Comparison of instrumental variable analysis using a new instrument with risk adjustment methods to reduce confounding by indication

Using the global randomization test as a Mendelian randomization falsification test for the exclusion restriction assumption

Mendelian randomization may give biased causal estimates if the instrument affects the outcome not solely via the exposure of interest (violating the exclusion restriction assumption). We demonstrate use of a global randomization test as a falsification test for the exclusion restriction assumption. Using simulations, we explored the statistical power of the randomization test to detect an association between a genetic instrument and a covariate set due to (a) selection bias or (b) horizontal pleiotropy, compared to three approaches examining associations with individual covariates: (i) Bonferroni correction for the number of covariates, (ii) correction for the effective number of independent covariates, and (iii) an r2 permutation-based approach. We conducted proof-of-principle analyses in UK Biobank, using CRP as the exposure and coronary heart disease (CHD) as the outcome. In simulations, power of the randomization test was higher than the other approaches for detecting selection bias when the correlation between the covariates was low (r2 < 0.1), and at least as powerful as the other approaches across all simulated horizontal pleiotropy scenarios. In our applied example, we found strong evidence of selection bias using all approaches (e.g., global randomization test p < 0.002). We identified 51 of the 58 CRP genetic variants as horizontally pleiotropic, and estimated effects of CRP on CHD attenuated somewhat to the null when excluding these from the genetic risk score (OR = 0.96 [95% CI: 0.92, 1.00] versus 0.97 [95% CI: 0.90, 1.05] per 1-unit higher log CRP levels). The global randomization test can be a useful addition to the MR researcher's toolkit.

Preparing European Nephrology for the next pandemic: lessons from the ERACODA collaboration

Owing to the vulnerability of patients with chronic kidney disease to infectious diseases, the coronavirus disease 2019 (COVID-19) pandemic has been particularly devastating for the nephrology community. Unfortunately, the possibility of future COVID-19 waves or outbreaks of other infectious diseases with pandemic potential cannot be ruled out. The nephrology community made tremendous efforts to contain the consequences of the COVID-19 pandemic. Despite this, the COVID-19 pandemic has highlighted several shortcomings in our response to the pandemic and has taught us important lessons that can be utilized to improve our preparedness for any future health crises of a similar nature. In this article we draw lessons from the European Renal Association COVID-19 Database (ERACODA) project, a pan-European collaboration initiated in March 2020 to understand the prognosis of COVID-19 in patients on kidney function replacement therapy. We discuss the challenges faced in generating timely and robust evidence for informed management of patients with kidney disease and give recommendations for our preparedness for the next pandemic in Europe. Limited collaboration, the absence of common data architecture and the sub-optimal quality of available data posed challenges in our response to COVID-19. Aligning different research initiatives, strengthening electronic health records, and involving experts in study design and data analysis will be important in our response to the next pandemic. The European Renal Association may take a leading role in aligning research initiatives via its engagement with other scientific societies, national registries, administrators and researchers.

Generating Practice-Based Evidence in the Use of Guideline-Recommended Combination Therapy for Secondary Prevention of Acute Myocardial Infarction

Background: Clinical guidelines recommend beta-blockers, angiotensin-converting enzyme inhibitors/angiotensin-receptor blockers, and statins for the secondary prevention of acute myocardial infarction (AMI). It is not clear whether variation in real-world practice reflects poor quality-of-care or a balance of outcome tradeoffs across patients. Methods: The study cohort included Medicare fee-for-service beneficiaries hospitalized 2007-2008 for AMI. Treatment within 30-days post-discharge was grouped into one of eight possible combinations for the three drug classes. Outcomes included one-year overall survival, one-year cardiovascular-event-free survival, and 90-day adverse events. Treatment effects were estimated using an Instrumental Variables (IV) approach with instruments based on measures of local-area practice style. Pre-specified data elements were abstracted from hospital medical records for a stratified, random sample to create "unmeasured confounders" (per claims data) and assess model assumptions. Results: Each drug combination was observed in the final sample (N = 124,695), with 35.7% having all three, and 13.5% having none. Higher rates of guideline-recommended treatment were associated with both better survival and more adverse events. Unmeasured confounders were not associated with instrumental variable values. Conclusions: The results from this study suggest that providers consider both treatment benefits and harms in patients with AMIs. The investigation of estimator assumptions support the validity of the estimates.

Assessing the ability of an instrumental variable causal forest algorithm to personalize treatment evidence using observational data: the case of early surgery for shoulder fracture

Background

Comparative effectiveness research (CER) using observational databases has been suggested to obtain personalized evidence of treatment effectiveness. Inferential difficulties remain using traditional CER approaches especially related to designating patients to reference classes a priori. A novel Instrumental Variable Causal Forest Algorithm (IV-CFA) has the potential to provide personalized evidence using observational data without designating reference classes a priori, but the consistency of the evidence when varying key algorithm parameters remains unclear. We investigated the consistency of IV-CFA estimates through application to a database of Medicare beneficiaries with proximal humerus fractures (PHFs) that previously revealed heterogeneity in the effects of early surgery using instrumental variable estimators.

