Review for 10.1186/s12876-025-03764-8 (2025)

Title: Association between hematocrit and mortality in critically ill patients with acute
pancreatitis: a retrospective cohort study
Version: 1 Date: 24 Jan 2025
Reviewer:  Ehsan Amini-Salehi
Reviewer's report:
Dear Editor,
Thank you for the opportunity to review the manuscript entitled "Association between
hematocrit and mortality in critically ill patients with acute pancreatitis: a retrospective cohort
study." This retrospective cohort study investigates the relationship between hematocrit (HCT)
levels and mortality in patients with acute pancreatitis (AP) in an intensive care unit (ICU)
setting. The analysis of 1,914 patients from the MIMIC-IV and MIMIC-III databases, with a
focus on a non-linear relationship between HCT levels and 28-day mortality, offers valuable
insights into the potential prognostic role of HCT in critically ill AP patients. The study
effectively utilizes advanced statistical models, including LOESS regression, restricted cubic
splines (RCS), and logistic regression, to explore the association between HCT levels and
mortality.
Statistical Comments:
Non-linear Relationships and Validation: The study does well in identifying a U-shaped
association between HCT and mortality. However, further clarification of the methods used for
non-linear regression (e.g., node selection in RCS regression) would enhance the transparency
of the analysis. It would be helpful to explain why specific percentiles (e.g., 5th, 35th, 65th,
95th) were selected as nodes, and if other node selections might have affected the results.
Subgroup Analyses and Interactions: While the manuscript includes subgroup analyses based
on various variables (e.g., sex, race, comorbidities), it would be beneficial to explore potential
interactions between HCT levels and treatment interventions (e.g., vasopressors, CRRT). For
example, does the effect of low or high HCT on mortality differ depending on whether patients
received specific treatments? Including this could provide more nuanced insights into how HCT
can be used to guide clinical management.
Potential Confounders: The study adjusts for important confounders such as age, sex, and disease
severity scores (SOFA, SAPS II), but it would be useful to explore other potential confounders,
such as prior medical history (e.g., cardiovascular or kidney diseases) and medication usage
(e.g., steroids, diuretics), which could impact both HCT levels and patient outcomes. The authors
might consider conducting a sensitivity analysis to assess the robustness of the results when
adjusting for additional confounders.
Clinical Comments:
Clinical Implications of HCT as a Prognostic Marker: The findings of this study suggest that
HCT levels, particularly low levels, are associated with increased mortality in critically ill
patients with AP. The manuscript would benefit from a deeper discussion of how HCT levels can
be integrated into clinical practice. For instance, how should clinicians use HCT levels to guide
clinical decision-making, particularly in the early stages of ICU admission for AP patients? Is
HCT monitoring helpful in identifying patients who may benefit from more intensive treatment
or interventions?
HCT and Fluid Resuscitation: Given the findings of the U-shaped relationship between HCT
and mortality, it would be valuable for the authors to discuss the role of HCT in guiding fluid
resuscitation in critically ill AP patients. Does adjusting fluid therapy based on HCT levels
improve patient outcomes, and how might this impact treatment protocols in the ICU?
Long-Term Mortality and Prognosis: The study focuses on 28-day mortality, but it would be
helpful to discuss whether HCT also plays a role in longer-term outcomes, such as 90-day or
1-year mortality. A brief mention of whether HCT levels have predictive value for long-term
survival would further enhance the clinical relevance of the study.
Consideration of HCT in Other Acute Conditions: The manuscript focuses on AP, but HCT
could potentially be a useful marker in other acute conditions requiring ICU care, such as sepsis
or traumatic brain injury. It would be interesting to briefly mention whether HCT has been
explored as a prognostic marker in these conditions, and if future studies could compare its role
across different critical illnesses.