Validation of Arterio Venous Access Stage Classification by Using Machine Learning in Prediction of Vascular Access Creation and Uninterrupted Use of the Vascular Access for Dialysis
Conditions: Arteriovenous Graft, Arteriovenous Fistula, Dialysis Access Malfunction, Kidney Failure, Dialysis Related Complication
Sponsor: Vascular surgery, University hospital Královské Vinohrady, Prague

VAVASC TRIAL – STUDY PROTOCOL, NCT04796558 
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Name of project 
Validation of AVAS classification by using machine learning in 
prediction of vascular access creation and in the prediction of 
uninterrupted use of the vascular access for dialysis 
Acronym of the project 
VAVASC trial (Validation of the Arterio Venous Access Stage 
Classification) trial 
Web page  
www.vavasc.com  
ClinicalTrial identifier 
NCT04796558 
Leader of the project 
Balaz, P, O’Neill, S., Lawrie, K.,  
Type of the study 
Prospective, multi-centre, international, collaborative 
Registration  
None 
Number of patients included  
Minimum 500, optimal 1000 
Start of the study 
2021 
Estimated end of the study 
2023-2024 
Ethics committee approval 
Yes. This should be reviewed in each centre, and if necessary 
each centre should have approval of its own ethics committee.  
However, please note that this is an observational study that is 
collecting data from existing medical records. In many centres 
(e.g. those with routine ultrasound arteriovenous mapping) 
there will be no alteration to patient care. There is therefore 
unlikely to be a requirement for patient information or 
consent.  
If ethical approval is required in individual centres it could 
potentially be obtained from a Proportionate Review Service. If 
applicable, participating units should also register with local 
audit/clinical governance structures and gain permission from 
the Caldicott Guardian. 
Informed consent 
Depends on the centre and decision of the ethical board of 
each centre 
Database (data storage) 
Electronic database - eCRF (Waldauf, P.) 
Statistic analysis 
Predictive modelling by using machine learning (Waldauf, P., 
O’Neill, S.) 
Financial support 
No 

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Background 
 
Ultrasound of upper limb vessels as a part of preoperative 
assessment of patients referred for arteriovenous access 
placement has been recommended repeatedly in several 
studies and guidelines. Each patient needing arterio-venous 
access (AVA) is unique and has different possibilities for fistula 
creation that depend on many factors as well the anatomical 
condition of inflow arteries and outflow veins, the so-called 
‘arteriovenous access map’.  In 2020 we created, published 
and retrospectively evaluated the inter-rater reliability of the 
AVAS classification, which is a simplified way of sharing the 
information about suitability for access creation depending on 
vascular anatomy (doi: 10.1093/ckj/sfaa189). 
However, before routine use of the AVAS classification system 
in clinical practise it requires prospective validation and 
comparison with other clinical factors. Finally, whether the 
AVAS classification can be used for the prediction of vascular 
access function as defined by uninterrupted use of vascular 
access for dialysis without need for any access 
intervention/procedures (SONG-HD, doi: 
10.1053/j.ajkd.2017.12.003) remains to be tested.  
This project has two main parts:  
1. Validation of AVAS classification with and without 
combination with other factors using a predictive 
statistical model. 
2. Validation of AVAS classification in terms of prediction 
of uninterrupted use of successfully created vascular 
access for dialysis.  
The data will be collected prospectively. Both parts of the 
project will be taking place simultaneously.  
Working hypothesis  
Part 1: AVAS classification with/without selective clinical 
parameters is a useful tool for sharing information about the 
type of AVA which will be created. 
Part 2: Increasing AVAS with/without selective clinical 
parameters is an accurate predictive tool for the prediction of 
the uninterrupted use of successfully created vascular access 
for dialysis. 

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Socio Economic aspect 
Classification of vascular access is important for improving 
efficiency of communication across multi-disciplinary teams, 
which helps streamline care and avoids errors.  
At the individual patient level it is critical for communicating 
vascular access complexity and thus ensuring preservation of 
precious access.  
At a unit level, in the NHS best practice tariff criteria are based 
on national guidance and expert opinion that are intended to 
drive improvements in processes of care.  
The best practice tariff for haemodialysis is that 80% of 
patients on haemodialysis should receive dialysis via a 
functioning arteriovenous fistula.  
Individual units with complex vascular access populations may 
be unfairly penalised for not meeting this target. A 
classification system for vascular access would help define 
vascular access populations, leading to fairer comparison of 
unit performance and appropriate remuneration for the cost 
of care.   
Methodology 
Data will be collected prospectively (Belfast City Hospital, UK, 
University hospital Královské Vinohrady Prague CZ). Other 
centres around the world will be asked for cooperation 
(announcement will be posted via scientific societies, Twitter, 
ResearchGate, LinkedIn, Facebook, Kidney Academy etc.)  in 
March 2021. The data collected will be the parameters of the 
vessels on the upper limb, in order to be able to evaluate AVAS 
(VAVASC FORM). Along with anatomical dispositions of the 
patients, other parameters will be collected.  
Obligatory parameters (parameters A): 
- 
Side of the arm:  
 
Left 
 
Right 
- 
Dominant hand: 
 
Left 
 
Right 
- 
Allen's test: 
 
 
Positive         Negative 
(A negative Allen’s test is demonstration of a complete 
palmar arch and intact collateral blood flow to the 
hand) 
- 
Sex: 
 
 
 
M 
 
F 
- 
Age: 
 
 
 
………………………….. 

