A review of covariate selection for non-experimental comparative effectiveness research

Conformity motives for alcohol use are associated with risky sexual behavior among alcohol-dependent patients in residential substance abuse treatment

Alcohol misuse is associated with a variety of negative outcomes, including risky sexual behavior (RSB). In an attempt to better identify the subset of individuals at greatest risk for these negative outcomes, a growing body of research has begun to examine the role of alcohol use motives in risk for alcohol use-related negative outcomes. Although the majority of research in this area has focused on coping motives, conformity motives may be particularly relevant to outcomes such as RSB. Specifically, conformity motives may operate as a proxy risk factor for RSB, reflecting the tendency to engage in interpersonally-oriented risk behaviors in order to avoid rejection, interpersonal conflict, or social ostracism. Therefore, the current study examined the relation between conformity motives for alcohol use and RSB in a sample of 94 patients in a residential substance abuse treatment center. Results indicated that conformity motives were associated with RSB above and beyond other motives for alcohol use, as well as relevant covariates. Findings support the notion that conformity motives may operate as a proxy risk factor that could assist in identifying individuals at elevated risk for engaging in RSB.

Comparative analysis of the cost and effectiveness of generic and brand-name antibiotics: the case of uncomplicated urinary tract infection

PURPOSE

Generic medications used for chronic diseases are beneficial in containing healthcare costs and improving drug accessibility. However, the effects of generic drugs in acute and severe illness remain controversial. This study aims to investigate treatment costs and outcomes of generic antibiotics prescribed for adults with a urinary tract infection in outpatient settings.

METHODS

The data source was the Longitudinal Health Insurance Database of Taiwan. We included outpatients aged 20 years and above with a urinary tract infection who required one oral antibiotic for which brand-name and generic products were simultaneously available. Drug cost and overall healthcare expense of the index consultation, healthcare cost during a 42-day follow-up period, and treatment failure rates were the main dependent variables. Data were compared between brand-name and generic users from the entire cohort and a propensity score-matched samples.

RESULTS

Results from the entire cohort and propensity score-matched samples were similar. Daily antibiotic cost was significantly lower among generic users than brand-name users. Significant lower total drug claims of the index consultation only existed in patients receiving the investigated antibiotics, while the drug price between brand-name and generic versions were relatively large (e.g., >50%). The overall healthcare cost of the index consultation, healthcare expenditure during a 42-day follow-up period, and treatment failure rates were similar between the two groups.

CONCLUSIONS

Compared with those treated with brand-name antibiotics, outpatients who received generic antibiotics had equivalent treatment outcomes with lower drug costs. Generic antibiotics are effective and worthy of adoption among outpatients with simple infections indicating oral antibiotic treatment. Copyright © 2016 John Wiley & Sons, Ltd.

Explanation and Elaboration Document for the STROBE-Vet Statement: Strengthening the Reporting of Observational Studies in Epidemiology-Veterinary Extension

The STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) statement was first published in 2007 and again in 2014. The purpose of the original STROBE was to provide guidance for authors, reviewers, and editors to improve the comprehensiveness of reporting; however, STROBE has a unique focus on observational studies. Although much of the guidance provided by the original STROBE document is directly applicable, it was deemed useful to map those statements to veterinary concepts, provide veterinary examples, and highlight unique aspects of reporting in veterinary observational studies. Here, we present the examples and explanations for the checklist items included in the STROBE-Vet statement. Thus, this is a companion document to the STROBE-Vet statement methods and process document (JVIM_14575 "Methods and Processes of Developing the Strengthening the Reporting of Observational Studies in Epidemiology-Veterinary (STROBE-Vet) Statement" undergoing proofing), which describes the checklist and how it was developed.

Daily hassles, mother-child relationship, and behavior problems in Muslim Arab American adolescents in immigrant families

OBJECTIVE

This longitudinal study examines reciprocal and dynamic relations among daily hassles, the mother-child relationship, and adolescent behavior problems and whether the relations differed by sociodemographic variables.

