Toward Better Estimation of Total Blood Volume in Obese Patients Undergoing Apheresis

Estimating total blood volume (TBV) in obese individuals remains a critical yet unresolved challenge in apheresis medicine. Our prior work demonstrated that commonly used TBV formulas exhibit significant variability, particularly at higher BMI ranges. This study builds on those findings to test modified algorithms that produce mid-spectrum apheresis parameters and mitigate extreme over- or underestimation. Using a standardized artificial dataset and retrospective clinical data from obese patients, we evaluated the performance of modified versions of the Lemmens-Bernstein formula and Gilcher's Rule. We assessed output consistency, alignment with empirically defined expected ranges, and potential clinical impact on apheresis parameters. A modified Lemmens-Bernstein formula (LB-60) yielded TBV estimates within an expected range for obese women and resolved extreme overshooting of an empiric expected range at higher BMIs. For obese men, both the LB-60 and a modified Gilcher's Rule (Gilchers-65) performed comparably. These formulas produced mid-spectrum apheresis parameters and mitigated extreme over- or underestimation. We recommend using a modified Lemmens-Bernstein formula for obese women, and either it or a modified Gilcher's Rule for obese men. These represent practical interim solutions while the field moves toward direct TBV measurement.