Different algorithms for glycemic control will yield different results

Abstract

To the Editor, We read with interest Abdelmalak et al.’s recent randomized controlled trial of insulin infusion algorithms. As stated in the title, ‘‘validation’’ of the algorithm is successful as reported. However, further statistical comparisons reported between the groups (Table 2) lose significance once the significant differences between the two treatment algorithms are appreciated. The conventional group is noteworthy in that so few patients (15%) were treated with insulin compared with those treated in the intensive group (90%). While the targets of glycemic control differed between the two groups, it is unclear how the conventional group could be expected to achieve glycemic control with such infrequent use of insulin. If an appropriate comparison is to be made between the two groups, treatment initiation should be equivalent. In the target group, insulin was started at a glucose level exactly that of the upper target limit (6.1 mmoL L). However, in the conventional group, insulin was introduced at a glucose level of 11.9 mmoL L, which is 7.5% above the upper target limit (11.1 mmoL L). Given the anticipated delay to achieve target range after start of insulin, the conventional group was disadvantaged from the outset, and assigning statistical significance to the % time in the relative target range favours the intensive group (Table 2). Furthermore, the desired target range prejudices the conventional treatment group further as that of the intensive group is significantly narrower (27-37% of outer limits vs 10-11%, respectively), again favouring the intensive group since % time within target is a reported measure. In Table 2, assigned statistical significance to differences in time within a glucose range of 4.4-6.1 mmoL L or even [ 6.1 mmoL L will obviously favour the intensive group, since the conventional group never received insulin at a glucose 8.3 mmoL L. We appreciate the authors’ publication of a detailed safe and effective insulin strategy. However, although statistical differences in glucose measures were found between the two groups, we caution that these are to be expected given the inherent inequalities assigned to the non-insulin conventional group management. Future prospective evaluations could include the same initial glucose trigger followed by divergent insulin algorithms. If separate triggers are chosen, insulin must be initiated at an equivalent point within the trigger range, and ranges should be mathematically comparable.