Recalibrating single-study effect sizes using hierarchical Bayesian models

Introduction

There are growing concerns about commonly inflated effect sizes in small neuroimaging studies, yet no study has addressed recalibrating effect size estimates for small samples. To tackle this issue, we propose a hierarchical Bayesian model to adjust the magnitude of single-study effect sizes while incorporating a tailored estimation of sampling variance.

Methods

We estimated the effect sizes of case-control differences on brain structural features between individuals who were dependent on alcohol, nicotine, cocaine, methamphetamine, or cannabis and non-dependent participants for 21 individual studies (Total cases: 903; Total controls: 996). Then, the study-specific effect sizes were modeled using a hierarchical Bayesian approach in which the parameters of the study-specific effect size distributions were sampled from a higher-order overarching distribution. The posterior distribution of the overarching and study-specific parameters was approximated using the Gibbs sampling method.

Results

The results showed shrinkage of the posterior distribution of the study-specific estimates toward the overarching estimates given the original effect sizes observed in individual studies. Differences between the original effect sizes (i.e., Cohen's d) and the point estimate of the posterior distribution ranged from 0 to 0.97. The magnitude of adjustment was negatively correlated with the sample size (r = -0.27, p < 0.001) and positively correlated with empirically estimated sampling variance (r = 0.40, p < 0.001), suggesting studies with smaller samples and larger sampling variance tended to have greater adjustments.

Discussion

Our findings demonstrate the utility of the hierarchical Bayesian model in recalibrating single-study effect sizes using information from similar studies. This suggests that Bayesian utilization of existing knowledge can be an effective alternative approach to improve the effect size estimation in individual studies, particularly for those with smaller samples.

White matter microstructure differences in individuals with dependence on cocaine, methamphetamine, and nicotine: Findings from the ENIGMA-Addiction working group

BACKGROUND

Nicotine and illicit stimulants are very addictive substances. Although associations between grey matter and dependence on stimulants have been frequently reported, white matter correlates have received less attention.

METHODS

Eleven international sites ascribed to the ENIGMA-Addiction consortium contributed data from individuals with dependence on cocaine (n = 147), methamphetamine (n = 132) and nicotine (n = 189), as well as non-dependent controls (n = 333). We compared the fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD) and mean diffusivity (MD) of 20 bilateral tracts. Also, we compared the performance of various machine learning algorithms in deriving brain-based classifications on stimulant dependence.

RESULTS

The cocaine and methamphetamine groups had lower regional FA and higher RD in several association, commissural, and projection white matter tracts. The methamphetamine dependent group additionally showed lower regional AD. The nicotine group had lower FA and higher RD limited to the anterior limb of the internal capsule. The best performing machine learning algorithm was the support vector machine (SVM). The SVM successfully classified individuals with dependence on cocaine (AUC = 0.70, p < 0.001) and methamphetamine (AUC = 0.71, p < 0.001) relative to non-dependent controls. Classifications related to nicotine dependence proved modest (AUC = 0.62, p = 0.014).

CONCLUSIONS

Stimulant dependence was related to FA disturbances within tracts consistent with a role in addiction. The multivariate pattern of white matter differences proved sufficient to identify individuals with stimulant dependence, particularly for cocaine and methamphetamine.

Do the evolutionary interactions between moths and bats promote niche partitioning between bats and birds?

Ecological theory suggests that the coexistence of species is promoted by the partitioning of available resources, as in dietary niche partitioning where predators partition prey. Yet, the mechanisms underlying dietary niche partitioning are not always clear. We used fecal DNA metabarcoding to investigate the diets of seven nocturnal insectivorous bird and bat species. Low diet overlap (2%-22%) supported resource partitioning among all species. Differences in diet corresponded with species identity, prey detection method, and foraging behavior of predators. Insects with ultrasonic hearing capabilities were consumed significantly more often by birds than bats, consistent with an evolved avoidance of echolocating strategies. In turn, bats consumed a greater proportion of noneared insects such as spruce budworms. Overall, our results suggest that evolutionary interactions among bats and moths translate to dietary niche partitioning and coexistence among bats and nocturnal birds.