Methods

IV-CFA was used to estimate patient-specific early surgery effects on both beneficial and detrimental outcomes using different combinations of algorithm parameters and estimate variation was assessed for a population of 72,751 fee-for-service Medicare beneficiaries with PHFs in 2011. Classification and regression trees (CART) were applied to these estimates to create ex-post reference classes and the consistency of these classes were assessed. Two-stage least squares (2SLS) estimators were applied to representative ex-post reference classes to scrutinize the estimates relative to known 2SLS properties.

Results

IV-CFA uncovered substantial early surgery effect heterogeneity across PHF patients, but estimates for individual patients varied with algorithm parameters. CART applied to these estimates revealed ex-post reference classes consistent across algorithm parameters. 2SLS estimates showed that ex-post reference classes containing older, frailer patients with more comorbidities, and lower utilizers of healthcare were less likely to benefit and more likely to have detriments from higher rates of early surgery.

Conclusions

IV-CFA provides an illuminating method to uncover ex-post reference classes of patients based on treatment effects using observational data with a strong instrumental variable. Interpretation of treatment effect estimates within each ex-post reference class using traditional CER methods remains conditional on the extent of measured information in the data.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-022-01663-0.

Association of Surgical Treatment With Adverse Events and Mortality Among Medicare Beneficiaries With Proximal Humerus Fracture

IMPORTANCE

Meta-analyses of randomized clinical trials suggest that the advantages and risks of surgery compared with conservative management as the initial treatment for proximal humerus fracture (PHF) vary, or are heterogeneous across patients. Substantial geographic variation in surgery rates for PHF suggests that the optimal rate of surgery across the population of patients with PHF is unknown.

OBJECTIVE

To use geographic variation in treatment rates to assess the outcomes associated with higher rates of surgery for patients with PHF.

DESIGN, SETTING, AND PARTICIPANTS

This comparative effectiveness research study analyzed all fee-for-service Medicare beneficiaries with proximal humerus fracture in 2011 who were continuously enrolled in Medicare Parts A and B for the 365-day period before and immediately after their index fracture. Data analysis was performed January through June 2019.

EXPOSURE

Undergoing 1 of the commonly used surgical procedures in the 60 days after an index fracture diagnosis.

MAIN OUTCOMES AND MEASURES

Risk-adjusted area surgery ratios were created for each hospital referral region as a measure of local area practice styles. Instrumental variable approaches were used to assess the association between higher surgery rates and adverse events, mortality risk, and cost at 1 year from Medicare's perspective for patients with PHF in 2011. Instrumental variable models were stratified by age, comorbidities, and frailty. Instrumental variable estimates were compared with estimates from risk-adjusted regression models.

RESULTS

The final cohort included 72 823 patients (mean [SD] age, 80.0 [7.9] years; 13 958 [19.2%] men). The proportion of patients treated surgically ranged from 1.8% to 33.3% across hospital referral regions in the United States. Compared with conservatively managed patients, surgical patients were younger (mean [SD] age, 80.4 [8.1] years vs 78.0 [7.2] years; P < .001) and healthier (Charlson Comorbidity Index score of 0, 14 863 [24.4%] patients vs 3468 [29.1%] patients; Function-Related Indicator score of 0, 20 720 [34.0%] patients vs 4980 [41.8%] patients; P < .001 for both), and a larger proportion were women (49 030 [80.5%] patients vs 9835 [82.5%] patients; P < .001). Instrumental variable analysis showed that higher rates of surgery were associated with increased total costs ($8913) during the treatment period, increased adverse event rates (a 1-percentage point increase in the surgery rate was associated with a 0.19-percentage point increase in the 1-year adverse event rate; β = 0.19; 95% CI, 0.09-0.27; P < .001), and increased mortality risk (a 1-percentage point increase in the surgery rate was associated with a 0.09-percentage point increase in the 1-year mortality rate; β = 0.09; 95% CI, 0.04-0.15; P < .01). Instrumental variable mortality results were even more striking for older patients and those with higher comorbidity burdens and greater frailty. Risk-adjusted estimates suggested that surgical patients had higher costs (increase of $17 278) and more adverse events (a 1-percentage point increase in the surgery rate was associated with a 0.12-percentage point increase in the 1-year adverse event rate; β = 0.12; 95% CI, 0.11 to 0.13; P < .001) but lower risk of mortality after PHF (a 1-percentage point increase in the surgery rate was associated with a 0.01-percentage point decrease in the 1-year mortality rate; β = -0.01; 95% CI, -0.015 to -0.005; P < .001).

