The association of standard Kt/V and surface area-normalized standard Kt/V with clinical outcomes in hemodialysis patients

Abstract

Introduction: A previous study demonstrated that the surface area-normalized standard Kt/V (SAstdKt/V) was better associated with mortality than standard Kt/V (stdKt/V). This study investigates the association of SAstdKt/V and stdKt/V with mortality, anemia, and hypoalbuminemia in a larger patient cohort with a longer follow-up period.

Methods: We included adult patients on thrice-weekly hemodialysis in the USRDS database and excluded amputated patients. StdKt/V and SAstdKt/V were calculated from the available single-pool Kt/V. Patients were categorized into five groups according to their stdKt/V and SAstdKt/V: <2.00, 2.00-2.19, 2.20-2.39, 2.40-2.59, and ≥2.60. Hazard ratios (HR) and odds ratios (OR) were calculated using Cox and logistic regression analysis respectively.

Findings: There were 507,656 patients included in the analysis. The patients had a median age of 65.5 years with a median follow-up period of 2 years. Thirty-four percent died during follow-up. HRs for mortality progressively decreased as SAstdKt/V increased in both unadjusted and adjusted models. Unlike SAstdKt/V, HRs were the lowest in the categories with stdKt/V of 2.40-2.59 and they increased in the higher stdKt/V category. The adjusted HR for SAstdKt/V vs. stdKt/V were 0.68 vs. 0.62 in the category of 2.40-2.59, and 0.63 vs. 0.73 in the category of ≥2.60. The adjusted ORs for anemia progressively decreased as SAstdKt/V increased, whereas ORs decreased to the lowest in stdKt/V category 2.40-2.59 and increased in the ≥2.60 category. The adjusted ORs for hypoalbuminemia progressively decreased as SAstdKt/V and stdKt/V increased which were both 0.45 in 2.40-2.59 category and decreased to 0.29 and 0.42 in the ≥2.60 category.

Discussion: SAstdKt/V is better associated with mortality, anemia, and hypoalbuminemia than stdKt/V. SAstdKt/V is a better parameter in defining hemodialysis dosing which can be calculated by an available online tool. Further studies to determine the optimal SAstdKt/V dose required to achieve improved clinical outcomes with better cost-effectiveness are needed.

Keywords: Adequacy of dialysis; anemia; nutrition; survival.

Figure 1

The study flow. HD, hemodialysis; RRT, renal replacement therapy, spKt/V, single-pool Kt/V; USRDS, United States Renal Data System.

Figure 2

The survival curves for mortality among patients who were in 5 different categories of standard Kt/V (stdKt/V) (Figure 2A) and surface area-normalized standard Kt/V (SAstdKt/V) (Figure 2B). The number of patients at risk were shown in Table S3 and S4 in supplementary.

Figure 3

The hazard ratio (HR) and 95% confidence interval for mortality: (A) unadjusted, adjusted by (B) age, gender, race, and Hispanic ethnicity, (C) age, gender, race, Hispanic ethnicity, and comorbidities, and (D) age, gender, race, Hispanic ethnicity, comorbidities, serum albumin, and dialysis vintage. The adjusted odds ratio (OR) and 95% confidence interval for (E) anemia (defined by hemoglobin level of less than 10 g/dL) by age, gender, race, Hispanic ethnicity, comorbidities, serum albumin, and dialysis vintage, and (F) for hypoalbuminemia (defined by serum albumin level of less than 3.5 g/dL) by age, gender, race, Hispanic ethnicity, comorbidities, and dialysis vintage. The group with stdKt/V and SAstdKt/V of 2.00–2.19 were used as reference group. The unadjusted OR for anemia and hypoalbuminemia were shown in supplementary Figure S1.