Variation of urinary protein to creatinine ratio during the day in women with suspected pre-eclampsia.
OBJECTIVE
To investigate the stability throughout the day of the protein to creatinine ratio (PCR) in spot urine, to demonstrate whether the PCR is a valid alternative for 24-hour protein investigation in pregnant women.


METHODS
Prospective study.


METHODS
Tertiary referral university centre.


METHODS
Women suspected of having pre-eclampsia, admitted to the Erasmus Medical Centre.


METHODS
Twenty-four-hour urine collections and simultaneously three single voided 5-ml aliquots were obtained at 8 a.m., 12 a.m. (noon) and 5 p.m. A PCR was measured in each specimen and compared with the 24-hour protein excretion.


METHODS
The 24-hour proteinuria and PCR measured in spontaneous voids.


RESULTS
The PCRs correlated strongly with each other and with the 24-hour protein excretion but did show variation throughout the day (mean coefficient of variation 36%; 95% confidence interval 31-40%). The coefficient of variation was unrelated to the degree of 24-hour proteinuria. Receiver operating characteristics curves to discriminate between values below and greater than or equal to the threshold of 0.3 g protein per 24-hour had an area under the curve of respectively 0.94 (8 a.m.), 0.96 (noon) and 0.97 (5 p.m.). Sensitivities at 8 a.m., noon and 5 p.m. were respectively 89%, 96% and 94%; specificities were 75%, 78% and 78% with the proposed PCR cut-off of 30 mg/mmol (0.26 g/g) (National Institute for Health and Care Excellence guidelines).There is no evidence of a difference between the three measurement times regarding the sensitivities and specificities.


CONCLUSIONS
The PCR determined in spot urine varies throughout the day but is a valid alternative for 24-hour urine collections in pregnant women. It is especially useful to rapidly identify clinically relevant proteinuria.
Department of Obstetrics and Gynaecology, Division of Obstetrics and Prenatal Medicine, Erasmus Medical Centre, Rotterdam, the Netherlands; Department of Internal Medicine, Erasmus Medical Centre, Rotterdam, the Netherlands.
K
K
Verdonk
I C
IC
Niemeijer
W C J
WC
Hop
Y B
YB
de Rijke
E A P
EA
Steegers
A H
AH
van den Meiracker
W
W
Visser
D000328:Adult; D002940:Circadian Rhythm; D003404:Creatinine / Q000652:urine*; D005260:Female; D006801:Humans; D011225:Pre-Eclampsia / Q000175:diagnosis / Q000652:urine*; D011247:Pregnancy; D011446:Prospective Studies; D011507:Proteinuria; D012372:ROC Curve; D012680:Sensitivity and Specificity; D059349:Urine Specimen Collection / Q000379:methods*
D003404:Creatinine
24-hour urine collection; pre-eclampsia; pregnancy; protein to creatinine ratio; proteinuria