Association between Glomerular Filtration Rate and β-Thalassemia Major: A Systematic Review and Meta-Analysis
Round 1
Reviewer 1 Report
Glomerular filtration rate in thalassemia patients is a controversial issue, with reports both of decreased glomerular filtration rate and of glomerular hyper filtration.
The authors correctly indicate that this is the only meta-analysis on the topic. In general, the study is carefully performed but there are some issues that need to be addressed which will require re-analysis.
1. The most significant point is that "thalassemia" is not one but several diseases. Reviewing Table 2, nearly all the studies involve beta thalassemia major (in one case described as "transfusion dependent beta thalassemia major, which is somewhat redundant since by definition thalassemia major is transfusion dependent). In particular, sickle thalassemia is an entirely different entity than nonsickle thalassemia, with the complication of hypoxia/reperfusion events due to sickle hemoglobin. This is not comparable to nonsickle thalassemia. The studies of Ghobrial and Katopidis should be excluded because they are about sickle thalassemia. The study of Saghir is just characterized as "thalassemia", and there are suggestions in the manuscript that it also includes sickle thalassemia patients. If it is possible, only the beta thalassemia major patients from that study should be included in the analysis. If it is not possible, then that study should be excluded from the analysis. Just looking at the Forest plots, it is likely that excluding these three studies would not substantially alter the findings.
2. In Table 2, the number of patients in each study should be included.
3. It appears from Table 2 that a number of the studies focused only on children or children and adolescents/young adults. Some studies did involve patients clearly in the adult range. This is not a problem but it is something that needs to be stated more clearly in the manuscript.
4. After the reanalysis suggested above, the title should be changed to indicate that this is about beta thalassemia major.
Author Response
1. We would like to acknowledge your crucial observation, positive comments and would like to thank you for all the significant suggestions. We removed all 3 contradictory studies (i.e. Ghobrial 2015, Katopodis 1997 and Saghir 2020) from our analysis, re-analyzed all the data, and modified the manuscript accordingly as per your suggestion.
2. Thank you so much for your kind suggestion. We have added both the number of patients and healthy participants in Table-2 as per your suggestion.
3. Thanks a lot for your remarkable concern. We have added a sentence mentioning the overall age range of the study participants according to your suggestion (Line-).
4. Thank you very much for another important observation regarding the title. After reanalysis, we have replaced the word “thalassemia” with “beta thalassemia major” in the title.
Reviewer 2 Report
Q1: line 48: . “Sickle cell anemia on the other hand results due to the heterozygosity of the β-thalassemia and sickle cell genes [2, 3].”
“Mutations in the HBB gene cause sickle cell disease. The HBB gene provides instructions for making one part of hemoglobin. Hemoglobin consists of four protein subunits, typically, two subunits called alpha-globin and two subunits called beta-globin. The HBB gene provides instructions for making beta-globin. Various versions of beta-globin result from different mutations in the HBB gene. One particular HBB gene mutation produces an abnormal version of beta-globin known as hemoglobin S (HbS). Other mutations in the HBB gene lead to additional abnormal versions of beta-globin such as hemoglobin C (HbC) and hemoglobin E (HbE). HBB gene mutations can also result in an unusually low level of beta-globin; this abnormality is called beta thalassemia
In people with sickle cell disease, at least one of the beta-globin subunits in hemoglobin is replaced with hemoglobin S. In sickle cell anemia (also called homozygous sickle cell disease), which is the most common form of sickle cell disease, hemoglobin S replaces both beta-globin subunits in hemoglobin. In other types of sickle cell disease, just one beta-globin subunit in hemoglobin is replaced with hemoglobin S. The other beta-globin subunit is replaced with a different abnormal variant, such as hemoglobin C. For example, people with sickle-hemoglobin C (HbSC) disease have hemoglobin molecules with hemoglobin S and hemoglobin C instead of beta-globin. If mutations that produce hemoglobin S and beta thalassemia occur together, individuals have hemoglobin S-beta thalassemia (HbSBetaThal) disease.
Abnormal versions of beta-globin can distort red blood cells into a sickle shape. The sickle-shaped red blood cells die prematurely, which can lead to anemia. Sometimes the inflexible, sickle-shaped cells get stuck in small blood vessels and can cause serious medical complications.”
(https://medlineplus.gov/genetics/condition/sickle-cell-disease/#causes).”
Q2: Line 133: your data show that the thalassemia and GFR from pubmed is “18”. However, I searched the website and found the number is “28”???
The googlescholar results are 5230.
A better way to show your readers is that how many articles you acquired on which day you approached, and how many articles are left after your screened.
Q3: table 1 where are the “Overall score (%)” from?
Q4: Please see your table 2. Some of studies enrolled children and some were adults.
We know that GFR is different in people with different ages (Please see file:///C:/Users/tlogin/Downloads/children-09-01995.pdf).
Do you think that it is fair to put children and adults equally to investigate the effects of thalassemia on the GFR ?
