Protein requirements and provision in hospitalised COVID-19 ward and ICU patients: Agreement between calculations based on body weight and height, and measured bioimpedance lean body mass.

Background: A large proportion of hospitalised COVID-19 patients are overweight. There is no consensus in the literature on how lean body mass (LBM) can best be estimated to adequately guide nutritional protein recommendations in hospitalised patients who are not at an ideal weight. We aim to explore which method best agrees with lean body mass as measured by bioelectric impedance (LBM) in this population.

Methods: LBM was calculated by five commonly used methods for 150 hospitalised COVID-19 patients previously included in the BIAC-19 study; total body weight, regression to a BMI of 22.5, regression to BMI 27.5 when BMI>30, and the equations described by Gallagher and the ESPEN ICU guideline. Error-standard plots were used to assess agreement and bias compared to LBM. The actual protein provided to ICU patients during their stay was compared to targets set using LBM and LBM calculated by other methods.

Results: All methods to calculate LBM suffered from overestimation, underestimation, fixed- and proportional bias and wide limits of agreement compared to LBM. Bias was inconsistent across sex and BMI subgroups. Twenty-eight ICU patients received a mean of 51.19 (95%-BCa CI 37.1;64.1) grams of protein daily, accumulating to a mean of 61.6% (95%-BCa CI 43.2;80.8) of Target during their ICU stay. The percentage received of the target as calculated by the LBM method for males was the only one to not differ significantly from the percentage received of Target (mean difference 1.4% (95%-BCa CI -1.3;4.6) p = 1.0).

Conclusions: We could not identify a mathematical method for calculating LBM that had an acceptable agreement with LBM as derived from BIA for males and females across all BMI subgroups in our hospitalised COVID-19 population. Consequently, discrepancies when assessing the adequacy of protein provision in ICU patients were found. We strongly advise using baseline LBM to guide protein dosing if possible. In the absence of BIA, using a method that overestimates LBM in all categories may be the only way to minimise underdosing of nutritional protein.

Trial Registration: The protocol of the BIAC-19 study, of which this is a post-hoc sub-analysis, is registered in the Netherlands Trial Register (number NL8562).