In preeclampsia, should we use Urine Albumin-to-Creatinine Ratio (UACR) or Urine Protein-to-Creatinine Ratio (UPCR) for assessing proteinuria?

Proteinuria Assessment in Preeclampsia: UPCR is Recommended

In preeclampsia, you should use Urine Protein-to-Creatinine Ratio (UPCR), not Urine Albumin-to-Creatinine Ratio (UACR). 1

Primary Recommendation

The International Society for the Study of Hypertension in Pregnancy (ISSHP) explicitly states that there is currently insufficient data to recommend using urinary albumin/creatinine ratio (UACR) for preeclampsia assessment. 1 In contrast, UPCR is the endorsed standard for quantifying proteinuria in suspected preeclampsia. 1

Practical Assessment Algorithm

Initial Screening

• Begin with automated dipstick urinalysis (or careful visual dipstick if automated unavailable). 1
• If dipstick shows ≥1+ proteinuria (≥30 mg/dL), proceed to quantification with spot UPCR. 1
• If dipstick is negative, further testing is generally not required at that time. 1

Diagnostic Threshold

• UPCR ≥30 mg/mmol (or ≥0.3 mg/mg) indicates significant proteinuria and confirms the diagnosis when combined with new-onset hypertension after 20 weeks gestation. 1

When 24-Hour Collection is Still Needed

• Confirming nephrotic syndrome (proteinuria >5 g/24h), which has implications for thromboprophylaxis decisions. 1
• When UPCR results are borderline or inconsistent with clinical presentation. 1

Evidence Supporting UPCR Over UACR

Why UPCR is Preferred

• UPCR correlates strongly with 24-hour urine protein (correlation coefficient r=0.88, p<0.001), making it a reliable alternative. 2
• UPCR demonstrates 89% sensitivity and 100% specificity at the 30 mg/mmol cutoff for diagnosing preeclampsia. 3
• The test is faster, more practical, and eliminates collection errors inherent to 24-hour urine samples. 1, 2, 3

Why UACR is Not Recommended

• The ISSHP guidelines explicitly note that evidence for UACR remains insufficient and await results from ongoing studies like the Diagnostic Accuracy in Preeclampsia using Proteinuria Assessment trial. 1
• While one study showed UACR correlation with disease severity and outcomes 4, this single study is insufficient to override guideline recommendations against its routine use.

Clinical Significance of Proteinuria Quantification

Prognostic Value

• Massive proteinuria (>5 g/24h) is associated with more severe neonatal outcomes and earlier delivery. 1
• UPCR >900 mg/mmol (or >500 mg/mmol if age >35 years) correlates with worse maternal outcomes. 1
• However, delivery decisions should not be based solely on proteinuria degree—clinical context and other features of preeclampsia severity take precedence. 1

Important Caveats

Proteinuria is Not Required for Diagnosis

• Preeclampsia can be diagnosed without proteinuria if new-onset hypertension after 20 weeks is accompanied by other end-organ dysfunction (thrombocytopenia, renal insufficiency, liver dysfunction, pulmonary edema, or neurological symptoms). 1

False Results

• Dipstick testing may miss some proteinuric cases, but when missed, total protein excretion is usually <400 mg/day. 1
• UPCR <30 mg/mmol occasionally gives false-negative results for abnormal 24-hour proteinuria, though again typically when total excretion is minimal. 1
• Dipstick accuracy improves with automated readers and is most reliable at values >1 g/L (2+). 1

Monitoring Considerations

• If proteinuria is initially diagnosed but subsequent dipsticks become negative, repeat quantification with UPCR to confirm whether true proteinuria persists. 1
• Maternal monitoring should include repeated assessments for proteinuria if not already present, along with twice-weekly blood tests for hemoglobin, platelets, liver and renal function. 1