A cost effectiveness analysis of dialysis graft thrombosis treatment
Yen-Ni Hung1, Po-Jen Ko2, Shiao-Chi Wu 3
1
Institute of Public Health, National Yang-Ming University
2
Division of Thoracic and Cardiovascular Surgery, Chang-Gung Memorial Hospital
3
Institute of Health and Welfare Policy, National Yang-Ming University
Address correspondence to: Shiao-Chi Wu, No. 155, Sec. 2, Li-Nong St., Taipei 112,
Taiwan
1
Abstract
Objectives. To evaluate the necessity and effectiveness of different adjunctive
therapies used with dialysis graft surgical thrombectomy.Method.We reviewed the
records of 590 consecutive surgical dialysis graft thrombectomies performed in a
medical center between Aug. 2001 and Aug. 2003. All cases underwent Fogarty
thrombecotmies and were classified into four groups: ONLY group, those receiving
surgical thrombectomies using Fogarty thrombectomy catheter alone (300 cases);
ANGIO group, those receiving thrombectomies plus intraoperative angioplasties of
graft outlets (110 cases); REVS group, those receiving thrombectomies plus graft
outlet surgical revisions (126 cases) and SEQL group, those receiving
thrombectomies plus sequential balloon angioplasties, over separate sessions (54
cases). Age, gender, graft age, co-morbidity and primary patency of the graft were
also reviewed. Cost of each group was determined by the average time, professional
labor, and materials used complete all the procedures. Results. Patient in all four
groups had similar demographic characteristics and comorbidities (p>0.05). The mean
primary patency of four groups are 1.99±4.02, 7.21±7.61, 8.35±9.53, 7.26±6.99
(months), respectively. The effectiveness (primary patency period ) of ONLY group
was statistically inferior to that of the other three groups. Although the methods used
to treat graft outlet stenosis in ANGIO, REVS, and SEQL groups were found to be
equally effective, REVS group was found to be the most cost effective ( 2.76-2.94
USD/per patency day , with different salary level) ,the second cost effective was
ONLY group (2.81-3.14 USD/per patency day) ,the third was group ANGIO group
(3.13-3.27 USD/per patency daty) and SEQL group is the most expensive 3.16-3.37
USD/per patency day). Conclusion.Although cost-effectiveness of thrombectomy
alone (ONLY group) was found to be similar to that of REVS group and cheaper than
the modalities used for ANGIO and SEQL groups, it result in much more inferior
outcome. Based on our findings, thrombectomy plus graft outlet surgical revision had
the best primary patency and was most cost-effective. However, from patients’ aspect,
it will be more covenient and less painstaking to be treated for all the medical
problems surrounding graft outlet stenosis at one time. Considering the invasiveness,
procedure time and the effectiveness of the procedures, intraoperative angioplasty of
graft outlet is the most reasonable adjunct treatment of graft outlet stenosis associated
with trombectomies.
Key words: cost-effecctiveness analysis; vascular access; thrombectomy
2
Introduction
The incidence rate of end stage renal disease(ESRD) of Taiwan is the highest in
the world (384 persons/per million /per year), and the prevalence rate is the second
highest(1,631/per million)(USRDS, 2006), just next to Japan.Care of patients with
ESRD is resoruce intense, according to National Health Insurance statistics, ESRD
patients spend 5.86% of total expenditure(Department of Health, 2005).
About 93% of ESRD patients in Taiwan are under Hemodialysis(HD)(USRDS,
2006). Patient who choose HD need vascular access before initiation of dialysis.They
may choose native arteiovenous fistula (AVF), a synthetic graft, or central venous
catheter. In Taiwan, many choosing synthetic grafts for vascular access.
A functional and patent dialysis access can ensure the effectiveness of renal
replacement therapy. Neglect of dialysis access monitor and shortness of effective
care may lead to complications such as dialysis access thrombosis, stenosis, infection,
aneurysm, rupture or pseudoaneurysm and in turns give to large amount of extra
medical expenses(Hakim & Himmelfarb, 1998). According to the literatures,
some15.7~25% of admissions in dialysis patients are due to dialysis access related
complications (Feldman, Kobrin, & Wasserstein, 1996; Hakim & Himmelfarb, 1998;
Manns et al., 2005). The strategy of clinical intervention correlates highly to the
quality of dialysis access care(Arnold, 2000; Beathard & Litchfield, 2004; Lee et al.,
2002; Manns et al., 2005; Pisoni et al., 2002; Young et al., 2002). Different strategies
of clinical intervention to cope with the complications may lead to different cost of
medical care. To find a cost efficient strategy of treatment when coping with
complications of dialysis access is so important for the payers, institutions and the
government.
