Review for 10.1186/s12876-024-03540-0 (2024)

Title: Association between serum iron status and the risk of colorectal cancer in US adults: a
cross-sectional analysis of NHANES 2001–2020
Version: 1 Date: 14 Oct 2024
Reviewer:  Amira A A Othman
Reviewer's report:
First of all
I want to congratulate the authors on their work. In this study, Zhou et al used data from the 2001
to 2020 National Health and Nutrition Examination Survey (NHANES) for adult Americans,
this research aims to investigate the potential association between serum iron status and the
risk of colorectal cancer in adult US citizens. The study did not find a statistically significant
correlation between serum iron status and the risk of colorectal cancer.
Iron is an essential element; however, iron overload is toxic to humans according to the iron
overload hypothesis. Experimental data have supported the idea that catalytic iron contributes to
carcinogenesis through increased reactive oxygen in tissues and subsequent oxidative damage
to DNA*. The iron overload hypothesis may be further supported by evidence in the literature,
including genetic iron overload. Hereditary hemochromatosis is a genetic iron disorder, which
causes iron overload. There is a consistent and strong link between hereditary hemochromatosis
and liver cancer; however, the link with other cancers is inconsistent**.
(*: doi.org/10.3389/fonc.2023.1223579 , ** doi.org/10.1158/1940-6207.CAPR-22-0151 ).
The authors tried to contribute to this field of research with new findings, nevertheless, there is
an observation for which sufficient justification must be obtained.
In general:
1. I wonder, the study belongs to Chinese authors and depends upon a survey designed to assess
the health and nutritional status of adults and children in the United States. Shall they evaluate
the potential association between serum iron status and the risk of colorectal cancer in Chinese
people, so that science can be enriched with more surveys?
2. The English writing level is shallow, and it is necessary to seek help from an English language
specialist to correct spelling and grammatical errors in the entire text.
3. Abbreviations must be fully written at first appearance (for example: TSAT, TIBC, etc.).
In Title:
4. The authors may consider indicating the locality at which the National Health and Nutrition
Examination Survey (NHANES) was performed and the age era of contributors.
I suggest “Association between serum iron status and the risk of colorectal cancer in US adults:
a cross-sectional analysis of NHANES 2001–2020” as an example.
In Abstract section
5. The background subsection should be the shortest part of the abstract. It should briefly outline
the following information: What is already known about the subject, related to the paper in
question. What is not known about the subject and hence what the study intended to examine
(or what the paper seeks to present). Please reconstruct it properly.
6.  The type of study: a population-based study.
7. In method:
- please use “Using data from the National Health and Nutrition Examination Survey (NHANES)
database spanning from 2001 to 2020, a cross-sectional study included 9504 participants was
performed to assess the relationship …….”.
- It would help if you described the aim of your statistical analysis.
- Nothing was mentioned about the participant’s age, sex, ethnicity, etc.
8. The last two parts of an abstract are the results and the conclusions. You should include the
results that reflect the most important parts of your findings. You do not need to squeeze in every
detail of these results, and it's best to focus clearly on your most significant findings, without
any future directions.
In the Introduction section:
9. Try to provide a summarized description of The National Health and Nutrition Examination
Survey (NHANES) in the background section. You may use the following
“NHANES (www.cdc.gov/nchs/nhanes) is designed to assess the health and nutritional status
of adults and children in the United States. The survey is distinctive in that it incorporates
both physical examinations and interviews. Several cross-sectional, nationally representative
health examination surveys are part of the NHANES program. Questions about demographics,
health insurance status, dietary habits, acute and chronic medical issues, mental health, and
prescription drug use are all included in the health interview. Exam components can change
between survey cycles but typically include blood pressure, dental exams, vision, hearing,
dermatology, fitness, balance and strength testing, respiratory testing, taste and smell, and
body measurements (weight, height, skin folds, body composition scans). Hematology, organ
and endocrine function (e.g., thyroid, kidney), environmental exposure, dietary biomarkers,
metabolic and cardiovascular health, and infectious disease are a few examples of laboratory
components.”.
In the Methods section:
10. Please move the sentences defining the NHANES to the introduction section rather than the
methodology section.
11.  The study utilized the 2001-2020 NHANES survey cycle, why did you extend the study
survey cycle?
12. The information on CRC is based on the question “Ever told you had cancer or malignancy?
" Should be “Has a doctor or other health professional ever told you that had CRC "
13. The information on CRC is based on the question “Ever told you had cancer or malignancy?”.
It does not give any information on the type of CRC (Primary colorectal lymphomas,
Gastrointestinal stromal tumors, Leiomyosarcomas, Carcinoid tumors, and Melanomas).
14. What was the source of the covariate data?
15. Statistical analysis:
- Why did not you choose mean ± standard error instead of mean ± standard deviation?
-   The Mann–Whitney U test is a nonparametric test and involves the summation of ranks. The
Mann–Whitney U test is applied to independent samples. T-test is used to compare the mean of
a continuous variable between a maximum of 2 groups. The Kruskal–Wallis test is a statistical
test used to compare two or more groups for a continuous or discrete variable. The Wilcoxon
rank-sum test is used to compare two independent samples, while the Wilcoxon signed-rank
test is used to compare two related samples, matched samples, or to conduct a paired difference
test of repeated measurements on a single sample to assess whether their population mean ranks
differ. How did you choose the proper test during your result analysis?
- In logistic regression analyses, is it multivariate or univariate? Please identify.
- “Three logistic regression models were employed to investigate the independent relationship
between serum iron status and the risk of colorectal cancer, with varying levels of adjustment
for potential confounders. Model 1 was unadjusted for covariates, while Model 2 included
adjustments for age, sex, and race. Model 3 was further adjusted for education, marital
status, PIR, BMI, alcohol intake, smoking status, physical activity, hypertension, diabetes, high
cholesterol levels, coronary heart disease, stroke, and cancer.” Could you please explain how
covariates were categorized?
- The generalized additive model and smoothed curve testing should be used to assess the
nonlinear relationship between circadian syndrome and gallstone disease.
- The analyses were performed with R (http://www.R-project.org, version X) and EmpowerStats
(http://www.empowerstats.com, version 4.2) or SPSS software.
In the Results section:
16. In Tables:
-You can title the statistical test column as “Test of significance” and use U= for the Mann–
Whitney U test, T= for the T-test, and #2 = for the Chi-square test, etc.
- abbreviations should be explained in the table foot.
17. Subgroup analyses must be performed to evaluate the effect of sarcopenia on gallstones and
their stability in different populations. Subgroup analyses based on differences in diagnostic
components were performed to elaborate correlations. The results were presented in forest plots
using odds ratios (ORs) and 95% confidence intervals (CIs).
18. Log2 logarithmic transformation shall be analyzed.
19. What about Quartile cut-off values?
In the Discussion section:
20. The discussion section is one of the final parts of a research paper, in which an author
describes, analyzes, and interprets their findings. They explain the significance of those results
and tie everything back to the research question(s). In this manuscript, there is confusion between
what should be written in the introduction section and the discussion section. Please reconstruct
the discussion section.
21. The discussion should explain how CRC prognosis.
22. Using a questionnaire instead of a clinical diagnosis is to be considered a study limitation.
In the conclusion section:
23. The conclusion should restate your main points and provide closure.