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A functioning vascular access (VA) is crucial to providing adequate hemodialysis (HD) and considered a critically important outcome by patients and healthcare professionals. VALID (Vascular Access outcome measure for function: a vaLidation study In hemoDialysis) aimed to validate a core outcome measure for VA function established via consensus among 918 health professionals and 237 patients and caregivers from 58 different countries.
Using the STARD guidelines for diagnostic accuracy studies, this prospective, multi-center, multinational validation study (NCT03969225) assessed the feasibility, agreement, and accuracy of measuring VA function, defined as the need for interventions to enable and maintain VA use for HD. The primary objective was to determine whether VA function can be measured accurately by clinical staff as part of routine clinical practice (Assessor 1) compared to the reference standard of documented VA procedures collected by a VA expert (Assessor 2) during 6 months of follow-up. Validity was assessed by the sensitivity and specificity of the VA intervention data with sensitivity corresponding to the proportion of correctly identified interventions by Assessor 1 compared to Assessor 2. Feasibility was assessed by average data collection time, feasibility questionnaires and semi-structured assessor interviews.
Across 7 countries (Australia, Canada, France, Netherlands, Malaysia, the United Kingdom and Switzerland) and 10 centers, 699 adults on HD were recruited between December 2019 and December 2021. Mean age was 63 years (standard deviation=16), 60% were male, 45% were diabetic and 74%, 19% and 8% dialyzed via arteriovenous fistula, catheter and graft, respectively. HD modalities included hospital-based HD (86%), satellite HD (8%), and home HD (6%). Overall, there were 359 VA interventions (rate=1.04 per patient-year). The most common interventions included 133 (37%) catheter-related procedures (exchange/insertion/removal/fibrin sheath disruption), 131 (36%) fistulograms with/without angioplasty/stenting, 43 (13%) surgical/endovascular AV access creation and 26 (7%) AV access revisions. Overall VA intervention data accuracy was 92% (95% confidence interval [CI] 91-94%) with high agreement (kappa=0.87) between Assessors 1 (n=15) and 2 (n=14). Cluster-corrected sensitivity was 81% (95%CI 75-85%) and specificity was 96% (95%CI 95-97%). Data collection took a median of 4 minutes (interquartile range 2-6min)/patient over 6 months. Based on feasibility questionnaires and supported by qualitative interviews, the majority of assessors 1 and 2 agreed or strongly agreed that it was easy to collect the number (67%/83%), type (73%/92%) and date (80%/92%) of VA procedures and to report the outcome as part of routine clinical care (66%/75%). Catheter removals were considered the most challenging VA procedure to collect.
Measuring VA function using a standardized, patient-centered core outcome as part of routine care is feasible with moderate accuracy. Consistent reporting of this core outcome in clinical research will enhance research quality and relevance and help better inform HD care.