Statistical analysis
Normality of data was checked using the Shapiro-Wilk test. Demographic
and baseline clinical characteristics, including comorbidities and blood
parameters, were expressed as median (IQR) for continuous variables and
as numbers (%) for categorical variables. Continuous variables were
compared between tofacitinib and controls using the Mann-Whitney U-test
test for two groups and the Kruskal Wallis test for three groups.
Categorical variables across groups were compared by the Fisher’s exact
test or Pearson’s χ² test.
All participants were followed up from the date of enrolment into the
study until discharge or death. We conducted a survival analysis and
compared the time to invasive mechanical ventilation or death between
the treatment groups using unweighted Kaplan-Meier curves and
univariable and multivariable Cox regression analysis with baseline
fixed covariates. The effect of treatment was evaluated using an
unadjusted and adjusted hazard ratio (HR) with 95% confidence interval
(CI). The baseline model was adjusted for inverse propensity score
weighting. Cox regression model validity was checked by evaluation of
the proportional hazard assumption using Schoenfeld residuals.
We considered a two-sided p value test of less than 0.05 to be
statistically significant. Statistical analyses were performed using IBM
SPSS Statistics, version 22 (IBM Corporation, USA).