This nicely designed and correctly performed randomized trial fills a gap in existing evidence. The presentation of data could be improved.

Major points:
1. Introduction: the authors need to make clearer the point of performing a specific trial on isCGM in sub optimally controlled T1DM adults. When reporting data on rtCGM, they should specified that the observed improvement of glycemic control could be determined by many different mechanisms (i.e., high frequency of glucose reading, greater accuracy in dose adjustment, etc.), including alarms for hypo- and hyperglycemia. Since such alarms are lacking in isCGM, results of trials on rtCGM cannot be automatically transferred to isCGM. On the other hand, available trials in T1DM were performed either in well-controlled adults (where the use of isCGM produced a reduction of hypos, but no further improvement of already satisfactory HbA1c levels), and in adolescents with very high HbA1c levels; the results of the latter trial cannot be extended to different populations of higher age and better glycemic control. Hence the need for the present trial.
2. Some more information on patients’ characteristics should be provided. In particular, some more information on self-management skills of enrolled patients is needed for a correct interpretation of results. The authors should provide information on standard (routine) approach in investigating centers to carbohydrate counting and bolus definition, and to education on the management of hyperglycemia and hyperglycemia; this information should be briefly recalled in the main text (when describing patients’ characteristics) and reported more extensively as supplementary online material.
3. In the interpretation of results, authors should provide some speculations on possible mechanisms underlying the amelioration of glucose control in the intervention group. Since measurement per se does not reduce average blood glucose, it is logical to think that the improvement of blood glucose is determined by behaviors in reaction to measured values, as confirmed by the fact that the improvement is evident only during wake time. In this respect, higher frequency of measurement (in comparison with traditional BGM), and the availability of a greater amount of data on the time course of glucose, could theoretically be the key factors for improving blood glucose. If this is true, the ability of patients to react appropriately to glucose measurements (and therefore their previous training on correction of hypo/hyperglycemia, carbohydrate counting and bolus determination) could be a very relevant moderating factor.
4. In the Discussion, the authors should recall the negative results of the trial performed in adult insulin-treated T2DM with isCGM, which did not reach the goal of superior reduction of HbA1c with respect to traditional BGM. The difference in results in these two adult populations could be the consequence of different characteristics of disease (I.e., residual insulin secretion and lower glucose variability in T2DM, with smaller margins for improvement) and/or different management of insulin therapy (e.g., lack of specific instructions on bolus determination and correction of hyperglycemia in T2DM - see point 3)
5. The main clinical difference between isCGM and rtCGM is the availability of alarms for hypo/hyperglycemia. With an alarmed isCGM, the only residual difference from a rtCGM is that, for reading glucose values, the patient would need to scan the sensor with the smartphone, instead of directly looking at the screen of the smartphone. I doubt that this difference could produce differential effects on glucose control; therefore, I would expect alarmed isCGM to perform similarly to rtCGM. Therefore, I suggest to reformulate the statements on alarmed isCGM in Discussion, 4th par. Notably, the alarmed device is already available in many countries.
6. The number of drop-outs was not negligible, considering the relatively short duration of the study, with a possible unbalance between the two treatment arms. This should be added Amon g the limitations of the study.

Minor points:
a. Introduction, 2nd par.: although traditional BGM is not painless, I would not define it “painful”
b. Introduction, 2nd par.: please avoid brand names in the text, with the inly exception of Methods (where the brand name of the device used should be specified, possibly between brackets.
c. Introduction, 2nd par: local reimbursement policies and proportion of patients using isCGM in individual countries is of limited interest for an International readership. Please erase.
d. Methods: please specify the meaning of “stable” insulin doses
e. The insulin titration algorithms used in the study should be reported, at least as online appendix
f. Discussion, end of page 14: Please replace “is accordant to” with “is in line with” or “is consistent with”.
g. Discussion 3rd par.: the term “adequate” for frequency of scans is inappropriate, since there is no recognized target in scan frequency to be used as reference.
h. Discussion, end of 3rd par.: a sentence cannot begin with “And”.
i. Legends in Figure 1 are probably inverted (in the present form, the graph suggests that time in range was lower, and MBG and time above range higher, in the intervention group)

All issues have been satisfactorily addressed

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