Abstract Background Instrumental variable (IV) analysis holds the potential to estimate treatment effects from observational data. IV analysis potentially circumvents unmeasured confounding but makes a number of assumptions, such as that the IV shares no common cause with the outcome. When using treatment preference as an instrument, a common cause, such as a preference regarding related treatments, may exist. We aimed to explore the validity and precision of a variant of IV analysis where we additionally adjust for the provider: adjusted IV analysis. Methods A treatment effect on an ordinal outcome was simulated (beta − 0.5 in logistic regression) for 15.000 patients, based on a large data set (the IMPACT data, n = 8799) using different scenarios including measured and unmeasured confounders, and a common cause of IV and outcome. We compared estimated treatment effects with patient-level adjustment for confounders, IV with treatment preference as the instrument, and adjusted IV, with hospital added as a fixed effect in the regression models. Results The use of patient-level adjustment resulted in biased estimates for all the analyses that included unmeasured confounders, IV analysis was less confounded, but also less reliable. With correlation between treatment preference and hospital characteristics (a common cause) estimates were skewed for regular IV analysis, but not for adjusted IV analysis. Conclusion When using IV analysis for comparing hospitals, some limitations of regular IV analysis can be overcome by adjusting for a common cause. Trial registration We do not report the results of a health care intervention.

Background In traumatic brain injury (TBI), large between-center differences in treatment and outcome for patients managed in the intensive care unit (ICU) have been shown. The aim of this study is to explore if European neurotrauma centers can be clustered, based on their treatment preference in different domains of TBI care in the ICU. Methods Provider profiles of centers participating in the Collaborative European Neurotrauma Effectiveness Research in TBI study were used to assess correlations within and between the predefined domains: intracranial pressure monitoring, coagulation and transfusion, surgery, prophylactic antibiotics, and more general ICU treatment policies. Hierarchical clustering using Ward’s minimum variance method was applied to group data with the highest similarity. Heat maps were used to visualize whether hospitals could be grouped to uncover types of hospitals adhering to certain treatment strategies. Results Provider profiles were available from 66 centers in 20 different countries in Europe and Israel. Correlations within most of the predefined domains varied from low to high correlations (mean correlation coefficients 0.2–0.7). Correlations between domains were lower, with mean correlation coefficients of 0.2. Cluster analysis showed that policies could be grouped, but hospitals could not be grouped based on their preference. Conclusions Although correlations between treatment policies within domains were found, the failure to cluster hospitals indicates that a specific treatment choice within a domain is not a proxy for other treatment choices within or outside the domain. These results imply that studying the effects of specific TBI interventions on outcome can be based on between-center variation without being substantially confounded by other treatments. Trial registration We do not report the results of a health care intervention.

Background There is a growing interest in assessment of the quality of hospital care, based on outcome measures. Many quality of care comparisons rely on binary outcomes, for example mortality rates. Due to low numbers, the observed differences in outcome are partly subject to chance. We aimed to quantify the gain in efficiency by ordinal instead of binary outcome analyses for hospital comparisons. We analyzed patients with traumatic brain injury (TBI) and stroke as examples. Methods We sampled patients from two trials. We simulated ordinal and dichotomous outcomes based on the modified Rankin Scale (stroke) and Glasgow Outcome Scale (TBI) in scenarios with and without true differences between hospitals in outcome. The potential efficiency gain of ordinal outcomes, analyzed with ordinal logistic regression, compared to dichotomous outcomes, analyzed with binary logistic regression was expressed as the possible reduction in sample size while keeping the same statistical power to detect outliers. Results In the IMPACT study (9578 patients in 265 hospitals, mean number of patients per hospital = 36), the analysis of the ordinal scale rather than the dichotomized scale (‘unfavorable outcome’), allowed for up to 32% less patients in the analysis without a loss of power. In the PRACTISE trial (1657 patients in 12 hospitals, mean number of patients per hospital = 138), ordinal analysis allowed for 13% less patients. Compared to mortality, ordinal outcome analyses allowed for up to 37 to 63% less patients. Conclusions Ordinal analyses provide the statistical power of substantially larger studies which have been analyzed with dichotomization of endpoints. We advise to exploit ordinal outcome measures for hospital comparisons, in order to increase efficiency in quality of care measurements. Trial registration We do not report the results of a health care intervention.

