Statistical analysis
Descriptive statistics were used to compare the patients with and without prior therapeutic anticoagulation and to estimate the prevalence of the outcomes. Categorical parameters were presented as counts with percentages, continuous parameters with medians and interquartile ranges, based on their non-normal distribution tested with the Shapiro-Wilk test. Comparisons were performed using Mann-Whitney U test or Chi-Squared test as appropriate. In order to compare the outcomes while adjusted for potential confounding resulting from the non-randomized design of our observational study, we applied propensity score-matching methods. In our database, 174 (15%) patients had missing information for BMI. Therefore, we first imputed BMI values with single imputation using predicted values from multivariable models including age, sex, hypertension, diabetes mellitus, and the outcome mortality. Propensity scores were generated using a multivariable logistic regression model with prior therapeutic anticoagulation use as outcome and the 17 variables previously stated as predictors. The patients with therapeutic anticoagulation were subsequently matched in a 1:3 ratio with patients without therapeutic anticoagulation prior to admission on these propensity scores with Nearest Neighbor Matching techniques without replacement and a caliper width of 0·1 of the standard deviation of the logit of the propensity score. To evaluate the balance of measured confounders between exposed and unexposed groups, we calculated the standardized mean difference (SMD). An SMD <0.25 indicated balance of matched cohorts.30
Associations between prior therapeutic use of anticoagulants and the outcomes overall in hospital mortality, admission to ICU, occurrence of PE, critical respiratory state, and the need for invasive mechanical ventilation were estimated as risk ratios (RR) with 95% confidence intervals (CI). Estimating the differences in length of hospital stay between the two groups was performed using Mann-Whitney U test stratified by mortality.
In our secondary analysis, we compared VKA versus no therapeutic anticoagulation, DOAC versus no therapeutic anticoagulation and VKA versus DOAC on the before mentioned outcome parameters. Matching was performed using R-software/studio Version 1.3.1093 and statistical analysis were performed using STATA/SE 16.0 (Stata Corp, TX, USA).