Faculty Bibliography

BACKGROUND AND AIMS:Frailty, as measured by the Liver Frailty Index (LFI), is associated with liver transplant (LT) waitlist mortality. We sought to identify an optimal LFI cutoff that predicts waitlist mortality. APPROACH AND RESULTS:Adults with cirrhosis awaiting LT without hepatocellular carcinoma at nine LT centers in the United States with LFI assessments were included. Multivariable competing risk analysis assessed the relationship between LFI and waitlist mortality. We identified a single LFI cutoff by evaluating the fit of the competing risk models, searching for the cutoff that gave the best model fit (as judged by the pseudo-log-likelihood). We ascertained the area under the curve (AUC) in an analysis of waitlist mortality to find optimal cutoffs at 3, 6, or 12 months. We used the AUC to compare the discriminative ability of LFI+Model for End Stage Liver Disease-sodium (MELDNa) versus MELDNa alone in 3-month waitlist mortality prediction. Of 1,405 patients, 37 (3%), 82 (6%), and 135 (10%) experienced waitlist mortality at 3, 6, and 12 months, respectively. LFI was predictive of waitlist mortality across a broad LFI range: 3.7-5.2. We identified an optimal LFI cutoff of 4.4 (95% confidence interval [CI], 4.0-4.8) for 3-month mortality, 4.2 (95% CI, 4.1-4.4) for 6-month mortality, and 4.2 (95% CI, 4.1-4.4) for 12-month mortality. The AUC for prediction of 3-month mortality for MELDNa was 0.73; the addition of LFI to MELDNa improved the AUC to 0.79. CONCLUSIONS:LFI is predictive of waitlist mortality across a wide spectrum of LFI values. The optimal LFI cutoff for waitlist mortality was 4.4 at 3 months and 4.2 at 6 and 12 months. The discriminative performance of LFI+MELDNa was greater than MELDNa alone. Our data suggest that incorporating LFI with MELDNa can more accurately represent waitlist mortality in LT candidates.

BACKGROUND:Secondary hyperparathyroidism (SHPT) affects nearly all patients on maintenance dialysis therapy. SHPT treatment options have considerably evolved over the past 2 decades, but vary in degree of improvement in SHPT. Therefore, we hypothesize that the risks of adverse outcomes after kidney transplantation (KT) may differ by SHPT treatment. METHODS:Using the SRTR and Medicare claims data, we identified 5,094 adults (age≥18) treated with cinacalcet or parathyroidectomy for SHPT prior to receiving KT between 2007-2016. We quantified the association between SHPT treatment and delayed graft function and acute rejection using adjusted logistic models and tertiary hyperparathyroidism (THPT), graft failure, and death using adjusted Cox proportional hazards; we tested whether these associations differed by patient characteristics. RESULTS:Of 5094 KT recipients who were treated for SHPT while on dialysis, 228 (4.5%) underwent parathyroidectomy and 4866 (95.5%) received cinacalcet. There was no association between treatment of SHPT and posttransplant delayed graft function, graft failure or death. However, compared to patients treated with cinacalcet, those treated with parathyroidectomy had a lower risk of developing THPT (aHR=0.56, 95%CI: 0.35-0.89) post-KT. Furthermore, this risk differed by dialysis vintage (pinteraction=0.039). Among patients on maintenance dialysis therapy for ≥3 years prior to KT (n=3,477, 68.3%), the risk of developing THPT was lower when treated with parathyroidectomy (aHR=0.43, 95%CI: 0.24-0.79). CONCLUSIONS:Parathyroidectomy should be considered as treatment for SHPT, especially in KT candidates on maintenance dialysis for ≥3 years. Additionally, patients treated with cinacalcet for SHPT should undergo close surveillance for development of tertiary hyperparathyroidism post-KT.

BACKGROUND:Placing an arteriovenous fistula (AVF) in older hemodialysis patients at great risk of primary failure leads to prolonged dependency on central venous catheter (CVC). A model which accurately predicts AVF maturation can facilitate better clinical determination for AVF placement. METHODS:We assembled a retrospective cohort of 14 892 patients aged 67 years and older who started hemodialysis with a CVC between 7/1/2010 and 6/30/2012 and had a subsequent, incident AVF placement from the United States Renal Data System (USRDS). We used random survival forests (RSF) with competing risks to identify important predictors for AVF maturation. RESULTS:Approximately 49.7% patients achieved AVF maturation and 13.6% had a competing event. The median time to maturation was 4 (IQR: 3-5) months. Patient's gender had the highest variable importance (VIMP, 0.0027), followed by race, being institutionalized, days on hemodialysis without an AVF, estimated glomerular filtration rate, and body mass index with borderline importance (VIMP ≥0.0005). The out-of-bag (OOB) error rate of the RSF was 45.3% and 45.8% for AVF maturation in the training and validation data sets, respectively. CONCLUSIONS:Predictors in USRDS data have limited ability to predict AVF maturation. Patient's gender might be considered as the most important predictor for AVF maturation.