Background: Comparing outcomes across hospitals to learn from best performing hospitals can be valuable. However, reliably identifying best performance is challenging. This study assesses the possibility to distinguish best performing hospitals on single outcomes and consistency of performance on different outcomes. Methods: Data were derived from the Dutch ColoRectal Audit 2013-2015. Outcomes considered were textbook outcome (colon), (circumferential) resection margins, (serious) complications, mortality, and 'failure to rescue'. To include uncertainty in rankings, random effect logistic regression models were used to calculate expected ranks (ERs), for each hospital and outcome. Rankability was calculated for each outcome, as a measure of reliability of ranking. Furthermore, correlation between ERs on different outcomes was assessed. Correlation was considered weak <0.40, moderate between 0.40 - 0.59 and strong >0.60. Results: The study included 32 143 patients; of whom 11 373 were treated in 2015 across 84 hospitals, 8181 colon and 3192 rectal cancer patients. In this one-year period 'Postoperative complications' had the highest rankability for colon (57%) and rectal (41%) surgery. No (group of) hospital(s) had the highest ER(s) on all outcomes. Correlation between ERs of outcomes was moderate in 2 (of 25) and strong in 4 (of 25) combinations. Rankability of colorectal mortality increased from 14% in 2015 to 35% when data over 2013-2015 were used. Conclusion: The highest reliability of identifying best performance based on an outcome was 57%. However, the balance between reliability and relevance of outcomes is vulnerable. No (group of) hospital(s) could be identified as best performer on all outcomes. Performance was not consistent on outcomes. (C) 2020 Published by Elsevier Ltd.

BACKGROUND: For many major surgical procedures, the outcomes are better when performed by surgeons with higher procedure volumes. The purpose of this study was to examine the relations between surgeon procedure volume and the outcomes of Dupuytren's surgery. METHODS: The authors conducted an observational study from 2011 to 2014 at six dedicated hand surgery practice sites in The Netherlands. Five hundred eighty-eight patients underwent surgery for Dupuytren's contracture performed by one of the 16 surgeons. The main exposure variable was annual surgeon volume. Outcome measures were the degree of residual contracture, full release rate, and any postoperative adverse event examined within 3 months of surgery. RESULTS: Mean annual surgeon volume was 51 among the 16 surgeons(range; 4-86) procedures. The majority of patients had primary disease (79 percent) and underwent open fasciectomy (74 percent). Multivariable regression analyses showed that surgeon volume was linearly related to all three outcomes, and identified no optimal volume threshold. Performing 10 additional procedures annually was independently associated with nearly 0.8 degree less residual contracture (p = 0.002), 9 percent higher odds of attaining a full release (p = 0.037), and 11 percent lower odds of an adverse event (p < 0.001). Nonetheless, patient-related factors had larger impacts on all three clinical outcomes than surgeon volume. CONCLUSIONS: In this study of practicing hand surgeons, surgeon volume varied widely, and a higher volume was associated with less postoperative residual contracture, higher full release rates, and fewer adverse events. This implies that increasing surgeon's procedure volume provides an opportunity for improving the outcomes of Dupuytren's surgery. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Report cards on the health care system increasingly report provider-specific performance on indicators that measure the quality of health care delivered. A natural reaction to the publishing of hospital-specific performance on a given indicator is to create ‘league tables’ that rank hospitals according to their performance. However, many indicators have been shown to have low to moderate rankability, meaning that they cannot be used to accurately rank hospitals. Our objective was to define conditions for improving the ability to rank hospitals by combining several binary indicators with low to moderate rankability. Monte Carlo simulations to examine the rankability of composite ordinal indicators created by pooling three binary indicators with low to moderate rankability. We considered scenarios in which the prevalences of the three binary indicators were 0.05, 0.10, and 0.25 and the within-hospital correlation between these indicators varied between − 0.25 and 0.90. Creation of an ordinal indicator with high rankability was possible when the three component binary indicators were strongly correlated with one another (the within-hospital correlation in indicators was at least 0.5). When the binary indicators were independent or weakly correlated with one another (the within-hospital correlation in indicators was less than 0.5), the rankability of the composite ordinal indicator was often less than at least one of its binary components. The rankability of the composite indicator was most affected by the rankability of the most prevalent indicator and the magnitude of the within-hospital correlation between the indicators. Pooling highly-correlated binary indicators can result in a composite ordinal indicator with high rankability. Otherwise, the composite ordinal indicator may have lower rankability than some of its constituent components. It is recommended that binary indicators be combined to increase rankability only if they represent the same concept of quality of care.

