Facility-Level Comorbidity Burden and Use of AVF Access

The preferred access type for patients receiving maintenance hemodialysis is arteriovenous fistula (AVF). Compared with tunneled catheters or arteriovenous grafts, AVFs are associated with superior patency, lower rates of infection, and reduced mortality. During the past decade, use of AVFs has increased; however, there are concerns about vascular access options in patients with higher comorbidity burden.

Previous studies have shown that patient comorbid conditions and factors such as female sex, Black race, and older age are associated with lower AVF use. Nevertheless, some centers have high rates of AVF placement even among patients with multiple comorbid conditions. Claudia Dahlerus, PhD, and colleagues conducted a retrospective cohort study designed to use both incident and prevalent comorbid conditions to stratify dialysis facilities based on their overall comorbidity burden vis-à-vis the association with facility-level AVF use. To compare the impact of patient- versus facility-level comorbidity on AVF use, the researchers conducted both patient- and facility-analyses. Results of the study were reported in the American Journal of Kidney Diseases [2020;75(6):879-886].

The study participants were Medicare beneficiaries receiving hemodialysis for 1 year or more in dialysis facilities in the United States. The researchers utilized Centers for Medicare & Medicaid Services Medicare claims and clinical and administrative data from CROWNWeb for 5813 US dialysis facilities with 11 or more patients from September 2014 through August 2015.

Study predictors were facility-level burden of patient comorbid conditions and patient characteristics. For the patient-level analysis, the outcome of interest was AVF use as the sole vascular access at the end of each reporting month in the study period. For the facility-level analysis, the primary outcome was the monthly percentage of AVF use (defined as the total number of AVFs in use divided by the total number of patient-months at each facility) at the end of the reporting month. An AVF was considered the sole vascular access if it was in use for the last treatment of the reporting month with two needles (or one needle with an approved single-needle device) and no catheter present. A long-term catheter was defined as present if the catheter was in use on the last treatment of the reporting month and the prior 2 months.

The study population included 315,919 prevalent hemodialysis patients (3,072,080 patient-months) at the 5813 eligible dialysis facilities. On average, the number of comorbid conditions per patient-month was progressively greater with greater facility comorbidity burden (range, 2.1-5.1). Compared with facilities with low comorbidity burden, those with high comorbidity burden had older patients (65.1 years vs 61.8 years), a higher proportion of female patients (45.8% vs 44.3%) and patients with a nursing home stay in the previous year (14.5% vs 6.6%), and lower proportions of Black patients (28.8% vs 39.5%). There was no significant difference between the two groups in the proportion of Hispanic patients (13.9% vs 14.0%).

In each of the comorbidity groupings, diabetes and heart disease were most prevalent. In the lowest comorbidity burden facilities, 50.9% of patients had diabetes and 42.6% had cardiovascular disease; in the facilities with the highest comorbidity burden, 82.0% had diabetes and 88.0% had cardiovascular disease. Overall, the prevalence of peripheral vascular disease was 47.9% (range, 26.1% in the lowest comorbidity burden facilities to 73.2% in the highest comorbidity burden facilities).

The overall percentage of AVF use was 65.8% (67.1% in the low and 63.9% in the high comorbidity facilities, respectively). The highest comorbidity burden facilities (>99th percentile) had the lowest percentage of patients with an AVF (55.2%). The mean percentage of patients with a long-term catheter was lowest in the low comorbidity burden facilities (9.5%) and highest in the highest comorbidity burden facilities (18.5%).

Results of patient-level analysis showed significant associations between younger age, non-Black race, male sex, Hispanic ethnicity, higher body mass index, and prior nephrology care with higher odds of AVF use. Patients aged 25 to 29 years of age had 6% higher odds of an AVF than patients 60 to 75 years of age. Having nephrology care prior to dialysis initiation was associated with a 22% higher odds of an AVF. Patient factors associated with lower odds of an AVF included age of ≥75 years, a nursing home stay in the prior year, and dialysis vintage of ≥5 years.

In facility-level analysis, facility-level AVF use differences between comorbidity burden groups were adjusted for average patient characteristics within the same facility. Greater facility-level comorbidity burden from the 61st to the 99th deciles was associated with progressively lower AVF use. Facilities with lower comorbidity burden were associated with small but steadily greater AVF use. The lowest comorbidity burden was associated with 2.64 percentage point greater facility-level AVF use. Following adjustment for comorbid conditions, the associations of other patient factors such as age, sex, race, and ethnicity were markedly attenuated.

There were some limitations to the findings cited by the authors, including limiting the study population to the Medicare population on maintenance dialysis for ≥1 year, and not accounting for facility characteristics such as geographic location, size, staffing ratios, or ownership characteristics.

“In summary, we demonstrate that there is little variation in dialysis facility AVF use across a spectrum of comorbidity burden, suggesting that other factors such as facility practice patterns likely play an important role in determining rates of AVF use.”

Takeaway Points

  1. Patients with high comorbidity burden are less likely to use an arteriovenous fistula (AVF) for hemodialysis vascular access; researchers conducted a retrospective cohort study to examine variation in facility-level use of AVFs across a facility-level burden of patient comorbid conditions.
  2. The cohort included Medicare beneficiaries receiving maintenance hemodialysis for 1 year or longer.
  3. Following adjustment for patient characteristics, there were only small differences in facility rates of AVF use with the exception of high or low levels of comorbidity burden.