CONCLUSIONS AND RELEVANCE

This study found that higher rates of surgery for treatment of patients with PHF were associated with increased costs, adverse event rates, and risk of mortality. Orthopedic surgeons should be aware of the harms of extending the use of surgery to more clinically vulnerable patient subgroups.

Treatment Setting and Outcomes of Cystic Fibrosis Pulmonary Exacerbations

RATIONALE

There are important gaps in knowledge of the optimal treatment of cystic fibrosis pulmonary exacerbations. Previous observational studies comparing inpatient with outpatient treatment have suffered from methodologic weaknesses, especially indication bias.

OBJECTIVES

We analyzed data from the Epidemiologic Study of Cystic Fibrosis using techniques to control for indication bias to determine whether there is an advantage to inpatient treatment of cystic fibrosis pulmonary exacerbations.

METHODS

We identified typical pulmonary exacerbations in patients ages 6 years and older during the 3-year observation period ending in 2005. In our primary analysis, we used the instrumental variables method, implemented using two-stage least squares regression, to evaluate the effect of the proportion of total time that intravenous treatment was administered on an inpatient (versus outpatient) basis on the likelihood of return of percent predicted forced expiratory volume in 1 second to greater than or equal to 90% of baseline post-treatment. We also evaluated two other indicators of treatment setting, three other measures of treatment response, and two alternative modeling techniques, and we also looked for differences between children and adults.

RESULTS

Our final analysis included 4,497 pulmonary exacerbations in 2,773 individual patients at 75 sites. We calculated the mean proportion of intravenous treatment time that was provided in the hospital setting at each site. The median across sites was 0.581 (interquartile range, 0.396-0.753). The median treatment success rate across sites was 74.2% (interquartile range, 67.9 to 79.2%). Univariate analysis and two-stage least squares models showed a positive relationship between treatment success and proportion of inpatient treatment days. Our primary model revealed an absolute increase of 9.08% (95% confidence interval, 2.55-15.61; P = 0.006) in the achievement of a return of percent predicted forced expiratory volume in 1 second to greater than or equal to 90% of baseline comparing complete inpatient treatment with no inpatient treatment. Treatment response was not related to duration of intravenous therapy. Similar results were found for all our modeling techniques and outcomes.

CONCLUSIONS

Patients with cystic fibrosis treated at sites with more reliance on inpatient treatment were more likely to achieve successful forced expiratory volume in 1 second recovery. There was no relationship between treatment duration and recovery of forced expiratory volume in 1 second.

Treatment for Rotator Cuff Tear Is Influenced by Demographics and Characteristics of the Area Where Patients Live

Background:

Atraumatic rotator cuff tear is a common orthopaedic complaint for people >60 years of age. Lack of evidence or consensus on appropriate treatment for this type of injury creates the potential for substantial discretion in treatment decisions. To our knowledge, no study has assessed the implications of this discretion on treatment patterns across the United States.

Methods:

All Medicare beneficiaries in the United States with a new magnetic resonance imaging (MRI)-confirmed atraumatic rotator cuff tear were identified with use of 2010 to 2012 Medicare administrative data and were categorized according to initial treatment (surgery, physical therapy, or watchful waiting). Treatment was modeled as a function of the clinical and demographic characteristics of each patient. Variation in treatment rates across hospital referral regions and the presence of area treatment signatures, representing the extent that treatment rates varied across hospital referral regions after controlling for patient characteristics, were assessed. Correlations between measures of area treatment signatures and measures of physician access in hospital referral regions were examined.

Results:

Among patients who were identified as having a new, symptomatic, MRI-confirmed atraumatic rotator cuff tear (n = 32,203), 19.8% were managed with initial surgery; 41.3%, with initial physical therapy; and 38.8%, with watchful waiting. Patients who were older, had more comorbidity, or were female, of non-white race, or dual-eligible for Medicaid were less likely to receive surgery (p < 0.0001). Black, dual-eligible females had 0.42-times (95% confidence interval [CI], 0.34 to 0.50) lower odds of surgery and 2.36-times (95% CI, 2.02 to 2.70) greater odds of watchful waiting. Covariate-adjusted odds of surgery varied dramatically across hospital referral regions; unadjusted surgery and physical therapy rates varied from 0% to 73% and from 6% to 74%, respectively. On average, patients in high-surgery areas were 62% more likely to receive surgery than the average patient with identical measured characteristics, and patients in low-surgery areas were half as likely to receive surgery than the average comparable patient. The supply of orthopaedic surgeons and the supply of physical therapists were associated with greater use of initial surgery and physical therapy, respectively.

Conclusions:

Patient characteristics had a significant influence on treatment for atraumatic rotator cuff tear but did not explain the wide-ranging variation in treatment rates across areas. Local-area physician supply and specialty mix were correlated with treatment, independent of the patient’s measured characteristics.