Mapping cortical and subcortical asymmetries in substance dependence: Findings from the ENIGMA Addiction Working Group

Brain asymmetry reflects left-right hemispheric differentiation, which is a quantitative brain phenotype that develops with age and can vary with psychiatric diagnoses. Previous studies have shown that substance dependence is associated with altered brain structure and function. However, it is unknown whether structural brain asymmetries are different in individuals with substance dependence compared with nondependent participants. Here, a mega-analysis was performed using a collection of 22 structural brain MRI datasets from the ENIGMA Addiction Working Group. Structural asymmetries of cortical and subcortical regions were compared between individuals who were dependent on alcohol, nicotine, cocaine, methamphetamine, or cannabis (n = 1,796) and nondependent participants (n = 996). Substance-general and substance-specific effects on structural asymmetry were examined using separate models. We found that substance dependence was significantly associated with differences in volume asymmetry of the nucleus accumbens (NAcc; less rightward; Cohen's d = 0.15). This effect was driven by differences from controls in individuals with alcohol dependence (less rightward; Cohen's d = 0.10) and nicotine dependence (less rightward; Cohen's d = 0.11). These findings suggest that disrupted structural asymmetry in the NAcc may be a characteristic of substance dependence.

Estimating life expectancy among older multimorbid adults to personalize preventive care

Background

Providing high value care and avoiding care overuse is a challenge among older multimorbid adults. There is evidence on benefits and harms of cancer screening and cardiovascular diseases (CVD) preventive treatment up to the age of 75. However, this evidence is not directly applicable to older multimorbid patients. Because each cancer and CVD preventive care has a specific lagtime to benefit, many guidelines recommend tailoring preventive care according to the estimated life expectancy (LE). However, there is no tool to estimate LE among multimorbid patients. Our objectives are therefore to develop new mortality risk prognostic indices and to derive a new LE estimator, what will help clinicians tailoring preventive care in older multimorbid adults.

Methods and Results

We conduct a prospective cohort study by extending the follow-up of 822 patients in Bern, Switzerland, included in the OPtimising thERapy to prevent Avoidable hospital admissions in Mulitmorbid older people (OPERAM) study over 3 years. Detailed information about cancer screening and CVD preventive treatment will be collected. We will identify variables independently associated with mortality and weight the variables to create 1 year and 3 year mortality prognostic indices. We will transform the 3 year prognostic index into a LE estimator. Preliminary results will be presented at the congress.

Conclusions

We will develop the first life expectancy estimator specifically for older multimorbid adults. This tool will help clinicians to tailor cardiovascular and cancer preventive care in older multimorbid adults.

Key messages

Because of the lagtime to benefit, personalizing preventive care by estimated life expectancy is recommended. We will provide the first life expectancy estimator for older multimorbid adults.

Fatal PML associated with efalizumab therapy: insights into integrin αLβ2 in JC virus control

OBJECTIVES

Progressive multifocal leukoencephalopathy (PML) has become much more common with monoclonal antibody treatment for multiple sclerosis and other immune-mediated disorders.

METHODS

We report 2 patients with severe psoriasis and fatal PML treated for ≥3 years with efalizumab, a neutralizing antibody to αLβ2-leukointegrin (LFA-1). In one patient, we conducted serial studies of peripheral blood and CSF including analyses of leukocyte phenotypes, migration ex vivo, and CDR3 spectratypes with controls coming from HIV-infected patients with PML. Extensive pathologic and histologic analysis was done on autopsy CNS tissue of both patients.

RESULTS

Both patients developed progressive cognitive and motor deficits, and JC virus was identified in CSF. Despite treatment including plasma exchange (PE) and signs of immune reconstitution, both died of PML 2 and 6 months after disease onset. Neuropathologic examination confirmed PML. Efalizumab treatment was associated with reduced transendothelial migration by peripheral T cells in vitro. As expression levels of LFA-1 on peripheral T cells gradually rose after PE, in vitro migration increased. Peripheral and CSF T-cell spectratyping showed CD8+ T-cell clonal expansion but blunted activation, which was restored after PE.

CONCLUSIONS

From these data we propose that inhibition of peripheral and intrathecal T-cell activation and suppression of CNS effector-phase migration both characterize efalizumab-associated PML. LFA-1 may be a crucial factor in homeostatic JC virus control.

