Association of Kidney Function Tests with a Cardio-Ankle Vascular Index in Community-Dwelling Individuals with a Normal or Mildly Decreased Estimated Glomerular Filtration Rate
, Nan-Chen Hsieh 3, Shu-Fang Vivienne Wu 4, Shih-Yen Weng 1 and Jia-Ping Wu 1Round 1
Reviewer 1 Report
The following comments need attention:
1. A clear hypothesis for this study is lacking.
2. It is not good practice to include more participants when you have not reached the required power. Calculation of the number of subjects which is necessary to test a hypothesis needs to be done upfront.
3. Given that participants were recruited from a large community-based cohort, the number of individuals included in this study is small. How did the investigators prevent inclusion bias?
4. The presentation of results is rather poor.
5. Although it may be reasonable in clinical practice to divide people on the basis of their eGFR, this is less justified in analyses such as the present one. It would be better to treat the data as a continuum in all analyses.
6. A large number of variables were included in the linear regression but a rationale for all these factors is lacking. In addition, one of the factors that is extremely important but has not been included in the analysis, is age. A higher age may cause both a lower renal function and more atherosclerosis.
7. What exactly do we learn from this study? The mere fact that eGFR was independently related to CAVI in a statistical model does not necessarily mean that eGFR independently modifies the atherosclerotic process. Moreover, data form the literature are not unanimous in this respect. Is the present study the final verdict and, if yes, why?
Author Response
Dear Reviewer
Thank you very much for your detailed review and good points which had certainly helped the authors have a better revision in the light of your suggestions.
Please find bellow a point by point explanations of the changes have been made throughout the text. We also turned on the track changes option of Microsoft Word for better tracking of the changes we made to the manuscript.
A clear hypothesis for this study is lacking.Answer: We tried to make our hypothesis clearer. The main objective of this study was to evaluate the correlation of renal function tests with CAVI in community-dwelling individuals with a normal (≥90) or slightly decreased (60~89) eGFR. The independence of the association of renal function tests with CAVI was also evaluated. We tried to see which index has more correlation with eGFR, ABI or CAVI.
It is not good practice to include more participants when you have not reached the required power. Calculation of the number of subjects which is necessary to test a hypothesis needs to be done upfront.Answer: Thank you very much for your attention to this point. As our study is a part of a bigger study, the authors were trying to find the relationship between CAVI and eGFR, and by examining our data, we found out that our study has enough power. By reporting the power of our study, we tried to ascertain that the results are valid. But as you mentioned correctly, it is better to do it upfront and we consider it in our future studies.
Given that participants were recruited from a large community-based cohort, the number of individuals included in this study is small. How did the investigators prevent inclusion bias?Answer: Thank you very much for mentioning inclusion bias. Unfortunately, there is a chance of inclusion bias and we mentioned this fact in the shortcomings of our article. “Another shortcoming in this study is that the participants were recruited from a large community-based cohort and the number of individuals included in this study is small. So the inclusion bias can threat the validity of the results and must be considered in the future studies.”
The presentation of results is rather poor.Answer: Authors tried to add figures and change table 3 in order to make a better presentation.
Although it may be reasonable in clinical practice to divide people on the basis of their eGFR, this is less justified in analyses such as the present one. It would be better to treat the data as a continuum in all analyses.Answer: Thank you very much for the suggestion. We agree that it is better to be treated as a continuous variable in our study. Correlation analysis were added to this study using eGFR as a continuum, and all the multivariate analysis used eGFR as a continuum, but to clarify the clinical aspect of our article, we categorized in only one table to see the differences between groups.
A large number of variables were included in the linear regression but a rationale for all these factors is lacking. In addition, one of the factors that is extremely important but has not been included in the analysis, is age. A higher age may cause both a lower renal function and more atherosclerosis.Answer: Thank you very much for your attention. Age is an important factor in our analysis and should be considered. We had considered age, in the calculation of eGFR, so the use of this variable in the multivariate analysis is redundant and has a large inflation and tolerance and after statistical consultation, we decided to only consider age in the eGFR variable.
