benevolence or malevolence of voices. Youth with BPD appraised their voices as more omnipotent and of higher social rank in relation to themselves, compared with youth with SZ. In both diagnostic groups, beliefs about malevolence and omnipotence of voices were correlated with more resistance toward voices, and beliefs about benevolence with more engagement with voices. In addition, perceiving the voices as being of higher social rank than oneself and negative voice content were both independent predictors of depression, irrespective of diagnostic group. In contrast, negative appraisals of voices did not predict anxiety after adjusting for negative voice content. Conclusions: This study replicated the link between negative appraisals of voices and depression that has been found in adults with SZ in a mixed diagnostic youth sample. It, thus, provides preliminary evidence that the cognitive model of AVH can be applied to understanding and treating voices in youth with BPD.

Effects of stroke injury on the shear modulus of the lower leg muscle during passive dorsiflexion

Contractures are common complications of a stroke. The spatial location of the increased stiffness among plantar flexors and its variability among survivors remain unknown. This study assessed the mechanical properties of the lower leg muscles in stroke survivors during passive dorsiflexions. Stiffness was estimated through the measurement of the shear modulus. Two experiments were independently conducted, in which participants lay supine: with the knee extended ( experiment 1, n = 13 stroke survivors and n = 13 controls), or with the knee flexed at 90° ( experiment 2, n = 14 stroke survivors and n = 14 controls). The shear modulus of plantar flexors [gastrocnemius medialis (three locations), gastrocnemius lateralis (three locations), soleus (two locations), flexor digitorum longus, flexor hallucis longus), peroneus longus] and dorsiflexors (tibialis anterior and extensor digitorum longus) was measured using ultrasound shear wave elastography during passive dorsiflexions (2°/s). At the same ankle angle, stroke survivors displayed higher shear modulus than controls for gastrocnemius medialis and gastrocnemius lateralis (knee extended) and soleus (knee flexed). Very low shear modulus was found for the other muscles. The adjustment for muscle slack angle suggested that the increased shear modulus was arising from consequences of contractures. The stiffness distribution between muscles was consistent across participants with the highest shear modulus reported for the most distal regions of gastrocnemius medialis (knee extended) and soleus (knee flexed). These results provide a better appreciation of stiffness locations among plantar flexors of stroke survivors and can provide evidence for the implementation of clinical trials to evaluate targeted interventions applied on these specific muscle regions.

NEW & NOTEWORTHY The shear modulus of 13 muscle regions was assessed in stroke patients using elastography. When compared with controls, shear modulus was increased in the gastrocnemius muscle (GM) when the knee was extended and in the soleus (SOL) when the knee was flexed. The distal regions of GM and SOL were the most affected. These changes were consistent in all the stroke patients, suggesting that the regions are a potential source of the increase in joint stiffness.

Confidence intervals for the Mann–Whitney test

The Mann–Whitney test is a commonly used non-parametric alternative of the two-sample t-test. Despite its frequent use, it is only rarely accompanied with confidence intervals of an effect size. If reported, the effect size is usually measured with the difference of medians or the shift of the two distribution locations. Neither of these two measures directly coincides with the test statistic of the Mann–Whitney test, so the interpretation of the test results and the confidence intervals may be importantly different. In this paper, we focus on the probability that random variable X is lower than random variable Y. This measure is often referred to as the degree of overlap or the probabilistic index; it is in one-to-one relationship with the Mann–Whitney test statistic. The measure equals the area under the ROC curve. Several methods have been proposed for the construction of the confidence interval for this measure, and we review the most promising ones and explain their ideas. We study the properties of different variance estimators and small sample problems of confidence intervals construction. We identify scenarios in which the existing approaches yield inadequate coverage probabilities. We conclude that the DeLong variance estimator is a reliable option regardless of the scenario, but confidence intervals should be constructed using the logit scale to avoid values above 1 or below 0 and the poor coverage probability that follows. A correction is needed for the case when all values from one sample are smaller than the values of the other. We propose a method that improves the coverage probability also in these cases.

MRI Outperforms [18F]AV-1451 PET as a Longitudinal Biomarker in Progressive Supranuclear Palsy

BACKGROUND

Elevated uptake of the [¹⁸ F]AV-1451 tau-PET ligand has been observed cross-sectionally in subjects with progressive supranuclear palsy (PSP). However, it is unknown how the ligand performs longitudinally in PSP. We aimed to determine how regional measures of change on [¹⁸ F]AV-1451 PET perform as longitudinal biomarkers of PSP compared with the more established biomarker of rate of midbrain atrophy.