INTRODUCTION:Multifactorial biological processes underpin dysregulation over several individual physiological systems. However, it is challenging to characterize and model this multisystemic dysregulation and its relationship with individual physiologic systems. We operationalized a theory-driven measure of multisystem dysregulation and empirically tested for measurement differences by key characteristics. METHODS:We used the Women's Health and Aging Studies (WHAS) I and II (N = 649), and the Health ABC study (N = 1515). Twelve biomarkers representing multiple systems including stress response (e.g., inflammation), endocrine system, and energy regulation were identified. A series of confirmatory factor analyses (CFA) were conducted to evaluate the interplay between physiological systems and underlying multisystem dysregulation. We evaluated convergent criterion validity of a score for multisystem dysregulation against the physical frailty phenotype, and predictive criterion validity with incidence of walking difficulty and mortality. RESULTS:A bifactor CFA, a model in which dysregulation of individual systems proceeds independently of generalized dysregulation, fit data well in WHAS (RMSEA: 0.019; CFI: 0.977; TLI: 0.961) and Health ABC (RMSEA: 0.047; CFI: 0.874; TLI: 0.787). The general dysregulation factor was associated with frailty (OR: 2.2, 95 % CI: 1.4, 3.5), and elevated risk of incident walking difficulty and mortality. Findings were replicated in Health ABC. DISCUSSION:Biomarker data from two epidemiologic studies support the construct of multisystem physiological dysregulation. Results further suggest system-specific and system-wide processes have unique and non-overlapping contributions to dysregulation in biological markers.

OBJECTIVES:Over 40% of individuals in the United States with end-stage kidney disease have obesity. Little is known about renal dietitian perspectives on obesity management in the setting of dialysis dependence. DESIGN AND METHODS:An online 21-item survey was distributed to 118 renal dietitians via individual outreach and a professional organization e-mail listserv. Four themes were explored: the burden of obesity among dialysis patients, concepts of healthy weight loss, weight loss approaches, and challenges of obesity management in dialysis settings. Respondents were asked to rank approaches and biomarkers for obesity management from 0 (least important or not used) to 100 (most important). Free text fields were provided in each category for additional comments. RESULTS:Thirty-one renal dietitians responded to the survey (26% response rate). The majority of respondents (90%) indicated that access to kidney transplantation was the main reason that dialysis patients with obesity desired weight loss. Calorie restriction was rated as the most common weight loss approach, and dry weight as the most important weight loss biomarker. Nearly 40% of respondents do not alter their nutritional approach when dialysis patients with obesity are losing weight, and 42% of respondents do not monitor changes in waist circumference. Exercise, diet counseling, and stress management were variably prioritized as weight loss management strategies. Barriers to obesity management in dialysis settings included lack of time, lack of training in weight loss counseling, and gaps in current renal nutritional guidelines. CONCLUSION:Despite the high prevalence of obesity among individuals with end-stage kidney disease, the results of this survey suggest that current approaches to obesity management in dialysis settings are highly variable. Many renal dietitians lack time to counsel patients on healthy weight loss strategies. Nutritional guidelines are also needed to support people with dialysis dependence and obesity who desire or require weight loss.

INTRODUCTION:"Frailty" has attracted attention for its promise of identifying vulnerable older adults, hence its potential use to better tailor geriatric health care. There remains substantial controversy, however, regarding its nature and ascertainment. Recent years have seen a proliferation of frailty assessment methods. We argue that the development of frailty assessments should be grounded in "validation"-the process of substantiating that a measurement accurately and precisely measures what it intends, identify unresolved measurement issues, and highlight measurement-related considerations for clinical practice. METHODS:Principles for validating frailty measures are elucidated. We follow principles-articulated, for example, by Borsboom-in which a construct must be clearly defined and then analyses undertaken to substantiate that a measurement accurately and precisely measures what it intends. Key elements are content validity, criterion validity, and construct validity, with an emphasis on the latter. RESULTS:We illustrate the principles for a physical frailty phenotype construct. CONCLUSIONS:Unresolved conceptual issues include the roles of intersecting concepts such as cognition, disease severity, and disability in frailty measurement, conceptualization of frailty as a state versus a continuum, and the potential need for dynamic measures and systems concepts in furthering understanding of frailty. Clinical considerations include needs to distinguish interventions designed to address frailty "symptoms" versus underlying physiology, improve "prefrailty" measures intended to screen individuals early in their frailty progression, address feasibility demands, and further visioning followed by rigorous efficacy research to address the landscape of potential uses of frailty assessment in clinical practice.