*5.1. Mortality*

Mortality, expressed as a% of study sample based on conversion from the absolute figures, was presented in two studies [26,29]. Both of these studies examined the facial vein route, with [29] additionally comparing with the retrobulbar sample route. These studies evaluated serial sampling at intervals of up to one week. Frolich et al. 2018 also made comparisons with single-sample groups. It is worth noting that the study by Forbes et al. 2010 [26] was a retrospective case-control study with some variation in blood sampling interval and a concurrent study design, potentially confounding interpretation of findings. Due to a sole pairwise comparison both single and serial sampling comparison have been synthesised narratively and are not supplemented with a table.

In a retrospective study [26] with facial vein sampling performed serially, a mortality rate of 4/214 mice was observed (≈2%). Frolich et al. 2018 [29] reported a substantially higher mortality rate of (4/12, 33%) when mice were serially sampled by the facial vein route. There was no associated mortality with the single-sample facial vein route or retrobulbar routes, or serial retrobulbar sampling [29]. Both studies utilised a similar sampling interval of approximately 1 week.
