End-of-trial analyses
SECONDARY
Primary analyses will calculate odds ratios for the main effects of interventions using a binomial generalised linear mixed model fitted to the aggregate number of primary outcomes recorded in each 9-month period by site with the denominator as the number of donations recorded by site-period (defined by NHSBT as a complete donation or a partial donation). Adjustments will be made for the baseline prognostic variables considered for balancing at randomisation (i.e. historical VVR rates, total numbers of donors bled, and type of site), plus dummy variables for the four nine-month periods of intervention, and a random effect for the site. Key secondary analyses related to the primary outcome will include an assessment of interactions of interventions and possible variation of the main effects by period and baseline characteristics. Analyses of other secondary outcomes will follow the same approach as for the primary outcome.