Q5: Line 236-238 Thalassemia results in chronic anemia from the decreased synthesis of functional hemoglobin. Anemia lowers the blood's ability to transport oxygen, which causes tissue hypoxia, notably in the kidneys and thus causes renal hypoxia.
If your statements in line 236-238 are corrective, the adults should suffer more damage than the children with thalassemia due to “chronic anemia”. However, your figure 5 and figure 6 did not show such differences. Why?
Q6: line 244-249: The upsurge of oxidative stress by creating an imbalance between the antioxidant defense mechanism and the generation of reactive oxygen species (ROS) inside the body may occur because of thalassemia. The renal vasculature and glomeruli may be harmed through the oxidative stress, ultimately impairing the GFR. Thalassemia can also interfere with the renal tubules, which are crucial for reabsorbing filtered chemicals and preserving fluid and electrolyte balance.
These statements are also facing the same problems in Q5. Normally, aging is presumed to be due to the effects of ROS. Adults may suffer more ROS attack than children do. Please explain why your data cannot show any results to support this basic concept?
Author Response
Q1. We would like to thank you for your kind and crucial observations. As we have modified the whole manuscript focusing on β-TM only, we have excluded “Line 48” (Current line no. 50).
Q2. Thank you so much for your kind concern. The exact search strategy can be found in the supplementary file through which we found 18 articles on PubMed and 25 articles on Google Scholar. The article number remained the same on PubMed and 2 articles have been enhanced in google scholar which has been modified in the PRISMA diagram (Figure 1).
Pubmed:
(((glomerular[Title/Abstract]) OR (gfr[Title/Abstract])) AND (Thalassemia[Title/Abstract])) AND ((((randomized control trial[Title/Abstract]) OR (rct[Title/Abstract])) OR (case control[Title/Abstract])) OR (healthy[Title/Abstract]))= 18 article
Google Scholar:
allintitle: glomerular thalassemia= 27
Q3. Thank you very much for your concern. The issue regarding the overall score (%) has been explained in Line no. 98-104.
Q4: We would like to appreciate and thank you for your concern regarding the age variation and GFR. According to the article you provided entitled “Glomerular Filtration Rate Assessment in Children (Children 2022, 9, 1995. https://doi.org/10.3390/)”, they claimed that for age>24 months (2 years) mean GFR is approximately 104.4 mL/min/1.73 m2. Another study (Title: Should the definition of CKD be changed to include age-adapted GFR criteria? YES, DOI: https://doi.org/10.1016/j.kint.2019.08.033) says that the mean GFR is approximately 107 mL/min/1.73 m2 for adults aged between 20-30. Besides, according to their investigation GFR rate generally reduces in even older persons (age>50).
The age range of our study varies between 8.30-33.5 years. Therefore, this age range plausibly does not occur any significant differences in GFR and thus does not have an impact on the outcome of this study.
Q5: Thank you so much for this observation. As we see in the previous point that the GFR of our study population supposes to be similar as per the investigation of previous research (DOI: https://doi.org/10.1016/j.kint.2019.08.033) (Children 2022, 9, 1995. https://doi.org/10.3390/), therefore there are no significant changes found regarding the age due to “chronic anemia” among beta-thalassemia patients rather the impact of it distributed equally on all the beta-thalassemia patients.
Q6. Thanks a lot for your concern. Similar to the answer to Q5 and Q6, we found that the study population did not have any variation in GFR based on their age range. Therefore, the main concern regarding the ROS is that it may have prompted the deterioration of renal vasculature and glomeruli, ultimately impairing the GFR in all beta-thalassemia patients as compared to the healthy participants in the study population which has been found in our meta-analysis.
Reviewer 3 Report
The results of this meta-analysis are straightforward and affirm that renal dysfunction is one of the health consequences of thalassemia. While their summation of the literature doesn’t empirically establish that hypoxia associated with anemia is the direct cause, or if the effects of iron overload due to treatment is a more specific mediator of the damage to nephrons in the kidney, the important take home message is correct: clinicians should be aware of the need to monitor kidney function in thalassemia patients.
The authors correctly note in the Discussion (lines 293-295) that there are many different ways to assess renal clearance. Typically, in the clinical setting, it is initially done with eGFR, which is calculated from serum creatinine levels. It seems that almost all included studies used the estimated eGFR.
293. GFR can be determined through the identification of the clearance rate of different endogenous or ex- ogenous biomarkers such as inulin, creatinine, Cystatin C, iohexol etc. and all are clinically accepted [24, 38, 39].
So perhaps in the Introduction they should modify the sentence on line 63-64, which could be interpreted to suggest that some of their cited investigations were actually directly measuring the sum contribution of individual nephrons. That is true at the textbook level, but perhaps it needs a qualifying statement given that most survey studies do not employ the necessary tools used in nephrology to more specifically assess the kidney, such as with a timed clearance of imaging dyes.