What exactly do we learn from this study? The mere fact that eGFR was independently related to CAVI in a statistical model does not necessarily mean that eGFR independently modifies the atherosclerotic process. Moreover, data form the literature are not unanimous in this respect. Is the present study the final verdict and, if yes, why?Answer: As you mentioned our study does not show the progress of the disease, it should be discussed in prospective cohort studies. But it shows the relationship and can be used as a starting point for future studies. This shortcoming has been added to the discussion part to further clarify this point. “At last, eGFR was independently related to CAVI in a statistical model does not necessarily mean that eGFR independently modifies the atherosclerotic process. Presence of such conclusions should be confirmed by prospective cohorts.”
At the end of this revision, please accept our sincere thanks and appreciations of your challenging suggestions and comments and we tried our best to make this manuscript worthy enough for the publication and we surely consider your useful comments for our future works.
Best Regards
Javad
Reviewer 2 Report
This manuscript by Javad et al. proposes that to determine whether the estimated glomerular filtration rate (eGFR) and other renal function tests are independent factors associated with arterial stiffness in community-dwelling individuals. This is an important question to reveal the link association among renal injury and arterial function specifically atherosclerosis. However, some minor recommendations may improve the conclusion of this study.
Comments:
1. High-fat diet play's a key role in the development of atherosclerosis and linked renal injury, it could lead to arterial stiffness. It is not clear in this present study did authors considered the type of diet (vegan/ non-vegan etc.) while enrolling for this study. Authors need to discuss the diet has any role in renal injury independent of arterial function.
2. Authors could discuss, whether lipid (LDL, Cholesterol, TGL) are playing any role in eGFR in this current study.
3. Authors also need to discuss the significance and novelty of this study. There is a similar by Ian Ford et al., plos. Med 2009 demonstrated the low eGFR independently associated with risk of CVD events.
Author Response
Dear Reviewer
Thank you very much for your detailed review and good points which had certainly helped the authors have a better revision in the light of your suggestions.
Please find bellow a point by point explanations of the changes have been made throughout the text. We also turned on the track changes option of Microsoft Word for better tracking of the changes we made to the manuscript.
High-fat diet play's a key role in the development of atherosclerosis and linked renal injury, it could lead to arterial stiffness. It is not clear in this present study did authors considered the type of diet (vegan/ non-vegan etc.) while enrolling for this study. Authors need to discuss the diet has any role in renal injury independent of arterial function.Answer: As you correctly mentioned, diet has an important impact on the renal injury and health. Although high protein diet shows a weak relationship for developing renal injury, high fat diet has been shown to have an impact on renal health through different mechanisms. Authors tried to emphasis on this matter by adding a paragraph to the discussion part as follows:
Another factor that should be considered in the renal injury is the diet. Although protein restriction in the diet of individuals with existing kidney disease can be beneficial, there is not much evidence that this restriction can help the individuals without kidney disease to avoid renal injury [20]. On the other hand, high fat diet consumption has an important effect on renal disease. This role might be due to the renal lipid accumulation and the increases in inflammatory cytokines. High fat consumption diet induces glomeruli retraction and renal dysfunction [21]. Unfortunately, the data on the diet of the individuals were not available in our study and we suggest that future studies contain information about the participants’ high fat consumption diet and consider it as an important covariate in their analysis.
Authors could discuss, whether lipid (LDL, Cholesterol, TGL) are playing any role in eGFR in this current study.
Answer: Thank you for this suggestion. Analysis on the relationship of lipid profile and eGFR shows that there is not a significant correlation between LDL, HDL and TGL with eGFR as the Pearson’s correlation coefficients between LDL, HDL and TGL with eGFR are -0.003, 0.038 and -0.022 (all P values>0.05).
