Have had to take my two children for pcr tests lately. It's hard as son is autistic so it's incredible difficult anyway and it's no easier with the 6 year old daughter! My son was all wriggly and I was worried I hadn't got enough sample on the swab but it came back as positive so it picked something up. What would happen if the swab doesn't collect enough sample or nothing at all due to incorrect procedure used? Would the result be invalid or show as negative? Even on myself I worry if I'm doing it right !