Instrumental Variable Analyses and Selection Bias

Instrumental variables (IV) are used to draw causal conclusions about the effect of exposure E on outcome Y in the presence of unmeasured confounders. IV assumptions have been well described: (1) IV affects E; (2) IV affects Y only through E; (3) IV shares no common cause with Y. Even when these assumptions are met, biased effect estimates can result if selection bias allows a noncausal path from E to Y. We demonstrate the presence of bias in IV analyses on a sample from a simulated dataset, where selection into the sample was a collider on a noncausal path from E to Y. By applying inverse probability of selection weights, we were able to eliminate the selection bias. IV approaches may protect against unmeasured confounding but are not immune from selection bias. Inverse probability of selection weights used with IV approaches can minimize bias.

Cesarean delivery rates among family physicians versus obstetricians: a population-based cohort study using instrumental variable methods

BACKGROUND

Previous research suggests that family physicians have rates of cesarean delivery that are lower than or equivalent to those for obstetricians, but adjustments for risk differences in these analyses may have been inadequate. We used an econometric method to adjust for observed and unobserved factors affecting the risk of cesarean delivery among women attended by family physicians versus obstetricians.

METHODS

This retrospective population-based cohort study included all Canadian (except Quebec) hospital deliveries by family physicians and obstetricians between Apr. 1, 2006, and Mar. 31, 2009. We excluded women with multiple gestations, and newborns with a birth weight less than 500 g or gestational age less than 20 weeks. We estimated the relative risk of cesarean delivery using instrumental-variable-adjusted and logistic regression.

RESULTS

The final cohort included 776 299 women who gave birth in 390 hospitals. The risk of cesarean delivery was 27.3%, and the mean proportion of deliveries by family physicians was 26.9% (standard deviation 23.8%). The relative risk of cesarean delivery for family physicians versus obstetricians was 0.48 (95% confidence interval [CI] 0.41-0.56) with logistic regression and 1.27 (95% CI 1.02-1.57) with instrumental-variable-adjusted regression.

INTERPRETATION

Our conventional analyses suggest that family physicians have a lower rate of cesarean delivery than obstetricians, but instrumental variable analyses suggest the opposite. Because instrumental variable methods adjust for unmeasured factors and traditional methods do not, the large discrepancy between these estimates of risk suggests that clinical and/or sociocultural factors affecting the decision to perform cesarean delivery may not be accounted for in our database.

Geographic variation in inhaled corticosteroid use for children with persistent asthma in Medicaid

OBJECTIVE

Geographic variation in the rates of inhaled corticosteroid (ICS) use for children with persistent asthma in Medicaid has been reported, but the source of this variation is unknown. The objective of this study was to quantify the geographic variation in ICS use for children with persistent asthma in Medicaid that remains after adjusting for the characteristics of children in an area.

METHODS

Data from the 2005-2007 Medicaid Analytic eXtract files were used. Frequent fills of short-acting beta₂-agonist (SABA) were used to identify children 5-18 years of age with persistent asthma across the United States. A child was considered to have used an ICS if the child initially filled an ICS following frequent SABA use. Areas were determined using published methods, and the unadjusted ICS rate and the area treatment ratio for ICS, which adjusted for demographic and clinical characteristics, were calculated for each area.

RESULTS

Of 15,917 children, 13% used an ICS. The median unadjusted ICS rate for all areas was 10% but ranged from 0% to 64%. ICS use was less than expected for more than half of the areas based on the characteristics of the children in the area, but use was nearly five times what was expected in some areas. Areas with higher than expected ICS use were found contiguous to areas with lower than expected use.

CONCLUSIONS

Geographic variation in ICS not attributable to the demographic and clinical characteristics of the children in an area exists and could prove useful in the struggle to reduce asthma exacerbation rates.

Emerging technologies to measure neighborhood conditions in public health: implications for interventions and next steps

Adverse neighborhood conditions play an important role beyond individual characteristics. There is increasing interest in identifying specific characteristics of the social and built environments adversely affecting health outcomes. Most research has assessed aspects of such exposures via self-reported instruments or census data. Potential threats in the local environment may be subject to short-term changes that can only be measured with more nimble technology. The advent of new technologies may offer new opportunities to obtain geospatial data about neighborhoods that may circumvent the limitations of traditional data sources. This overview describes the utility, validity and reliability of selected emerging technologies to measure neighborhood conditions for public health applications. It also describes next steps for future research and opportunities for interventions. The paper presents an overview of the literature on measurement of the built and social environment in public health (Google Street View, webcams, crowdsourcing, remote sensing, social media, unmanned aerial vehicles, and lifespace) and location-based interventions. Emerging technologies such as Google Street View, social media, drones, webcams, and crowdsourcing may serve as effective and inexpensive tools to measure the ever-changing environment. Georeferenced social media responses may help identify where to target intervention activities, but also to passively evaluate their effectiveness. Future studies should measure exposure across key time points during the life-course as part of the exposome paradigm and integrate various types of data sources to measure environmental contexts. By harnessing these technologies, public health research can not only monitor populations and the environment, but intervene using novel strategies to improve the public health.

