Predictive factors for kidney damage in febrile urinary tract infection. Usefulness of procalcitonin, "Beyond the Abstract," by Elena Lucas Sáez

BERKELEY, CA (UroToday.com) - Urinary tract infection (UTI) is one of the most common bacterial infections in children. Lack of symptom specificity in younger patients, frequent association with malformations of the urinary tract, and the possibility of permanent renal damage require multiple complementary tests in daily practice.

There is no consensus in clinical practice protocols and guidelines concerning the complementary examinations that should be carried out following a first episode of febrile UTI, but there is an attempt to find an indicator that limits invasive tests to those patients at greater risk of developing renal scarring. Various molecules have been proposed as possible markers for renal damage. In recent years, the most studied marker was procalcitonin (PCT), due to its rapid and specific response to serious bacterial infections.

The aim of this study was to assess the usefulness of PCT and other analytical (leukocytes, CRP, etc.) and clinical (age, hours of fever, etc.) parameters as indicators of acute and permanent renal damage in children after their first episode of febrile UTI. Our study includes a considerably-sized group with respect to similar studies published to date, with high theoretical possibility of acute scinitgraphic affectation due to analytical alterations presented on admission (leukocyte count above the upper value of the normal range according to age and/or CRP levels > 30mg/l). In addition, a DMSA scan, the gold standard for renal damage diagnosis, was performed on all patients. Ours was a retrospective multicentre study. The statistical study included descriptive, receiver operating characteristic (ROC) curves and multiple logistic regression. In addition, it included a multivariate analysis to independently determine the association between the variables of interest and renal involvement. We included 219 patients, aged between 1 week and 14 years (68% under 1 year). The mean PCT values were significantly higher in patients with acute pyelonephritis with respect to normal acute DMSA (4.8 vs 1.44; p=0.0001), without achieving that significance for late-affected DMSA (6.5 vs 5.05; p=0.6). The area under the ROC curve for PCT was 0.64 (CI 95% 0.55-0.72) for acute renal damage, and 0.62 (CI 95% 0.44-0.80) for permanent damage, with optimum statistical cut-off values of 0.85 and 1.17ng/ml. Multivariate analysis for acute renal damage only found correlation with PCT (Odds Ratio [OR] 1.2 (CI 95% 1.06-1.4, p=0.005), and hours of fever (OR for less than 6 hours of fever 0.4 (CI 95% 0.2-1.02, p=0.05). In patients with renal scarring, PCT showed an OR 1.0 (CI 95% 0.9-1.1, p=0.6). The results of our study demonstrate certain usefulness of PCT for predicting acute renal damage in patients undergoing their first episode of febrile UTI. Although we cannot establish PCT cut-off values, in those patients with low PCT levels, ultrasound normality, and good initial evolution, the performance of acute-phase DMSA could be prevented.

Our study has certain limitations. Firstly, it was a retrospective study. Second, the urine collection method in a significant percentage of cases was via perineal bag and not using a sterile technique, as recommended in the latest clinical practice guidelines. However, having two urine cultures -- with growth of the same bacterium and in significant number, as well as urinalysis with inflammatory signs -- minimises the possibility of false positives. Finally, of the 142 patients with acute-phase DMSA, only 99 late DMSA were performed during the study, since in some cases sufficient time had not elapsed for it to be carried out (5 patients). or the initial scintigraphic affectation was mild and clinical evolution satisfactory (16 patients). Some patients were also lost to follow-up (22 cases, 10% of the sample). Due to this small sample of patients with renal scarring, we were not able to obtain concluding statistical data. PCT and the duration of fever were the only parameters statistically associated with early renal damage. PCT and renal scarring did not reach statistical significance.

Written by:
Lucas-Sáez E, Ferrando-Monleón S, Marín-Serra J, Bou-Monterde R, Fons-Moreno J, Peris-Vidal A, Hervás-Andrés A. 
Departamento de Pediatría, Hospital Manises, Manises, Valencia (Spain).

Reference: Nefrologia. 2014;34(4):451-7.
doi: 10.3265/Nefrologia.pre2014

Predictive factors for kidney damage in febrile urinary tract infection. Usefulness of procalcitonin - Abstract

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