METHODS

Sixteen subjects with PSP underwent 2 serial [¹⁸ F]AV-1451 tau-PET scans and 3-Tesla MRI over 12 months and were age- and sex-matched to 39 healthy controls with longitudinal [¹⁸ F]AV-1451 PET. Median [¹⁸ F]AV-1451 uptake was calculated for each scan for regions of interest across the brain and divided by uptake in cerebellar crus to create standard uptake value ratios. Midbrain volume on MRI was also calculated for each scan. Sample sizes required to power placebo-controlled treatment trials were calculated.

RESULTS

Rate of midbrain atrophy was significantly increased in PSP compared with controls. [¹⁸ F]AV-1451 regional change measures were significantly increased in PSP compared with controls in the pallidum, precentral cortex, dentate nucleus of the cerebellum, and midbrain. Change over time in the PSP Rating Scale correlated with change in midbrain volume but did not correlate with change in the [¹⁸ F]AV-1451 measures. Smallest sample-size estimates were obtained with rate of midbrain atrophy, followed by the PSP Rating Scale, with both outperforming [¹⁸ F]AV-1451 measures.

CONCLUSIONS

[¹⁸ F]AV-1451 tau-PET measures increase over time in subjects with PSP, but longitudinal [¹⁸ F]AV-1451 measures may not perform as well as rate of midbrain atrophy as biomarkers for PSP clinical trials. © 2018 International Parkinson and Movement Disorder Society.

Probable Post-traumatic Stress Disorder and Self-harming Behaviour: Potential Barriers to Employment?

The current study screened for post-traumatic stress disorder (PTSD) and self-harming behaviours, often related to borderline personality disorder (BPD), among individuals in a job centre considered unemployable primarily for psychological reasons. Participants (N = 112) filled in questionnaires on PTSD symptoms (n = 62) and self-harming behaviours (n = 59) as part of participating in team-meetings providing the individuals with a return-to-work plan. Differences in demographic variables between individuals with and without valid protocols were small to moderate. Of the individuals filling in the PTSD questionnaire 40% fulfilled criteria for probable PTSD and 31% of the individuals filling in the questionnaire on self-harming behaviours reported five or more types of self-harming behaviours. Only a minority of these individuals had PTSD or BPD respectively mentioned in their case records. Further investigation of the prevalence of PTSD and self-harming behaviour among individuals considered unemployable is warranted as well as an enhanced focus in jobcentres and other institutions supporting employability on detection and treatment of PTSD and early signs of BPD.

Confidence intervals of the Mann-Whitney parameter that are compatible with the Wilcoxon-Mann-Whitney test

For the two-sample problem, the Wilcoxon-Mann-Whitney (WMW) test is used frequently: it is simple to explain (a permutation test on the difference in mean ranks), it handles continuous or ordinal responses, it can be implemented for large or small samples, it is robust to outliers, it requires few assumptions, and it is efficient in many cases. Unfortunately, the WMW test is rarely presented with an effect estimate and confidence interval. A natural effect parameter associated with this test is the Mann-Whitney parameter, φ = Pr[ X<Y ] + 0.5 Pr[X = Y ]. Ideally, we desire confidence intervals on φ that are compatible with the WMW test, meaning the test rejects at level α if and only if the 100(1 - α)% confidence interval on the Mann-Whitney parameter excludes 1/2. Existing confidence interval procedures on φ are not compatible with the usual asymptotic implementation of the WMW test that uses a continuity correction nor are they compatible with exact WMW tests. We develop compatible confidence interval procedures for the asymptotic WMW tests and confidence interval procedures for some exact WMW tests that appear to be compatible. We discuss assumptions and interpretation of the resulting tests and confidence intervals. We provide the wmwTest function of the asht R package to calculate all of the developed confidence intervals.

Validation of a Novel Inverted Peg Transfer Task: Advancing Beyond the Regular Peg Transfer Task for Surgical Simulation-Based Assessment

OBJECTIVE

To evaluate the validity of a novel inverted peg transfer (iPT) task for assessing laparoscopic skills of novices and experts and compare iPT to the regular PT (rPT) task to ensure surgical trainee acquisition of an adequate advanced laparoscopic skills level for safe laparoscopic practice in the operating room.