Influence of neighborhood-level factors on social support in early-stage breast cancer patients and controls

RATIONALE

Low social support has been linked to negative health outcomes in breast cancer patients.

OBJECTIVE

We examined associations between perceived social support, neighborhood socioeconomic deprivation, and neighborhood-level social support in early-stage breast cancer patients and controls.

METHODS

This two-year longitudinal study in the United States included information collected from telephone interviews and clinical records of 541 early-stage patients and 542 controls recruited from 2003 to 2007. Social support was assessed using the Medical Outcomes Study Social Support Survey (MOS-SS). Residential addresses were geocoded and used to develop measures including neighborhood social support (based on MOS-SS scores from nearby controls) and neighborhood socioeconomic deprivation (a composite index of census tract characteristics). Latent trajectory models were used to determine effects of neighborhood conditions on the stable (intercept) and changing (slope) aspects of social support.

RESULTS

In a model with only neighborhood variables, greater socioeconomic deprivation was associated with patients' lower stable social support (standardized estimate = -0.12, p = 0.027); neighborhood-level social support was associated with social support change (standardized estimate = 0.17, p = 0.046). After adding individual-level covariates, there were no direct neighborhood effects on social support. In patients, neighborhood socioeconomic deprivation was associated with support indirectly through marriage, insurance status, negative affect, and general health. In controls, neighborhood socioeconomic deprivation was associated with support indirectly through marriage (p < 0.05).

CONCLUSION

Indirect effects of neighborhood socioeconomic deprivation on social support differed in patients and controls. Psychosocial and neighborhood interventions may help patients with low social support, particularly patients without partnered relationships in deprived areas.

Geographic variation in the use of adjuvant therapy among elderly patients with resected non-small cell lung cancer

OBJECTIVES

The purpose of this study was to assess to what extent geographic variation in adjuvant treatment for non-small cell lung cancer (NSCLC) patients would remain, after controlling for patient and area-level characteristics.

MATERIALS AND METHODS

A retrospective cohort of 18,410 Medicare beneficiaries with resected, stage I-IIIA NSCLC was identified from the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked database. Adjuvant therapies were classified as adjuvant chemotherapy (ACT), postoperative radiation therapy (PORT), or no adjuvant therapy. Predicted treatment probabilities were estimated for each patient given their clinical, demographic, and area-level characteristics with multivariate logistic regression. Area Treatment Ratios were used to estimate the propensity of patients in a local area to receive an adjuvant treatment, controlling for characteristics of patients in the area. Areas were categorized as low-, mid- and high-use and mapped for two representative SEER registries.

RESULTS

Overall, 10%, 12%, and 78% of patients received ACT, PORT and no adjuvant therapy, respectively. Age, sex, stage, type and year of surgery, and comorbidity were associated with adjuvant treatment use. Even after adjusting for patient characteristics, substantial geographic treatment variation remained. High- and low-use areas were tightly juxtaposed within and across SEER registries, often within the same county. In some local areas, patients were up to eight times more likely to receive adjuvant therapy than expected, given their characteristics. On the other hand, almost a quarter of patients lived in local areas in which patients were more than three times less likely to receive ACT than would be predicted.

CONCLUSION

Controlling for patient and area-level covariates did not remove geographic variation in adjuvant therapies for resected NSCLC patients. A greater proportion of patients were treated less than expected, rather than more than expected. Further research is needed to better understand its causes and potential impact on outcomes.

Toward a clearer portrayal of confounding bias in instrumental variable applications

Recommendations for reporting instrumental variable analyses often include presenting the balance of covariates across levels of the proposed instrument and levels of the treatment. However, such presentation can be misleading as relatively small imbalances among covariates across levels of the instrument can result in greater bias because of bias amplification. We introduce bias plots and bias component plots as alternative tools for understanding biases in instrumental variable analyses. Using previously published data on proposed preference-based, geography-based, and distance-based instruments, we demonstrate why presenting covariate balance alone can be problematic, and how bias component plots can provide more accurate context for bias from omitting a covariate from an instrumental variable versus non-instrumental variable analysis. These plots can also provide relevant comparisons of different proposed instruments considered in the same data. Adaptable code is provided for creating the plots.

Outcomes of deliveries by family physicians or obstetricians: a population-based cohort study using an instrumental variable

BACKGROUND

Previous research has suggested that obstetric outcomes are similar for deliveries by family physicians and obstetricians, but many of these studies were small, and none of them adjusted for unmeasured selection bias. We compared obstetric outcomes between these provider types using an econometric method designed to adjust for unobserved confounding.

