The value of the urinary protein:creatinine ratio for the detection of significant proteinuria in women with suspected preeclampsia

To explore the correlation between urinary protein:creatinine ratio and 24‐h excretion of protein, we studied 149 women referred to a day assessment unit for investigations for suspected preeclampsia. Paired samples were obtained for measurement of urinary protein:creatinine ratio and 24‐h protein excretion. Collection of a 24‐h urine sample was validated by the daily creatinine excretion. The outcome measure was proteinuria of 300 mg/day or more. Inaccurate 24‐h collection was observed in 17% of women. All women ( n  = 56) with a protein:creatinine ratio >60 mg/mM had significant proteinuria. No woman with protein:creatinine ratio <18 mg/mM ( n  = 20) had significant proteinuria. We recommend that a dual cut‐off should be used for excluding and “ruling in” the diagnosis of significant proteinuria. A 24‐h urine collection should be used only for urinary protein:creatinine ratio values between 18 and 60 mg/mM in the detection of significant proteinuria.