METHOD

Three waves of data about adolescent daily hassles, quality of the mother-child relationship, and adolescent behavior problems were collected from 454 Arab Muslim adolescents and their immigrant mothers over a 3-year period. Cross-lagged structural equation modeling (SEM) was used to examine reciprocal relations among the study variables.

RESULTS

Relations between the mother-child relationship and adolescent behavior problems were reciprocal, with a poor mother-child relationship contributing to greater behavior problems and behavior problems contributing to a decline in the quality of the mother-child relationship. Relations involving daily hassles were unidirectional: A better mother-child relationship contributed to fewer daily hassles and behavior problems contributed to more daily hassles but daily hassles did not contribute to more behavior problems. Father's education was the only sociodemographic variable that was significant: Adolescents with more highly educated fathers had a better mother-child relationship and fewer behavioral problems.

CONCLUSIONS

Findings suggest that Arab American Muslim adolescents with behavior problems are differentially exposed to daily hassles but daily hassles are not the best point of intervention. Bidirectional relations between the mother-child relationship and adolescent behavior problems suggest intervening to improve the mother-child relationship and manage symptoms of adolescent behavior problems. (PsycINFO Database Record

A Bayesian nonparametric approach to marginal structural models for point treatments and a continuous or survival outcome

Marginal structural models (MSMs) are a general class of causal models for specifying the average effect of treatment on an outcome. These models can accommodate discrete or continuous treatments, as well as treatment effect heterogeneity (causal effect modification). The literature on estimation of MSM parameters has been dominated by semiparametric estimation methods, such as inverse probability of treatment weighted (IPTW). Likelihood-based methods have received little development, probably in part due to the need to integrate out confounders from the likelihood and due to reluctance to make parametric modeling assumptions. In this article we develop a fully Bayesian MSM for continuous and survival outcomes. In particular, we take a Bayesian nonparametric (BNP) approach, using a combination of a dependent Dirichlet process and Gaussian process to model the observed data. The BNP approach, like semiparametric methods such as IPTW, does not require specifying a parametric outcome distribution. Moreover, by using a likelihood-based method, there are potential gains in efficiency over semiparametric methods. An additional advantage of taking a fully Bayesian approach is the ability to account for uncertainty in our (uncheckable) identifying assumption. To this end, we propose informative prior distributions that can be used to capture uncertainty about the identifying "no unmeasured confounders" assumption. Thus, posterior inference about the causal effect parameters can reflect the degree of uncertainty about this assumption. The performance of the methodology is evaluated in several simulation studies. The results show substantial efficiency gains over semiparametric methods, and very little efficiency loss over correctly specified maximum likelihood estimates. The method is also applied to data from a study on neurocognitive performance in HIV-infected women and a study of the comparative effectiveness of antihypertensive drug classes.

Access to alcohol and heart disease among patients in hospital: observational cohort study using differences in alcohol sales laws

OBJECTIVE

 To investigate the relation between alcohol consumption and heart disease by using differences in county level alcohol sales laws as a natural experiment.

DESIGN

 Observational cohort study using differences in alcohol sales laws.

SETTING

 Hospital based healthcare encounters in Texas, USA.

POPULATION

 1 106 968 patients aged 21 or older who were residents of "wet" (no alcohol restrictions) and "dry" (complete prohibition of alcohol sales) counties and admitted to hospital between 2005 and 2010, identified using the Texas Inpatient Research Data File.

OUTCOME MEASURES

 Prevalent and incident alcohol misuse and alcoholic liver disease were used for validation analyses. The main cardiovascular outcomes were atrial fibrillation, acute myocardial infarction, and congestive heart failure.

RESULTS

 Residents of wet counties had a greater prevalence and incidence of alcohol misuse and alcoholic liver disease. After multivariable adjustment, wet county residents had a greater prevalence (odds ratio 1.05, 95% confidence interval 1.01 to 1.09; P=0.007) and incidence (hazard ratio 1.07, 1.01 to 1.13; P=0.014) of atrial fibrillation, a lower prevalence (odds ratio 0.83, 0.79 to 0.87; P<0.001) and incidence (hazard ratio 0.91, 0.87 to 0.99; P=0.019) of myocardial infarction, and a lower prevalence (odds ratio 0.87, 0.84 to 0.90; P<0.001) of congestive heart failure. Conversion of counties from dry to wet resulted in statistically significantly higher rates of alcohol misuse, alcoholic liver disease, atrial fibrillation, and congestive heart failure, with no detectable difference in myocardial infarction.