METHODS

We performed a retrospective population-based cohort study of all Canadian (except Quebec) hospital births with delivery by family physicians and obstetricians at more than 20 weeks gestational age, with birth weight greater than 500 g, between Apr. 1, 2006, and Mar. 31, 2009. The primary outcomes were the relative risks of in-hospital perinatal death and a composite of maternal mortality and major morbidity assessed with multivariable logistic regression and instrumental variable-adjusted multivariable regression.

RESULTS

After exclusions, there were 3600 perinatal deaths and 14,394 cases of maternal morbidity among 799,823 infants and 793,053 mothers at 390 hospitals. For deliveries by family physicians v. obstetricians, the relative risk of perinatal mortality was 0.98 (95% confidence interval [CI] 0.85-1.14) and of maternal morbidity was 0.81 (95% CI 0.70-0.94) according to logistic regression. The respective relative risks were 0.97 (95% CI 0.58-1.64) and 1.13 (95% CI 0.65-1.95) according to instrumental variable methods.

INTERPRETATION

After adjusting for both observed and unobserved confounders, we found a similar risk of perinatal mortality and adverse maternal outcome for obstetric deliveries by family physicians and obstetricians. Whether there are differences between these groups for other outcomes remains to be seen.

Health Care Utilization and Treatment Persistence Associated with Oral Paliperidone and Lurasidone in Schizophrenia Treatment

BACKGROUND

Oral paliperidone and lurasidone are new second-generation antipsychotics (SGAs). Empirical evidence on the comparative costs and persistence of these 2 agents are absent in the literature.

OBJECTIVE

To assess health care use and persistence associated with the 2 new agents oral paliperidone and lurasidone and other SGAs.

METHODS

Schizophrenia patients who initiated SGA therapy were identified in the January 2007-June 2013 claims databases of a large managed care organization. Multivariate regressions using aripiprazole as the comparator were conducted. Ordinary least squares regressions were used to estimate the total medical and pharmacy costs associated with each drug. Poisson regressions were conducted to evaluate the frequency of hospitalizations and emergency department (ED) visits associated with each drug. A censored regression model was used to evaluate the comparative persistence. Sensitivity analyses using generalized linear models, two-part models, hurdle models, and instrumental variable regressions were also performed.  

RESULTS

Compared with aripiprazole, paliperidone was not associated with significantly different total costs, yet lurasidone was associated with lower total costs (-$7,052; 95% CI = -$9,221, -$4,882). Lurasidone was also associated with significantly lower medical services costs (-$5,025; 95% CI = -$7,096, -$2,955), drug costs (-$2,026; 95% CI = -$2,695, -$1,357), hospital costs (-$3,026; 95% CI = -$4,731, -$1,321), outpatient costs (-$1,999; 95% CI = -$2,536, -$1,463), and ED costs (-$2,284; 95% CI = -$3,069, -$1,499), whereas paliperidone did not have significant effects on any types of costs. Paliperidone users had fewer ED visits (-0.25; 95% CI = -0.42, -0.08), while lurasidone users had fewer hospitalizations (-5.98; 95% CI = -6.61, -5.35) and fewer ED visits (-2.51; 95% CI = -2.92, -2.10). Both paliperidone and lurasidone were associated with lower levels of treatment persistence.

CONCLUSIONS

Paliperidone does not associate with lower total costs compared with commonly used SGAs, whereas lurasidone is associated with lower total health costs. Thus, high access fees of lurasidone are not necessarily a major concern in prescription.

Statin use after acute myocardial infarction by patient complexity: are the rates right?

BACKGROUND

Guidelines suggest statin use after acute myocardial infarction (AMI) should be close to universal in patients without safety concerns yet rates are much lower than recommended, decline with patient complexity, and display substantial geographic variation. Trial exclusions have resulted in little evidence to guide statin prescribing for complex patients.

OBJECTIVE

To assess the benefits and risks associated with higher rates of statin use after AMI by baseline patient complexity.

RESEARCH DESIGN

Sample includes Medicare fee-for-service patients with AMIs in 2008-2009. Instrumental variable estimators using variation in local area prescribing patterns by statin intensity as instruments were used to assess the association of higher statin prescribing rates by statin intensity on 1-year survival, adverse events, and cost by patient complexity.

RESULTS

Providers seem to have individualized statin use across patients based on potential risks. Higher statin rates for noncomplex AMI patients were associated with increased survival rates with little added adverse event risk. Higher statin rates for complex AMI patients were associated with tradeoffs between higher survival rates and higher rates of adverse events.

