Precision Medicine in the Transition to Dialysis and Personalized Renal Replacement Therapy

Launched in 2016, the overarching goal of the Precision Medicine Initiative is to promote a personalized approach to disease management that takes into account an individual's unique underlying biology and genetics, lifestyle, and environment, in lieu of a one-size-fits-all model. The concept of precision medicine is pervasive across many areas of nephrology and has been particularly relevant to the care of advanced chronic kidney disease patients transitioning to end-stage kidney disease (ESKD). Given many uncertainties surrounding the optimal transition of incident ESKD patients to dialysis and transplantation, as well as the high mortality rates observed during this delicate transition period, there is a pressing urgency for implementing precision medicine in the management of this population. Although the traditional paradigm has been to commence incident hemodialysis patients on a 3 times/week treatment regimen, largely driven by adequacy targets, there has been growing recognition that alternative treatment regimens (ie, incremental hemodialysis) may be preferred among certain subpopulations when taking into consideration factors such as patients' residual kidney function, volume status fluctuations, symptoms, and preferences. In this review, we examine the origins of current practices in how dialysis is initiated among incident ESKD patients; incremental dialysis therapy as a dynamic and patient-centric approach that is tailored to patients' unique characteristics; recent data on the incremental hemodialysis regimen and outcomes; and future research directions using a precision nephrology approach to ESKD management with the potential to develop novel approaches, tools, and collaborative efforts to improve the health, well-being, and survival of this population.

Incremental Hemodialysis: The University of California Irvine Experience

Incremental hemodialysis has been examined as a viable hemodialysis regimen for selected end-stage renal disease (ESRD) patients. Preservation of residual kidney function (RKF) has been the driving impetus for this approach given its benefits upon the survival and quality of life of dialysis patients. While clinical practice guidelines recommend an incremental start of dialysis in peritoneal dialysis patients with substantial RKF, there remains little guidance with respect to incremental hemodialysis as an initial renal replacement therapy regimen. Indeed, several large population-based studies suggest that incremental twice-weekly vs. conventional thrice-weekly hemodialysis has favorable impact upon RKF trajectory and survival among patients with adequate renal urea clearance and/or urine output. In this report, we describe a case series of 13 ambulatory incident ESRD patients enrolled in a university-based center's Incremental Hemodialysis Program over the period of January 2015 to August 2016 and followed through December 2016. Among five patients who maintained a twice-weekly hemodialysis schedule vs. eight patients who transitioned to thrice-weekly hemodialysis, we describe and compare patients' longitudinal case-mix, laboratory, and dialysis treatment characteristics over time. The University of California Irvine Experience is the first systemically examined twice-weekly hemodialysis practice in North America. While future studies are needed to refine the optimal approaches and the ideal patient population for implementation of incremental hemodialysis, our case-series serves as a first report of this innovative management strategy among incident ESRD patients with substantial RKF, and a template for implementation of this regimen.

Infrequent dialysis: a new paradigm for hemodialysis initiation

Nearly a half-century ago, the thrice-weekly hemodialysis schedule was empirically established as a means to provide an adequate dialysis dose while also treating the greatest number of end-stage renal disease (ESRD) patients using limited resources. Landmark trials of hemodialysis adequacy have historically been anchored to thrice-weekly regimens, but a recent randomized controlled trial demonstrated that frequent hemodialysis (six times per week) confers cardiovascular and survival benefits. Based on these collective data and experience, clinical practice guidelines advise against a less than thrice-weekly treatment schedule in patients without residual renal function, yet provide limited guidance on the optimal treatment frequency when substantial native kidney function is present. Thus, during the transition from Stage 5 chronic kidney disease to ESRD, the current paradigm is to initiate hemodialysis on a "full-dose" thrice-weekly regimen even among patients with substantial residual renal function. However, emerging data suggest that frequent hemodialysis accelerates residual renal function decline, and infrequent regimens may provide better preservation of native kidney function. Given the high mortality rates during the first 6 months of hemodialysis and the survival benefits of preserved native kidney function, initiation with twice-weekly treatment schedules ("infrequent hemodialysis") with an incremental increase in frequency over time may provide an opportunity to optimize patient survival. This review outlines the clinical benefits of post-hemodialysis residual renal function, studies of twice-weekly treatment regimens, and the potential risks and benefits of infrequent hemodialysis.

Evaluation of renal Kt/V as a marker of renal function in predialysis patients

BACKGROUND

The use of renal Kt/V (r-Kt/V) as an indicator for the need of dialysis initiation has been recommended in the NKF-DOQI guidelines. In analogy to clinical practice in peritoneal dialysis, a fall of r-Kt/V below a threshold of 2.0 per week may indicate inadequate renal toxin elimination. However, there are no studies linking r-Kt/V with other parameters of glomerular filtration rate (GFR) in predialysis patients, and the validity of r-Kt/V as parameter for timing of dialysis initiation is unknown.

METHODS

Renal function was assessed repeatedly in 125 patients (N = 465 measurements). In predialysis patients (r-Kt/V <2.5 per week) r-Kt/V was compared with creatinine [CCr], urea [CUr], averaged creatinine/urea clearance [CCr/Ur], Cockcroft-Gault formula [CCG], and MDRD prediction equation 6 (MDRD6-GFR). The diagnostic performance of r-Kt/V as a parameter for timing the initiation of dialysis was evaluated.

RESULTS

Renal Kt/V <2.5 was prevalent in 24.9% of cases (N = 116, mean 1.92 +/- 0.34). In this group mean CCr was 13.8 +/- 4.9, mean CUr 6.7 +/- 1.3, and CCr/Ur 10.2 +/- 2.9 mL/min/1.73 m2. There was no correlation of r-Kt/V with serum creatinine and MDRD6-GFR, but a significantly positive correlation with CCr/Ur (r2 = 0.3382, P < 0.001). Sensitivity of r-Kt/V to detect CCr/Ur < 10.5 mL/min/1.73 m2, defined as the threshold for dialysis initiation, was 73.6% with a specificity of 91.9%.

CONCLUSIONS

These results suggest that r-Kt/V is a parameter of acceptable specificity but poor sensitivity for the timing of dialysis initiation. Additional measures of renal function, such as the average of measured creatinine and urea clearance, also should be taken into consideration when deciding on the timing of dialysis initiation prior to the development of clinical signs of uremia and malnutrition.