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Monitoring residual kidney function in haemodialysis patients using timed urine collections: validation of the use of estimated blood results to calculate GFR

Lindley, Elizabeth; Keane, David; Belcher, John; Fernandes Da Silva Jeffcoat, Nancy; Davies, Simon; trial investigators, BISTRO

Monitoring residual kidney function in haemodialysis patients using timed urine collections: validation of the use of estimated blood results to calculate GFR Thumbnail


Authors

Elizabeth Lindley

David Keane

Nancy Fernandes Da Silva Jeffcoat

BISTRO trial investigators



Abstract

OBJECTIVE: With growing recognition of the benefits of preserving residual kidney function (RKF) and use of incremental treatment regimes, the incentive to measure residual clearance in haemodialysis patients is increasing. Interdialytic urine collections used to monitor RKF in research studies are considered impractical in routine care, partly due to the requirement for blood samples before and after the collection. Plasma solute levels can be estimated if patients are in 'steady state', where urea and creatinine concentrations increase at a constant rate between dialysis sessions and are reduced by a constant ratio at each session. Validation of the steady state assumption would allow development of simplified protocols for urine collections in HD patients. APPROACH: Equations were derived for estimating plasma urea and creatinine at the start or end of the interdialytic interval for patients in steady state. Data collected during the BISTRO study was used to assess the agreement between measured and estimated plasma levels and the effect of using estimated levels on the calculated glomerular filtration rate (GFR). MAIN RESULTS: The mean difference between GFR calculated with estimated plasma levels for the HD session after the collection and a full set of measured levels was 2.0% (95% limits of agreement -10.7% to +14.7%, N = 316). Where plasma levels for the session before the collection were estimated, the mean difference was 1.2% (limits of agreement -10.3% to +7.9%, N = 275). SIGNIFICANCE: Using estimated levels for one session led to a clinically significant difference in the calculated GFR for less than 3% of the collections studied. This indicates that the steady state assumption can be used to estimate solute levels when determining GFR from timed urine collections. A pragmatic approach to monitoring RKF in HD would be for patients to collect for approximately 24 hours before routine bloods are taken.

Citation

Lindley, E., Keane, D., Belcher, J., Fernandes Da Silva Jeffcoat, N., Davies, S., & trial investigators, B. (2022). Monitoring residual kidney function in haemodialysis patients using timed urine collections: validation of the use of estimated blood results to calculate GFR. Physiological Measurement, 43(8), Article 08NT01. https://doi.org/10.1088/1361-6579/ac80e8

Journal Article Type Article
Acceptance Date Jul 13, 2022
Online Publication Date Aug 3, 2022
Publication Date Jul 13, 2022
Publicly Available Date May 30, 2023
Journal Physiological Measurement
Print ISSN 0967-3334
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 43
Issue 8
Article Number 08NT01
DOI https://doi.org/10.1088/1361-6579/ac80e8
Publisher URL https://iopscience.iop.org/article/10.1088/1361-6579/ac80e8

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