DESIGN

Prospective crossover study.

SETTING

Multidisciplinary simulation center and motion analysis laboratory, Mayo Clinic.

PARTICIPANTS

Novices were medical students and surgical interns without laparoscopic experience. Experts were surgeons with at least 3 years of experience in laparoscopic surgery.

METHODS

This was the first exposure to iPT for both groups. Completion time and performance metrics were recorded. A scoring rubric was used to calculate a normalized performance score between 0 and 100. Wilcoxon rank sum and Mann-Whitney tests were performed with α = 0.05. Receiver-operating characteristic curves were graphed for the 2 task scores to assess the tasks' sensitivity and specificity in differentiating laparoscopic experience level.

MAIN OUTCOME MEASURES

Performance measures of completion time, transferred triangles, dropped triangles (errors), and the overall performance score on both tasks between- and within-subjects (i.e., novices and experts).

RESULTS

Thirty-six novices and eight experts participated. Both experts and novices had longer completion time and lower scores during iPT than rPT (p < 0.05). Within iPT, novice completion times were 144 seconds longer (p = 0.04), and performance score was 35 points lower than experts (p < 0.01). No differences between novices and experts were observed for completion time or performance scores (p > 0.05) for rPT. The iPT scores had a higher sensitivity and specificity than the rPT (area under the receiver-operating characteristic curve: iPT = 0.91; rPT = 0.69).

CONCLUSIONS

iPT is a valid assessment of advanced laparoscopic skills for surgical trainees with higher specificity and sensitivity than rPT. As advanced minimally invasive surgery becomes more common, it is important that tasks such as iPT be included in surgical simulation curricula and training assessment.

A Guide to Robust Statistical Methods in Neuroscience

There is a vast array of new and improved methods for comparing groups and studying associations that offer the potential for substantially increasing power, providing improved control over the probability of a Type I error, and yielding a deeper and more nuanced understanding of data. These new techniques effectively deal with four insights into when and why conventional methods can be unsatisfactory. But for the non-statistician, the vast array of new and improved techniques for comparing groups and studying associations can seem daunting, simply because there are so many new methods that are now available. This unit briefly reviews when and why conventional methods can have relatively low power and yield misleading results. The main goal is to suggest some general guidelines regarding when, how, and why certain modern techniques might be used. © 2018 by John Wiley & Sons, Inc.

The effect of active toe movement (AToM) on calf pump function and deep vein thrombosis in patients with acute foot and ankle trauma treated with cast - A prospective randomized study

BACKGROUND

Patients with foot and ankle trauma treated with cast are advised to perform toe movements to prevent venous thromboembolism (VTE). Our aim was to determine the effect of active toe movement on asymptomatic deep vein thrombosis (DVT) and venous calf pump function.

METHODS

Patients aged 18-60 years with acute foot and ankle trauma requiring below knee non weight bearing cast were randomized to intervention (regular active toe movement) or control groups (n=100). Patients had bilateral lower limb venous ultrasound to assess for DVT on discharge from clinic. Patients requiring chemical thromboprophylaxis were excluded.

RESULTS

78 completed the study. 27% sustained asymptomatic DVT, with no statistically significant difference in calf pump function or DVT incidence between groups. All DVT's occurred in the injured lower limb.

CONCLUSION

Active toe movement is not a viable strategy for thromboprophylaxis in patients with acute foot and ankle trauma treated with cast.

Predicting probable Alzheimer's disease using linguistic deficits and biomarkers

BACKGROUND

The manual diagnosis of neurodegenerative disorders such as Alzheimer's disease (AD) and related Dementias has been a challenge. Currently, these disorders are diagnosed using specific clinical diagnostic criteria and neuropsychological examinations. The use of several Machine Learning algorithms to build automated diagnostic models using low-level linguistic features resulting from verbal utterances could aid diagnosis of patients with probable AD from a large population. For this purpose, we developed different Machine Learning models on the DementiaBank language transcript clinical dataset, consisting of 99 patients with probable AD and 99 healthy controls.

RESULTS

Our models learned several syntactic, lexical, and n-gram linguistic biomarkers to distinguish the probable AD group from the healthy group. In contrast to the healthy group, we found that the probable AD patients had significantly less usage of syntactic components and significantly higher usage of lexical components in their language. Also, we observed a significant difference in the use of n-grams as the healthy group were able to identify and make sense of more objects in their n-grams than the probable AD group. As such, our best diagnostic model significantly distinguished the probable AD group from the healthy elderly group with a better Area Under the Receiving Operating Characteristics Curve (AUC) using the Support Vector Machines (SVM).

