Variability in creatinine excretion in adult diabetic, overweight men and women: consequences on creatinine-based classification of renal disease.
BACKGROUND
It is crucial to estimate renal function in diabetic patients. However, formulas are inadequate in this population whereas creatinine clearance (C(cr)) on a 24-h urine collection may be valuable only if we can improve its reproducibility.


OBJECTIVE
To evaluate in diabetic patients whether standardised procedures of 24-h urine collection improve the day-to-day variability in creatinine urinary excretion and the subsequent precision of the measured C(cr).


METHODS
The C(cr) from two consecutive 24-h urine collections was measured in 201 consecutive diabetic inpatients. Procedures of 24-h urine collection were standardised, and implementation was supervised at a diabetes clinic.


RESULTS
Pearson's correlation coefficients of the two 24-h creatinine urinary excretion were significant (r(2)=0.64 in women and r(2)=0.65 in men, p<0.0001) but the daily variability in creatinine urinary excretion was high (14.9% in women and 17.4% in men). As a consequence, the agreement between the two consecutive measurements of C(cr) was poor. First, Bland-Altman plots showed large 95% limits of agreement (-34.3 to 34.6 mL/min/1.73 m(2) in women and -39.0 to 52.0 mL/min/1.73 m(2) in men). Secondly, there was a poor agreement for classifying patients according to the National Kidney Foundation classification >90, 60-89.9, 30-59.9, and <30 mL/min/1.73 m(2) (Kappa coefficients=0.61, 0.42, 0.65, and 0.74, respectively).


CONCLUSIONS
Despite standardised procedures of 24-h urine collection, day-to-day variability in creatinine urinary excretion in adult diabetic men and women remains important, and may lead to misclassification of renal disease.
Jacobi
David
D
CHRU de Tours, Service de Médecine Interne et Nutrition, France. jacobi@med.univ-tours.fr
Lavigne
Christian
C
Halimi
Jean-Michel
JM
Fierrard
Hélène
H
Andres
Christian
C
Couet
Charles
C
Maillot
François
F
D000328:Adult; D000368:Aged; D003404:Creatinine / Q000652:urine*; D003928:Diabetic Nephropathies / Q000145:classification / Q000175:diagnosis* / Q000652:urine*; D003950:Diagnostic Techniques, Urological / Q000592:standards*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009765:Obesity; D050177:Overweight; D015203:Reproducibility of Results; D013048:Specimen Handling; D014556:Urine
D003404:Creatinine