CONCLUSIONS

Higher rates of statin use for noncomplex AMI patients are associated with outcome rate changes similar to existing evidence. For the complex patients in our study, who were least represented in existing trials, higher statin-use rates were associated with survival gains and higher adverse event risks not previously documented. Policy interventions promoting higher statin-use rates for complex patients may need to be reevaluated taking careful consideration of these tradeoffs.

Performing both propensity score and instrumental variable analyses in observational studies often leads to discrepant results: a systematic review

OBJECTIVES

Propensity score (PS) and instrumental variable (IV) are analytical techniques used to adjust for confounding in observational research. More and more, they seem to be used simultaneously in studies evaluating health interventions. The present review aimed to analyze the agreement between PS and IV results in medical research published to date.

STUDY DESIGN AND SETTING

Review of all published observational studies that evaluated a clinical intervention using simultaneously PS and IV analyses, as identified in MEDLINE and Web of Science.

RESULTS

Thirty-seven studies, most of them published during the previous 5 years, reported 55 comparisons between results from PS and IV analyses. There was a slight/fair agreement between the methods [Cohen's kappa coefficient = 0.21 (95% confidence interval: 0.00, 0.41)]. In 23 cases (42%), results were nonsignificant for one method and significant for the other, and IV analysis results were nonsignificant in most situations (87%).

CONCLUSION

Discrepancies are frequent between PS and IV analyses and can be interpreted in various ways. This suggests that researchers should carefully consider their analytical choices, and readers should be cautious when interpreting results, until further studies clarify the respective roles of the two methods in observational comparative effectiveness research.

Geographic access and age-related variation in chemotherapy use in elderly with metastatic breast cancer

Significant age-related variation in chemotherapy use has been observed among elderly patients with metastatic breast cancer (MBC), which may be partly attributable to geographic access factors such as local area physician practice culture and local health care system capacity. The purpose of the paper was to examine how age may modify the effect of geographic access on chemotherapy use in elderly patients with MBC. This was a retrospective cohort study based on the surveillance, epidemiology, and end results-Medicare-linked database of 1992-2002. Chemotherapy use was defined as at least one chemotherapy-related claim within 6-month post-diagnosis. Geographic access to cancer care was measured by four variables: patient travel time to the nearest oncologist practice, local area per capita number of oncologists, local area per capita number of hospices, and local area chemotherapy rate. Using multivariate logistic regression model, both aggregate models with interaction terms and subgroup analyses were conducted. Among 4,533 elderly with MBC, 30.16 % used chemotherapy. Chemotherapy use decreased with age. Both the aggregate model with interaction terms and the subgroup analysis showed that local area chemotherapy rate was positively associated with chemotherapy use (P = .0004 in the whole group; in the subgroup analyses, P < .0001, P = .0006, P = .0006, P = .18, P = .026, respectively). In addition, subgroup analysis showed that, among patients aged 85+ years old, local area oncologist supply was negatively associated with chemotherapy use (P = .028). The impact of geographic access to cancer care is the greatest among the oldest group, for whom the clinical evidence is the least certain.

Long-term benefits of inhaled corticosteroids in asthma: the propensity score method

PURPOSE

The aim of this study was to apply a propensity score approach to assess the long-term benefits of inhaled corticosteroids (ICS) on respiratory health in asthma.

METHODS

This analysis was conducted on adults with persistent asthma from the Epidemiological study on the Genetics and Environment of Asthma, a 12-year follow-up study. ICS exposure was assessed by questionnaire. Change in lung function over the follow-up period, asthma control, and health-related quality of life (asthma quality of life questionnaire) were assessed by standardized and validated methods.

RESULTS

Among 245 adults with persistent asthma, 78 (31.8%) were regularly/continuously exposed to ICS (≥6 months/year, ICS++ ) and 167 never/irregularly exposed to ICS (<6 months/year, ICS+/- ) over the follow-up period. Compared with ICS+/- subjects, a nonsignificant trend for a slower lung function decline (mL/year) was observed in ICS++ subjects (β [95%CI] = -11.4 [-24.9; 2.0]). The ICS++ subjects did not have better controlled asthma and higher health-related quality of life as compared with ICS+/- subjects.

CONCLUSIONS

Applying a propensity score method did not offer evidence of a statistical significant long-term benefit of ICS on respiratory health in adults with persistent asthma regularly or continuously exposed to ICS over a long period.