CONCLUSIONS

Experimental and statistical evaluations suggest that using ML algorithms for learning linguistic biomarkers from the verbal utterances of elderly individuals could help the clinical diagnosis of probable AD. We emphasise that the best ML model for predicting the disease group combines significant syntactic, lexical and top n-gram features. However, there is a need to train the diagnostic models on larger datasets, which could lead to a better AUC and clinical diagnosis of probable AD.

Composite End Points in Clinical Trials of Heart Failure Therapy

Composite end points are popular outcomes in clinical trials of heart failure therapies. For example, a global rank composite is typically analyzed using a Mann–Whitney U test, and the results are summarized by the mean of ranks and a corresponding P value. The mean of ranks is uninformative, and a clinically meaningful estimate of the treatment effect is needed to communicate study results and facilitate an assessment of heterogeneity (the consistency of the effect across outcomes). The probability index is intuitive for clinicians, easy to calculate, and may be applied to various composites. We suggest a simple and familiar plot to assess heterogeneity across outcomes, which should be routine when analyzing composites. We think that the probability index provides an immediate and simple solution to an overt problem.

Effect-Size Measures as Descriptors of Assay Quality in High-Content Screening: A Brief Review of Some Available Methodologies

The field of high-content screening (HCS) typically uses measures of screen quality conceived for fairly straightforward high-throughput screening (HTS) scenarios. However, in contrast to HTS, image-based HCS systems rely on multidimensional readouts reporting biological responses associated with complex cellular phenotypes. Not only is the dimensionality in which the screens operate higher, but also the scale of the individual features describing the quantified phenotypic changes is often smaller than what is seen in one-dimensional HTS platforms. Therefore, the use of HTS-type quality measures to characterize HCS screens may severely underestimate the detection power of the assays used, and it may mislead the screening scientists regarding the necessary screen optimization. Also, traditional HTS-based measures are typically reported without any estimation of precision, which makes them unsuitable for computation of confidence intervals or for meta-analysis. This review summarizes the well-established statistical techniques for reporting effect sizes and argues that this broadly accepted methodology could be seamlessly integrated into HCS quality reporting, supplanting or even replacing measures such as Z' or S_w (assay window).

A practical divergence measure for survival distributions that can be estimated from Kaplan-Meier curves

This paper introduces a new simple divergence measure between two survival distributions. For two groups of patients, the divergence measure between their associated survival distributions is based on the integral of the absolute difference in probabilities that a patient from one group dies at time t and a patient from the other group survives beyond time t and vice versa. In the case of non-crossing hazard functions, the divergence measure is closely linked to the Harrell concordance index, C, the Mann-Whitney test statistic and the area under a receiver operating characteristic curve. The measure can be used in a dynamic way where the divergence between two survival distributions from time zero up to time t is calculated enabling real-time monitoring of treatment differences. The divergence can be found for theoretical survival distributions or can be estimated non-parametrically from survival data using Kaplan-Meier estimates of the survivor functions. The estimator of the divergence is shown to be generally unbiased and approximately normally distributed. For the case of proportional hazards, the constituent parts of the divergence measure can be used to assess the proportional hazards assumption. The use of the divergence measure is illustrated on the survival of pancreatic cancer patients. Copyright © 2016 John Wiley & Sons, Ltd.

