Yonsei Med J.  2016 Jan;57(1):103-110. 10.3349/ymj.2016.57.1.103.

Prediction of Cortical Defect Using C-Reactive Protein and Urine Sodium to Potassium Ratio in Infants with Febrile Urinary Tract Infection

• Jung SJ
• Lee JH

• KMID: 2466358
• DOI: http://doi.org/10.3349/ymj.2016.57.1.103

Abstract

PURPOSE
We investigated whether C-reactive protein (CRP) levels, urine protein-creatinine ratio (uProt/Cr), and urine electrolytes can be useful for discriminating acute pyelonephritis (APN) from other febrile illnesses or the presence of a cortical defect on 99mTc dimercaptosuccinic acid (DMSA) scanning (true APN) from its absence in infants with febrile urinary tract infection (UTI).
MATERIALS AND METHODS
We examined 150 infants experiencing their first febrile UTI and 100 controls with other febrile illnesses consecutively admitted to our hospital from January 2010 to December 2012. Blood (CRP, electrolytes, Cr) and urine tests [uProt/Cr, electrolytes, and sodium-potassium ratio (uNa/K)] were performed upon admission. All infants with UTI underwent DMSA scans during admission. All data were compared between infants with UTI and controls and between infants with or without a cortical defect on DMSA scans. Using multiple logistic regression analysis, the ability of the parameters to predict true APN was analyzed.
RESULTS
CRP levels and uProt/Cr were significantly higher in infants with true APN than in controls. uNa levels and uNa/K were significantly lower in infants with true APN than in controls. CRP levels and uNa/K were relevant factors for predicting true APN. The method using CRP levels, u-Prot/Cr, u-Na levels, and uNa/K had a sensitivity of 94%, specificity of 65%, positive predictive value of 60%, and negative predictive value of 95% for predicting true APN.
CONCLUSION
We conclude that these parameters are useful for discriminating APN from other febrile illnesses or discriminating true APN in infants with febrile UTI.

Keyword

Pyelonephritis; C-reactive protein; proteinuria; urine sodium-potassium ratio

MeSH Terms

Acute Disease
C-Reactive Protein/*analysis
Case-Control Studies
Fever/microbiology
Humans
Infant
Male
Potassium/*urine
Predictive Value of Tests
Prospective Studies
Proteinuria/diagnosis
Pyelonephritis/*diagnosis/radionuclide imaging
Sensitivity and Specificity
Sodium/*urine
*Technetium Tc 99m Dimercaptosuccinic Acid
Urinary Tract Infections/drug therapy/microbiology/*radionuclide imaging
C-Reactive Protein
Potassium
Sodium
Technetium Tc 99m Dimercaptosuccinic Acid

Figure

• 

  Fig. 1 Receiver operating characteristic curve between C-reactive protein (CRP) and true acute pyelonephritis (APN) (area under the curve=0.836, 95% confidence interval=0.77-0.9, p=0.000) when the value of the state variable was 1.

• 

  Fig. 2 Receiver operating characteristic (ROC) curve between the urine sodium-potassium ratio (uNa/K) and true acute pyelonephritis (APN) (area under the ROC curve=0.698, 95% confidence interval=0.607-0.788, p=0.000) when the value of the state variable was 0.

• 

  Fig. 3 Receiver operating characteristic (ROC) curve between urine sodium (uNa) and true acute pyelonephritis (APN) (area under the ROC curve=0.602, 95% confidence interval=0.51-0.695, p=0.044) when the value of the state variable was 0.

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