CD8+ T-cell immunity in chronic inflammatory demyelinating polyradiculoneuropathy

OBJECTIVE

Chronic inflammatory demyelinating polyradiculopathy (CIDP) is a common, but often misdiagnosed disease of the peripheral nervous system with assumed autoimmune pathogenesis. While current concepts of CIDP postulate a pathogenetic role of B cells and (auto)antibodies, the relevance of CD8 T cells present in the biopsies is still elusive. Thus, we asked whether nervous tissue infiltrating and blood-derived lymphocytes in CIDP are clonally expanded to evaluate the involvement of T cells in the pathogenesis of the disease.

METHODS

We characterized the clonal composition of the T-cell receptor repertoire in sural nerve biopsies (n = 25) and matching peripheral blood (n = 12) of patients with CIDP using PCR-based CDR3 spectratyping and subsequent DNA sequencing. As controls we used inflammatory myopathies (dermatomyositis, inclusion body myositis) and nonpathologic control biopsies. Immunohistochemistry was employed to visualize expanded CD8+ T-cell populations in sural nerve biopsies.

RESULTS

In contrast to controls, T cells in CIDP biopsies showed strong monoclonal and oligoclonal restrictions in their T-cell receptor repertoire. Strikingly, clonal expansions found in the biopsies were reflected in the CD8+ T-cell pool of patients' peripheral blood. Clones overlapping between blood and biopsy could be confirmed by CDR3 sequencing. Finally, the predominance of expanded nerve-infiltrating CD8+ T-cell clones was visualized by immunohistochemistry.

CONCLUSIONS

Together, these data provide strong evidence for an antigen-driven, major histocompatibility complex class I restricted, CD8+ T-cell-mediated attack against peripheral nerve tissue components contributing to the pathogenesis of CIDP.

Clonal expansions of pathogenic CD8+ effector cells in the CNS of myelin mutant mice

Tissue damage in the CNS is critically influenced by the adaptive immune system. Primary oligodendrocyte damage (by overexpression of PLP) leads to low-grade inflammation of high pathological impact, which is mediated by CD8+ T cells. To yield further insight into pathogenesis and nature of immune responses in myelin mutated mice, we here apply a detailed immunological characterization of CD8+ T cells in PLP-transgenic and aged wild type mice. We provide evidence that T effector cells accumulate in the CNS of PLP-transgenic and wild-type mice and show a higher level of activation in mutant mice, indicated by surface markers and clonal expansions, as demonstrated by T cell receptor CDR3-spectratype analysis. Vbeta-Jbeta similarities suggest specificity against a common antigen, albeit we could not find specific responses against myelin-antigen-derived peptides. The association of primary oligodendrocyte damage with secondary expansions of pathogenic cells underlines the role of adaptive immune reactions in neurodegenerative and neuroinflammatory diseases.

[Extended outcome assessment in endonasal sinus surgery]

BACKGROUND

Endonasal optically guided surgery has gained wide acceptance for treatment of chronic sinusitis. However, irrespective to the advent of minimally-invasive techniques, standard outcome assessment has not always reflected the increased technical and conceptual efforts. "Psychometric" instruments offer additional information on patients' perceptions of health. We analyzed the practical value of an extended outcome assessment.

METHODS

Standardized interviews were carried out with 103 patients pre- and postoperatively applying several psychometrical instruments ("SF-36" and other valid general health-status instruments besides disease-specific questionnaires, providing 124 items/questions altogether).

RESULTS

The diverse changes of subtle health status subscores as a rule paralleled each other and were concordant with traditional self-estimated global ratings of the surgical success by the patient. Significant postoperative changes of the "SF-36" questionnaire were especially seen in the subscale "bodily pain" and "level of energy". With few exceptions only, items reflecting any indirect burden of chronic sinusitis revealed less pronounced improvements postoperatively.

CONCLUSION

It appears legitimate to question the special benefits of extended psychometric outcome research in comparison to traditional global ratings for daily surgical practice.

Consent and release

Because school nursing practice by definition involves delivering services to minors, school nurses often find themselves with questions about consent. Because school districts, much like other health care providers, occasionally face liability for the undesired health care outcomes of their clients (i.e., students), another question that surfaces frequently deals with release from liability. Each question must be answered based on analysis of the specific facts and applicable laws. This article provides an overview of the principles that provide school nurses with general guidance on consent issues and release of liability and, by way of example, applies them in the answers to four specific questions forwarded by practicing school nurses.