3
Thrombosis is a major cause dialysis graft failure. Therefore, surgical
thrombectomy is often used to treat dialysis graft failure in the medical center.
However, more than 85% of the cases of dialysis graft thrombosis are caused by graft
outlet stenosis(Aruny et al., 1999; Turmel-Rodrigues et al., 2000). If the underlying
strictures of access is treated when doing the thrombectomy procedure, the patency of
the access may be enhanced significantly(Besarab, Sullivan, Ross, & Moritz, 1995;
"III. NKF-K/DOQI Clinical Practice Guidelines for Vascular Access: update 2000,"
2001; Sands & Miranda, 1995; Turmel-Rodrigues et al., 2000). Our institution started
adopting several different adjuct treatment modalities manage this problem since
2001. These adjunct theapies include intraoperative angioplasty of graft outlet, graft
outlet surgical revision, and sequential balloon angioplasty done over separate
sessions. This study evaluates the necessity and effectiveness of different adjunctive
therapies used with dialysis graft surgical thrombectomy.
Methods
Setting
The institution is a 2500 beds university affiliated teaching hospital. All cases of
dialysis graft thrombosis treated in the institution are by vascular surgeons section
using Fogarty thrombecotmies. Four vascular surgeons are responsible for the surgical
care of dialysis access problems. Since this is a referred center, most of the patients
treated were receiving dialysis therapy in the outside institution.
Data collection
Inclusion criteriae are all cases dialysis graft thrombectomy done in the
institution. However, only one procedure (the fisrt one) of one patient during the
study period were selected to be inculded. Procedures done under general anesthesia
were excluded from the study. A senior vascular surgeon were responsible for
4
reviewing the medical records of 590 qualified surgical dialysis graft thrombectomies
between 2001 and 2003. All these enrolled cases are classified into 4 groups
according to the type of treatments. The variables regarding demographic data,
medical condition and outcome (primary patency; time from dialysis access
thrombectomy procedure to first intervention or occlusion.) were collected from chart
and carefully reviewed. The medical expense for each group were calculated
according to standard costs.
Grouping
All the dialysis graft thrombosis were treated by surgical thrombectomy in
standard fashion to remove the thrombosis. According to the adjuvant therapy, the
enrolled cases were classified into 4 groups. Surgical thrombectomy group(ONLY
group), those receiving surgical thrombectomies using Fogarty thrombectomy
catheter alone (300 cases); intraprocedure angioplasty group (ANGIO group), those
receiving thrombectomies plus intraoperative angioplasties of graft outlets (110
cases); surgical revision group (REVS group), those receiving thrombectomies plus
graft outlet surgical revisions (126 cases) and sequential balloon group (SEQL group),
those receiving thrombectomies plus sequential balloon angioplasties, over separate
sessions (54 cases).
Evaluation of effectiveness and cost
Effectiveness of treatment is measured in terms of duration of primary
patency(months).
We took the perspective of the health care provider and included ONLY group
direct health care related cost. Societal costs were excluded. Direct cost include labor
and material. Different treatment involved different type of professional labors and
took different time to complete all medical procedures. Labor cost of each group was
5
determined by the average time of procedures , average salary of different type of
professional labor, and materials used.
The cost effectiveness of each group were examined in terms of the cost
effectiveness ration (CE ratio), which is in this study, the total cost divided by the
patency duration. The lower the CE ratio, the less cost needed to keep the graft open
for a certain duration.
Statistial analysis
Demographic characteristics and comorbidities of four groups were tested
using chi square and one-way ANOVA. Descriptive statistics were used to compare
the primary patecy of four groups. Differences resulting in p< 0.05 were considered
significant. The statistical analyses were perfomed using SPSS 14.0 for Windows.
The CE ratios of 4 groups were calculated and analysed, too.
