Review for 10.1186/s12876-020-01586-4 (2021)

Reviewer’s report
Title: 
Clinical features and outcomes of combined hepatocellular carcinoma and
cholangiocarcinoma versus hepatocellular carcinoma versus cholangiocarcinoma
after surgical resection: A propensity score matching analysis
Version: 
1 
Date: 
23 Aug 2020
Reviewer's report:
This study investigated the clinicopathological features and prognosis among
cHCC-CC, HCC, and CC groups, and found that OS and DFS in the cHCC-CC
group were not significantly different from those in the HCC or CC group after
PSM. However, this study is not much innovative, and has many problems.
1 P value in Table 1 is ill-defined and seems a mistake. Comparison between
cHCC-CC, HCC and CC should be maked between two groups, respectively.
2 In the fourth part of result, PSM between cHCC-CC and CC seems
unnecessary. OS and DFS analysis between cHCC-CC and CC group before
PSM are enough for prognosis comparison. Moreover, the number of cHCC-CC
patients,16, is too less for survival analysis. The last, the ratio of PSM between
cHCC-CC and HCC is one, and it may be the same between cHCC-CC and CC
group.
3 The caliper width of 0.2 in PSM analysis is too high, and the recommended
range is 0.02 to 0.05. It may be a clerical error.
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Is the study design appropriate to answer the research question (including the use
of appropriate controls), and are the conclusions supported by the evidence
presented?
No
Are the methods sufficiently described to allow the study to be repeated?
No
Is the use of statistics and treatment of uncertainties appropriate?
Yes
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Yes
Are the images in this manuscript (including electrophoretic gels and blots) free
from apparent manipulation?
No