Akaike's information criterion in generalized estimating equations

Predicting mortality risk in patients undergoing venovenous ECMO for ARDS due to influenza A (H1N1) pneumonia: the ECMOnet score

PURPOSE

The decision to start venovenous extracorporeal membrane oxygenation (VV ECMO) is commonly based on the severity of respiratory failure, with little consideration of the extrapulmonary organ function. The aim of the study was to identify predictors of mortality and to develop a score allowing a better stratification of patients at the time of VV ECMO initiation.

METHODS

This was a prospective multicenter cohort study on 60 patients with influenza A (H1N1)-associated respiratory distress syndrome participating in the Italian ECMOnet data set in the 2009 pandemic. Criteria for ECMO institution were standardized according to national guidelines.

RESULTS

The survival rate in patients treated with ECMO was 68 %. Significant predictors of death before ECMO institution by multivariate analysis were hospital length of stay before ECMO institution (OR = 1.52, 95 % CI 1.12-2.07, p = 0.008); bilirubin (OR = 2.32, 95 % CI 1.52-3.52, p < 0.001), creatinine (OR = 7.38, 95 % CI 1.43-38.11, p = 0.02) and hematocrit values (OR = 0.82, 95 % CI 0.72-0.94, p = 0.006); and mean arterial pressure (OR = 0.92, 95 % CI 0.88-0.97, p < 0.001). The ECMOnet score was developed based on these variables, with a score of 4.5 being the most appropriate cutoff for mortality risk prediction. The high accuracy of the ECMOnet score was further confirmed by ROC analysis (c = 0.857, 95 % CI 0.754-0.959, p < 0.001) and by an independent external validation analysis (c = 0.694, 95 % CI 0.562-0.826, p = 0.004).

CONCLUSIONS

Mortality risk for patients receiving VV ECMO is correlated to the extrapulmonary organ function at the time of ECMO initiation. The ECMOnet score is a tool for the evaluation of the appropriateness and timing of VV ECMO in acute lung failure.

Validation of orthopedic postoperative pain assessment methods for dogs: a prospective, blinded, randomized, placebo-controlled study

In the context of translational research, there is growing interest in studying surgical orthopedic pain management approaches that are common to humans and dogs. The validity of postoperative pain assessment methods is uncertain with regards to responsiveness and the potential interference of analgesia. The hypothesis was that video analysis (as a reference), electrodermal activity, and two subjective pain scales (VAS and 4A-VET) would detect different levels of pain intensity in dogs after a standardized trochleoplasty procedure. In this prospective, blinded, randomized study, postoperative pain was assessed in 25 healthy dogs during a 48-hour time frame (T). Pain was managed with placebo (Group 1, n = 10), preemptive and multimodal analgesia (Group 2, n = 5), or preemptive analgesia consisting in oral tramadol (Group 3, n = 10). Changes over time among groups were analyzed using generalized estimating equations. Multivariate regression tested the significance of relationships between pain scales and video analysis. Video analysis identified that one orthopedic behavior, namely ‘Walking with full weight bearing’ of the operated leg, decreased more in Group 1 at T24 (indicative of pain), whereas three behaviors indicative of sedation decreased in Group 2 at T24 (all p<0.004). Electrodermal activity was higher in Group 1 than in Groups 2 and 3 until T1 (p<0.0003). The VAS was not responsive. 4A-VET showed divergent results as its orthopedic component (4A-VETleg) detected lower pain in Group 2 until T12 (p<0.0009), but its interactive component (4A-VETbeh) was increased in Group 2 from T12 to T48 (p<0.001). Concurrent validity established that 4A-VETleg scores the painful orthopedic condition accurately and that pain assessment through 4A-VETbeh and VAS was severely biased by the sedative side-effect of the analgesics. Finally, the video analysis offered a concise template for assessment in dogs with acute orthopedic pain. However, subjective pain quantification methods and electrodermal activity need further investigation.

Shoulder arthroscopy simulator performance correlates with resident and shoulder arthroscopy experience

BACKGROUND

The technical skills required to perform arthroscopy are multifaceted and require supervised training and repetition. Obtaining this basic arthroscopic skill set can be costly and time-consuming. Simulation may represent a viable training source for basic arthroscopic skills. Our goal was to evaluate the correlation between timed task performance on an arthroscopic shoulder simulator and both resident experience and shoulder arthroscopy experience.

METHODS

Twenty-seven residents were voluntarily recruited from an orthopaedic residency program. Each subject was tested annually for three consecutive years on an arthroscopic shoulder simulator and objectively scored on time to completion of a standardized object localization task. Each subject's total number of shoulder arthroscopies, all arthroscopies, and cases were calculated according to postgraduate year from their Accreditation Council for Graduate Medical Education (ACGME) case log. Generalized estimating equation multivariate regression analysis was performed to determine the correlation between simulation performance and total numbers of shoulder arthroscopies, all arthroscopies, and cases.

RESULTS

Univariate analyses revealed that postgraduate year, total number of shoulder arthroscopies, total number of arthroscopies of any joint, and total number of surgical cases performed during residency training prior to testing were associated with the mean time required to complete the simulator task. The number of prior shoulder arthroscopies performed (r = 0.55) and postgraduate year in training (r = 0.60) correlated most strongly with simulator basic task performance. In the multivariate analysis, the number of prior shoulder arthroscopies and postgraduate year remained independent predictors of faster completion of the simulator task. For every additional postgraduate year, there was a sixteen-second improvement in the time required to complete the simulator task (p &lt; 0.005). Similarly, after controlling for the influence of postgraduate year, there was a twelve-second decrease in the time to complete the simulator task for every additional fifty shoulder arthroscopies performed during residency training (p &lt; 0.008).

CONCLUSIONS

These results showed a significant relationship between performance of basic arthroscopic tasks in a simulator model and the number of shoulder arthroscopies performed. The data confirmed our hypothesis that simulator performance is representative of both resident experience and shoulder arthroscopy experience.

CLINICAL RELEVANCE

This study suggests that greater resident clinical experience and shoulder arthroscopy experience are both reflected in improved performance of basic tasks on a shoulder simulator. These findings warrant further investigation to determine if training on a validated arthroscopic shoulder simulator would improve clinical arthroscopic skills.

Prenatal, perinatal, early life, and sociodemographic factors underlying racial differences in the likelihood of high body mass index in early childhood

OBJECTIVES

We investigated early childhood disparities in high body mass index (BMI) between Black and White US children.

METHODS

We compared differences in Black and White children's prevalence of sociodemographic, prenatal, perinatal, and early life risk and protective factors; fit logistic regression models predicting high BMI (≥ 95th percentile) at age 4 to 5 years to 2 nationally representative samples followed from birth; and performed separate and pooled-survey estimations of these models.

RESULTS

After adjustment for sample design-related variables, models predicting high BMI in the 2 samples were statistically indistinguishable. In the pooled-survey models, Black children's odds of high BMI were 59% higher than White children's (odds ratio [OR] = 1.59; 95% confidence interval [CI]= 1.32, 1.92). Sociodemographic predictors reduced the racial disparity to 46% (OR = 1.46; 95% CI = 1.17, 1.81). Prenatal, perinatal, and early life predictors reduced the disparity to nonsignificance (OR = 1.18; 95% CI = 0.93, 1.49). Maternal prepregnancy obesity and short-duration or no breastfeeding were among predictors for which racial differences in children's exposures most disadvantaged Black children.