Root Foraging Performance and Life-History Traits

Plants use their roots to forage for nutrients in heterogeneous soil environments, but different plant species vastly differ in the intensity of foraging they perform. This diversity suggests the existence of constraints on foraging at the species level. We therefore examined the relationships between the intensity of root foraging and plant body traits across species in order to estimate the degree of coordination between plant body traits and root foraging as a form of plant behavior. We cultivated 37 perennial herbaceous Central European species from open terrestrial habitats in pots with three different spatial gradients of nutrient availability (steep, shallow, and no gradient). We assessed the intensity of foraging as differences in root placement inside pots with and without a spatial gradient of resource supply. For the same set of species, we retrieved data about body traits from available databases: maximum height at maturity, mean area of leaf, specific leaf area, shoot lifespan, ability to self-propagate clonally, maximal lateral spread (in clonal plants only), realized vegetative growth in cultivation, and realized seed regeneration in cultivation. Clonal plants and plants with extensive vegetative growth showed considerably weaker foraging than their non-clonal or slow-growing counterparts. There was no phylogenetic signal in the amount of expressed root foraging intensity. Since clonal plants foraged less than non-clonals and foraging intensity did not seem to be correlated with species phylogeny, we hypothesize that clonal growth itself (i.e., the ability to develop at least partly self-sustaining ramets) may be an answer to soil heterogeneity. Whereas unitary plants use roots as organs specialized for both resource acquisition and transport to overcome spatial heterogeneity in resource supply, clonal plants separate these two functions. Becoming a clonal plant allows higher specialization at the organ level, since a typical clonal plant can be viewed as a network of self-sustainable harvesting units connected together with specialized high-throughput connection organs. This may be an effective alternative for coping with spatial heterogeneity in resource availability.

A potential mate influences reproductive development in female, but not male, pine siskins

The role of photoperiod in avian reproductive timing has been well studied, and we are increasingly recognizing the roles of other environmental cues such as social cues. However, few studies have evaluated the extent to which males and females of the same species respond similarly to the same type of cue. Moreover, previous studies have rarely examined how variation in the quality or nature of a given social cue might modulate its effect. Here, we examine the sensitivity of male and female pine siskins (Spinus pinus) to a potential mate as a stimulatory cue for gonadal recrudescence, and we investigate whether variation in the relationship between a bird and its potential mate modulates the effect of that potential mate. Birds were initially housed without opposite sex birds on a 12L:12D photoperiod with ad libitum food. After gonadal recrudescence had begun males and females were randomly paired with an opposite sex bird or housed alone. An additional group of males was paired with estradiol-implanted females. In males, these social treatments had no effect on testis length, cloacal protuberance length, luteinizing hormone (LH) levels, or testosterone levels. In females, presence of a potential mate had a significant and positive effect on ovary score, defeathering of the brood patch, and LH levels. Among paired birds, the degree of affiliation within a pair corresponded to the extent of reproductive development in females, but not males. Thus, reproductive timing in females appears to be sensitive to both the presence of a potential mate and her relationship with him.

The p-Value You Can't Buy

There is growing frustration with the concept of the p-value. Besides having an ambiguous interpretation, the p-value can be made as small as desired by increasing the sample size, n. The p-value is outdated and does not make sense with big data: Everything becomes statistically significant. The root of the problem with the p-value is in the mean comparison. We argue that statistical uncertainty should be measured on the individual, not the group, level. Consequently, standard deviation (SD), not standard error (SE), error bars should be used to graphically present the data on two groups. We introduce a new measure based on the discrimination of individuals/objects from two groups, and call it the D-value. The D-value can be viewed as the n-of-1 p-value because it is computed in the same way as p while letting n equal 1. We show how the D-value is related to discrimination probability and the area above the receiver operating characteristic (ROC) curve. The D-value has a clear interpretation as the proportion of patients who get worse after the treatment, and as such facilitates to weigh up the likelihood of events under different scenarios. [Received January 2015. Revised June 2015.].

What students do schools allocate to a cognitive-behavioural intervention? Characteristics of adolescent participants in Northern Sweden

BACKGROUND

Adolescents are a vulnerable group when it comes to the risk of developing depression. Preventing the onset of depressive episodes in this group is therefore a major public health priority. In the last decades, school-based cognitive-behavioural interventions have been a common primary prevention approach. However, evidence on what girls actually are allocated to such interventions when no researchers are involved is scarce.

OBJECTIVE

To explore how a selective cognitive-behavioural program (Depression In Swedish Adolescents) developed to prevent depression in adolescents, was implemented in a naturalistic setting in schools in northern part of Sweden. The focus was on characteristics of participants allocated to the intervention.

DESIGN

Cross-sectional baseline data on depressive symptoms, school environment and socio-economic factors were collected in 2011 by means of questionnaires in schools in a municipality in the northern part of Sweden. Intervention participants were identified in a follow-up questionnaire in 2012. Students (n=288) included in the analyses were in the ages of 14-15.

RESULTS

Sixty-six girls and no boys were identified as intervention participants. They reported higher levels of depressive symptoms, lower personal relative affluence, more sexual harassment victimization and less peer support compared to female non-participants (n=222). Intervention participants were more likely to attend schools with a higher proportion of low parental education levels and a lower proportion of students graduating with a diploma.

