A random spot urine sample from a pregnant woman shows a protein-to-creatinine ratio of 0.45 mg/mg. How does this value compare with the threshold for significant proteinuria in pre-eclampsia?

• A It is below the diagnostic threshold
• B It is uninterpretable and a 24-hour collection is always mandatory
• C It confirms nephrotic-range proteinuria
• D It exceeds the threshold of 0.3 mg/mg, equivalent to 300 mg protein per 24 hours ✓

Explanation

A spot urine protein-to-creatinine ratio of 0.3 mg/mg or greater is accepted as equivalent to 300 mg of protein in a 24-hour collection and satisfies the proteinuria criterion for pre-eclampsia. A value of 0.45 therefore exceeds the diagnostic threshold. Nephrotic-range proteinuria requires 3.5 g per day, corresponding to a ratio above 3.0. While a 24-hour collection remains the historical gold standard, guidelines accept the spot ratio precisely to avoid mandatory timed collections, so option B is incorrect.

Reference: Williams Obstetrics, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.