CONCLUSIONS

Racial disparities in early childhood high BMI were largely explained by potentially modifiable risk and protective factors.

Pansynaptic enlargement at adult cortical connections strengthened by experience

Behavioral experience alters the strength of neuronal connections in adult neocortex. These changes in synaptic strength are thought to be central to experience-dependent plasticity, learning, and memory. However, it is not known how changes in synaptic transmission between neurons become persistent, thereby enabling the storage of previous experience. A long-standing hypothesis is that altered synaptic strength is maintained by structural modifications to synapses. However, the extent of synaptic modifications and the changes in neurotransmission that the modifications support remain unclear. To address these questions, we recorded from pairs of synaptically connected layer 2/3 pyramidal neurons in the barrel cortex and imaged their contacts with high-resolution confocal microscopy after altering sensory experience by whisker trimming. Excitatory connections strengthened by experience exhibited larger axonal varicosities, dendritic spines, and interposed contact zones. Electron microscopy showed that contact zone size was strongly correlated with postsynaptic density area. Therefore, our findings indicate that whole synapses are larger at strengthened connections. Synaptic transmission was both stronger and more reliable following experience-dependent synapse enlargement. Hence, sensory experience modified both presynaptic and postsynaptic function. Our findings suggest that the enlargement of synaptic contacts is an integral part of long-lasting strengthening of cortical connections and, hence, of information storage in the neocortex.

Heterogeneity of inter-rater reliabilities of grant peer reviews and its determinants: a general estimating equations approach

Background

One of the most important weaknesses of the peer review process is that different reviewers’ ratings of the same grant proposal typically differ. Studies on the inter-rater reliability of peer reviews mostly report only average values across all submitted proposals. But inter-rater reliabilities can vary depending on the scientific discipline or the requested grant sum, for instance.

Goal

Taking the Austrian Science Fund (FWF) as an example, we aimed to investigate empirically the heterogeneity of inter-rater reliabilities (intraclass correlation) and its determinants.

Methods

The data consisted of N = 8,329 proposals with N = 23,414 overall ratings by reviewers, which were statistically analyzed using the generalized estimating equations approach (GEE).

Results

We found an overall intraclass correlation (ICC) of reviewer? ratings of ρ = .259 with a 95% confidence interval of [.249,.279]. In humanities the ICCs were statistically significantly higher than in all other research areas except technical sciences. The ICC in biosciences deviated statistically significantly from the average ICC. Other factors (besides the research areas), such as the grant sum requested, had negligible influence on the ICC.

Conclusions

Especially in biosciences, the number of reviewers of each proposal should be increased so as to increase the ICC.

Predicting Distal Radius Bone Strains and Injury in Response to Impacts Using Multi-Axial Accelerometers

Measuring a bone’s response to impact has traditionally been done using strain gauges that are attached directly to the bone. Accelerometers have also been used for this purpose because they are reusable, inexpensive and can be attached easily. However, little data are available relating measured accelerations to bone injury, or to judge if accelerometers are reasonable surrogates for strain gauges in terms of their capacity to predict bone injuries. Impacts were applied with a custom designed pneumatic impact system to eight fresh-frozen human cadaveric radius specimens. Impacts were repeatedly applied with increasing energy until ultimate failure occurred. Three multiaxial strain gauge rosettes were glued to the bone (two distally and one proximally). Two multiaxial accelerometers were attached to the distal dorsal and proximal volar aspects of the radius. Overall, peak minimum and maximum principal strains were calculated from the strain-time curves from each gauge. Peak accelerations and acceleration rates were measured parallel (axial) and perpendicular (off-axis) to the long axis of the radius. Logistic generalized estimating equations were used to create strain and acceleration-based injury prediction models. To develop strain prediction models based on the acceleration variables, Linear generalized estimating equations were employed. The logistic models were assessed according to the quasi-likelihood under independence model criterion (QIC), while the linear models were assessed by the QIC and the marginal R2. Peak axial and off-axis accelerations increased significantly (with increasing impact energy) across all impact trials. The best injury prediction model (QIC = 9.42) included distal resultant acceleration (p < 0.001) and donor body mass index (BMI) (p < 0.001). Compressive and tensile strains were best predicted by separate uni-variate models, including peak distal axial acceleration (R2 = 0.79) and peak off-axis acceleration (R2 = 0.79), respectively. Accelerometers appear to be a valid surrogate to strain gauges for measuring the general response of the bone to impact and predicting the probability of bone injury.

Is use of formal community services by older women related to changes in their informal care arrangements?

This paper examines how the relationships between the factors (predisposing, enabling and illness) of the 1973 Andersen framework and service use are influenced by changes in the caring role in older women of the 1921–26 cohort of the Australian Longitudinal Study on Women's Health. Outcome variables were the use of three formal community support services: (a) nursing or community health services, (b) home-making services and (c) home maintenance services. Predictor variables were survey wave and the following carer characteristics: level of education, country of birth, age, area of residence, ability to manage on income, need for care, sleep difficulty and changes in caring role. Carer changes were a significant predictor of formal service use. Their inclusion did not attenuate the relationship between the Andersen framework factors and service use, but instead provided a more complete representation of carers' situations. Women were more likely to have used support services if they had changed into or out of co-resident caring or continued to provide co-resident care for a frail, ill or disabled person, needed care themselves, and reported sleep difficulties compared with women who did not provide care. These findings are important because they indicate that support services are particularly relevant to women who are changing their caring role and who are themselves in need of care.

Approaches to increase arsenic awareness in Bangladesh: an evaluation of an arsenic education program

The objective of this study was to design and evaluate a household-level arsenic education and well water arsenic testing intervention to increase arsenic awareness in Bangladesh. The authors randomly selected 1,000 study respondents located in 20 villages in Singair, Bangladesh. The main outcome was the change in knowledge of arsenic from baseline to follow-up 4 to 6 months after the household received the intervention. This was assessed through a pre- and postintervention quiz concerning knowledge of arsenic. Respondents were between 18 and 102 years of age, with an average age of 37 years; 99.9% were female. The knowledge of arsenic quiz scores for study participants were significantly higher at follow-up compared with baseline. The intervention was effective in increasing awareness of the safe uses of arsenic-contaminated water and dispelling the misconception that boiling water removes arsenic. At follow-up, nearly all respondents were able to correctly identify the meaning of a red (contaminated) and green (arsenic safe) well relative to arsenic (99%). The educational program also significantly increased the proportion of respondents who were able to correctly identify the health implications of arsenic exposure. However, the intervention was not effective in dispelling the misconceptions in the population that arsenicosis is contagious and that illnesses such as cholera, diarrhea, and vomiting could be caused by arsenic. Further research is needed to develop effective communication strategies to dispel these misconceptions. This study demonstrates that a household-level arsenic educational program can be used to significantly increase arsenic awareness in Bangladesh.

