Confounding adjustment methods for multi-level treatment comparisons under lack of positivity and unknown model specification

Diop, Serigne Arona; Duchesne, Thierry; Cumming, Steven G.; Diop, Awa; Talbot, Denis

doi:10.1080/02664763.2021.1911966

Cited by 6 publications

(7 citation statements)

References 40 publications

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“…During our stepwise regression analyses using the likelihood ratio test, however, the sex variable was removed from the final multivariable regression models of both SM and WB. This is likely due to unknown functional relationships between sex and other independent variables, when explaining SM and WB occurrence [59]. Aguirre et al [31] also reported that sex was not a significant variable for breast myopathies, although raw frequency indicated that male broilers had more frequently WB and WS.…”

Section: Plos Onementioning

confidence: 99%

Prevalence of breast muscle myopathies (spaghetti meat, woody breast, white striping) and associated risk factors in broiler chickens from Ontario Canada

et al. 2022

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Spaghetti meat (SM), woody breast (WB), and white striping (WS) are myopathies that affect the pectoral muscle of fast-growing broiler chickens. The prevalence and possible risk factors of these myopathies have been reported in other countries, but not yet in Canada. Thus, the objective of this study was to assess the prevalence and risk factors associated with these myopathies in a representative population of Canadian broilers. From May 2019 to March 2020, 250 random breast fillets from each of 37 flocks (total, 9,250) were obtained from two processing plants and assessed for the presence and severity of myopathies. Demographic data (e.g., sex and average live weight), environmental conditions during the grow-out period (e.g., temperature), and husbandry parameters (e.g., vaccination) were collected for each flock. Associations between these factors and the myopathies were tested using logistic regression analyses. The prevalence of SM, severe WB, and mild or moderate WS was 36.3% (95% CI: 35.3–37.3), 11.8% (95% CI: 11.2–12.5), and 96.0% (95% CI: 95.6–96.4), respectively. Most (85.1%) of the fillets showed multiple myopathies. Regression analyses showed that the odds of SM increased with live weight (OR = 1.30, 95% CI 1.01–1.69) and higher environmental temperature during the grow-out period (OR = 1.75, 95% CI 1.31–2.34). The odds of WB increased with live weight (OR = 1.23, 95% CI 1.03–1.47) and when flocks were not vaccinated against coccidia (OR = 1.86, 95% CI 1.51–2.29). This study documents for the first time a high prevalence of myopathies in Ontario broilers, and suggests that these lesions may have a significant economic impact on the Canadian poultry industry. Our results indicate that environmental conditions and husbandry are associated with the development of breast myopathies, in agreement with the current literature. Future studies are needed to determine how risk factors can promote the occurrence of these conditions, in order to implement possible mitigating strategies.

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Section: Plos Onementioning

confidence: 99%

Prevalence of breast muscle myopathies (spaghetti meat, woody breast, white striping) and associated risk factors in broiler chickens from Ontario Canada

et al. 2022

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“… 29 Arona Diop and colleagues stated that the robust variance estimator used with OW is conservative. 30 Reifeis and Hudgens examined the performance of the robust variance estimator when used with ATT weights and found that the estimator may be either conservative or anticonservative, concluding that the resultant confidence intervals will not be valid. 31 We are unaware of the previous similar results for MW.…”

Section: Discussionmentioning

confidence: 99%

The performance of marginal structural models for estimating risk differences and relative risks using weighted univariate generalized linear models