An instrumental variable approach finds no associated harm or benefit with early dialysis initiation in the United States

The estimated glomerular filtration rate (eGFR) at dialysis initiation has been rising. Observational studies suggest harm, but may be confounded by unmeasured factors. As instrumental variable methods may be less biased we performed a retrospective cohort study of 310,932 patients starting dialysis between 2006 to 2008 and registered in the United States Renal Data System in order to describe geographic variation in eGFR at dialysis initiation and determine its association with mortality. Patients were grouped into 804 health service areas by zip code. Individual eGFR at dialysis initiation averaged 10.8 ml/min/1.73m² but varied geographically. Only 11% of the variation in mean health service areas-level eGFR at dialysis initiation was accounted for by patient characteristics. We calculated demographic-adjusted mean eGFR at dialysis initiation in the health service areas using the 2006 and 2007 incident cohort as our instrument and estimated the association between individual eGFR at dialysis initiation and mortality in the 2008 incident cohort using the 2 stage residual inclusion method. Among 89,547 patients starting dialysis in 2008 with eGFR 5 to 20 ml/min/1.73m², eGFR at initiation was not associated with mortality over a median of 15.5 months [hazard ratio 1.025 per 1 ml/min/1.73m² for eGFR 5 to 14 ml/min/1.73m²; and 0.973 per 1 ml/min/1.73m² for eGFR 14 to 20 ml/min/1.73m²]. Thus, there was no associated harm or benefit from early dialysis initiation in the United States.

Geographic variation in statin use for complex acute myocardial infarction patients: evidence of effective care?

BACKGROUND

Despite strong evidence to designate statin use for secondary prevention of cardiovascular disease (CVD) as "effective care," observational studies show that many patients with CVD do not receive statins. This suggests that statin prescribing decisions for complex CVD patients are preference sensitive.

OBJECTIVES

The aim of this study was to evaluate local area variation in statin prescribing for subsets of complex patients after acute myocardial infarction (AMI) to assess whether current statin prescribing patterns fit profiles of either "effective care" or "preference-sensitive care."

RESEARCH DESIGN AND SUBJECTS

This was a retrospective cohort study of 124,618 Medicare patients with fee-for-service parts A, B, and D benefits who were hospitalized with AMI in 2008 or 2009 with no evidence of AMI in the past 12 months.

MEASURES

Patient complexity was defined by the presence of diabetes, heart failure, and chronic kidney disease in the year before AMI admission. Local area practice styles for "no statin," "lower-intensity statins," and "high-intensity statins" were measured using the driving area for clinical care method. Statin prescribing rates for complex patient subsets were contrasted across patients grouped by local areas practice styles.

RESULTS

Lower statin treatment rates were observed for patients with complex conditions, especially among those with heart failure. However, substantial local area variation in statin prescribing is observed across all complex patient groups.

CONCLUSIONS

Despite guidelines promoting the use of statins for secondary prevention for CVD patients, substantial local area variation suggests that patient and provider beliefs and preferences weigh heavily in statin prescribing decisions.

What is the effect of area size when using local area practice style as an instrument?

OBJECTIVES

Discuss the tradeoffs inherent in choosing a local area size when using a measure of local area practice style as an instrument in instrumental variable estimation when assessing treatment effectiveness.

STUDY DESIGN

Assess the effectiveness of angiotensin converting-enzyme inhibitors and angiotensin receptor blockers on survival after acute myocardial infarction for Medicare beneficiaries using practice style instruments based on different-sized local areas around patients. We contrasted treatment effect estimates using different local area sizes in terms of the strength of the relationship between local area practice styles and individual patient treatment choices; and indirect assessments of the assumption violations.

RESULTS

Using smaller local areas to measure practice styles exploits more treatment variation and results in smaller standard errors. However, if treatment effects are heterogeneous, the use of smaller local areas may increase the risk that local practice style measures are dominated by differences in average treatment effectiveness across areas and bias results toward greater effectiveness.

CONCLUSION

Local area practice style measures can be useful instruments in instrumental variable analysis, but the use of smaller local area sizes to generate greater treatment variation may result in treatment effect estimates that are biased toward higher effectiveness. Assessment of whether ecological bias can be mitigated by changing local area size requires the use of outside data sources.

Survival implications associated with variation in mastectomy rates for early-staged breast cancer

Despite a 20-year-old guideline from the National Institutes of Health (NIH) Consensus Development Conference recommending breast conserving surgery with radiation (BCSR) over mastectomy for woman with early-stage breast cancer (ESBC) because it preserves the breast, recent evidence shows mastectomy rates increasing and higher-staged ESBC patients are more likely to receive mastectomy. These observations suggest that some patients and their providers believe that mastectomy has advantages over BCSR and these advantages increase with stage. These beliefs may persist because the randomized controlled trials (RCTs) that served as the basis for the NIH guideline were populated mainly with lower-staged patients. Our objective is to assess the survival implications associated with mastectomy choice by patient alignment with the RCT populations. We used instrumental variable methods to estimate the relationship between surgery choice and survival for ESBC patients based on variation in local area surgery styles. We find results consistent with the RCTs for patients closely aligned to the RCT populations. However, for patients unlike those in the RCTs, our results suggest that higher mastectomy rates are associated with reduced survival. We are careful to interpret our estimates in terms of limitations of our estimation approach.