The 24-hour urine collection: gold standard or historical practice?
OBJECTIVE
The objective of the study was to determine completeness of 24-hour urine collection in pregnancy.


METHODS
This was a retrospective laboratory/chart review of 24-hour urine collections at British Columbia Women's Hospital. Completeness was assessed by 24-hour urinary creatinine excretion (UcreatV): expected according to maternal weight for single collections and between-measurement difference for serial collections.


RESULTS
For 198 randomly selected pregnant women with a hypertensive disorder (63% preeclampsia), 24-hour urine collections were frequently inaccurate (13-54%) on the basis of UcreatV of 97-220 micromol/kg per day (11.0-25.0 mg/kg per day) or 133-177 micromol/kg per day (15.1-20.1 mg/kg per day) of prepregnancy weight (respectively). Lean body weight resulted in more inaccurate collections (24-68%). The current weight was frequently unavailable (28%) and thus not used. For 161 women (81% proteinuric) with serial 24-hour urine levels, a median [interquartile range] of 11 [5-31] days apart, between-measurement difference in UcreatV was 14.4% [6.0-24.9]; 40 women (24.8%) had values 25% or greater, exceeding analytic and biologic variation.


CONCLUSIONS
Twenty-four hour urine collection is frequently inaccurate and not a precise measure of proteinuria or creatinine clearance.
Côté
Anne-Marie
AM
Department of Nephrology, University of Sherbrooke, Sherbrooke, PQ, Canada.
Firoz
Tabassum
T
Mattman
André
A
Lam
Elaine M
EM
von Dadelszen
Peter
P
Magee
Laura A
LA
D000328:Adult; D015415:Biomarkers / Q000652:urine; D001955:British Columbia; D015331:Cohort Studies; D003404:Creatinine / Q000652:urine*; D005260:Female; D006176:Gynecology / Q000592:standards; D006785:Hospitals, University; D006801:Humans; D006973:Hypertension / Q000175:diagnosis* / Q000652:urine; D011225:Pre-Eclampsia / Q000175:diagnosis* / Q000652:urine; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000175:diagnosis* / Q000652:urine; D011256:Pregnancy Outcome; D011295:Prenatal Care / Q000592:standards; D012015:Reference Standards; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors; D016482:Urinalysis / Q000592:standards; D055815:Young Adult
D015415:Biomarkers; D003404:Creatinine