Austin

2024

Stat Methods Med Res

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We used Monte Carlo simulations to compare the performance of marginal structural models (MSMs) based on weighted univariate generalized linear models (GLMs) to estimate risk differences and relative risks for binary outcomes in observational studies. We considered four different sets of weights based on the propensity score: inverse probability of treatment weights with the average treatment effect as the target estimand, weights for estimating the average treatment effect in the treated, matching weights and overlap weights. We considered sample sizes ranging from 500 to 10,000 and allowed the prevalence of treatment to range from 0.1 to 0.9. We examined both the robust variance estimator when using generalized estimating equations with an independent working correlation matrix and a bootstrap variance estimator for estimating the standard error of the risk difference and the log-relative risk. The performance of these methods was compared with that of direct weighting. Both the direct weighting approach and MSMs based on weighted univariate GLMs resulted in the identical estimates of risk differences and relative risks. When sample sizes were small to moderate, the use of an MSM with a bootstrap variance estimator tended to result in the most accurate estimates of standard errors. When sample sizes were large, the direct weighting approach and an MSM with a bootstrap variance estimator tended to produce estimates of standard error with similar accuracy. When using a MSM to estimate risk differences and relative risks, in general it is preferable to use a bootstrap variance estimator than the robust variance estimator. We illustrate the application of the different methods for estimating risks differences and relative risks using an observational study on the effect on mortality of discharge prescribing of a beta-blocker in patients hospitalized with acute myocardial infarction.

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“…To adjust for confounding (age, sex, comorbidities (the age adjusted Charlson index), number of regular medications and vital signs as proxies for severity of illness), we used an overlap weights approach, wherein each individual receives a weight that is proportional to the inverse of their probability to choose a particular setting [23]. Confidence intervals were obtained using a robust variance estimator [24].…”

Section: Discussionmentioning

confidence: 99%

A value-based comparison of the management of respiratory diseases in walk-in clinics and emergency departments

et al. 2023

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Objectives Our aim was to compare some of the health outcomes and costs associated with value of care in emergency departments (ED) and walk-in clinics for ambulatory patients presenting with an acute respiratory disease. Methods A health records review was conducted from April 2016 through March 2017 in one ED and one walk-in clinic. Inclusion criteria were: (i) ambulatory patients at least 18 years old, (ii) discharged home with a diagnosis of upper respiratory tract infection (URTI), pneumonia, acute asthma, or acute exacerbation of chronic obstructive pulmonary disease. Primary outcome was the proportion of patients returning to any ED or walk-in clinic within three and seven days of the index visit. Secondary outcomes were the mean cost of care and the incidence of antibiotic prescription for URTI patients. The cost of care was estimated from the Ministry of Health's perspectives using time-driven activity-based costing. ResultsThe ED group included 170 patients and the walk-in clinic group 326 patients. The return visit incidences at three and seven days were, respectively, 25.9% and 38.2% in the ED vs. 4.9% and 14.7% in the walk-in clinic (adjusted relative risk (arr) of 4.7 (95% CI 2.6-8.6) and 2.7 (1.9-3.9)). The mean cost ($Cdn) of the index visit care was 116.0 (106.3-125.7) in the ED vs. 62.5 (57.7-67.3) in the walk-in clinic (mean difference of 56.4 (45.7-67.1)). Antibiotic prescription for URTI was 5.6% in the ED vs. 24.7% in the walk-in clinic (arr 0.2, 0.01-0.6). Conclusions This study is the first in a larger research program to compare the value of care between walk-in clinics and the ED. The potential advantages of walk-in clinics over EDs (lower costs, lower incidence of return visits) for ambulatory patients with respiratory diseases should be considered in healthcare planning. KeywordsValue of care • Health outcomes • Respiratory diseases • Outpatient visit • Emergency department • Return visits • Cost of care The results of this study were presented as a Poster at the annual conference of the Canadian Association of Emergency Physicians (CAEP), in Québec on May 30, 2022.

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Confounding adjustment methods for multi-level treatment comparisons under lack of positivity and unknown model specification

Cited by 6 publications

References 40 publications

Prevalence of breast muscle myopathies (spaghetti meat, woody breast, white striping) and associated risk factors in broiler chickens from Ontario Canada

Prevalence of breast muscle myopathies (spaghetti meat, woody breast, white striping) and associated risk factors in broiler chickens from Ontario Canada

The performance of marginal structural models for estimating risk differences and relative risks using weighted univariate generalized linear models

A value-based comparison of the management of respiratory diseases in walk-in clinics and emergency departments

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