Simplified quantification of urinary protein excretion in children

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J S Elises1, P D Griffiths, M D Hocking

  • 1Department of Nephrology, Children's Hospital, Birmingham, England.

Clinical Nephrology
|October 1, 1988
PubMed

Insights

Early morning urine protein/creatinine ratio (Up/Uc) accurately reflects overnight protein excretion. This cost-effective method is ideal for quantifying proteinuria in patients with kidney disease.

Area of Science:

  • Nephrology
  • Clinical Chemistry
  • Pediatric Nephrology

Background:

  • Accurate proteinuria quantification is crucial for diagnosing and monitoring renal disease.
  • Timed overnight urine collection is the traditional gold standard but is cumbersome.
  • Early morning urine samples offer a potentially simpler alternative.

Purpose of the Study:

  • To evaluate the early morning urine protein/creatinine ratio (Up/Uc) as a reliable substitute for timed overnight urine (ONU) protein excretion.
  • To establish the normal upper limit of Up/Uc in healthy children and adolescents.
  • To compare the utility and cost-effectiveness of Up/Uc versus albumin/creatinine ratio (Ua/Uc).

Main Methods:

  • Correlation analysis between Up/Uc in early morning urine (EMU) and ONU protein excretion rates in 71 patients.
  • Determination of the upper limit of Up/Uc in 377 healthy children and adolescents (aged 3-19) using the Coomassie Blue dye-binding method.
  • Measurement of albumin/creatinine ratios (Ua/Uc) in the same healthy cohort.

Main Results:

  • A strong linear correlation (r = 0.96) was found between EMU Up/Uc and ONU protein excretion.
  • An EMU Up/Uc of 5 mg/mmol corresponds to an ONU rate of 1 mg/h/m².
  • The upper limit of normal for Up/Uc in healthy subjects was established at 20 mg/mmol, and for Ua/Uc at 3 mg/mmol.
  • Day-to-day variations in Up/Uc and Ua/Uc were observed but remained within normal ranges longitudinally.

Conclusions:

  • EMU Up/Uc is a highly accurate, inexpensive, and practical method for quantifying proteinuria in renal disease patients.
  • It simplifies sample handling and avoids the complexities of timed urine collections.
  • While Ua/Uc is useful for microproteinuria studies, EMU Up/Uc is the preferred method for routine clinical practice.

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