Elevated blood glucose vs time. Elevated blood glucose vs time. Statistical process control p-chart of the proportion of diabetic patient days with elevated mean glucose (≥180 mg/dL) by month, comparing before, during and after the intervention (maintenance). Thérèse Franco et al. BMJ Open Qual 2017;6:e000059 © Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/