Background Despite widespread use of quality indicators, it remains unclear to what extent they can reliably distinguish hospitals on true differences in performance. Rankability measures what part of variation in performance reflects ‘true’ hospital differences in outcomes versus random noise. Objective This study sought to assess whether combining data into composites or including data from multiple years improves the reliability of ranking quality indicators for hospital care. Methods Using the Dutch National Medical Registration (2007–2012) for stroke, colorectal carcinoma, heart failure, acute myocardial infarction and total hiparthroplasty (THA)/ total knee arthroplasty (TKA) in osteoarthritis (OA), we calculated the rankability for in-hospital mortality, 30-day acute readmission and prolonged length of stay (LOS) for single years and 3-year periods and for a dichotomous and ordinal composite measure in which mortality, readmission and prolonged LOS were combined. Rankability, defined as (between-hospital variation/between-hospital+within hospital variation)×100% is classified as low (<50%), moderate (50%–75%) and high (>75%). Results Admissions from 555 053 patients treated in 95 hospitals were included. The rankability for mortality was generally low or moderate, varying from less than 1% for patients with OA undergoing THA/TKA in 2011 to 71% for stroke in 2010. Rankability for acute readmission was low, except for acute myocardial infarction in 2009 (51%) and 2012 (62%). Rankability for prolonged LOS was at least moderate. Combining multiple years improved rankability but still remained low in eight cases for both mortality and acute readmission. Combining the individual indicators into the dichotomous composite, all diagnoses had at least moderate rankability (range: 51%–96%). For the ordinal composite, only heart failure had low rankability (46% in 2008) (range: 46%–95%). Conclusion Combining multiple years or into multiple indicators results in more reliable ranking of hospitals, particularly compared with mortality and acute readmission in single years, thereby improving the ability to detect true hospital differences. The composite measures provide more information and more reliable rankings than combining multiple years of individual indicators.

Introduction Controversy exists about the optimal treatment for patients with a traumatic acute subdural haematoma (ASDH) and an intracerebral haematoma/contusion (t-ICH). Treatment varies largely between different regions. The effect of this practice variation on patient outcome is unknown. Here, we present the protocol for a prospective multicentre observational study aimed at comparing the effectiveness of different treatment strategies in patients with ASDH and/or t-ICH. Specifically, the aims are to compare (1) an acute surgical approach to an expectant approach and (2) craniotomy to decompressive craniectomy when evacuating the haematoma.Methods and analysis Patients presenting to the emergency room with an ASDH and/or an t-ICH are eligible for inclusion. Standardised prospective data on patient and injury characteristics, treatment and outcome will be collected on 1000 ASDH and 750 t-ICH patients in 60–70 centres within two multicentre prospective observational cohort studies: the Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) and Neurotraumatology Quality Registry (Net-QuRe). The interventions of interest are acute surgery, defined as surgery directly after the first CT at presentation versus late or no surgery and craniotomy versus decompressive craniectomy. The primary outcome measure is the Glasgow Outcome Score-Extended at 6 months. Secondary outcome measures include in-hospital mortality, quality of life and neuropsychological tests. In the primary analysis, the effect of treatment preference (eg, proportion of patients in which the intervention under study is preferred) per hospital will be analysed with random effects ordinal regression models, adjusted for casemix and stratified by study. Such a hospital-level approach reduces confounding by the indication. Sensitivity analyses will include propensity score matching, with treatment defined on patient level. This study is designed to determine the best acute management strategy for ASDH and t-ICH by exploiting the existing between-hospital variability in surgical management.Ethics and dissemination Ethics approval was obtained in all participating countries. Results of surgical management of ASDH and t-ICH/contusion will separately be submitted for publication in a peer-reviewed journal.Trial registration number NCT02210221 and NL 5761.