Results
The four patient groups exhibited similar demographic characteristics and
comorbidities. (p>0.05)(Table 1) except for the graft age and history of previous
thrombecomy. The graft age of ANGIO group is the oldest (22.19) and that of ONLY
group is the youngest (13.28). Similarly, the rate of positive previous thrombectomy
history is the highest among 4 groups and that of ONLY group is the lowest. Mean
primary patency after the thrombectomy procedure in groups A, B, C and D was
1.99(SD, 4.02), 7.21(SD, 7.61), 8.35(SD, 9.53) and 7.26(SD, 6.99) months,
respectively.
The effectiveness in terms of primary patency period of ONLY group was
statistically inferior to that of the other three groups. And the methods used to treat
graft outlet stenosis in ANGIO, REVS and SEQL group were found to be equally
6
effective. The total cost per treatment of ONLY group (surgical thrombectomy ONLY
group without any additional cost and time spent for adjuvant therapy) is the lowest
(168.0-187.5 US dollars). While the total cost of REVS group, thrombectomy
followed by surgical revision of graft, is the highest (691.9-737.5 US dollars). The CE
ratio of 4 groups was 2.81-3.14, 3.13-3.27, 2.76-2.94 and 3.16-3.37 (dollars/day)
respectively. That is, when we take into consideration the result of each treatment in
terms of primary patency, we found that REVS group is the most cost-effective. It
took ONLY group 2.76-2.94 dollars in terms of procedure cost to maintain per
patency day.
7
Discussion
Dialysis graft failure in hemodialysis patients is a common clinical problem
encountered by vascular surgeons. Venous stenosis is known to be the most common
contributing cause of thrombosis in dialysis grafts. According to K/DOQI guidelines
for vascular access,("Clinical practice guidelines for vascular access," 2006)
intraprocedure image study during thrombectomy of dialysis grafts should be
performed to detect any anatomic stenotic lesion. Although numerous of papers had
stated that address the underlying graft outlet stenosis is pertinent to the primary
patency of dialysis graft thrombectomy, to save procedure time and expense, many
surgeons in Taiwan still treat the graft thrombosis with ONLY group surgical
thrombectomy without any adjuvant treatment to the underlying lesion.
Different treatment modalities for preventing graft outlet stenosis have been
proposed to enhance the results of thrombectomy. Surgical revision (patch
angioplasty or jump graft revision) has long been considered an effective, reliable and
straightforward way of surgically treating the outlet stricture of thrombosed graft.
(Etheredge, Haid, Maeser, Sicard, & Anderson, 1983; Schwartz, McBrayer, Sloan,
Meneses, & Ennis, 1995; Wellington, 1983) Transuluminal balloon angioplasty has
also been used for treating underlying dialysis graft stenosis with satisfactory results.
Angioplasty treatment can be performed in a combined fashion (Anain, Shenoy,
O'Brien-Irr, Harris, & Dryjski, 2001; Ko, Liu, Hsieh, Chu, & Lin, 2003) during
thrombectomy or in a separate session after the surgery.(Maya & Allon, 2006;
McCutcheon, Weatherford, Maxwell, Hamann, & Stiles, 2003; Smith, Cragg,
Castaneda, & Hunter, 1989) Some reports suggest that surgical revision is superior to
transluminal balloon angioplasty in terms of long term patency in treating graft outlet
lesions.(Brooks, Sigley, May, & Mack, 1987; Huber, Buhler, & Seeger, 2004)
8
Conversely, other reports indicate that angioplasty results are not inferior to those of
revision.(Bitar, Yang, & Badosa, 1997; McCutcheon et al., 2003) Other newly
developed endovascular methods such as stenting with nitinal stents or covered stents
have shown promising results and may offer effective alternative adjuvant therapies
(Lombardi, Dougherty, Veitia, Somal, & Calligaro, 2002; Naoum, Irwin, & Hunter,
2006; Sreenarasimhaiah, Margassery, Martin, & Bander, 2005).
This study analyzed 4 different type of practice of graft thrombosis treatment.
We found that, in terms of effectiveness, ONLY group (surgical thrombectomy
ONLY group) yielded the worst results. This outcome again confirms that surgical
thrombectomy alone is inadequate for treating thrombosed dialysis grafts. Adjuvant
therapy is pertinent to the effectiveness of dialysis declotting procedure. ANGIO,
REVS and SEQL groups yielded similar primary patency rates statistically. This
observation suggests that adjuvant therapies for treating the underlying stenosis
produce similar results.