VAVASC TRIAL – STUDY PROTOCOL, NCT04796558 
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- 
Height:  
 
 
…………………………… 
- 
Weight: 
 
 
…………………………... 
- 
BMI: 
 
 
  
…………………………... 
- 
Diabetes: 
 
 
Yes 
 
No 
- 
CV line previous or current 
Yes 
 
No    
- 
Side of the CV line if place 
Left  
 
Right 
Non-obligatory parameters (parameters B): 
- 
Smoking history:  
 
Yes 
 
No 
- 
Hypertension:  
 
Yes 
 
No 
- 
Heart failure: 
 
 
Yes 
 
No 
- 
Ischemic heart disease:  
Yes 
 
No 
- 
Cancer (previous or current):  
Yes 
 
No 
In order to evaluate uninterrupted use of the vascular access 
for dialysis (part 2 of the study), we will follow the patients and 
do a time to event analysis of the arteriovenous accesses for 
one year after creation or up until the first intervention for 
maintaining patency has been performed. If the patient dies 
during follow up the date of death should be recorded. The 
data for this part will be collected prospectively (Belfast City 
Hospital, UK, University hospital Královské Vinohrady Prague, 
CZ and other centres).  
Predictive models will be used for validation of AVAS 
classification. The data will be registered via eCRF and analysed 
by Waldauf, P. and O’Neill, S. 
Methodology step-by-step   
1. Patient with need of AVA creation is assessed in 
outpatient clinic as usual. 
2. To reduce bias all consecutive patients must be 
captured.  
3. Each registered health care professional (HCP) in the 
participating centre in the VAVASC study has access to 
eCRF (electronic database). They can fill the collected 
data straight into the database or at a later date from 
the notes they usually take when recording 
arteriovenous mapping. If the HCP or centre prefers 
paper forms, a paper document (VAVASC FORM) can 

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be used and researchers from each centre will put the 
data from the paper form into the eCRF regularly. 
Collection of data into eCRF primarily is the preferable 
approach. If the HCP examining the patient has access 
to eCRF, they do not have to fill the paper VAVASC 
FORM.  
4. Patient is scanned using ultrasound and the vascular 
parameters are marked/registered (eCRF or VAVASC 
FORM). If the HCP wishes, they can evaluate the 
patient according to AVAS classification. The HCP can 
skip this step since the vascular parameters can be 
used to establish the AVAS by the VAVASC research 
group.  
5. Patients' risk factors are also marked/registered. Only 
“obligatory parameters” (parameters A) are necessary 
to collect. The HCP can also collect the parameters B, 
that are voluntary.  
For centres using paper form (VAVASC FORM)  
- 
If the centre/individual HCP prefers paper forms only, 
VAVASC FORM is stored in a prepared box in each 
clinic in the hospital entitled as “VAVASC“.  
- 
Researcher from each centre regularly collects the 
VAVASC FORM documents.  
- 
Researcher from each centre regularly enters obtained 
data from VAVASC FORM into the eCRF.  
- 
A similar approach may be used by centres that 
already record the information on the VASVASC form 
elsewhere (e.g. the medical records or centre specific 
arteriovenous maps) 
6. Patient is indicated for AVA as usual (not necessarily as 
is indicated by AVAS) 
7. Researcher from each centre regularly follows up the 
patients and enters type of AVA which was created 
into the eCRF. 
8. Researcher from each centre regularly follows up the 
patients and enter data about the fate of AVA for one 
year or up until the first intervention for maintaining 

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patency has been performed. If the patient dies during 
follow up the date of death should be recorded.  
Statistic method 
Predictive modelling using machine learning (O’Neill, S., 
Waldauf, P.) 
Responsibilities of the research team 
1. The centre lead registers interest with VAVASC 
research group, and will seek local ethical approval. 
2. Centre lead is responsible for ensuring the required 
data is collected by HCPs in the clinic, and supervising 
the data collectors in their centre.   
3. HCP in the clinic: Carries out arteriovenous mapping 
and records clinical data. 
4. HCP in the clinic or data collector fills the paper 
VAVASC FORM/ or fills the data into eCRF (computer) 
database, approx. 10 minutes. 
5. Data collector in each centre where eCRF is not used: 
may collect the VAVASC FORM and enter data into the 
eCRF, approx..1 hour/week 
6. Centre lead or data collector in each center regularly 
checks the patient follow up, approx. 1 hour/week 
7. Project leader of VAVASC group: regularly sends 
informative email about status of the study to all 
researchers (how many patients recruited, how many 
centres are active etc.).  
8. VASVASC group will analyse results and prepare 
manuscript. 
 Authorship 
Named author is a HCP who acts as a centre lead, and 
sets up the study in their centre including ethical 
approval. This HCP is also invited into the writing 
group, so they are able to participate in drafting and 
reviewing the final manuscript. 
 
Collaborator /collaborative author (also PubMed 
citable) is a HCP who collects patient data and enters 
the data in the eCRF or provides the data to the centre 
lead for entry. To reduce bias collaborators must 
capture consecutive patients. There is no minimum or 
maximum amount of consecutive patients that could 
be entered by a collaborator. However, each 
collaborator must collect data for patients who have 

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gone onto have successful vascular access creation and 
these patients must be followed up for the full follow 
up period. Unfortunately, in some cases attempts at 
vascular creation will fail so collaborators are 
encouraged to recruit as many consecutive patients as 
they can. To avoid disadvantaging and excluding low 
volume centres (which would impact the 
generalizability of the study) no time limit will be set 
for recruitment of consecutive patients. However, the 
eCRF will close to further data entry on X.