CONCLUSIONS

 Greater access to alcohol was associated with more atrial fibrillation and less myocardial infarction and congestive heart failure, although an increased risk of congestive heart failure was seen shortly after alcohol sales were liberalized.

Protocol of a randomized controlled trial of the fear of recurrence therapy (FORT) intervention for women with breast or gynecological cancer

Background

Clinically significant levels of fear of cancer recurrence (FCR) affect up to 49 % of cancer survivors and are more prevalent among women. FCR is associated with psychological distress, lower quality of life, and increased use of medical resources. Despite its prevalence, FCR is poorly addressed in clinical care. To address this problem, we first developed, and pilot tested a 6-week, 2 h, Cognitive-existential group intervention therapy that targeted FCR in survivors of breast or gynecological cancer. Following the positive outcome of the pilot, we are now testing this approach in a randomized clinical trial (RCT).

Goal and hypotheses: This multicenter, prospective RCT aims to test the efficacy of the intervention. The study hypotheses are that, compared to a control group, cancer survivors participating in the intervention (1) will have less FCR, (2) will show more favorable outcomes on the following measures: cancer-specific distress, quality of life, illness uncertainty, intolerance of uncertainty, perceived risk of cancer recurrence, and coping skills. We further postulate that the between-group differences will persist three and 6 months post-intervention.

Methods

Sixteen groups of seven to nine women are being allocated to the intervention or the control group. The control group receives a 6-week, 2 h, structurally equivalent support group. We are recruiting 144 cancer survivors from four hospital sites in three Canadian cities. The sample size was based on the moderate pre/post-test changes found in our pilot study and adjusted to the drop-out rates. Measurements: The primary outcome, FCR, is measured by the Fear of Cancer Recurrence Inventory. Secondary outcomes measured include cancer-specific distress, perceived risk of cancer recurrence, illness uncertainty, intolerance of uncertainty, coping, and quality of life. We use reliable and recognized valid scales. Participants are to complete the questionnaire package at four times: before the first group session (baseline), immediately after the sixth session, and 3 and 6 months post-intervention. Analysis: In the descriptive analysis, comparison of group equivalent baseline variables, identification of confounding/intermediate variables and univariate analysis are planned. Each participant’s trajectory is calculated using Generalized Estimating Equation models to determine the time and group effects, after considering the correlation structures of the groups. An intent-to-treat analysis approach may be adopted.

Discussion

Our Fear of Recurrence Therapy (FORT) intervention has direct implications for clinical service development to improve the quality of life for patients with breast (BC) and gynecological cancer (GC). Based on our pilot data, we are confident that the FORT intervention can guide the development of effective psychosocial cancer survivorship interventions to reduce FCR and improve psychological functioning among women with BC or GC.

Trial registration

Dr. Christine Maheu registered the trial with ISRCTN registry (Registration number: ISRCTN83539618, date assigned 03/09/2014).

Impact of Molecular Diagnostics for Tuberculosis on Patient-Important Outcomes: A Systematic Review of Study Methodologies

BACKGROUND

Several reviews on the accuracy of Tuberculosis (TB) Nucleic Acid Amplification Tests (NAATs) have been performed but the evidence on their impact on patient-important outcomes has not been systematically reviewed. Given the recent increase in research evaluating such outcomes and the growing list of TB NAATs that will reach the market over the coming years, there is a need to bring together the existing evidence on impact, rather than accuracy. We aimed to assess the approaches that have been employed to measure the impact of TB NAATs on patient-important outcomes in adults with possible pulmonary TB and/or drug-resistant TB.

METHODS

We first develop a conceptual framework to clarify through which mechanisms the improved technical performance of a novel TB test may lead to improved patient outcomes and outline which designs may be used to measure them. We then systematically review the literature on studies attempting to assess the impact of molecular TB diagnostics on such outcomes and provide a narrative synthesis of designs used, outcomes assessed and risk of bias across different study designs.

