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Biological variation of measured and estimated glomerular filtration rate in patients with chronic kidney disease

Rowe, Ceri, Sitch, Alice J., Barratt, Jonathan, Brettell, Elizabeth A., Cockwell, Paul, Dalton, R. Neil, Deeks, Jon J., Eaglestone, Gillian, Pellatt-Higgins, Tracy, Kalra, Philip A., and others. (2019) Biological variation of measured and estimated glomerular filtration rate in patients with chronic kidney disease. Kidney International, 96 (2). pp. 429-435. ISSN 0085-2538. (doi:10.1016/j.kint.2019.02.021) (KAR id:74554)

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https://dx.doi.org/10.1016/j.kint.2019.02.021

Abstract

When assessing changes in glomerular filtration rate (GFR) it is important to differentiate pathological change from intrinsic biological and analytical variation. GFR is measured using complex reference methods (e.g. iohexol clearance). In clinical practice measurement of creatinine and cystatin C is used in equations (e.g. Modification of Diet in Renal Disease [MDRD] or Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI]) to provide estimated GFR. We studied biological variability of measured and estimated GFR in twenty nephrology outpatients (10 male, 10 female; median age 71, range 50-80 years) with moderate CKD (GFR 30-59 mL/min/1.73 m2). Patients underwent weekly GFR measurement by iohexol clearance over four consecutive weeks. Simultaneously GFR was estimated using the MDRD, CKD-EPIcreatinine, CKD-EPIcystatinC and CKD-EPIcreatinine+cystatinC equations. Within-subject biological variation (CVI) expressed as a percentage [95% CI] for the MDRD (5.0% [4.3-6.1]), CKD-EPIcreatinine (5.3% [4.5-6.4]), CKD-EPIcystatinC (5.3% [4.5-6.5]), and CKD-EPIcreatinine+cystatinC (5.0% [4.3-6.2]) equations were broadly equivalent. CVI values for MDRD and CKD- EPIcreatinine+cystatinC were lower (p=0.027 and p=0.022 respectively) than that of measured GFR (6.7% [5.6-8.2]). Reference change values (RCV), the point at which a true change in a biomarker in an individual can be inferred to have occurred with 95% probability were calculated: using the MDRD equation, positive and negative RCVs were 15.1% and 13.1% respectively. If an individual’s baseline MDRD estimated GFR (mL/min/1.73 m2) was 59, significant increases or decreases would be to values >68 or <51 respectively. Within-subject variability of estimated GFR is lower than measured GFR. RCVs can be used to understand GFR changes in clinical practice.

Item Type: Article
DOI/Identification number: 10.1016/j.kint.2019.02.021
Uncontrolled keywords: biological variation, creatinine, cystatin C, glomerular filtration rate, iohexol, kidney disease, MDRD, CKD-EPI
Divisions: Faculties > Social Sciences > School of Social Policy Sociology and Social Research > Centre for Health Services Studies
Depositing User: Tracy Pellatt-Higgins
Date Deposited: 24 Jun 2019 15:32 UTC
Last Modified: 07 Mar 2020 00:00 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/74554 (The current URI for this page, for reference purposes)
Pellatt-Higgins, Tracy: https://orcid.org/0000-0002-2543-461X
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