Stool sampling
Fe-Col® fecal sample collection kits
Stool samples were collected by the participant at home on the morning (or within 24 h) of their testing visit using Fe-Col® fecal sample collection kits (Alpha laboratories Ltd). Participants were instructed to store their sample in the fridge (or a cool place) following collection. Upon receipt at the lab, samples were refrigerated, then (within ∼1 h) the collection tube was sanitized (Clinell wipes, GAMA Healthcare Ltd) before being stored at –80°C prior to analysis.