This paragraph added to the results section.
And we discussed it as follows:
About the role of lipid profile on GFR, some studies show that triglyceride level is independently associated with GFR [22]. We found no association between lipid profile and eGFR in our study and confirming the presence or lack of this relationship needs more studies on this field.
Authors also need to discuss the significance and novelty of this study. There is a similar by Ian Ford et al., plos. Med 2009 demonstrated the low eGFR independently associated with risk of CVD events.
Answer: thank you for this comment. As we mentioned in the discussion part: “Ours is the first study to evaluate the independence of the association of renal function tests with the CAVI.” In contrast with the study of Ian Ford et al., plos. Med 2009, we did not mortality rate and heart failure outcomes. CAVI as reported as an index for arterial stiffness might be used in the report of mortality or cardiovascular events. The novelty of our study was to link between this index and eGFR as an index of renal disease.
We discuss this matter further by adding the important article that you mentioned to our discussion, hope it further clarify the novelty of our study.
Ours is the first study to evaluate the independence of the association of renal function tests with the CAVI. As low eGFR independently associated with risk of cardiovascular events [23], and we found that CAVI is associated with eGFR, so studies that can link CAVI to cardiovascular events due to the impact on renal function can link CAVI to cardiovascular events in individuals with renal function impairment.
At the end of this revision, I would like to thank you for your role in this revision on behalf of all the authors.
Best Regards
Javad
Author Response File: 
Author Response.docx
Reviewer 3 Report
Please rename the title in the sense that you change word „slightly“ to word „mildly“ decreased, since eGFR of 60-89 is a mildly decreased GFR per definition.
Experimental section
1st paragraph – replace „summery“ with „summary“.
Replace „citizens“ with participants and please use it uniformly throughout the manuscript.
4th paragraph – please remove „on them“ from the first sentence. It is redundant.
Statistical methodology
34 participants were excluded from the study due to various reasons. Can the authors show by secondary analysis that these participants did not significantly differ in baseline parameters compared to included patients?
Authors should define which covariates were adjusted for in the multivariable linear regression model. This is not explicitly stated. Which covariates were used to assess the independent relationship of eGFR and CAVI?
We fully lack data on pharmacotherapy in this cohort. While this is a community-dwelling population some of the included patients likely used drugs such as antihypertensives, statins, diuretics, etc. and this has not been reported. Furthermore, all these drugs could impact on glomerular filtration and make an impact on measured endpoints. In this way, we have a large degree of uncertainty since this has not been reported. Authors should report this data, if available, and if not, this should be listed as a major shortcoming of the paper.
Results
Change column „60-90“ to column „60-89“ which would be more correct.
Authors should report Table 3 with standardized and unstandardized beta coefficients and respective p-value, after adjustment for all relevant covariates in the model including BUN, HbA1c, age, sex, BMI, hypertension and report those results.
Table 3 looks rather busy, please remove all unnecessary parameters except those that were significant in the multivariable regression model and include all information on the covariates for which model was adjusted for. As stated above, please report unstandardized and standardized beta coefficients and respective p-values.
Since this work is based on the relationship of CAVI and eGFR, with the logic that higher stiffness (therefore, higher CAVI) is associated with worse GFR, it would be very important to provide a linear graph (X-Y scatter plot) depicting the linear relationship of these two variables.
I would be interested to see how ABI correlates with CAVI your cohort? Additionally, would be interesting to see who has stronger associated with glomerular function in your cohort, ABI or CAVI?
The discussion should be expanded with relevant references while the Introduction section should make a better overview of CAVI methodology compared to ABI so that the average reader understands its advantages and pitfalls
Author Response
Dear Reviewer
Thank you very much for your precise recommendations, comments and points that definitely helped us a lot in this revision.
The authors tried their best to incorporate your suggestions and comments into the main text and explain the changes made one by one, we also turned on the track changes option of Microsoft Word for better tracking of the changes we made to the manuscript.
