Question

• How useful are C-reactive protein (CRP) and procalcitonin in predicting pyelonephritis in children suspected of having a UTI?

Clinical Bottom Lines

1. CRP is less specific than procalcitonin in predicting pyelonephritis in children.
2. Procalcitonin is a useful marker for pyelonephritis in children but is not available at our institution.
3. Clinical diagnosis of pyelonephritis remains the gold standard.

Summary of Key Evidence

1. CRP was 100% sensitive and 26% specific for pyelonephritis.  The positive likelihood ratio (LR) for CRP is only 1.19 whereas the LR(-) is 0.
2. Procalcitonin was 70% sensitive and 83% specific for pyelonephritis.  The LR(+) for procalcitonin is 4.12 and the LR(-) is 0.36
3. For a positive test, procalcitonin increases the pre- to post-test probability of pyelonephritis more than CRP does.  However, to rule out pyelonephritis, a negative CRP is the most helpful.

Additional Comments

• Because of the low LR(-) for CRP, a negative test is useful in deciding whether to stop IV antibiotics once they have been started.
• DMSA scanning and procalcitonin are not readily available as screening diagnostic tools.
• Clinical suspicion of pyelonephritis based on pain, fever, and clinical appearance remain most useful.

Citation

1. Benador N, et al.  Procalcitonin is a Marker of Severity of Renal Lesions in Pyelonephritis.  Pediatrics. 102(6):1422-1425, 1998.
2. Stokland E, et al.  Early ^99mTc Dimercaptosuccinic Acid (DMSA) Scintigraphy in Symptomatic First-time Urinary Tract Infection.  Acta Paediatr. 85:430-436, 1996.
3. Monneret G, et al.  Procalcitonin and C-reactive Protein Levels in Neonatal Infections.  Acta Paediatr. 86:209-212, 1997.
4. Benador D, et al.  Cortical Scintigraphy in the Evaluation of Renal Parenchymal Changes in Children with Pyelonephritis.  J Pediatrics. 124:14-20, 1994.
5. Rushton HG.  The Evaluation of Acute Pyelonephritis and Renal Scarring with Technetium 99m-dimercaptosuccinic Acid Renal Scintigraphy:  Evolving concepts and Future Directions.  Pediatric Nephrol. 11:108-120, 1997.

CAT Author: Donna M. Martin, MD

CAT Appraisers: John Frohna, MD

Date appraised: May 10, 1999