The authors reply
Several important questions are also raised regarding how diagnoses and interventions may differ across body mass index (BMI) categories. As noted with the example of sepsis and septic shock, interest in specific diagnoses would likely require a more detailed analysis to standardize ambiguous diagnoses or those which evolve over time. The scope of our study (2) was a population-based study, rather than detailed analyses of specific subpopulations. We agree a subsequent study or studies may be warranted to explore the relationship between BMI, mortality, and nutrition in subpopulations such as those with septic shock or those receiving specific ICU treatments.
Regarding the use of APACHE IV, interventions and resuscitation provided during the first 24 hours should not theoretically attenuate the mortality predictions as APACHE methodology uses the worst values during the day of admission (3). Therefore, any improvement in physiology observed due to resuscitation should not reduce the predicted probability of mortality. Lastly, we agree obtaining complete data for all of the various elements of APACHE IV can be difficult and the 857,875 patients with APACHE scores available reflect those without any missing data, indicating rather robust data collection. Although we believe the proportion of patients without enough data to generate an APACHE IV prediction is relatively modest given the burden of data required, it is certainly possible bias can be introduced. However, as an observational study with an inherent potential for bias, our goal was to generate interest in new areas of research where more specific questions regarding the role of nutrition, nutritional status, and mortality can be explored using study designs which can better minimize bias and eliminate confounding.
Dr. Zhou disclosed work for hire. Dr. Liu disclosed he is an employee for Philips Healthcare, which provided the data for the analysis. Dr. Hassan received funding from Philips Healthcare. Dr. Badawi received funding from Philips Healthcare and ICMed. Dr. Harris has disclosed that she does not have any potential conflicts of interest.