An information criterion for marginal structural models

Marginal structural models were developed as a semiparametric alternative to the G-computation formula to estimate causal effects of exposures. In practice, these models are often specified using parametric regression models. As such, the usual conventions regarding regression model specification apply. This paper outlines strategies for marginal structural model specification and considerations for the functional form of the exposure metric in the final structural model. We propose a quasi-likelihood information criterion adapted from use in generalized estimating equations. We evaluate the properties of our proposed information criterion using a limited simulation study. We illustrate our approach using two empirical examples. In the first example, we use data from a randomized breastfeeding promotion trial to estimate the effect of breastfeeding duration on infant weight at 1 year. In the second example, we use data from two prospective cohorts studies to estimate the effect of highly active antiretroviral therapy on CD4 count in an observational cohort of HIV-infected men and women. The marginal structural model specified should reflect the scientific question being addressed but can also assist in exploration of other plausible and closely related questions. In marginal structural models, as in any regression setting, correct inference depends on correct model specification. Our proposed information criterion provides a formal method for comparing model fit for different specifications.

Modeling spring habitat requirements of the endangered brown eared pheasant Crossoptilon mantchuricum in the Huanglong Mountains, Shaanxi Province, China

A detailed understanding of the habitat needs of brown eared pheasants (Crossoptilon mantchuricum) is essential for conserving the species. We carried out field surveys in the Huanglong Mountains of Shaanxi Province, China, from March to June in 2007 and 2008. We arrayed a total of 206 grid plots (200 × 200 m) along transects in 2007 and 2008 and quantified a suite of environmental variables for each one. In the optimal logistic regression model, the most important variables for brown eared pheasants were slope degree, tree cover, distance to nearest water, cover and depth of fallen leaves. Hosmer and Leweshow goodness-of-fit tests explained that logistic models for the species were good fits. The model suggested that spring habitat selection of the brown eared pheasant was negatively related to distance to nearest water and slope degree, and positively to cover of trees and cover and depth of fallen leaves. In addition, the observed detected and undetected grids in 2007 did not show significant differences with predictions based on the model. These results showed that the model could well predict the habitat selection of brown eared pheasants. Based on these predictive models, we suggest that habitat management plans incorporating this new information can now focus more effectively on restrictions on the number of tourists entering the nature reserve, prohibition of firewood collection, livestock grazing, and medicinal plant harvesting by local residents in the core areas, protection of mixed forest and sources of the permanent water in the reserve, and use of alternatives to firewood.

Does tobacco-control mass media campaign exposure prevent relapse among recent quitters?

OBJECTIVE

To determine whether greater mass media campaign exposure may assist recent quitters to avoid relapse.

METHOD

Using date of data collection and postcode, media market estimates of televised tobacco-control advertising exposure measured by gross ratings points (GRPs) were merged with a replenished cohort study of 443 Australians who had quit in the past year. Participants' demographic and smoking characteristics prior to quitting, and advertising exposure in the period after quitting, were used to predict relapse 1 year later.

RESULTS

In multivariate analysis, each increase in exposure of 100 GRPs (i.e., 1 anti-smoking advertisement) in the three-month period after the baseline quit was associated with a 5% increase in the odds of not smoking at follow-up (OR = 1.05, 95% CI 1.02-1.07, p < 0.001). This relationship was linear and unmodified by length of time quit prior to the baseline interview. At the mean value of 1081 GRPs in the 3 months after the baseline-quit interview, the predicted probability of being quit at follow-up was 52%, whereas it was 41% for the minimum (0) and 74% for the maximum (3,541) GRPs.

CONCLUSION

Greater exposure to tobacco-control mass media campaigns may reduce the likelihood of relapse among recent quitters.

Development and Evaluation of Two Pecan Scab Prediction Models

Fusicladium effusum (syn. Cladosporium caryigenum), causal agent of pecan scab, is the most economically important pathogen of pecan (Carya illinoinensis). A weather-based advisory is currently used in Oklahoma to assess the need for fungicide application and requires the accumulation of scab hours. A scab hour is defined as an hour with average temperature ≥21.1°C and relative humidity ≥90%. To assess the validity of the thresholds in the advisory, repeated ratings of disease severity were taken on fruit at five locations during the 1994-96 and 2009-10 growing seasons, resulting in a total of eight site years. Hourly weather variables were also examined, including temperature, relative humidity, dew point, dew point depression, total solar radiation, and total rainfall. Rain and disease severity were converted to binomial variables where a rain event (≥2.5 mm) and disease severity (≥25%) were coded as 1 and all other events as 0. Logistic regression models adjusted for correlated data were developed using generalized estimating equations. Two models were developed: a temperature/relative humidity model and a dew point/dew point depression model. For the temperature/relative humidity model, the best fitting model included all main effects. Using this model, validation exercises assuming no rain and total solar radiation of 22.5 MJ m^-2 resulted in a 0.45 probability of pecan scab development when the temperature was 21°C and relative humidity was 90%. Findings of this model were further validated during field studies that evaluated different combinations of temperature and relative humidity thresholds for scheduling fungicide applications. These analyses indicated that the current thresholds of temperature and relative humidity are viable, but a modification of the relative humidity component should be considered. For the dew point/dew point depression model, a reduced model, including dew point, dew point depression, and the binomial rain variable, was considered adequate for explaining scab events, which suggests that future model building to describe pecan scab epidemics should include dew point, dew point depression, rain, and total solar radiation as independent variables. This article originally appeared in the January issue, Volume 96, pages 117-123. It was changed to correct errors in a measurement conversion that appeared throughout.

Predictors of high-grade esophagitis after definitive three-dimensional conformal therapy, intensity-modulated radiation therapy, or proton beam therapy for non-small cell lung cancer

INTRODUCTION

We analyzed the ability of various patient- and treatment-related factors to predict radiation-induced esophagitis (RE) in patients with non-small cell lung cancer (NSCLC) treated with three-dimensional conformal radiation therapy (3D-CRT), intensity-modulated radiation therapy (IMRT), or proton beam therapy (PBT).

METHODS AND MATERIALS

Patients were treated for NSCLC with 3D-CRT, IMRT, or PBT at MD Anderson from 2000 to 2008 and had full dose-volume histogram (DVH) data available. The endpoint was severe (grade≥3) RE. The Lyman-Kutcher-Burman (LKB) model was used to analyze RE as a function of the fractional esophageal DVH, with clinical variables included as dose-modifying factors.

RESULTS

Overall, 652 patients were included: 405 patients were treated with 3D-CRT, 139 with IMRT, and 108 with PBT; corresponding rates of grade≥3 RE were 8%, 28%, and 6%, respectively, with a median time to onset of 42 days (range, 11-93 days). A fit of the fractional DVH LKB model demonstrated that the fractional effective dose was significantly different (P=.046) than 1 (fractional mean dose) indicating that high doses to small volumes are more predictive than mean esophageal dose. The model fit was better for 3D-CRT and PBT than for IMRT. Including receipt of concurrent chemotherapy as a dose-modifying factor significantly improved the LKB model (P=.005), and the model was further improved by including a variable representing treatment with >30 fractions. Examining individual types of chemotherapy agents revealed a trend toward receipt of concurrent taxanes and increased risk of RE (P=.105).

