Objective To determine the variability of protein excretion in patients with proteinuric hypertension and the accuracy of either a urinary protein/creatinine ratio or a Multistix examination for the estimation of a 24 h protein excretion.

Design An indwelling urinary catheter was placed for 24 h and successive 8 h specimens examined.

Setting A tertiary referral hospital in Cape Town, South Africa.

Subjects 22 women with significant proteinuria in pregnancy were studied.

Main outcome measures The urine volume, protein excretion and creatinine excretion in eight hourly periods were measured. Multistix examination of each specimen was recorded.

Results A large coefficient of variation in urine volume (41%), amount of protein excreted (44%) and the amount of creatinine excreted (22%) in the eight hourly specimens were noted. The protein creatinine ratio did not accurately predict the 24 h protein excretion. The Multistix examination was less accurate with increasing amounts of proteinuria. The amount of creatinine excreted correlated with the volume of urine passed (r = 0.43).

Conclusion The analysis of a 24 h specimen or urine for protein excretion remains the best method of monitoring proteinuria in pregnancy. The amount of creatinine excreted in 24 h cannot be used as an index of completeness of collection of the 24 h specimen.