CONCLUSIONS

The developers of the intervention originally intended the program to be universal or selective, but it was implemented as targeted in these schools. It is important for school administrations to adhere to program fidelity when it comes to what students it is aimed for. Implications for effectivenss trials of cognitive-behavioural interventions in the school setting is discussed.

Sample size calculations for clinical trials targeting tauopathies: a new potential disease target

Disease-modifying therapies are being developed to target tau pathology, and should, therefore, be tested in primary tauopathies. We propose that progressive apraxia of speech should be considered one such target group. In this study, we investigate potential neuroimaging and clinical outcome measures for progressive apraxia of speech and determine sample size estimates for clinical trials. We prospectively recruited 24 patients with progressive apraxia of speech who underwent two serial MRI with an interval of approximately 2 years. Detailed speech and language assessments included the Apraxia of Speech Rating Scale and Motor Speech Disorders severity scale. Rates of ventricular expansion and rates of whole brain, striatal and midbrain atrophy were calculated. Atrophy rates across 38 cortical regions were also calculated and the regions that best differentiated patients from controls were selected. Sample size estimates required to power placebo-controlled treatment trials were calculated. The smallest sample size estimates were obtained with rates of atrophy of the precentral gyrus and supplementary motor area, with both measures requiring less than 50 subjects per arm to detect a 25% treatment effect with 80% power. These measures outperformed the other regional and global MRI measures and the clinical scales. Regional rates of cortical atrophy, therefore, provide the best outcome measures in progressive apraxia of speech. The small sample size estimates demonstrate feasibility for including progressive apraxia of speech in future clinical treatment trials targeting tau.

Increasing the power of the Mann-Whitney test in randomized experiments through flexible covariate adjustment

The Mann-Whitney U test is frequently used to evaluate treatment effects in randomized experiments with skewed outcome distributions or small sample sizes. It may lack power, however, because it ignores the auxiliary baseline covariate information that is routinely collected. Wald and score tests in so-called probabilistic index models generalize the Mann-Whitney U test to enable adjustment for covariates, but these may lack robustness by demanding correct model specification and do not lend themselves to small sample inference. Using semiparametric efficiency theory, we here propose an alternative extension of the Mann-Whitney U test, which increases its power by exploiting covariate information in an objective way and which lends itself to permutation inference. Simulation studies and an application to an HIV clinical trial show that the proposed permutation test attains the nominal Type I error rate and can be drastically more powerful than the classical Mann-Whitney U test.

Comparing college smokers' and dual users' expectancies towards cigarette smoking

BACKGROUND

As no agreed upon definition exists for dual use (i.e., individuals who concurrently use more than one form of tobacco), this population remains largely unstudied in the substance use literature, despite increases in smokeless tobacco use among young adults. Individuals 18-25years of age report the highest rates of smokeless tobacco use, dual use, and cigarette use. The current study compared the smoking outcome expectancies of college student dual users to those who reported only smoking cigarettes.

METHODS

The Short Form of the Smoking Consequences Questionnaire was used to examine potential differences in positive or negative expectations regarding cigarette use.

RESULTS

Data from this study suggest that smokers believe that smoking will lead to greater positive consequences ("cigarettes taste good"), negative reinforcement ("cigarettes help me deal with anger"), and weight/appetite reduction ("smoking controls my appetite") when compared to dual users. Conversely, dual users believed that smoking would lead to greater negative consequences (e.g., "smoking is taking years off of my life").

DISCUSSION

These results may help to explain why some smokers choose not to use smokeless tobacco products for harm reduction or smoking cessation purposes, as well as why increases are being observed in smokeless tobacco rates among young adults.

Test Statistics and Confidence Intervals to Establish Noninferiority between Treatments with Ordinal Categorical Data

The problem for establishing noninferiority is discussed between a new treatment and a standard (control) treatment with ordinal categorical data. A measure of treatment effect is used and a method of specifying noninferiority margin for the measure is provided. Two Z-type test statistics are proposed where the estimation of variance is constructed under the shifted null hypothesis using U-statistics. Furthermore, the confidence interval and the sample size formula are given based on the proposed test statistics. The proposed procedure is applied to a dataset from a clinical trial. A simulation study is conducted to compare the performance of the proposed test statistics with that of the existing ones, and the results show that the proposed test statistics are better in terms of the deviation from nominal level and the power.