CONCLUSIONS

Fractional dose (dose rate) and number of fractions (total dose) distinctly affect the risk of severe RE, estimated using the LKB model, and concurrent chemotherapy improves the model fit. This risk of severe RE is underestimated by this model in patients receiving IMRT.

Social familiarity governs prey patch-exploitation, -leaving and inter-patch distribution of the group-living predatory mite Phytoseiulus persimilis

BACKGROUND

In group-living animals, social interactions and their effects on other life activities such as foraging are commonly determined by discrimination among group members. Accordingly, many group-living species evolved sophisticated social recognition abilities such as the ability to recognize familiar individuals, i.e. individuals encountered before. Social familiarity may affect within-group interactions and between-group movements. In environments with patchily distributed prey, group-living predators must repeatedly decide whether to stay with the group in a given prey patch or to leave and search for new prey patches and groups.

METHODOLOGY/PRINCIPAL FINDINGS

Based on the assumption that in group-living animals social familiarity allows to optimize the performance in other tasks, as for example predicted by limited attention theory, we assessed the influence of social familiarity on prey patch exploitation, patch-leaving, and inter-patch distribution of the group-living, plant-inhabiting predatory mite Phytoseiulus persimilis. P. persimilis is highly specialized on herbivorous spider mite prey such as the two-spotted spider mite Tetranychus urticae, which is patchily distributed on its host plants. We conducted two experiments with (1) groups of juvenile P. persimilis under limited food on interconnected detached leaflets, and (2) groups of adult P. persimilis females under limited food on whole plants. Familiar individuals of both juvenile and adult predator groups were more exploratory and dispersed earlier from a given spider mite patch, occupied more leaves and depleted prey more quickly than individuals of unfamiliar groups. Moreover, familiar juvenile predators had higher survival chances than unfamiliar juveniles.

CONCLUSIONS/SIGNIFICANCE

We argue that patch-exploitation and -leaving, and inter-patch dispersion were more favorably coordinated in groups of familiar than unfamiliar predators, alleviating intraspecific competition and improving prey utilization and suppression.

Police confrontations among street-involved youth in a Canadian setting

BACKGROUND

Street-level policing has been recognized as a driver of health-related harms among people who inject drugs (IDU). However, the extent of interaction between police and street-involved youth has not been well characterized. We examined the incidence and risk factors for police confrontations among street-involved youth in a Canadian setting.

METHODS

Using data derived from participants enrolled in the At-Risk Youth Study (ARYS) between 2005 and 2011, we assessed factors associated with being stopped, searched, or detained by police without arrest in the previous six months using generalized estimating equations (GEE) with logit link for binary outcomes.

RESULTS

Among 991 participants followed during the study period, 440 (44.4%) reported being stopped, searched, or detained by police for an incidence density of 49.20 (95% confidence interval [CI]: 36.42-65.01) per 100 person years. In multivariate GEE analyses, factors associated with police confrontations included: male gender (adjusted odds ratio [AOR]=1.35), homelessness (AOR=2.05), recent incarceration (AOR=1.78), daily cannabis use (AOR=1.31), daily heroin injecting (AOR=1.36), crack pipe/syringe sharing (AOR=1.61), injection drug use (AOR=1.37), public drug use (AOR=2.19), sex work involvement (AOR=1.67), and drug dealing (AOR=1.49) (all p<0.05). In total, 19.0% of participants reported that police confiscated their drug paraphernalia without arresting them. Additionally, 16.9% of individuals reported experiencing violence at the hands of police.

CONCLUSION

We found that various factors, such as homelessness and markers of more severe addiction, increased the likelihood of being confronted by police, and police confrontations were associated with markers of health-related harm among street youth. These findings highlight the need for social and structural interventions that best enable police to fulfil public safety and public order objectives without negatively influencing health behaviours of street youth.

A double-blind randomized controlled trial of N-acetylcysteine in cannabis-dependent adolescents

OBJECTIVE

Preclinical findings suggest that the over-the-counter supplement N-acetylcysteine (NAC), via glutamate modulation in the nucleus accumbens, holds promise as a pharmacotherapy for substance dependence. The authors investigated NAC as a novel cannabis cessation treatment in adolescents, a vulnerable group for whom existing treatments have shown limited efficacy.

METHOD

In an 8-week double-blind randomized placebo-controlled trial, treatment-seeking cannabis-dependent adolescents (ages 15-21 years; N=116) received NAC (1200 mg) or placebo twice daily as well as a contingency management intervention and brief (&lt;10 minutes) weekly cessation counseling. The primary efficacy measure was the odds of negative weekly urine cannabinoid test results during treatment among participants receiving NAC compared with those receiving placebo, in an intent-to-treat analysis. The primary tolerability measure was frequency of adverse events, compared by treatment group.

RESULTS

Participants receiving NAC had more than twice the odds, compared with those receiving placebo, of having negative urine cannabinoid test results during treatment (odds ratio=2.4, 95% CI=1.1-5.2). Exploratory secondary abstinence outcomes favored NAC but were not statistically significant. NAC was well tolerated, with minimal adverse events.

CONCLUSIONS

This is the first randomized controlled trial of pharmacotherapy for cannabis dependence in any age group to yield a positive primary cessation outcome in an intent-to-treat analysis. Findings support NAC as a pharmacotherapy to complement psychosocial treatment for cannabis dependence in adolescents.

Intergroup conflict: Ecological predictors of winning and consequences of defeat in a wild primate population

In many social species, competition between groups is a major factor proximately affecting group-level movement patterns and space use and ultimately shaping the evolution of group living and complex sociality. Here we evaluated the factors influencing group-level dominance among 5 social groups of wild baboons (Papio cynocephalus), in particular focusing on the spatial determinants of dominance and the consequences of defeat. When direct conflict occurred between conspecific baboon groups, the winning group was predicted by differences in the number of adult males in each group and/or groups that had used the areas surrounding the encounter location more intensively than their opponent in the preceding 9 or 12 months. Relative intensity of space use over shorter timescales examined (3 and 6 months) was a poor predictor of the interaction's outcome. Losing groups but not winning groups experienced clear short-term costs. Losing groups used the area surrounding the interaction less following an agonistic encounter (relative to their intensity of use of the area prior to the interaction). These findings offer insight into the influences and consequences of intergroup competition on group-level patterns of space use.

Longitudinal association between early life socio-environmental factors and attention function at the age 11 years

Prenatal and early-life exposures can affect the course of children's neuropsychological development well into pre-adolescence, given the vulnerability of the developing brain. However, it is unknown which socio-environmental factors at early childhood can influence specific cognitive processes like attention at a later age. In this study, we aim to determine social and environmental exposures in early childhood that may be associated with attention function of 11-year-olds. We measured attention function using the continuous performance test-II (CPT-II) on 393 11-year old children from the Menorca's birth-cohort within the INMA-project (Spain), and pre-selected a list of socio-environmental observations taken when they were up to 4 years of age. We found that earlier socio-environmental characteristics, such as parental social class, educational level and maternal mental health are associated with later inattentive and impulsive symptomatology through a higher rate of omission and commission errors. In addition, omission errors were higher in children with atopy and lower in those whose mothers took dietary supplementation with folic acid and vitamins during pregnancy. Breastfeeding played a protective role against commission errors, while higher DDE and PCBs levels at age 4 were associated with slow speed response. Our findings suggest that a number of life socio-environmental factors during prenatal life and early childhood, such as socio-demographic characteristics, breastfeeding, maternal nutritional supplementation with folic acid and vitamins and exposure to some organochlorine compounds may influence inattentive and hyperactive/impulsive symptomatology during pre-adolescence.

