Reading current publications on vascular access, I still see the same endpoints far too often: primary and secondary patency. They are established, easy to compare and fit neatly into Kaplan–Meier curves. But do they really tell us whether an access does its job?

What patency measures and what it doesn't

Primary patency ends with the first intervention or the first occlusion. It does not tell us whether the access could be cannulated at all. A patent but immature fistula counts as a success, even while the patient is still dialysed through a catheter.

Secondary patency ends only when the access is finally abandoned. It can therefore look excellent even when it conceals repeated thrombectomies, angioplasties and weeks of catheter dependence. The curve counts the result, not the effort required to achieve it.

Both may look impressive on paper and still tell us surprisingly little about the patient's actual experience.

A patent access is not necessarily a functional access.

Three questions a patency curve can't answer

1. Can the access be cannulated? Primary patency does not equal a usable access.

2. How many interventions did it take? Secondary patency shows the result, not the burden of repeated procedures.

3. How long was the patient on a catheter? Catheter days are invisible in patency rates, although they are associated with infection, hospitalisation and mortality.

What patients and experts consider important

This question has already been addressed internationally. The SONG-HD initiative (Standardised Outcomes in Nephrology – Haemodialysis) developed a core outcome set for haemodialysis trials together with patients, caregivers and health professionals. Vascular access is one of these core outcomes.

A systematic review within SONG-HD found 1,426 different access-related measures across 168 trials, which shows how inconsistent reporting is.

In a subsequent consensus workshop, vascular access function was emphasised as a core outcome. Proposed criteria included uninterrupted use of the access without additional interventions and the ability to reliably deliver the prescribed dialysis.

What this means in practice

Patency rates will keep their place. They are established and allow comparison with earlier studies. But when we evaluate new techniques, devices or care pathways, we should also report what matters to patients. Possible endpoints include:

- Time to first successful cannulation

- Catheter-free days

- Interventions per access-year

These measures are less elegant than a Kaplan–Meier curve. In return, they reflect what patients, dialysis nurses and nephrologists experience every day.

Your view?

Which outcome matters most to you: time to first cannulation, catheter-free days or the number of interventions? Or does your centre report something entirely different? I look forward to your feedback via the contact form or on LinkedIn.

Reference: Viecelli AK, Tong A, O'Lone E, et al. Report of the Standardized Outcomes in Nephrology–Hemodialysis (SONG-HD) Consensus Workshop on Establishing a Core Outcome Measure for Hemodialysis Vascular Access. Am J Kidney Dis. 2018. doi:10.1053/j.ajkd.2017.12.003

Conflicts of interest: The author declares no conflicts of interest.