Sample size
Sample size was calculated using the formula [11]: Sample size (per equally-sized group) = 16 ÷ (E/S)2. A desired effect (E) size of HbA1c of 1% based on the results of the UKPDS [12] and an audit described above which provided a mean HbA1c of 8.48% and a standard deviation (S) of the mean of 1.94% gave a sample size of 61 patients in each arm.