Adherence to and effectiveness of highly active antiretroviral treatment for HIV infection: assessing the bidirectional relationship

BACKGROUND

It is well established that high adherence to HIV-infected patients on highly active antiretroviral treatment (HAART) is a major determinant of virological and immunologic success. Furthermore, psychosocial research has identified a wide range of adherence factors including patients' subjective beliefs about the effectiveness of HAART. Current statistical approaches, mainly based on the separate identification either of factors associated with treatment effectiveness or of those associated with adherence, fail to properly explore the true relationship between adherence and treatment effectiveness. Adherence behavior may be influenced not only by perceived benefits-which are usually the focus of related studies-but also by objective treatment benefits reflected in biological outcomes.

METHODS

Our objective was to assess the bidirectional relationship between adherence and response to treatment among patients enrolled in the ANRS CO8 APROCO-COPILOTE study. We compared a conventional statistical approach based on the separate estimations of an adherence and an effectiveness equation to an econometric approach using a 2-equation simultaneous system based on the same 2 equations.

RESULTS

Our results highlight a reciprocal relationship between adherence and treatment effectiveness. After controlling for endogeneity, adherence was positively associated with treatment effectiveness. Furthermore, CD4 count gain after baseline was found to have a positive significant effect on adherence at each observation period. This immunologic parameter was not significant when the adherence equation was estimated separately. In the 2-equation model, the covariances between disturbances of both equations were found to be significant, thus confirming the statistical appropriacy of studying adherence and treatment effectiveness jointly.

CONCLUSIONS

Our results, which suggest that positive biological results arising as a result of high adherence levels, in turn reinforce continued adherence and strengthen the argument that patients who do not experience rapid improvement in their immunologic and clinical statuses after HAART initiation should be prioritized when developing adherence support interventions. Furthermore, they invalidate the hypothesis that HAART leads to "false reassurance" among HIV-infected patients.

Effects of predation and habitat structure on the abundance and population structure of the rock shrimp Rhynchocinetes typus (Caridea) on temperate rocky reefs

Human disturbances, such as overfishing, may disrupt predator-prey interactions and modify food webs. Underwater surveys were carried out at six shallow-water reef barrens in temperate waters of northern-central Chile from October to December 2010 to describe the effects of predation, habitat complexity (low, medium and high) and refuge availability on the abundance and population structure of the rock shrimp Rhynchocinetes typus (Rhynchocinetidae), an important mesoconsumer on subtidal hard substrata. Three sites were within managed (restricted access) areas for fishermen, and three were unmanaged (open-access). Field observations and tethering experiments were conducted to examine the relationship between fish and shrimp abundances, and the relative predation rates on shrimps. Direct effects of predation on R. typus body-size distribution were examined from shrimps collected in the field and fish stomachs. The presence and the abundance of R. typus increased with habitat reef complexity and refuge availability. Shrimp abundance was negatively related to fish abundance in managed areas, but not in open-access areas, where shrimp densities were the highest. Also, predation rates and body-size distribution of shrimps were unrelated, although fish consumed more large shrimps than should be expected from their distribution in the field. R. typus occurred most often in shelters with wide openings, offering limited protection against predators, but providing potential aggregation sites for shrimps. Overall, direct effects of predation on shrimp densities and population structure were weak, but indirect effects on shrimp distribution within reefs appear to have been mediated through behavioural responses. Our study highlights the need to assess both numerical and behavioural responses of prey to determine the effects of predator loss on mesoconsumer populations.

Air pollution and symptoms of depression in elderly adults

BACKGROUND

Although the effect of air pollution on various diseases has been extensively investigated, few studies have examined its effect on depression.

OBJECTIVES

We investigated the effect of air pollution on symptoms of depression in an elderly population.

METHODS

We enrolled 537 participants in the study who regularly visited a community center for the elderly located in Seoul, Korea. The Korean version of the Geriatric Depression Scale-Short Form (SGDS-K) was used to evaluate depressive symptomatology during a 3-year follow-up study. We associated ambient air pollutants with SGDS-K results using generalized estimating equations (GEE). We also conducted a factor analysis with items on the SGDS-K to determine which symptoms were associated with air pollution.

RESULTS

SGDS-K scores were positively associated with interquartile range (IQR) increases in the 3-day moving average concentration of particulate matter with an aerodynamic diameter ≤ 10 μm (PM10) [17.0% increase in SGDS-K score, 95% confidence interval (CI): 4.9%, 30.5%], the 0-7 day moving average of nitrogen dioxide [NO2; 32.8% (95% CI: 12.6%, 56.6%)], and the 3-day moving average of ozone [O3; 43.7% (95% CI: 11.5%, 85.2%)]. For these three pollutants, factor analysis showed that air pollution was more strongly associated with emotional symptoms such as feeling happy and satisfied than with somatic or affective symptoms.

CONCLUSIONS

Our study suggests that increases in PM10, NO2, and O3 may increase depressive symptoms among the elderly. Of the symptoms evaluated, ambient air pollution was most strongly associated with emotional symptoms.

Trends in antibiotic use in Massachusetts children, 2000-2009

OBJECTIVE

Antibiotic use rates have declined dramatically since the 1990s. We aimed to determine if, when, and at what level the decline in antibiotic-dispensing rates ended and which diagnoses contributed to the trends.

METHODS

Antibiotic dispensings and diagnoses were obtained from 2 health insurers for 3- to <72-month-olds in 16 Massachusetts communities from 2000 to 2009. Population-based antibiotic-dispensing rates per person-year (p-y) were determined according to year (September-August) for 3 age groups. Fit statistics were used to identify the most likely year for a change in trend. Rates for the first and last years were compared according to antibiotic category and associated diagnosis.

RESULTS

From 2000-2001 to 2008-2009, the antibiotic-dispensing rate for 3- to <24-month-olds decreased 24% (2.3-1.8 antibiotic dispensings per p-y); for 24- to <48-month-olds, it decreased 18% (1.6-1.3 antibiotic dispensings per p-y); and for 48- to <72-month-olds, it decreased 20% (1.4-1.1 antibiotic dispensings per p-y). For 3- to <48-month-olds, rates declined until 2004-2005 and remained stable thereafter; the downward trend for 48- to <72-month-olds ended earlier in 2001-2002. Among 3- to <24-month-olds, first-line penicillin use declined 26%. For otitis media, the dispensing rate decreased 14% and the diagnosis rate declined 9%, whereas the treatment fraction was stable at 63%.

CONCLUSIONS

The downward trend in antibiotic dispensings to young children in these communities ended by 2004-2005. This trend was driven by a declining otitis media diagnosis rate. Continued monitoring of population-based dispensing rates will support efforts to avoid returning to previous levels of antibiotic overuse.