Background: For many major surgical procedures, the outcomes are better when performed by surgeons with higher procedure volumes. The purpose of this study was to examine the relations between surgeon procedure volume and the outcomes of Dupuytren’s surgery. Methods: The authors conducted an observational study from 2011 to 2014 at six dedicated hand surgery practice sites in The Netherlands. Five hundred eighty-eight patients underwent surgery for Dupuytren’s contracture performed by one of the 16 surgeons. The main exposure variable was annual surgeon volume. Outcome measures were the degree of residual contracture, full release rate, and any postoperative adverse event examined within 3 months of surgery. Results: Mean annual surgeon volume was 51 among the 16 surgeons(range; 4-86) procedures. The majority of patients had primary disease (79 percent) and underwent open fasciectomy (74 percent). Multivariable regression analyses showed that surgeon volume was linearly related to all three outcomes, and identified no optimal volume threshold. Performing 10 additional procedures annually was independently associated with nearly 0.8 degree less residual contracture ( p = 0.002), 9 percent higher odds of attaining a full release ( p = 0.037), and 11 percent lower odds of an adverse event ( p < 0.001). Nonetheless, patient-related factors had larger impacts on all three clinical outcomes than surgeon volume. Conclusions: In this study of practicing hand surgeons, surgeon volume varied widely, and a higher volume was associated with less postoperative residual contracture, higher full release rates, and fewer adverse events. This implies that increasing surgeon’s procedure volume provides an opportunity for improving the outcomes of Dupuytren’s surgery. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Introduction: Observational studies of interventions are at risk for confounding by indication. The objective of the current study was to define the circumstances for the validity of methods to adjust for confounding by indication in observational studies. Patients and methods: We performed post hoc analyses of data prospectively collected from three European and North American traumatic brain injury studies including 1,725 patients. The effects of three interventions (intracranial pressure [ICP] monitoring, intracranial operation and primary referral) were estimated in a proportional odds regression model with the Glasgow Outcome Scale as ordinal outcome variable. Three analytical methods were compared: classical covariate adjustment, propensity score matching and instrumental variable (IV) analysis in which the percentage exposed to an intervention in each hospital was added as an independent variable, together with a random intercept for each hospital. In addition, a simulation study was performed in which the effect of a hypothetical beneficial intervention (OR 1.65) was simulated for scenarios with and without unmeasured confounders. Results: For all three interventions, covariate adjustment and propensity score matching resulted in negative estimates of the treatment effect (OR ranging from 0.80 to 0.92), whereas the IV approach indicated that both ICP monitoring and intracranial operation might be beneficial (OR per 10% change 1.17, 95% CI 1.01-1.42 and 1.42, 95% CI 0.95-1.97). In our simulation study, we found that covariate adjustment and propensity score matching resulted in an invalid estimate of the treatment effect in case of unmeasured confounders (OR ranging from 0.90 to 1.03). The IV approach provided an estimate in the similar direction as the simulated effect (OR per 10% change 1.04-1.05) but was statistically inefficient. Conclusion: The effect estimation of interventions in observational studies strongly depends on the analytical method used. When unobserved confounding and practice variation are expected in observational multicenter studies, IV analysis should be considered.

Objective: High surgeon procedural volume has been linked to better outcomes for a variety of surgical procedures, but the impact of surgeon volume on outcomes of Dupuytren surgery remains uncertain. Materials and Methods: We used data from a quality-of-care registry from 6 hand surgery practice sites between 2011 and 2014. We included 561 patients with the Dupuytren disease who underwent fasciectomy (71%) or percutaneous needle fasciotomy (29%) by 16 hand surgeons. Outcomes were the degree of residual contracture and adverse events assessed at 6 to 12 weeks after treatment. Relations between volume and outcomes were examined using linear and logistic regression models, with adjustment for patient characteristics and the type of procedure. Nonlinearity was assessed with restricted cubic splines. Results: Overall, mean residual contracture (total active extension deficit) at follow-up was 24°, which corresponded to a postprocedure improvement of 65%. Forty-seven percent of patients experienced at least 1 adverse event, with neuropraxia (12%), scar sequelae (12%), and wound healing problems (8%) being the three most common events. Surgeon volume was inversely related to the degree of residual contracture: Every 58 additional procedures performed annually were associated with 5° less residual contracture at follow-up ( P, .03). Moreover, surgeon volume had an inverse effect on overall events (odds ratio per 50 additional procedures, 0.86, P, .01). Conclusions: Even among experienced hand surgeons, patients treated by surgeons performing high volumes of Dupuytren surgery had better outcomes in terms of residual contracture and adverse events. The findings of this study suggest that surgeons may improve outcomes by increasing their annual procedural volume for these specific interventions.