Diagnostic efficiency and quality indexes of several markers of renal function for detecting the loss of parenchyma in paediatric patients.
BACKGROUND
We analysed a large sample of children diagnosed with urinary tract malformations and/or infections and calculated diagnostic efficiency and quality indexes for five different functional markers, with the goal of testing which is the most sensitive for detecting a loss of renal parenchyma.


METHODS
Ours was a cross-sectional retrospective study in which the clinical histories of 179 paediatric patients (91 male and 88 female) were evaluated. In 102 of these patients (57%), a scintigraphy revealed loss of parenchyma. The most commonly observed morphological type of damage was renal scarring. All patients had undergone at least one desmopressin urine concentration test. We also analysed albumin/creatinine and N-acetyl-glucosaminidase (NAG)/creatinine ratios, glomerular filtration rate (GFR), and urine volume.


RESULTS
By distributing patients according to normal/abnormal scintigraphy, we observed statistically significant differences between the two groups in maximum urine osmolality and GFR. Urine volume was elevated in 31.3% of cases (sensitivity: 37.9%; specificity: 81.8%) and 24% had a defect in renal concentrating ability (sensitivity: 30.4%; specificity: 84.8%). Urinary albumin excretion was high in 12.2% of patients, and 7.2% had a high NAG/creatinine ratio. GFR was low in only 5.7% of patients. These last two markers were the least sensitive but most specific for detecting a loss of renal parenchyma (100%).


CONCLUSIONS
In our study, the most sensitive functional tests for detecting the loss of renal parenchyma were the two that take into account the ability of the kidney to manage water, i.e. urine volume and maximum urine osmolality. These two tests had specificity >80%. However, the maximum specificity was obtained by the NAG/creatinine ratio and GFR, which were, conversely, the least sensitive tests. A normal GFR does not necessarily show normal renal function.
Sección de Nefrología Pediátrica, Hospital Universitario Nuestra Señora de Candelaria, Carretera del Rosario, 145. 38010 Santa Cruz de Tenerife, Spain. vgarcianieto@gmail.com
Víctor M
VM
García-Nieto
María
M
Afonso-Coderch
Victoria E
VE
García-Rodríguez
Margarita
M
Monge-Zamorano
M José
MJ
Hernández-González
M Isabel
MI
Luis-Yanes
D000118:Acetylglucosaminidase / Q000652:urine; D000293:Adolescent; D000419:Albuminuria / Q000209:etiology / Q000652:urine; D001284:Atrophy / Q000175:diagnosis; D015415:Biomarkers / Q000652:urine*; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood / Q000652:urine; D003430:Cross-Sectional Studies; D003894:Deamino Arginine Vasopressin; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007223:Infant; D007668:Kidney / Q000000981:diagnostic imaging / Q000473:pathology*; D007671:Kidney Concentrating Ability; D008297:Male; D009994:Osmolar Concentration; D011877:Radionuclide Imaging; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014552:Urinary Tract Infections / Q000000981:diagnostic imaging / Q000473:pathology / Q000652:urine*; D014564:Urogenital Abnormalities / Q000000981:diagnostic imaging / Q000473:pathology / Q000652:urine*; D014718:Vesico-Ureteral Reflux / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology / Q000652:urine
D015415:Biomarkers; D003404:Creatinine; D000118:Acetylglucosaminidase; D003894:Deamino Arginine Vasopressin