The reliability of glomerular filtration rate measured from plasma clearance: a multi-centre study of 1,878 healthy potential renal transplant donors.
OBJECTIVE
The objective of the study was to undertake a clinical audit of departmental performance in the measurement of glomerular filtration rate (GFR) using the coefficient of variation (CV) of extracellular fluid volume (ECFV) as the benchmark. ECFV is held within narrow limits in healthy subjects, narrower than GFR, and should therefore have a low CV.


METHODS
Fifteen departments participated in this retrospective study of healthy renal transplant donors. Data were analysed separately for men (n ranged from 28 to 115 per centre; total = 819) and women (n = 28-146; 1,059). All centres used the slope-intercept method with blood sample numbers ranging from two to five. Subjects did not fast prior to GFR measurement. GFR was scaled to body surface area (BSA) and corrected for the single compartment assumption. GFR scaled to ECFV was calculated as the terminal slope rate constant and corrected for the single compartment assumption. ECFV/BSA was calculated as the ratio of GFR/BSA to GFR/ECFV.


RESULTS
The departmental CVs of ECFV/BSA and GFR/BSA ranged from 8.3 to 25.8% and 12.8 to 21.9%, respectively, in men, and from 9.6 to 21.1% and 14.8 to 23.7%, respectively, in women. Both CVs correlated strongly between men and women from the same centre, suggesting department-specific systematic errors. GFR/BSA was higher in men in 14 of 15 centres, whereas GFR/ECFV was higher in women in 14 of 15 centres. Both correlated strongly between men and women, suggesting regional variation in GFR.


CONCLUSIONS
The CV of ECFV/BSA in normal subjects is a useful indicator of the technical robustness with which GFR is measured and, in this study, indicated a wide variation in departmental performance.
Department of Nuclear Medicine, Royal Sussex County Hospital, Brighton, UK. a.m.peters@bsms.ac.uk
A Michael
AM
Peters
Bethany
B
Howard
Mark D J
MD
Neilly
Nagabhushan
N
Seshadri
Ravin
R
Sobnack
Claire A
CA
Hooker
Andrew
A
Irwin
Hayley
H
Snelling
Thomas
T
Gruning
Laura
L
Perry
Neva H
NH
Patel
Richard S
RS
Lawson
Gregory
G
Shabo
Nigel
N
Williams
Surendra
S
Dave
Mark C
MC
Barnfield
D000328:Adult; D000368:Aged; D019985:Benchmarking; D015992:Body Mass Index; D001835:Body Weight; D045604:Extracellular Fluid / Q000378:metabolism; D005260:Female; D005919:Glomerular Filtration Rate; D006262:Health; D006801:Humans; D016030:Kidney Transplantation; D019520:Living Donors; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012737:Sex Factors; D055815:Young Adult