2.2 Statistical considerations
Descriptive and comparative statistics were used to present the results
of this non-interventional observational study. Continuous variables are
reported as mean ± standard deviation or median and interquartile range
(if not normally distributed). Categorical data are expressed as numbers
(percentages). Only patients for whom data on the primary outcome
(HAMD-17 score evaluation) were available at baseline and at the end of
the follow up period were included in the statistical analysis. Adjusted
means and standard errors were calculated with generalized linear
modelling to explore associations between the observed antidepressive
effectiveness of agomelatine and clinically important parameters. For
this, univariate regression modeling was performed using the following
covariates for adjustment analysis: age, sex, baseline total HAMD-17
score, severity of COVID-19 infection, time since COVID-19 infection
onset, and status of taking any antidepressants prior to the enrollment
visit. The level of statistical significance for the univariate analysis
was set at P<0.05. For each significant predictor identified
in the univariate analysis we also conducted multivariate linear
regression modelling.
To estimate required study sample size the following assumptions were
made. We calculated that approximately 28 study subjects would be
sufficient to detect at least a 3.0-point difference between the sample
and population means with 90% power at a 0.005 one-sided significance
level. Considering the observational nature of the study a dropout rate
of approximately 30% was assumed. A minimum number of 40 outpatients
was therefore required to be enrolled in the study.
RESULTS
A total of 104 patients were enrolled. One patient did not meet the
inclusion criterium for depression severity at baseline and was
excluded. Data for 103 (99.03%) patients therefore comprised the full
analysis set (FAS). One patient in the FAS terminated participation in
the study prematurely due to a lack of treatment effect with
agomelatine, requiring the administration of another antidepressant.
Patient baseline demographic and clinical characteristics are presented
in Table 1. Participants were mostly female (73 [70.9%])
with a mean age of 44.0±13.3 years. The majority was employed (79.6%)
and none of the patients had received any prior treatment with
antidepressants. At baseline, 21.4% of patients reported they had
suffered moderate COVID-19 infection in the past 3 months, and 78.6%
had a history of mild COVID-19. The mean time from infection onset until
the enrollment visit was 2.1±0.7 months. Initial assessment of the
severity of the depressive episode showed that patients were almost
equally distributed between mild (n=55, 53.4%) and moderate (n=48,
46.6%) depression. The mean total HAMD-17 score at baseline was
16.3±4.7 and mean scores for the two anxiety components of the HAMD-17
scale (questions 10 and 11) were 1.4±0.9 and 1.3±0.8, respectively. Mean
baseline SF-36 QoL scores were 39.7±8.4 for the physical component and
37.2±8.7 for the mental component of the questionnaire.