Cost of human resources is the major part of medical expense in the dialysis
graft thrombosis treatments. According to our study, the total cost per procedure of
ONLY group is the least expensive among 4 groups. It was obviously that surgical
thrombectomy ONLY group yields the lowest cost per every procedure.
Unfortunately, according to our study and the literatures, the result of pure surgical
thrombectomy does not last long. The primary patency of ONLY group was inferior
to all the other 3 group significantly.
ANGIO, REVS and SEQL groups yields the
similar primary patency. However, in terms of CE ratio, REVS group (adjuvant
therapy with surgical revision) was the most cost-effective group. (Lowest CE ratio).
It seems that with the adjuvant treatment of revision, although the operation wound is
bigger and the operation time is longer, the treatment can maintain the graft patent at
lowest cost.
9
The opportunity cost, including loss of work days, cost of traveling…etc, was
not taken into consideration in this review. The treatment of graft stenosis was
performed by interventionist in a different session and venue \ following the surgical
thrombectomy. Thus from the view point of the patient, the fashion of treatment in
SEQL group increase the commute time and waiting time. In spite of the similar
effectiveness of treatment (primary patency) and CEratio, we think that the treatment
of SEQL group is more inconvenient for the patients and medical personnel. Both
ANGIO and REVS groups yield similar patency rate and reasonable CE ratio in this
review. Although the surgical revision needs a bigger wound and more procedure
time, the low cost may offset the shortcomings of invasiveness. Surgeons may choose
the type of adjuvant procedure based on their techniques and preference.
The true cost of procedure includes direct and indirect costs, such as operation
room, equipment and other supplies. Owing to the difficulty in acquiring the exact
amount of indirect expense of procedure, the indirect cost was not calculated and
analyzed in the review. This may lead to the underestimation of cost in this review;
especially in SEQL group (the procedure was split into 2 parts and held in separate
venues). The total procedure time of REVS and SEQL groups were similar,
considering the CE ratio of 2 groups, REVS group seems better than SEQL group in
terms of cost-effectiveness.
Comparing ANGIO and REVS group, although the CE ratio of REVS group is
better than group, the procedure time of revision group was longer (25 more minutes
per procedure) than REVS group. In addition, balloon angioplasty as an adjuvant
therapy decreased the invasiveness (degree of pain, length of wound…etc) in contrast
to the revision group. Thus, choosing the method of REVS group (concomitant
balloon angioplasty) to treat the dialysis graft outlet thrombosis during thrombectomy
procedure will be a reasonable choice. As for the inferiority of primary patency in
10
ONLY group, We don’t suggest surgical thrombectomy ONLY group to treat the
graft thrombosis.
From the view point of government or health insurance institutions, the
treatment with relative low CE ratio should be encouraged. Not ONLY group we can
control the medical expense on dialysis graft thrombectomy, but also can enhance the
quality of care in dialysis graft problems.
Conclusion
Although cost-effectiveness of thrombectomy alone (ONLY group) was found
to be similar to that of REVS group and cheaper than the modalities used for ANGIO
groups and SEQL, it result in much more inferior outcome. Based on our findings,
thrombectomy plus graft outlet surgical revision (REVS group) had the best primary
patency and was most cost-effective. However, from patients’ aspect, it will be more
covenient and less painstaking to be treated for all the medical problems surrounding
graft outlet stenosis at one time. Considering the invasiveness, procedure time and the
effectiveness of the procedures, intraoperative angioplasty of graft outlet is the most
reasonable adjunct treatment of graft outlet stenosis associated with trombectomies.
