2.5. Outcomes
SECONDARY
Our first primary outcome was the frequency of days with any URTI symptoms (FSD—frequency of symptomatic days). This was the ratio calculated based on enumerating days with presence of any degree of URTI symptoms (1–3 URTI score) and dividing this by the number of days within the period of interest (Our second primary outcome was the average gravity score (AGS) of URTI symptoms. This was a ratio calculated after summarizing the URTI scores (0–3) and dividing them by the number of days within the period of interest.Both of the primary outcomes were analyzed over the entire 21-week (147 days) period of the experiment, as well as within several periods, namely 4, 8, 12, 14, 16, 18 and 20 weeks counted from the beginning of supplementation.Our secondary outcome was the number of URTI episodes (NUE) over the entire trial period. This required finding a subjective definition of an episode, which would fit the most accurate medical description of URTI and allow for a credible enumeration of such episodes in our trial. We decided to define an URTI episode as at least 3 days of symptoms at the 2nd severity level, being separated by at least 3 asymptomatic days.