Impact of Morbid Obesity on Liver Transplant Candidacy and Outcomes: National and Regional Trends.

BACKGROUND: Body mass index (BMI) limits for liver transplant (LT) candidacy are controversial. In this study, we evaluate waitlist and post-LT outcomes, and prognostic factors and examine regional patterns of LT waitlist registration in patients with BMI ≥40 versus BMI 18-39. METHODS: United Network for Organ Sharing (UNOS) data were analyzed to assess waitlist dropout, post-LT survival, and prognostic factors for patient survival. The distribution of waitlisted patients with BMI ≥40 was compared with the Centers for Disease Control Behavioral Risk Factors Surveillance System data to explore the rates of morbid obesity in the general population of each UNOS region. RESULTS: Post-LT outcomes demonstrate a small but significantly lower 1- and 3-y overall survival for patients with BMI ≥45. Risk factors for post-LT mortality for patients with BMI ≥40 included age >60 y, prior surgery, and diabetes on multivariable analysis. Model for End-Stage Liver Disease >30 was significant on univariable analysis only, likely due to the limited number of patients with BMI ≥40; however, median Model for End-Stage Liver Disease scores in this BMI group were higher than those in patients with lower BMI across all UNOS regions. Patients with BMI ≥40 had a higher waitlist dropout in 4 regions. Comparison with BRFSS data illustrated that the proportion of waitlisted patients with BMI ≥40 was significantly lower than the observed rates of morbid obesity in the general population in 3 regions. CONCLUSIONS: While BMI ≥45 is associated with modestly lower patient survival, careful selection may equalize these numbers.

Comparability of methods used in the sampling of primate behavior.

Two measures of a behavior are defined as comparable if one is predictable from the other. The comparability of one-zero, instantaneous, actual-frequency, and actual-duration sampling was investigated using a Monte Carlo simulation to extend the range of sampling intervals beyond those ordinarily found in the literature. Several combinations of bout time, rate of response, and observation interval were simulated. Comparability between one-zero or instantaneous scores and actual frequency or actual duration was higher for higher behavior rates, decreased with longer observation intervals, and was usually higher for longer bout times. Curves of ß2s from multiple regression analyses revealed a fundamental difference in the source of one-zero and instanteous predictability. Both actual frequency and actual duration contributed substantially to one-zero predictability, indicating high comparability between one-zero scores and a weighted combination of actual frequency and actual duration. Once the contribution of actual duration to instantaneous scores was accounted for, actual frequency contributed virtually nothing additional. Long-standing meanings of validity, reliability, and comparability were applied to the findings, resulting in the conclusion that all of the sampling methods are useful, depending upon the researcher's approach, resources, and problem.