63. Theoretically, the GFR is the outcome of the total 63 number of nephrons times the average single-nephron GFR [7].
It seems that most of the cited studies employed the Schwartz formula to calculate eGFR from serum creatinine levels. Perhaps in the Discussion, they should discuss whether this is the optimal formula to employ with thalassemia patients given that it yields a different value than some others, such as the MDRD and Cockcroft-Gault formulas. There has also been considerable controversy in the nephrology literature about the value of including corrections for both sex and race.
Would those corrections be of importance for comparing the findings in Asian populations to those on euro-American and African patients.
Minor writing.
Line 23 Abstract. Did they intend to write? even more strongly supports…..
Line 28. The sentence might read better if they wrote: are associated with…
Rather than are correlated to
Line 44. The sentence would read better if they wrote ‘clearly highlights’ rather than ‘clearly presents’
Line 50. Did they intend to write ‘necessitates’ or ‘requries’ rather than ‘implies’
Line 67. This long sentence probably should be divided into 2 sentences. Alternatively, they could put a semi-colon rather than a comma before “however”.
Interestingly, GFR was also found to have a correlation with 67 thalassemia, however, in several investigations, a positive correlation between GFR and 68 thalassemia was identified and in some other cases GFR was detected to have an inverse 69 relation with thalassemia [13, 14].
Line 179. This sentence would read better if they wrote “all data were’. But if they like ‘every single”, then it would have to be” every single datum” Datum is the singular form; data is the plural form.
Line 23 Abstract. Did they intend to write? even more strongly supports…..
Line 28. The sentence might read better if they wrote: are associated with…
Rather than are correlated to
Line 44. The sentence would read better if they wrote ‘clearly highlights’ rather than ‘clearly presents’
Line 50. Did they intend to write ‘necessitates’ or ‘requries’ rather than ‘implies’
Line 67. This long sentence probably should be divided into 2 sentences. Alternatively, they could put a semi-colon rather than a comma before “however”.
Interestingly, GFR was also found to have a correlation with 67 thalassemia, however, in several investigations, a positive correlation between GFR and 68 thalassemia was identified and in some other cases GFR was detected to have an inverse 69 relation with thalassemia [13, 14].
Line 179. This sentence would read better if they wrote “all data were’. But if they like ‘every single”, then it would have to be” every single datum” Datum is the singular form; data is the plural form.
Author Response
Thank you very much for your valuable suggestion regarding the lack of a specific assessment of the kidney especially in survey-based studies in Line-63. Your suggested modification has been incorporated accordingly (Current line no. 66-69).
Again, thank you so much for your concern regarding the optimal GFR measurement formula. We assessed that due to the slight age variation both the Schwartz and CKD-EPI formula has been used in Capolongo 2020 and for the other studies, the Schwartz formula was validated regarding the age of participants. We have elaborated in the discussion section (Line 316-323).
We have also incorporated other GFR measuring formulas and their connections with sex and race in the discussion section (Line 323-326) as per your valuable suggestion.
Minor writing:
Thank you very much for your crucial observation regarding the writing. Minor writing corrections have been done accordingly as per your valuable suggestions, as follows-
Line 23 Abstract- the word “more” has been input.
Line 28: The term “correlated to” has been replaced by “associated with” (Current line no. 29).
Line 44: the word “presents” has been replaced by “highlights” (Current line no. 45).
Line 50: the word “Implies” has been replaced with “necessitates” (Current line no. 52).
Line 67: Comma has been replaced with Semi-colon (Current line no. 71).
Line 179: “Every single data was” has been replaced by “All data were” (Current Line no. 189).
Round 2
Reviewer 1 Report
The authors have been responsive to reviewer comments resulting in an improved manuscript.
1. On line 184, the minimum age should be referred to as 8.3 years, not as 8.30.
Author Response
Thanks you for all of your comments. The minimum age has been changed to 8.3 years (on line 184)
Reviewer 2 Report
it seems that the authors have made a great work in revision according to the reviewers comments. I would like to recommend this work to be accepted.
Author Response
Thank you!
Reviewer 3 Report
The authors have been responsive to the prior review. No further requests.
It is a worthwhile summation of the extant literature, and confirmatory of the conclusions of the individual studies.
Minor writing suggestion for one of the new sentences added in response to the prior review.
the phrase 'hardly employ' is awkward in english.
It would be better to write:. ..... many of the survey studies were unable to employ the more sophisticated and quantitative tests used in clinical nephrology to specifically assess the kidney, such as with a time clearance of imaging dyes.
Lines 66-67
however in practical condi tion many of the surveys based studies hardly employ the necessary tools used in nephrology to more specifically assess the kidney, such as with a timed clearance of imaging
Author Response
"however in practical condition many of the surveys based studies hardly employ the necessary tools used in nephrology to more specifically assess the kidney, such as with a timed clearance of imaging" has been changed to "many of the survey studies were unable to employ the more sophisticated and quantitative tests used in clinical nephrology to specifically assess the kidney, such as with a time clearance of imaging dyes." on line 66-67.
Thank you for your comment.
