Properly calculating estat phtest in the presence of stratified hazards

The Schoenfeld residual-based test for proportional-hazards violations in the Cox duration model is predicated on a key assumption pertaining to homoskedasticity in the residuals. This assumption is likely to be violated in the presence of stratified hazards, which is noted in estat phtest’s help file. We provide a wrapper command, stratph, that implements a straightforward modification to the residual-based diagnostic that corrects for the potential assumption violation. We use the stratified hazards example from the stcox help file to demonstrate the stratph command’s workings.

A Differential Therapeutic Consideration for use of Corticosteroids According to Established COVID-19 Clinical Phenotypes in Critically Ill Patients

Background: The steroids are currently used as standard treatment for severe COVID-19. However, the evidence is weak. Our aim is to determine if the use of corticosteroids was associated with Intensive Care Unit (ICU) mortality among whole population and pre-specified clinical phenotypes.Methods: A secondary analysis derived from multicenter, observational study of adult critically ill patients with confirmed COVID-19 disease admitted to 63 ICUs in Spain. Three phenotypes were derived by non-supervised clustering analysis from whole population and classified as (A: severe, B: critical and C: life-threatening). The primary outcome was ICU mortality. We performed a Multivariate analysis after propensity score full matching (PS), Cox proportional hazards (CPH), Cox covariate time interaction (TIR), Weighted Cox Regression (WCR) and Fine-Gray analysis(sHR) to assess the impact of corticosteroids on ICU mortality according to the whole population and distinctive patient clinical phenotypes. Results: A total of 2,017 patients were analyzed, 1171(58%) with corticosteroids. After PS, corticosteroids were shown not to be associated with ICU mortality (OR:1.0,95%CI:0.98-1.15). Corticosteroids were administered in 298/537(55.5%) patients of “A” phenotype and their use was not associated with ICU mortality (HR=0.85[0.55-1.33]). A total of 338/623(54.2%) patients in “B” phenotype received corticosteroids. The CPH (HR =0.65 [0.46-0.91]) and TIR regression (1- 25 day tHR=0.56[0.39-0.82] and >25 days tHR=1.53[1.03-7.12]) showed a biphasic effect of corticosteroids due to proportional assumption violation. No effect of corticosteroids on ICU mortality was observed when WCR was performed (wHR=0.72[0.49-1.05]). Finally, 535/857(62.4%) patients in “C” phenotype received corticosteroids. The CPH (HR=0.73[0.63-0.98]) and TIR regression (1- 25 day tHR=0.69[ 0.53-0.89] and >25 days tHR=1.30[ 1.14-3.25]) showed a biphasic effect of corticosteroids and proportional assumption violation. However, wHR (0.75[0.58-0.98]) and sHR (0.79[0.63-0.98]) suggest a protective effect of corticosteroids on ICU mortality. Conclusion: Our finding warns against the widespread use of corticosteroids in all critically ill patients with COVID-19 at moderate-high dose. Only patients with the highest severity could benefit from steroid treatment although this effect on clinical outcome was minimized during ICU stay.

Do Heritability Estimates of Political Phenotypes Suffer From an Equal Environment Assumption Violation? Evidence From an Empirical Study

Using data from the Minnesota Twins Political Survey, this paper tests for the presence of unequal environments (EEA) by zygosity in political attitudes. Equal environment measures used include shared bedroom, friends, classes, and dressing alike. Results show an EEA violation at p < .05 in 5% of the models tested. The violations' impact on heritability estimates and their confidence levels appear random in magnitude and direction. No reasonable post hoc explanation emerged for understanding the presence of the violation in some items but not others. This article establishes reasonable priors for the absence of EEA violations in political phenotypes based on the tested environmental components. The findings place the burden on critics to present theoretical work on the specific mechanisms of EEA violations based on which additional empirical assessments could (and should) be conducted.