If you look through the start of this document - hey.nhs.uk/wp/wp-content/up... - they explain how they reached their ranges. They had to tweak the standard ranges from the BCSH by comparing their assay results with the UK standard.
They tested their ranges and almost 5% of normal people test ‘low’ and almost 10% test ‘intermediate’.
I’ve checked the Stitching website Sleepybunny. Looks like they’ve had a re-vamp - the flowchart document doesn’t appear to be available in their English translations section any longer.
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