11
Talbe 1 Demographic data and risk factors of 4 groups
ONLY
(n=300)
ANGIO
(n=110)
REVS
(n=126)
SEQL
(n=54)
P
value
64.39(12.84)
128(42.7)
13.28(12.79)
63.74(14.20)
51(46.4)
22.19(14.84)
64.13(11.49)
45(35.7)
14.59(12.84)
59.91(14.35)
23(42.6)
17.57(14.40)
***
Previous-thrombecto
178(59.3)
86(78.2)
87(69.0)
41(75.9)
**
my(%)
Comorbidity no. (%)
DM(%)
Hypertension(%)
Heart dis. (%)
Other (%)
Primary patency(SD)
134(44.7)
142(47.3)
79(26.3)
41(13.7)
1.99(4.02)
45(40.9)
62(56.4)
24(21.8)
9(8.2)
7.21(7.61)
48(38.1)
62(49.2)
25(19.8)
14(11.1)
8.35(9.53)
25(46.3)
31(57.4)
16(29.8)
4(7.4)
7.26(6.99)
***
Mean age-y(SD)
Male sex (%)
Graft age(SD)
* P<0.05, **p <0.005, *** p<0.0005
Table 2 Standard of procedure time,type of professional labor, and material of 4
groups
ONLY
ANGIO
REVS
SEQL
Labor
Physician
30min*1
45min*1
70min*1
Nurse
30min*2
45min*2
70min*2
Technician
Material
Forgarty
1. Forgarty
1. Forgarty
thrombectomy
thrombectomy
thrombect
catheter
catheter
omy
2. Non-compliant
catheter
70min*1
30min*2
40min*1
1. Forgarty
thrombectomy
catheter
2. Non-compliant
angioplasty
2. Prosthetic
balloon
graft
catheter
guidewire
3. Contrast
medium *
50ml
4. Pressure gauge
angioplasty
balloon
catheter
guidewire
3. Contrast
medium *
50ml
4. Pressure gauge
12
Table 3 cost effectiveness analysis
ONLY
Cost a
Labor cost b
Material
Total cost
Effectiveness
Patency duration (months)
Patency duration (days)
Cost effectiveness ratio c
ANGIO
REVS
SEQL
18.0-37.5
27.0-56.3
41.9-87.5
38.3-83.9
150.0
650.0
650.0
650.0
168.0-187.5 677.0-706.3 691.9-737.5 688.3-733.9
1.99
59.7
2.81-3.14
7.21
216.3
3.13-3.27
a
Cost is caculated in US dallors.
physician’s cost caculate with different salary level
c
CE ratio=Total cost/ patency duration (days)
b
13
8.35
250.5
2.76-2.94
7.26
217.8
3.16-3.37
References
Anain, P., Shenoy, S., O'Brien-Irr, M., Harris, L. M., & Dryjski, M. (2001). Balloon
angioplasty for arteriovenous graft stenosis. J Endovasc Ther, 8(2), 167-172.
Arnold, W. P. (2000). Improvement in hemodialysis vascular access outcomes in a
dedicated access center. Semin Dial, 13(6), 359-363.
Aruny, J. E., Lewis, C. A., Cardella, J. F., Cole, P. E., Davis, A., Drooz, A. T., et al.
(1999). Quality improvement guidelines for percutaneous management of the
thrombosed or dysfunctional dialysis access. Standards of Practice Committee
of the Society of Cardiovascular & Interventional Radiology. J Vasc Interv
Radiol, 10(4), 491-498.
Beathard, G. A., & Litchfield, T. (2004). Effectiveness and safety of dialysis vascular
access procedures performed by interventional nephrologists. Kidney Int,
66(4), 1622-1632.
Besarab, A., Sullivan, K. L., Ross, R. P., & Moritz, M. J. (1995). Utility of
intra-access pressure monitoring in detecting and correcting venous outlet
stenoses prior to thrombosis. Kidney Int, 47(5), 1364-1373.
Bitar, G., Yang, S., & Badosa, F. (1997). Balloon versus patch angioplasty as an
adjuvant treatment to surgical thrombectomy of hemodialysis grafts. Am J
Surg, 174(2), 140-142.
Brooks, J. L., Sigley, R. D., May, K. J., Jr., & Mack, R. M. (1987). Transluminal
angioplasty versus surgical repair for stenosis of hemodialysis grafts. A
randomized study. Am J Surg, 153(6), 530-531.
Clinical practice guidelines for vascular access. (2006). Am J Kidney Dis, 48 Suppl 1,
S248-273.
Department of Health. (2005). Statistical annual report of medical care, National
Health Insurance:Cost of Main Diseases in Outpatient and Inpatient Service
by Gender and Age Groups.
Etheredge, E. E., Haid, S. D., Maeser, M. N., Sicard, G. A., & Anderson, C. B.
(1983). Salvage operations for malfunctioning polytetrafluoroethylene
hemodialysis access grafts. Surgery, 94(3), 464-470.
Feldman, H. I., Kobrin, S., & Wasserstein, A. (1996). Hemodialysis vascular access
morbidity. J Am Soc Nephrol, 7(4), 523-535.
Hakim, R., & Himmelfarb, J. (1998). Hemodialysis access failure: a call to action.