Clinical features of parricide in patients with schizophrenia

OBJECTIVE

This study aimed to investigate the factors associated with parricide in patients with schizophrenia who committed homicide.

METHOD

Among patients with schizophrenia who were in the National Institute of Forensic Psychiatry between November and December 2007, 88 patients who committed homicides were enrolled; 59 had committed parricide, and 29 had killed strangers. Medical charts, written expert opinions, written records of police or prosecutors, and court decisions were reviewed. Direct interviews with patients were also conducted.

RESULTS

Significant factors associated with parricide among homicidal patients with schizophrenia were living with the victim, female sex of the victim, and offense-provoking events including scolding, threatening forced hospitalisation, and forcing medication on the patient before the homicide. Capgras syndrome was present at a significantly higher rate in the parricide group than in the stranger group. Drug compliance at the time of the offence was low in both groups.

CONCLUSIONS

Untreated psychotic symptoms such as Capgras syndrome, living with elderly parents, especially mothers, and conflicts caused by victims' scolding, threatening forced hospitalisation, and forcing medication on the patients are associated with parricide among homicide offenders with schizophrenia.

A cluster-based randomized controlled trial promoting community participation in arsenic mitigation efforts in Bangladesh

OBJECTIVE

To reduce arsenic (As) exposure, we evaluated the effectiveness of training community members to perform water arsenic (WAs) testing and provide As education compared to sending representatives from outside communities to conduct these tasks.

METHODS

We conducted a cluster based randomized controlled trial of 20 villages in Singair, Bangladesh. Fifty eligible respondents were randomly selected in each village. In 10 villages, a community member provided As education and WAs testing. In a second set of 10 villages an outside representative performed these tasks.

RESULTS

Overall, 53% of respondents using As contaminated wells, relative to the Bangladesh As standard of 50 μg/L, at baseline switched after receiving the intervention. Further, when there was less than 60% arsenic contaminated wells in a village, the classification used by the Bangladeshi and UNICEF, 74% of study households in the community tester villages, and 72% of households in the outside tester villages reported switching to an As safe drinking water source. Switching was more common in the outside-tester (63%) versus community-tester villages (44%). However, after adjusting for the availability of arsenic safe drinking water sources, well switching did not differ significantly by type of As tester (Odds ratio = 0.86[95% confidence interval 0.42-1.77). At follow-up, among those using As contaminated wells who switched to safe wells, average urinary As concentrations significantly decreased.

CONCLUSION

The overall intervention was effective in reducing As exposure provided there were As-safe drinking water sources available. However, there was not a significant difference observed in the ability of the community and outside testers to encourage study households to use As-safe water sources. The findings of this study suggest that As education and WAs testing programs provided by As testers, irrespective of their residence, could be used as an effective, low cost approach to reduce As exposure in many As-affected areas of Bangladesh.

Incidence and risk factors for non-fatal overdose among a cohort of recently incarcerated illicit drug users

BACKGROUND

Release from prison is associated with a markedly increased risk of both fatal and non-fatal drug overdose, yet the risk factors for overdose in recently released prisoners are poorly understood. The aim of this study was to identify risk and protective factors for non-fatal overdose (NFOD) among a cohort of illicit drug users in Vancouver, Canada, according to recent incarceration.

METHODS

Prospective cohort of 2515 community-recruited illicit drug users in Vancouver, Canada, followed from 1996 to 2010. We examined factors associated with NFOD in the past six months separately among those who did and did not also report incarceration in the last six months.

RESULTS

One third of participants (n=829, 33.0%) reported at least one recent NFOD. Among those recently incarcerated, risk factors independently and positively associated with NFOD included daily use of heroin, benzodiazepines, cocaine or methamphetamine, binge drug use, public injecting and previous NFOD. Older age, methadone maintenance treatment and HIV seropositivity were protective against NFOD. A similar set of risk factors was identified among those who had not been incarcerated recently.

CONCLUSIONS

Among this cohort, and irrespective of recent incarceration, NFOD was associated with a range of modifiable risk factors including more frequent and riskier patterns of drug use. Not all ex-prisoners are at equal risk of overdose and there remains an urgent need to develop and implement evidence-based preventive interventions, targeting those with modifiable risk factors in this high risk group.

Predictors of treatment outcomes among depressed women with childhood sexual abuse histories

BACKGROUND

A notable portion (21%) of female patients receiving treatment for depression in community mental health centers (CMHC) has childhood sexual abuse (CSA) histories. Treatment outcomes in this population are heterogeneous; identifying factors associated with differential outcomes could inform treatment development. This exploratory study begins to address the gap in what is known about predictors of treatment outcomes among depressed women with sexual abuse histories.

METHOD

Seventy women with major depressive disorder and CSA histories in a CMHC were randomly assigned to interpersonal psychotherapy (n = 37) or usual care (n = 33). Using generalized estimating equations, we examined four pretreatment predictor domains (i.e. sociodemographic characteristics, clinical features, social and physical functioning, and trauma features) potentially related to depression treatment outcomes.

RESULTS

Among sociodemographic characteristics, Black race/ethnicity, public assistance income, and unemployment were associated with less depressive symptom reduction over the course of treatment. Two clinical features, chronic depression and borderline personality disorder, were also related to less reduction in depressive symptoms across the treatment period.

CONCLUSION

Our results demonstrate the clinical relevance of attending to predictors of depressed women with CSA histories being treated in public sector mental health centers. Particular sociodemographic characteristics and clinical features among these women may be significant indicators of risk for relatively poorer treatment outcomes.

Red cell distribution width improves the simplified acute physiology score for risk prediction in unselected critically ill patients

Introduction

Recently, red cell distribution width (RDW), a measure of erythrocyte size variability, has been shown to be a prognostic marker in critical illness. The aim of this study was to investigate whether adding RDW has the potential to improve the prognostic performance of the simplified acute physiology score (SAPS) to predict short- and long-term mortality in an independent, large, and unselected population of intensive care unit (ICU) patients.

Methods

This observational cohort study includes 17,922 ICU patients with available RDW measurements from different types of ICUs. We modeled the association between RDW and mortality by using multivariable logistic regression, adjusting for demographic factors, comorbidities, hematocrit, and severity of illness by using the SAPS.

Results

ICU-, in-hospital-, and 1-year mortality rates in the 17,922 included patients were 7.6% (95% CI, 7.2 to 8.0), 11.2% (95% CI, 10.8 to 11.7), and 25.4% (95% CI, 24.8 to 26.1). RDW was significantly associated with in-hospital mortality (OR per 1% increase in RDW (95%CI)) (1.14 (1.08 to 1.19), P < 0.0001), ICU mortality (1.10 (1.06 to 1.15), P < 0.0001), and 1-year mortality (1.20 (95% CI, 1.14 to 1.26); P < 0.001). Adding RDW to SAPS significantly improved the AUC from 0.746 to 0.774 (P < 0.001) for in-hospital mortality and 0.793 to 0.805 (P < 0.001) for ICU mortality. Significant improvements in classification of SAPS were confirmed in reclassification analyses. Subgroups demonstrated robust results for gender, age categories, SAPS categories, anemia, hematocrit categories, and renal failure.

