Dimercaptosuccinic acid renal scanning and high serum procalcitonin accurately predict vesicoureteral reflux in children with a first febrile urinary tract infection, according to data from two new studies appearing in the January issue of the Journal of Pediatrics.
An accurate predictor of vesicoureteral reflux (VUR) in children with a first febrile urinary tract infection (UTI) could help avoid unnecessary voiding cystourethrographies (VCUGs). Although a VCUG is routinely recommended for all children with a first febrile UTI, it exposes them to radiation, is painful and expensive, has been associated with a risk of iatrogenic UTI, and is often refused by parents.
“Neither [study] can be considered definitive, yet both are exciting work which may well change practice in the future,” Dr. Thomas Welch, chair of pediatrics at the State University of New York, Syracuse, said in an accompanying editorial (J. Pediatr. 2007;150:A3).
The first study was a 10-year retrospective review of 142 children under age 2 years who presented with an initial UTI and underwent both a VCUG and technetium-99m-labeled dimercaptosuccinic acid (DMSA) renal scan at a tertiary care general hospital. There were 77 boys and 65 girls.
Of these, 139 (98%) children had either positive leukocyte esterase or microscopic evidence of pyuria and 3 (2%) did not have pyuria but were positive for nitrite (J. Pediatr. 2007;150:96–9).
Results of DMSA scanning obtained within 2 days after diagnosis indicated that 99 (70%) had findings compatible with acute pyelonephritis and 2 (1.4%) had evidence of previous renal scarring.
VCUG performed 1 month after diagnosis showed evidence of VUR in 42 (29.6%) children. A total of 63 renal units exhibited reflux on VCUG, including 45 with grade I, II, or III reflux, and 18 with grade IV or V.
The sensitivity and specificity of abnormalities on DMSA renal scan for detecting the presence of VUR on VCUG were 88% and 36%, Dr. Min-Hua Tseng and colleagues from the department of pediatrics, Tri-Service General Hospital, National Defense Medical Center, in Taipei, Taiwan, reported. Positive and negative predictive values were 37% and 88%, respectively.
The authors acknowledge the limitations of a retrospective study, including the possibility of selection bias that might have resulted in the extraordinarily high rate of high-grade reflux.
“Nonetheless, we believe that the data indicating that a normal DMSA renal scan [elimates] the need for VCUG in evaluating young children after first UTI is so striking that it is likely real,” they wrote.
The second study was a secondary analysis of prospective hospital-based cohort studies of 398 patients, aged 1 month to 4 years, with a first febrile UTI conducted at eight centers in seven European countries.
Procalcitonin (PCT), a recently identified early marker of bacterial infection, was prospectively measured in serum at admission with the LUMItest PCT immunoluminometric assay or the BRAHMS PCT-Q semiquantitative rapid test (J. Pediatr. 2007;150:89–95).
Their mean age was 13 months. VUR was diagnosed in 101 (25%) children, and it was grade 3 or higher in 46 (12%). The median serum concentration was significantly higher in children with VUR than it was in those without (1.6 ng/mL vs. 0.7 ng/mL) and increased significantly with the VUR grade, Dr. Sandrine Leroy of Saint-Vincent de Paul Hospital and Université Paris Descartes in Paris and associates reported.
High PCT, defined as 0.5 ng/mL or greater, was significantly associated with VUR (odds ratio 2.3). The association remained significant (OR 2.5) in a logistic regression analysis of 368 patients, even after adjusting for such cofactors as family history of uropathy, male gender, young age, urinary tract dilation on ultrasonography, high serum C-reactive protein at admission, and urine collection technique.
A high PCT level predicted VUR with high sensitivity: 75% for all-grade VUR and 100% for grade 4 or 5 VUR. Specificity was 43% regardless of VUR grade.
Even though high PCT did not offer 100% sensitivity for the prediction of all grades of VUR, the authors propose that the current systematic screening strategy for VUR be replaced with a PCT-based selective approach.
“One way to deal with this lack of [PCT] sensitivity is to accept that VUR will remain undiagnosed for some patients after a first febrile UTI. The potential adverse consequences of this practice should be balanced against the debatable efficacy of treatments (secondary antibiotic prophylaxis and surgery) for children with VUR and the possibility that low-grade VUR and even high-grade VUR can spontaneously disappear,” the authors said.
Additionally, a PCT-based approach would reduce overall costs by 30% by averting 38% of routine VCUGs, which cost about $150 per test, compared with about $15 per PCT, the authors concluded.