RESULTS

We found 25 eligible studies that assessed a wide range of outcomes and utilized a variety of experimental and observational study designs. Many potentially strong design options have never been used. We found that much of the available evidence on patient-important outcomes comes from a small number of settings with particular epidemiological and operational context and that confounding, time trends and incomplete outcome data receive insufficient attention.

CONCLUSIONS

A broader range of designs should be considered when designing studies to assess the impact of TB diagnostics on patient outcomes and more attention needs to be paid to the analysis as concerns about confounding and selection bias become relevant in addition to those on measurement that are of greatest concern in accuracy studies.

Comparison of high-dimensional confounder summary scores in comparative studies of newly marketed medications

OBJECTIVE

To compare confounding adjustment by high-dimensional propensity scores (hdPSs) and historically developed high-dimensional disease risk scores (hdDRSs) in three comparative study examples of newly marketed medications: (1) dabigatran vs. warfarin on major hemorrhage; (2) on death; and (3) cyclooxygenase-2 inhibitors vs. nonselective nonsteroidal anti-inflammatory drugs on gastrointestinal bleeds.

STUDY DESIGN AND SETTING

In each example, we constructed a concurrent cohort of new and old drug initiators using US claims databases. In historical cohorts of old drug initiators, we developed hdDRS models including investigator-specified plus empirically identified variables and using principal component analysis and lasso regression for dimension reduction. We applied the models to the concurrent cohorts to obtain predicted outcome probabilities, which we used for confounding adjustment. We compared the resulting estimates to those from hdPS.

RESULTS

The crude odds ratio (OR) comparing dabigatran to warfarin was 0.52 (95% confidence interval: 0.37-0.72) for hemorrhage and 0.38 (0.26-0.55) for death. Decile stratification yielded an OR of 0.64 (0.46-0.90) for hemorrhage using hdDRS vs. 0.70 (0.49-1.02) for hdPS. ORs for death were 0.69 (0.45-1.06) and 0.73 (0.48-1.10), respectively. The relative performance of hdDRS in the cyclooxygenase-2 inhibitors example was similar.

CONCLUSION

hdDRS achieved similar or better confounding adjustment compared to conventional regression approach but worked slightly less well than hdPS.

Comparing high-dimensional confounder control methods for rapid cohort studies from electronic health records

Aims:

Electronic health records (EHR), containing rich clinical histories of large patient populations, can provide evidence for clinical decisions when evidence from trials and literature is absent. To enable such observational studies from EHR in real time, particularly in emergencies, rapid confounder control methods that can handle numerous variables and adjust for biases are imperative. This study compares the performance of 18 automatic confounder control methods.

Methods:

Methods include propensity scores, direct adjustment by machine learning, similarity matching and resampling in two simulated and one real-world EHR datasets.

Results & conclusions:

Direct adjustment by lasso regression and ensemble models involving multiple resamples have performance comparable to expert-based propensity scores and thus, may help provide real-time EHR-based evidence for timely clinical decisions.

Intravenous immunoglobulin use in septic shock patients after emergency laparotomy

OBJECTIVES

The role of intravenous immunoglobulin (IVIG) as an adjunctive treatment for abdominal sepsis remains controversial.

METHODS

Mechanically ventilated septic shock patients following emergency laparotomy for perforation of the lower intestinal tract were identified in the Japanese Diagnosis Procedure Combination inpatient database from July 2010 to March 2013. The effect of IVIG use on 28-day mortality was evaluated using propensity score and instrumental variable analyses.

RESULTS

Eligible patients (n = 4919) treated at 845 hospitals were divided into IVIG (n = 2085) and control (n = 2834) groups. Propensity score matching created a matched cohort of 1081pairs with and without IVIG treatment. Although significant mortality differences existed between the IVIG and control groups in the unmatched analysis (20.6% vs. 18.3%; difference, 2.3%; 95% confidence interval [CI], 0.07-4.5), there were no significant differences in the propensity score-matched analysis (20.4% vs. 19.3%; difference, 1.1%; 95% CI, -2.3-4.5). Analysis employing the pattern of hospital IVIG use as an instrumental variable showed that IVIG use was not associated with reduced mortality (difference -2.5; 95% CI, -6.5-1.6).