Conclusions

RDW is a promising independent short- and long-term prognostic marker in ICU patients and significantly improves risk stratification of SAPS. Further research is needed the better to understand the pathophysiology underlying these effects.

Impact of higher hemoglobin targets on blood pressure and clinical outcomes: a secondary analysis of CHOIR

BACKGROUND

Targeting a higher hemoglobin in patients with chronic kidney disease leads to adverse cardiovascular outcomes, yet the reasons remain unclear. Herein, we sought to determine whether changes in erythropoiesis-stimulating agent (ESA) dose and in hemoglobin were predictive of changes in blood pressure (BP) and whether these changes were associated with cardiovascular outcomes.

METHODS

In this secondary analysis of 1421 Correction of Hemoglobin and Outcomes in Renal Disease (CHOIR) participants, mixed model analyses were used to describe monthly changes in ESA dose and hemoglobin with changes in diastolic BP (DBP) and systolic BP (SBP). Poisson modeling was performed to determine whether changes in hemoglobin and BP were associated with the composite end point of death or cardiovascular outcomes.

RESULTS

Monthly average DBP, but not SBP, was higher in participants in the higher hemoglobin arm. Increases in ESA doses and in hemoglobin were significantly associated with linear increases in DBP, but not consistently with increases in SBP. In models adjusted for demographics and comorbid conditions, increases in ESA dose (>0 U) and larger increases in hemoglobin (>1.0 g/dL/month) were associated with poorer outcomes [event rate ratio per 1000 U weekly dose per month increase 1.05, (1.02-1.08), P = 0.002 and event rate ratio 1.70 (1.02-2.85), P = 0.05, respectively]. However, increasing DBP was not associated with adverse outcomes [event rate ratio 1.01 (0.98-1.03), P = 0.7].

CONCLUSION

Among CHOIR participants, higher hemoglobin targets, increases in ESA dose and in hemoglobin were associated both with increases in DBP and with higher event rates; however, increasing DBP was not associated with adverse outcomes.

Developmental trajectory and environmental moderation of the effect of ALDH2 polymorphism on alcohol use

BACKGROUND

In the aldehyde dehydrogenase 2 (ALDH2) gene, the ALDH2*2 allele, prevalent in East Asian populations, encodes an enzyme with severely reduced activity, thereby disrupting the normal metabolism of alcohol. Possession of the ALDH2*2 allele has been repeatedly shown to be associated with lower risk for alcohol dependence and reduced alcohol use. However, relatively few studies have considered whether the magnitude of the effect of ALDH2 polymorphism upon drinking is related to developmental stage or varies by environmental context.

METHODS

In a longitudinally assessed sample of 356 adopted adolescents and young adults of East Asian descent, we examined the progression over time of the relationship between ALDH2 genotype and multiple measures of drinking behavior. We also sought to determine whether the environmental influences of nonbiological parent and elder sibling alcohol use and misuse, as well as deviant peer behavior, moderated the effect of ALDH2 genotype upon alcohol use.

RESULTS

Across all measures of alcohol use, the association between ALDH2*2 allele possession and reduced drinking went from negligible to moderate between mid-adolescence and early adulthood. A combined index of adoptive parent alcohol use and misuse consistently moderated the protective effect of the ALDH2*2 allele across the measures of quantity and frequency of alcohol use, and symptomology, such that high parental alcohol use and misuse reduced the protective effect of the ALDH2*2 allele, while low parental alcohol use and misuse enhanced the effect of the allele. Neither a combined index of elder sibling alcohol use and misuse, nor deviant peer behavior was consistently related to the effect of ALDH2 genotype.

CONCLUSIONS

The protective effect of the ALDH2*2 allele increases over the course of adolescence and young adulthood and is modified by the environmental influence of parental alcohol use and misuse. As such, ALDH2 provides a model system for exploring the nature of gene-environment interplay across development.

Poor achievement of guidelines-recommended targets in type 2 diabetes: findings from a contemporary prospective cohort study

AIMS

To prospectively evaluate diabetes management in the primary care setting and explore factors related to guideline-recommended triple target achievement [blood pressure (BP) ≤ 130/80 mmHg, A1C ≤ 7% and low-density lipoprotein (LDL)-cholesterol < 2.5 mmol/l].

METHODS

Baseline, 6 and 12 month data on clinical and laboratory parameters were measured in 3002 patients with type 2 diabetes enrolled as part of a prospective quality enhancement research initiative in Canada. A generalised estimating equation model was fitted to assess variables associated with triple target achievement.

RESULTS

At baseline, 54%, 53% and 64% of patients, respectively, had BP, A1C and LDL-cholesterol at target; all three goals were met by 19% of patients. The percentage of individuals achieving these targets significantly increased during the study [60%, 57%, 76% and 26%, respectively, at the final visit, p < 0.0001 except for A1C, p = 0.27]. A much smaller proportion of patients had adequate control during the entire study period [30%, 39%, 53% and 7%, respectively]. In multivariable analysis, women, patients younger than 65 years and patients of Afro-Canadian origin were less likely to achieve the triple target.

DISCUSSION

As part of a quality enhancement research initiative, we observed important improvements in the attainment of guidelines-recommended targets in patients with type 2 diabetes followed for a 12-month period in the primary care setting; however, many individuals still failed to achieve and especially maintain optimal goals for therapy, particularly the triple target. Results of the multivariable analysis reinforce the need to address barriers to improve diabetes care, particularly in more susceptible groups.

Diagnostic performance of gray-scale US and elastography in solid thyroid nodules

PURPOSE

To evaluate the diagnostic performance of gray-scale ultrasonography (US) and elastography in differentiating benign and malignant thyroid nodules.

MATERIALS AND METHODS

This was an institutional review board-approved retrospective study with waiver of informed consent. A total of 703 solid thyroid nodules in 676 patients (mean age, 49.7 years; range, 18-79 years) were included; there were 556 women (mean age, 49.5 years; range, 20-74 years) and 120 men (mean age, 50.7 years; range, 18-79 years). Nodules with marked hypoechogenicity, poorly defined margins, microcalcifications, and a taller-than-wide shape were classified as suspicious at grayscale US. Findings at elastography were classified according to the Rago criteria and the Asteria criteria. The diagnostic performances of gray-scale US and elastography were compared. For comparison between the diagnostic performances of gray-scale US and the combination of gray-scale US and elastography, three sets of criteria were assigned: criteria set 1, nodules with any suspicious grayscale US feature were assessed as suspicious; criteria set 2, Rago criteria were added as suspicious features to criteria set 1; and criteria set 3, Asteria criteria were added as suspicious features to criteria set 1. The diagnostic performances of gray-scale US, elastography with Rago criteria, and elastography with Asteria criteria, and odds ratios (ORs) with 95% confidence intervals for predicting thyroid malignancy were compared using generalized estimating equation analysis.

