Review for 10.1186/s12876-020-01377-x (2020)

Reviewer’ s report
Title: Expression of tumor pyruvate kinase M2 isoform in plasma and stool of patients with
colorectal cancer or adenomatous polyps
Version: 1Date: 30 Dec 2019
Reviewer's report:
This study examines the expression of pyruvate kinase M2 isoform in plasma and stool of patients
with colorectal cancer or adenomatous polyps as a possible cancer and polyp screening approach.Statistically significant findings for both polyps and cancer are demonstrated in both stool andplasma samples.Results are thus interesting and provocative.There are a number of issues, however, that need to be addressed:1. Why were participants referred for colonoscopy? The study population appears to be high riskin view of fraction of subjects with polyp and cancer findings. Thus, were participants referredbecause of positive screening, the presence of symptoms, family history or other reasons. Thisneeds to be given.2. Some results are given for adenoma sizes, but the sizes of adenomas are never given. Thisneeds to be shown in a table so readers can judge the results better.3. Additionally, The statements in the last paragraph of the discussion are confusing concerningcancer and polyp sizes: "In our study, the specimen size of tumor was not the original size becauseit was based on the biopsy sample. The same situation applied for polyp samples except for thetime when polypectomy was performed, having an original." Were polyp and cancer sizesdetermined by the colonoscopist, or only from specimens given to the pathologists? Polyp sizeestimates by the colonoscopist would be very important to considering polyp size results. If a
polyp was removed completely and in one specimen, then pathology sizes would be appropriate.
Otherwise, they mean little.4. As no difference was noted with polyp size in stool sample, it is even more important tospecifically know polyp sizes.5. Numbers of polyps by histology are not high enough to conclusively state that marker resultsdo not differ by histopathology of the polyp.6. Did any patients with cancer also have polyps.7. The conclusion is overstated. The tumor marker, pyruvate kinase M2 isoform, cannot berecommended for general screening until a study is done applying it in a general screeningpopulation. That would be a random population over age 40 or 50 who are coming for averagerisk screening. Results might be very different in such a population.Minor comments:1. The word "besides" is inappropriately used. It should be replaced in each case by:"additionally," "therefore," "as apposed to," or another term, whichever is appropriate to thesentence.2. In table one, the word tumor should be replaced by cancer or malignancy.
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
Yes
Does the work include the necessary controls?
If not, please specify which controls are required in your comments to the authors.
YesAre the conclusions drawn adequately supported by the data shown?
If not, please explain in your comments to the authors.
No
Are you able to assess any statistics in the manuscript or would you recommend an
additional statistical review?If an additional statistical review is recommended, please specify what aspects require furtherassessment in your comments to the editors.
I am able to assess the statisticsQuality of written English
Please indicate the quality of language in the manuscript:
Needs some language corrections before being publishedDeclaration of competing interests
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