Redes públicas, descentralizadas y comunitarias de salud en Bolivia

Health sector reform in Bolivia is based primarily on the principles of decentralization and equity, and with the objectives of improving quality and of expanding health services coverage in rural and low-income areas of the country. As an experiment in reform, the Bolivian Ministry of Health and Social Welfare, the department of La Paz, and the municipality of El Alto signed an agreement with a nongovernmental organization (NGO), transferring to the NGO the overall management of one of the health services networks in El Alto. The transfer was based on a management contract that had process and outcome indicators for the network. A year after implementation began, the preliminary results suggest that through the agreement the quality of management and services has improved, health services coverage has expanded, and the network's primary care services have been strengthened. Bed occupancy rates are generally very low in secondary hospitals in Bolivia, with that figure being just 43% in the department of La Paz in 1999. However, in the second 6 months of operation of the El Alto network the occupancy rate for the network's hospital reached 84%. Between the first 6 months of 1999 and the same period in 2000, outpatient consultations increased by 55% in the network (83% in the hospital and 18% in the network's primary care centers). Over that same period, institutional deliveries increased by 41% and the percentage of deliveries in the primary care centers grew from 5% of the total to 9%. A recent user survey found that 87% of the people receiving care in the network felt highly satisfied with the service they had received, and 75% of the persons surveyed said they would recommend the service to others. These are not typical data for health services in Bolivia. This pilot effort suggests that a change in the organization and management of a health services network, with a separation of the roles of purchaser and provider, combined with management based on results and with community participation in the process, can improve the quality and efficiency of those health services, stimulate demand for them, and increase user satisfaction.

School health services after Cedar Rapids Independent School District v. Garret F

In 1999, the U.S. Supreme Court ruled that "school health services" include nursing services that are required for students needing one-on-one ("private-duty") nursing care to attend school. This ruling settled opposing federal court interpretations of the Individuals with Disabilities Education Act, clarifying the rights of students with complex medical needs and the responsibility of school districts to provide them with an appropriate educational program. In responding to the challenges and opportunities raised by this decision, school nurses must understand the implications for school nursing practice and for school districts, educate their school leaders and communities, and provide leadership for creative and collaborative problem solving.

Delegation and supervision in school settings. Standards, issues and guidelines for practice (Part 1)

Part one of this article reviews nursing standards and practice issues related to the delegation of nursing activities to, and the supervision of, unlicensed assistive personnel. Part two, which will be published in a future issue, provides specific strategies, practices and resources to assist school nurses to apply these standards and concepts in their everyday school nursing practice.

Effects of somatostatin and captopril on glomerular prostaglandin E2 production in normal and diabetic rats

Somatostatin (SRIH) has recently been shown to be effective in reversing many of the early changes of diabetic nephropathy. It is unknown whether SRIH exerts its protective effects via its ability to suppress growth hormone (GH) or via other direct renal effects. Since changes in glomerular prostaglandin (PG) E2 production are thought to be an important part of the underlying pathophysiology of diabetic nephropathy, we sought to determine if SRIH altered glomerular PG E2 production in the rat. Whole glomeruli isolated from streptozotocin-diabetic rats and from controls were incubated with either saline, captopril, or varying concentrations of SRIH, and PG E2 production was determined by direct radioimmunoassay of media. Incubation with captopril (10(-4) M) resulted in equivalent increases in PG E2 production in glomeruli from both control and diabetic rats (140.8 +/- 12.8% and 150.2 +/- 18.9% respectively). Incubation with high concentrations of SRIH (10(-6) M) also resulted in significant increases in glomerular PG E2 production in both diabetic and control rats. However, at low SRIH concentrations (10(-10) M), glomerular PG E2 production was increased only in the diabetic rats (167.0 +/- 11.4% vs 95.3 +/- 9.2% in normals). We conclude that SRIH increases glomerular PG E2 production, and that glomeruli from diabetic rats appear to be more sensitive to lower concentrations of SRIH when compared to normal rats. It is possible that this effect on PG E2 production may underlie the favorable effects of SRIH on the glomerulus in diabetes.

School health records: nursing practice and the law

School nurses are increasingly faced with professional-legal dilemmas related to student health records and documentation. This article provides guidance in an often extremely confusing area, as well as recommendations for policy and practice changes that might help simplify the search for resolutions.