Don't think that's your answer. All meters read whole blood and most (all now?) in the UK market are calibrated to give results as if from plasma.
The Pura tech sheet confirms that it's plasma calibrated.
https://www.mylife-pura.co.uk/tl_files/pdf/4204371_V01-Pura-Produktkarte-A5-GB.pdf
I think the problem is that meters are considered to be accurate if the result falls within +/?20% of a lab test. So if a lab tested your blood and found it to be 6mmol your meter could read anything from 4.8 to 7.2 and be considered to be working fine.In practice they are normally better than this What really matters is if they are consistent,so you know what to do on the basis of your meter reading.
The manufacturers have been resisting changing the rules for ages but
things might improve a little in the near future. An international standard (ISO) is being discussed. The recommendation is an accuracy of +/- 20 mg/dl (1.11 mmol/l) for glucose values under 100 mg/dl (5.56 mmol/l) and +/- 20% for higher glucose values