Please rename the title in the sense that you change word „slightly“ to word „mildly“ decreased, since eGFR of 60-89 is a mildly decreased GFR per definition.
Answer: Done
1st paragraph – replace „summery“ with „summary“.
Answer: Done
Replace „citizens“ with participants and please use it uniformly throughout the manuscript.
Answer: Done
4th paragraph – please remove „on them“ from the first sentence. It is redundant.
Answer: Done
34 participants were excluded from the study due to various reasons. Can the authors show by secondary analysis that these participants did not significantly differ in baseline parameters compared to included patients?
Answer: Thank you very much for paying attention to this important matter. For this reason a complete secondary analysis was done once without excluding those participants and results have been shown as a table as follows; meanwhile explanation on the fact that baseline parameters have not been influenced by this fact has been added to the results section: “Secondary analysis by keeping all the 198 individuals showed that analysis of baseline parameters base on GFR in table 1 were not affected by the exclusion of those 34 individuals and the excluded individuals had the same baseline characteristics (appendix 1).”
We may also include these results as supplementary data, based on your suggestions.
Appendix 1. Distribution of study parameters at different levels of the glomerular filtration rate (GFR) in all the individuals before the exclusion of 34 individuals from the study
|
Parameter |
Mean±SD Number (%) |
GFR (ml/min/1.73 m2) |
||
|
60~90 |
≥90 |
p value |
||
|
Overall |
198 (100) |
74(37.37) |
124(62.63) |
- |
|
Age (years) |
63.42±9.37 |
70.21±7.15 |
59.37±8.12 |
<0.001 |
|
Sex (male) |
83 (41.92) |
38 (51.35) |
36(36.29) |
0.052 |
|
BMI (kg/m2) |
24.78±3.61 |
24.61±3.26 |
24.89±3.81 |
0.604 |
|
WC (cm) |
80.68±9.97 |
81.34±9.61 |
80.29±10.19 |
0.477 |
|
HC (cm) |
94.04±6.87 |
92.99±6.20 |
94.45±7.18 |
0.147 |
|
ABI |
2.21±0.12 |
2.19±0.12 |
2.23±0.11 |
0.078 |
|
SBP (mmHg) |
130.02±17.31 |
134.12±15.87 |
127.57±17.73 |
0.009 |
|
DBP (mmHg) |
80.72±10.37 |
81.51±10.43 |
80.25±10.35 |
0.408 |
|
T2DM |
28 (14.14) |
14 (18.92) |
14 (11.29) |
0.145 |
|
HTN |
70 (35.35) |
37 (50.00) |
33 (26.61) |
0.001 |
|
IHD |
22 (11.11) |
12 (16.22) |
10 (8.06) |
0.101 |
|
FH |
49 (24.74) |
21 (28.37) |
28 (22.58) |
0.181 |
|
SMK |
45 (22.73) |
20 (27.03) |
25 (20.16) |
0.295 |
|
Pack-years |
0.89±4.68 |
1.31±6.00 |
0.64±3.68 |
0.333 |
|
Alc |
73 (36.87) |
28 (37.84) |
45 (36.29) |
0.879 |
|
Alc. vol. (ml) |
129.89±308.40 |
153.78±384.54 |
115.64±253.03 |
0.401 |
|
Exercise |
161 (81.31) |
62 (83.78) |
99 (79.84) |
0.573 |
|
Exe. freq. per week |
3.47±3.42 |
3.97±3.53 |
3.18±3.34 |
0.116 |
|
CAVI |
8.64±1.11 |
9.06±0.96 |
8.38±1.11 |
<0.001 |
Authors should define which covariates were adjusted for in the multivariable linear regression model. This is not explicitly stated. Which covariates were used to assess the independent relationship of eGFR and CAVI?