Kidney Int, 54(4), 1029-1040.
Huber, T. S., Buhler, A. G., & Seeger, J. M. (2004). Evidence-based data for the
hemodialysis access surgeon. Semin Dial, 17(3), 217-223.
14
III. NKF-K/DOQI Clinical Practice Guidelines for Vascular Access: update 2000.
(2001). Am J Kidney Dis, 37(1 Suppl 1), S137-181.
Ko, P. J., Liu, Y. H., Hsieh, H. C., Chu, J. J., & Lin, P. J. (2003). Initial experience
during balloon angioplasty assisted surgical thrombectomy for thrombosed
hemodialysis grafts. Chang Gung Med J, 26(3), 178-183.
Lee, H., Manns, B., Taub, K., Ghali, W. A., Dean, S., Johnson, D., et al. (2002). Cost
analysis of ongoing care of patients with end-stage renal disease: the impact of
dialysis modality and dialysis access. Am J Kidney Dis, 40(3), 611-622.
Lombardi, J. V., Dougherty, M. J., Veitia, N., Somal, J., & Calligaro, K. D. (2002). A
comparison of patch angioplasty and stenting for axillary venous stenoses of
thrombosed hemodialysis grafts. Vasc Endovascular Surg, 36(3), 223-229.
Manns, B., Tonelli, M., Yilmaz, S., Lee, H., Laupland, K., Klarenbach, S., et al.
(2005). Establishment and maintenance of vascular access in incident
hemodialysis patients: a prospective cost analysis. J Am Soc Nephrol, 16(1),
201-209.
Maya, I. D., & Allon, M. (2006). Outcomes of thrombosed arteriovenous grafts:
comparison of stents vs angioplasty. Kidney Int, 69(5), 934-937.
McCutcheon, B., Weatherford, D., Maxwell, G., Hamann, M. S., & Stiles, A. (2003).
A preliminary investigation of balloon angioplasty versus surgical treatment of
thrombosed dialysis access grafts. Am Surg, 69(8), 663-667; discussion 668.
Naoum, J. J., Irwin, C., & Hunter, G. C. (2006). The use of covered nitinol stents to
salvage dialysis grafts after multiple failures. Vasc Endovascular Surg, 40(4),
275-279.
Pisoni, R. L., Young, E. W., Dykstra, D. M., Greenwood, R. N., Hecking, E.,
Gillespie, B., et al. (2002). Vascular access use in Europe and the United
States: results from the DOPPS. Kidney Int, 61(1), 305-316.
Sands, J. J., & Miranda, C. L. (1995). Prolongation of hemodialysis access survival
with elective revision. Clin Nephrol, 44(5), 329-333.
Schwartz, C. I., McBrayer, C. V., Sloan, J. H., Meneses, P., & Ennis, W. J. (1995).
Thrombosed dialysis grafts: comparison of treatment with transluminal
angioplasty and surgical revision. Radiology, 194(2), 337-341.
Smith, T. P., Cragg, A. H., Castaneda, F., & Hunter, D. W. (1989). Thrombosed
polytetrafluoroethylene hemodialysis fistulas: salvage with combined
thrombectomy and angioplasty. Radiology, 171(2), 507-508.
Sreenarasimhaiah, V. P., Margassery, S. K., Martin, K. J., & Bander, S. J. (2005).
Salvage of thrombosed dialysis access grafts with venous anastomosis stents.
Kidney Int, 67(2), 678-684.
15
Turmel-Rodrigues, L., Pengloan, J., Baudin, S., Testou, D., Abaza, M., Dahdah, G., et
al. (2000). Treatment of stenosis and thrombosis in haemodialysis fistulas and
grafts by interventional radiology. Nephrol Dial Transplant, 15(12),
2029-2036.
USRDS. (2006). Annual data report 2006- chapter 12 international comparison
Wellington, J. L. (1983). Salvage of thrombosed polytetrafluoroethylene dialysis
fistulas by interposition grafting. Can J Surg, 26(5), 463-465.
Young, E. W., Dykstra, D. M., Goodkin, D. A., Mapes, D. L., Wolfe, R. A., & Held,
P. J. (2002). Hemodialysis vascular access preferences and outcomes in the
Dialysis Outcomes and Practice Patterns Study (DOPPS). Kidney Int, 61(6),
2266-2271.
16