CONCLUSIONS

There may be no significant association between IVIG use and mortality in mechanically ventilated septic shock patients after emergency laparotomy.

Use of recombinant human soluble thrombomodulin in patients with sepsis-induced disseminated intravascular coagulation after intestinal perforation

BACKGROUND

Anticoagulant therapy has been evaluated with respect to its potential usefulness in reducing the high mortality rates associated with severe sepsis, including sepsis-induced disseminated intravascular coagulation (DIC) after intestinal perforation. We examined the hypothesis that recombinant human soluble thrombomodulin (rhTM) is effective in the treatment of patients with septic shock with sepsis-induced DIC after laparotomy for intestinal perforation.

METHODS

We performed propensity-score and instrumental variable analyses of the Japanese Diagnosis Procedure Combination in-patient database, a nationwide administrative database. The main outcome was 28-day in-hospital all-cause mortality.

RESULTS

We categorized eligible patients (n = 2202) from 622 hospitals into the rhTM group (n = 726) and control group (n = 1476). Propensity-score matching created 621 matched pairs of patients with and without rhTM. There was neither significant difference in 28-day mortality between the two groups in the unmatched analysis (rhTM vs. control, 25.3 vs. 23.4%, respectively; difference, 1.9%; 95% CI, -1.9 to 5.7) nor in the propensity-score-matched analysis (rhTM vs. control, 26.1 vs. 24.8%, respectively; difference, 1.3%; 95% CI, -3.6 to 6.1). The logistic analysis showed no significant association between the use of rhTM and the mortality in propensity-score-matched patients (OR, 1.1; 95% CI, 0.82-1.4). The instrumental variable analyses, using the hospital rhTM-prescribing proportion as the variable, found that receipt of rhTM was not associated with the reduction in the mortality (risk difference, -6.7%; 95% CI, -16.4 to 3.0).

CONCLUSION

We found no association between administration of rhTM and 28-day mortality in mechanically ventilated patients with septic shock and concurrent DIC after intestinal perforation.

Recombinant human soluble thrombomodulin and mortality in severe pneumonia patients with sepsis-associated disseminated intravascular coagulation: an observational nationwide study

BACKGROUND

The association between recombinant human soluble thrombomodulin (rhTM) use and mortality in patients with sepsis-associated disseminated intravascular coagulation (DIC) remains controversial.

OBJECTIVES

To examine the hypothesis that rhTM could be effective in the treatment of patients with sepsis-associated DIC following severe pneumonia.

METHODS

Propensity score and instrumental variable analyses using a nationwide administrative database, the Japanese Diagnosis Procedure Combination inpatient database, were used. The main outcome was 28-day in-hospital all-cause mortality.

RESULTS

Eligible patients (n = 6342) from 936 hospitals were categorized into the rhTM group (n = 1280) or control group (n = 5062). Propensity score matching created a matched cohort of 1140 pairs with and without rhTM. No significant difference in 28-day mortality was documented between the two groups in the unmatched analysis (rhTM vs. control, 37.0%, 474/1280 vs. 36.9%, 1866/5062; odds ratio [OR], 1.00; 95%CI, 0.98-1.03), nor in the propensity-matched analysis (37.6%, 429/1140 vs. 37.0%, 886/1140; OR, 1.01; 95%CI, 0.93-1.10). The logistic regression analysis did not show a significant association between the use of rhTM and 28-day mortality in propensity-matched patients (OR, 1.00; 95%CI, 0.87-1.22). An analysis using the hospital rhTM-prescribing rate as an instrumental variable found that receipt of rhTM was not associated with reduction in mortality at 28 days (risk difference, 0.008; 95% CI, -0.08-0.98).

CONCLUSIONS

This large retrospective nationwide study demonstrated that there might be little association between the use of rhTM and mortality in severe pneumonia patients with sepsis-associated DIC. A multinational randomized trial is required to confirm this.