Answer: Thank you very much for your suggestion, we added the covariates that we controlled for at the bottom of the table 3. Table 3 has been changed to conform your suggestions. As we used age and sex in the eGFR formula, we have not controlled for those covariates. Using them will cause tolerance and inflation in the regression analysis.
We fully lack data on pharmacotherapy in this cohort. While this is a community-dwelling population some of the included patients likely used drugs such as antihypertensives, statins, diuretics, etc. and this has not been reported. Furthermore, all these drugs could impact on glomerular filtration and make an impact on measured endpoints. In this way, we have a large degree of uncertainty since this has not been reported. Authors should report this data, if available, and if not, this should be listed as a major shortcoming of the paper.
Answer: Thank you very much for this suggestion, unfortunately our data on these matters are so scarce and due to massive missing data, we could not have those factors included in our study. We had listed these shortcomings in the discussion part: “Furthermore, we could not include data on pharmacotherapy in this study due to massive missing data regarding the use of medications in our participants. We strongly suggest considering the use of medications such as antihypertensives, statins, diuretics, etc. which could impact on glomerular filtration rate and make an impact on the measured endpoints in the future studies.”
Change column „60-90“ to column „60-89“ which would be more correct.
Answer: Done
Authors should report Table 3 with standardized and unstandardized beta coefficients and respective p-value, after adjustment for all relevant covariates in the model including BUN, HbA1c, age, sex, BMI, hypertension and report those results.
Answer: Done
Table 3 looks rather busy, please remove all unnecessary parameters except those that were significant in the multivariable regression model and include all information on the covariates for which model was adjusted for. As stated above, please report unstandardized and standardized beta coefficients and respective p-values.
Since this work is based on the relationship of CAVI and eGFR, with the logic that higher stiffness (therefore, higher CAVI) is associated with worse GFR, it would be very important to provide a linear graph (X-Y scatter plot) depicting the linear relationship of these two variables.
Answer: Showing the result as scatter plot seems to be a good idea as we seek their relationship. So, as you suggested a scatter plot and the resulted analysis has been added to the results part as follows:
In order to observe the relationship between CAVI and eGFR, a correlation analysis was done and the scatter plot to show the relationship between these two parameters has been depicted. The correlation coefficient was -0.345 and the p-value<0.001. The plot can be seen in the Figure 1 (left).
(please see the attached file)
Figure 1- Scatter plot with 95% prediction ellipse between CAVI and eGFR (left) and between ABI and eGFR (right)
eGFR, estimated glomerular filtration rate (mL/min/1.73 m2); CAVI, cardio-ankle vascular index; ABI, ankle brachial index
eGFR, estimated glomerular filtration rate (mL/min/1.73 m2); CAVI, cardio-ankle vascular index
I would be interested to see how ABI correlates with CAVI your cohort? Additionally, would be interesting to see who has stronger associated with glomerular function in your cohort, ABI or CAVI?
Answer: Thank you very much to observe the point that ABI is also another index that the relationship can be interesting. However, the results of the relationship of CAVI and ABI and other indexes has been prepared in another manuscript that focuses on the vascular indexes as it can be beyond the objectives of this study. But as you suggested, ABI can be correlated to eGFR, as we had performed a correlation analysis between ABI and eGFR (correlation coefficient=0.05, P=0.47), as it is show as follows in Figure 1(right).
Figure 1- Scatter plot with 95% prediction ellipse between CAVI and eGFR (left) and between ABI and eGFR (right)
eGFR, estimated glomerular filtration rate (mL/min/1.73 m2); CAVI, cardio-ankle vascular index; ABI, ankle brachial index
The discussion should be expanded with relevant references while the Introduction section should make a better overview of CAVI methodology compared to ABI so that the average reader understands its advantages and pitfalls
Answer: Thank you very much for the suggestion, we added relevant references in the introduction part and brought to the picture the importance of this matter in the discussion part.
At the end of this revision, I would like to admire once again your effort in this revision and hope that I could answer all your concerns.
Best Regards
Javad
Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
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