Statistical analysis
We carried out chi-square analysis in order to compare the
biologics and non-biologics groups. We compared the characteristics of
the biologics patients and non-biologics patients, adopting the t-test
for continuous variables and the chi-square test for categorical
variables. The incidence of mortality was reported as the event rate
(proportion of events) and incidence density (number of events per 100
person-years). We adopted Cox proportional hazard model to compare the
risk of mortality between the two groups. Furthermore, we used the
Poisson regression model to compare the annual number of admissions for
autoimmune disease between the study groups, treating the
log-transformed follow-up year as an offset variable. Finally, the
hazard ratio of the patients of the two groups was calculated with
survival analysis. We considered a p -value < 0.05 to be
statistically significant. All data analysis was conducted using SAS
software version 9.4 (SAS Institute, Cary, NC).
- Ethics approval and consent to participate
This retrospective database analysis study involving human participants
was in accordance with the ethical standards of the institutional and
national research committee and with the 1964 Helsinki Declaration and
its later amendments or comparable ethical standards. The Longitudinal
Health Insurance Database 2005 provides only de-identified samples,
which Ethical approval was waived by the local Ethics Committee.