DNA analysis
Whole blood samples were taken at the first study visit and frozen. DNA was extracted from the first 110 whole blood samples received using the QIAamp DNA blood mini kit according to the manufacturer’s instructions. This set of samples were the first batches received from the various trial sites by the laboratory, and analysis was restricted to this group for purely logistical reasons relating to the COVID pandemic and subsequent funding. DNA genotyping was performed by Taqman qPCR using assays C2022135-10 and C15826314-10 on an ABI 7500 fast thermocycler according to the manufacturer’s instructions. Two samples did not amplify for rs2854464 and 3 samples did not amplify for rs10783486. Data from these individuals were not included in the analysis.