Adherence to Vitamin D Supplementation during Infancy—A Single Pediatric Primary Practice Retrospective Study

Round 1

Reviewer 1 Report

In this article, Vucak et al aimed to analyze the adherence to Vitamin D supplementation during infancy. The authors measured the adherence through the number of bottles used/child/year. The authors found that only 7.6% of infants had regular adherence to Vitamin D supplementation, and this was not correlated to neither the place of living nor the parents' educational level. This report is a great basis for more comprehensive studies that would analyze more factors including the actual blood Vitamin D levels of the infants.

-How was the parents' educational level analyzed per child? In other words, how was this variable analyzed if one child had one parent designated to one group and the other parent to another group? It seems that each child is analyzed twice, separately for each parent. Reference [16] of the Discussion section analyzed each infant once, based on the education of the head of the household only, and this seems to be a more appropriate methodology.

Author Response

We thank to the reviewer for a positive feedback. The reviewer is correct. Every parent (mother and father) has been taken into account and designated to his/her educational level group. Since we included 145 infant in our study, in Table 3 we indicated that N=290. We are aware that in ref. 16 only head of household educational status was analyzed. However, in Croatia both parents are equally responsible to take care of the child. Therefore, in our opinion, exclusion of one parents would not accurately present “parent education level” variable. At this moment, we decided not to make changes in our manuscript regarding this issue but are willing to do that at the later stage of reviewer process if reviewer and/or Editon find it necessary.

Reviewer 2 Report

The manuscript is a better version and is good to be published.

english needs minor checks.

Author Response

We thank to the reviewer for a positive feedback. Based on other reviewers comments, we made some changes in our manuscript. We hope that this improved the quality of the manuscript, and that Reviewer 2 would find it also acceptable for publication.

Reviewer 3 Report

The study is well-planned and the data presentation nice too. The number of patients uncluded are low.  7% is significantly lower than seen in other western countries

Author Response

We thank to the reviewer for a positive feedback. We were also surprised with these low numbers and are even more confident that studies like this are warranted. Based on other reviewers comments we made some changes in our manuscript. We hope that this improved the quality of the manuscript, and that Reviewer 3 would find it also acceptable for publication.

Reviewer 4 Report

The subject of the manuscript entitled "Adherence to vitamin D supplementation during infancy - a single pediatric primary practice retrospective study" is very important from the point of view of generally understood public health and the health consequences of preventive actions taken at an early stage of human development. The topic concerns the prevention of rickets and other disorders caused by vitamin D deficiency in newborns and infants. The problem of implementing recommendations regarding this prevention is very current and there is a need to study it and monitor prevention.

The aim of the study described in the reviewed manuscript was to assess the implementation of the assumptions of this prevention by doctors of a selected pediatric clinic in Croatia, i.e. the authors aimed to assess the frequency of prescribing a preventive preparation containing vitamin D to children attending this clinic. This is a much needed study, but it has been very vaguely described. I have great doubts about the terms used by the authors suggesting that the authors examined whether the children included in the study actually took the prescribed preparation and, moreover, "implemented" or "complied" with the recommendations regarding supplementation. This is clearly untrue, as the authors only collected information on how often doctors prescribed supplements to these children, not whether the children actually received the supplements. There are many such terms throughout the text that mislead the reader. In connection with the above, my first and most important comment is that the authors should clearly write throughout the text that the data they collected only concerns the prescription of prophylactic preparations by doctors. It is known that mere prescription is not enough, the prescription must be filled by the parents, and the preparation must also be administered to the child - and the authors have not examined this. It is true that in the Discussion section the authors included the sentence: "We assumed that a certain number of doses of the Plivit® D3 would be skipped for various reasons (forgetfulness, illness, travel, etc.)" (lines 176-178), but in they did not explain this in any way in the section on the material and methodology of the study. Whether and how the authors took into account the fact that some prescriptions could be re-prescribed (e.g. due to loss or breakage of the bottle?). Of course, it would be very valuable to reach the parents and find out whether they followed the doctor's recommendation, i.e. whether they filled the prescriptions and gave the supplement to the child. However, I understand that the authors had no way to access such data. All the more so, I would like to ask you to very precisely present the purpose of the study and the results obtained. The authors present a very limited scope of the study results, so please describe them very precisely.

The authors very aptly pointed out the limitations of their study, but it should be added that the study concerned only the prescription of preparations by doctors, they did not examine whether parents implemented this prevention, i.e. whether they filled the prescription and administered the preparation to the child.

Another important issue that raises my doubts is the division into two groups adopted by the authors. It makes no sense to me because it assumes a comparison of the implementation of the recommendation to prescribe two different preparations to children. In my opinion, such a comparison does not make much sense, because what question does it answer? Which preparation was prescribed more often by doctors? From a scientific point of view, what does this make sense? Additionally, in section 2 regarding the material and methodology of the study, the authors indicated the exclusion criterion from the study as: "Patients receiving another form of VD supplementation were excluded" - I understand that a preparation other than Plivit® D3. This is incomprehensible to me in the context of the fact that the division into two study groups was based on the type of preparation prescribed. Please be sure to specify this.

Additionally, I believe that the presented inclusion criteria for the study are insufficient. Why were only children prescribed a specific preparation included in the study? Were there no other inclusion criteria, e.g. no specific diseases, disorders, etc.?

Other notes:

- Table 1 has no in-text reference. In the footnote to this table, please also include an explanation of the division into groups so that the table is understandable without the need to read the text of the manuscript. Wouldn't it be worth including in this table the division into "regular users", "moderately users" and "irregulatory users" adopted by the authors?

- the manuscript should include a table regarding the characteristics of the studied group of children (e.g. age, perhaps birth weight, number of points on the Apgar scale and others) and their parents (in addition to education and place of residence, it would be good to take into account the economic situation, the number of household members and other . At this point I have another question: did all the children actually have two parents? Did the authors check this?)

As for the list of references, it contains only about 20 percent of current items, i.e. from the last 5 years. I suggest modifying or supplementing this section.

To sum up, I believe that although the data presented by the authors in the manuscript are very limited, they are very valuable. However, their publication definitely requires a very precise and unambiguous description.

Author Response

We thank to the reviewer #4 for really valuable comments which we partially implemented in the revised version of the manuscript. Our response is attached. We are confident that these changes improved our manuscript and hope it will be suitable for publication.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I would like to thank the authors for their additions to the manuscript. The methods are described clearly, and the discussion section provides the appropriate literature and study limitations. The manuscript now meets the criteria for publication.

Reviewer 4 Report

Dear authors, thank you for your comprehensive response to the comments contained in my review and for including most of them in the revised version of the manuscript.

The authors disagreed with some of my comments or suggestions, but addressed them comprehensively and convincingly.