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.