Use of Imputation and Decision Modeling to Improve Diagnosis and Management of Patients at Risk for New-Onset Diabetes After Transplantation.

BACKGROUND New-onset diabetes after transplantation (NODAT) is a complication of solid organ transplantation. We sought to determine the extent to which NODAT goes undiagnosed over the course of 1 year following transplantation, analyze missed or later-diagnosed cases of NODAT due to poor hemoglobin A1c (HbA1c) and fasting blood glucose (FBG) collection, and to estimate the impact that improved NODAT screening metrics may have on long-term outcomes. MATERIAL AND METHODS This was a retrospective study utilizing 3 datasets from a single center on kidney, liver, and heart transplantation patients. Retrospective analysis was supplemented with an imputation procedure to account for missing data and project outcomes under perfect information. In addition, the data were used to inform a simulation model used to estimate life expectancy and cost-effectiveness of a hypothetical intervention. RESULTS Estimates of NODAT incidence increased from 27% to 31% in kidney transplantation patients, from 31% to 40% in liver transplantation patients, and from 45% to 67% in heart transplantation patients, when HbA1c and FBG were assumed to be collected perfectly at all points. Perfect screening for kidney transplantation patients was cost-saving, while perfect screening for liver and heart transplantation patients was cost-effective at a willingness-to-pay threshold of $100 000 per life-year. CONCLUSIONS Improved collection of HbA1c and FBG is a cost-effective method for detecting many additional cases of NODAT within the first year alone. Additional research into both improved glucometric monitoring as well as effective strategies for mitigating NODAT risk will become increasingly important to improve health in this population.

Cardiorespiratory Fitness (Peak Oxygen Uptake): Safe and Effective Measure for Cardiovascular Screening Before Kidney Transplant.

BACKGROUND: Significant heterogeneity exists in practice patterns and algorithms used for cardiac screening before kidney transplant. Cardiorespiratory fitness, as measured by peak oxygen uptake (VO2peak), is an established validated predictor of future cardiovascular morbidity and mortality in both healthy and diseased populations. The literature supports its use among asymptomatic patients in abrogating the need for further cardiac testing. METHODS AND RESULTS: We outlined a pre-renal transplant screening algorithm to incorporate VO2peak testing among a population of asymptomatic high-risk patients (with diabetes mellitus and/or >50 years of age). Only those with VO2peak <17 mL/kg per minute (equivalent to <5 metabolic equivalents) underwent further noninvasive cardiac screening tests. We conducted a retrospective study of the a priori dichotomization of the VO2peak <17 versus ≥17 mL/kg per minute to determine negative and positive predictive value of future cardiac events and all-cause mortality. We report a high (>90%) negative predictive value, indicating that VO2peak ≥17 mL/kg per minute is effective to rule out future cardiac events and all-cause mortality. However, lower VO2peak had low positive predictive value and should not be used as a reliable metric to predict future cardiac events and/or mortality. In addition, a simple mathematical calculation documented a cost savings of ≈$272 600 in the cardiac screening among our study cohort of 637 patients undergoing evaluation for kidney and/or pancreas transplant. CONCLUSIONS: We conclude that incorporating an objective measure of cardiorespiratory fitness with VO2peak is safe and allows for a cost savings in the cardiovascular screening protocol among higher-risk phenotype (with diabetes mellitus and >50 years of age) being evaluated for kidney transplant.

Regional variation in kidney transplant outcomes: trends over time.

BACKGROUND AND OBJECTIVES: Clinical outcomes after kidney transplant have improved considerably in the United States over the past several decades. However, the degree to which this has occurred uniformly across the country is unknown. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Regional variations in graft failure after kidney transplant during three different time periods were examined. These time periods were chosen to coincide with major shifts in immunosuppressant usage: Era 1, cyclosporine usage, 1988 through 1989; Era 2, introduction of tacrolimus and mycophenolate mofetil, 1994 through 1995; and Era 3, widespread use of tacrolimus and mycophenolate mofetil, 1998 through 1999. Patient data were obtained from the United States Renal Data System database. For each period, regional differences in time from transplant to graft failure (organ removal, death, or return to dialysis) were examined. For each region, differences in graft failure over time were examined. RESULTS: One-year graft survival rates ranged from 76% to 83% between regions in Era 1 (n = 13,669), from 84% to 89% in Era 2 (n = 17,456), and from 87.5% to 92% in Era 3 (n = 20,375). Three-year graft survival ranged from 65% to 75% between regions in Era 1, from 84% to 89% in Era 2, and from 77% to 86% in Era 3. Adjusted models for donor and recipient characteristics showed improvements in graft survival over time in all United Network for Organ Sharing regions with minimal variation across regions. CONCLUSIONS: Regional differences in graft survival after kidney transplant are minimal, particularly when compared with the dramatic improvements in graft survival that have occurred over time.