RESULTS

Of 703 nodules, 217 were malignant and 486 were benign. Sensitivity, negative predictive value (NPV), and OR of gray-scale US for the 703 nodules were 91.7%, 94.7%, and 22.1, respectively, and these values were higher than the 15.7% and 65.4% sensitivity, 71.7% and 79.1% NPV, and 3.7 and 2.6 ORs found for elastography with Rago and Asteria criteria, respectively. Specificity, positive predictive value, and accuracy for criteria set 1 were significantly higher than those for criteria sets 2 and 3 for most of the nodule subgroups that were considered.

CONCLUSION

Elastography alone, as well as the combination of elastography and gray-scale US, showed inferior performance in the differentiation of malignant and benign thyroid nodules compared with gray-scale US features; elastography was not a useful tool in recommending fine-needle aspiration biopsy.

Trends in aminoglycoside use and gentamicin-resistant gram-negative clinical isolates in US academic medical centers: implications for antimicrobial stewardship

OBJECTIVE

To measure trends in aminoglycoside antibiotic use and gentamicin-resistant clinical isolates across a network of hospitals and compare network-level relationships with those of individual hospitals.

DESIGN

Longitudinal observational investigation.

SETTING

US academic medical centers.

PARTICIPANTS

Adult inpatients.

METHODS

Adult aminoglycoside use was measured from 2002 or 2003 through 2009 in 29 hospitals. Hospital-wide antibiograms assessed gentamicin resistance by proportions and incidence rates for Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, and Escherichia coli. Mixed-effects analysis of variance was used to assess the significance of changes in aminoglycoside use and changes in resistance rates and proportions. Generalized estimating equations were used to assess the relationship between aminoglycoside use and resistance.

RESULTS

Mean aminoglycoside use declined by 41%, reflecting reduced gentamicin (P < .0001) and tobramycin (P < .005) use; amikacin use did not change. The rate and proportion of gentamicin-resistant P. aeruginosa decreased by 48% (P < .0001) and 31% (P < .0001), respectively. The rate and proportion of gentamicin-resistant E. coli increased by 166% and 124%, respectively (P < .0001), and they were related to increasing quinolone resistance in E. coli. Resistance among K. pneumoniae and A. baumannii did not change. Relationships between aminoglycoside use and resistance at the network level were highly variable at the individual hospital level.

CONCLUSIONS

Mean aminoglycoside use declined in this network of US hospitals and was associated with significant and opposite changes in rates of resistance for some organisms and no change for others. At the individual hospital level, antibiograms appear to be an unreliable reflection of antibiotic use, at least for aminoglycosides.

Keratoplasty for corneal endothelial disease, 2001-2009

PURPOSE

To determine the rates of keratoplasty for corneal endothelial disease (CED) from 2001 to 2009 in a large managed care network in the United States, factors that affect which patients undergo this procedure and surgical outcomes.

DESIGN

A retrospective review of data from a longitudinal cohort study.

PARTICIPANTS

Beneficiaries with CED aged ≥ 40 years who were receiving eye care during 2001 to 2009.

METHODS

Rates of keratoplasty for CED were determined at 6-month intervals from January 2001 to December 2009. The mean number of postoperative visits and rates of severe adverse events in the year after keratoplasty surgery were monitored over the course of the decade. Univariable and multivariable logistic regression were performed to identify sociodemographic and other factors associated with undergoing keratoplasty for CED.

MAIN OUTCOME MEASURES

Odds of undergoing keratoplasty with 95% confidence intervals, changes in the number of postoperative visits, and rates of adverse events in the year after keratoplasty.

RESULTS

Of the 38 648 enrollees who met the inclusion criteria, 2187 underwent ≥ 1 keratoplasty surgeries from January 2001 to December 2009. After adjustment for confounding factors, individuals with CED had 47% increased odds of undergoing keratoplasty during 2007-2009 relative to 2001-2006. The mean number of postoperative visits to eyecare providers in the year after keratoplasty declined from 12.6 in 2001-2006 to 10.5 in 2007-2008. There was no difference in the proportion of enrollees who developed adverse events after keratoplasty over time.

CONCLUSIONS

In this analysis of claims data, from 2001 to 2009, a period during which there was an increase in the rate of endothelial keratoplasty, we observed a trend of greater rates of keratoplasty in patients with CED and fewer visits for postoperative care in the later years of the decade compared with the earlier years, along with no change in rates of severe adverse events.

Sample size determination for quadratic inference functions in longitudinal design with dichotomous outcomes

Quadratic inference functions (QIF) methodology is an important alternative to the generalized estimating equations (GEE) method in the longitudinal marginal model, as it offers higher estimation efficiency than the GEE when correlation structure is misspecified. The focus of this paper is on sample size determination and power calculation for QIF based on the Wald test in a marginal logistic model with covariates of treatment, time, and treatment-time interaction. We have made three contributions in this paper: (i) we derived formulas of sample size and power for QIF and compared their performance with those given by the GEE; (ii) we proposed an optimal scheme of sample size determination to overcome the difficulty of unknown true correlation matrix in the sense of minimal average risk; and (iii) we studied properties of both QIF and GEE sample size formulas in relation to the number of follow-up visits and found that the QIF gave more robust sample sizes than the GEE. Using numerical examples, we illustrated that without sacrificing statistical power, the QIF design leads to sample size saving and hence lower study cost in comparison with the GEE analysis. We conclude that the QIF analysis is appealing for longitudinal studies.

Liver/biliary injuries following chemoembolisation of endocrine tumours and hepatocellular carcinoma: lipiodol vs. drug-eluting beads

BACKGROUND & AIMS

Transarterial chemoembolisation (TACE) is usually performed by injecting an emulsion of a drug and iodised oil. Drug-eluting beads (DEBs) have undeniable pharmacological advantages by offering simultaneous embolisation and sustained release of the drug to the tumour. No data are currently available on liver/biliary injury following DEB-TACE. This study describes and compares liver/biliary injuries encountered with TACE in tumours developed in cirrhotic (hepatocellular carcinoma (HCC)) and non-cirrhotic (endocrine tumours (NETs)) livers.

METHODS

In consecutive patients treated for a well-differentiated metastatic NET (n=120) or a HCC (n=88), 684 CT- and MR-scans were analysed. Liver/biliary injuries were classified as follows: dilated bile duct, portal vein narrowing, portal venous thrombosis and biloma/liver infarct. A generalised estimating equation logistic regression model was used.

RESULTS

A liver/biliary injury followed 17.2% (82/476) of sessions in 30.8% (64/208) of patients. The occurrence of liver/biliary injury was associated with DEB-TACE (OR=6.63; p<0.001) irrespectively of the tumour type. Biloma/parenchymal infarct was strongly associated with both DEB-TACE (OR=9.78; p=0.002) and NETs (OR: 8.13; p=0.04). Biloma/liver infarcts were managed conservatively but were associated with an increase in serum levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatases, and gamma glutamyl transpeptidase (p=0.005, p=0.005, p=0.012, and p=0.006, respectively).

CONCLUSIONS

Liver/biliary injuries are independently associated with DEB-TACE. Biloma/liver infarct, the most serious injury, is independently associated with both DEB-TACE and NETs. The absence of such an association in TACE of HCC may be explained by the hypertrophied peribiliary plexus observed in cirrhosis, which protects against the ischemic/chemical insult of bile ducts. We suggest caution when using DEB-TACE in the non-cirrhotic liver.