Comparison Of Biochemical Parameters in Urinary Tract Infections
by Banu Ayca (1), Fikret V. Izzettin (1), Özer Pala (2), Christopher J. Destache (3), Sidney J. Stohs (3), Fikriye Uras (4)
(1) Marmara University, Faculty of Pharmacy, Biochemistry Department, Haydarpasa Istanbul, Turkey
(2) Haseki Hospital, Pediatrics Department, Istanbul, Turkey
(3) Creighton University School of Pharmacy & Allied Health Professions, Omaha, NE
(4) Haseki Hospital, Biochemistry Department, Istanbul, Turkey
PURPOSE: The aim of this study was to show the importance of monitoring biochemical parameters in the early detection and prognosis of pediatric urinary tract infection.
METHODS: Twenty-one patients (18 girls, 3 boys) aged between 2.5-14 years were included in this study. Different biochemical parameters both in serum and in 24 hr urine samples including N-actyl-beta-D-glucosaminidase (NAG), b-2 microglobulin (b-2M) and microalbumin were determined before and after treatments.
RESULTS: Urine cultures showed 71.4% E.coli and 13.4% Enterobacter ssp. and P.mirabilis, respectively. NAG concentrations were 3.3 times higher in pediatric UTI patients compared to pediatric control patients p < 0.001. Additionally, b-2M concentrations were 5.3 times higher in pediatric UTI patients compared to pediatric control patients, p < 0.001. Other biochemical parameters were not significantly different in pediatric UTI compared to pediatric control patients.
CONCLUSIONS: Our results indicate NAG and beta-2M are good indicators for early diagnosis and monitoring of pediatric patients with UTIs. Due to the lack of diurnal variations and stability of NAG this parameters is considered as a better indicator than b-2M.
KEY WORDS: N-acetyl-beta-D-glucosaminidase (NAG), beta-2 microglobulin (beta-2M), microalbumin, urinary tract infection (UTI), children, enzymuria.
Urinary tract infections (UTI) are the most frequently seen disease within the urinary system diseases (l). In pediatric infection diseases, the UTI is second in incidence after upper respiratory infections. Pediatric UTI is defined as > 105 CFU/ml bacteria in a clean-catch urine is cultured and presence of white blood cells in the urine (1,2).
The most frequently identified organisms causing UTIs include E. coli, Klebsiella spp. and P. mirabilis (1,2). The early diagnosis of the UTIs requires sensitive and specific laboratory tests. If untreated, UTIs can progress to bacteremia and rarely, shock.
For the first time in 1910, Thomson reported that the incidence of UTI in female children was higher than male and frequently without signs and symptoms (2). A total of 54% of female children in primary and secondary schools suffer at least one UTI before adulthood (l-3).
In the early diagnosis of lower urinary tract infections, the importance of measurement of enzyme activity like N-actyl-beta-D-*glucosaminidase (NAG) and beta-2 microglobulin (beta-2M) was reported in the literature (2,4).
This study investigated the value of monitoring of NAG, beta-2M as well as urine culture in pediatric patients with UTIs.
In this study 21 pediatric patients (18 girls and 3 boys) with UTI were monitored. Patient selection was based on the final diagnosis reached by the attending pediatric specialist in a large hospital in Istanbul. UTI was diagnosed based on established criteria. As a control group, 10 healthy children (5 boys, 5 girls) aged between 4-13 years were chosen for this study.
Biochemical parameters monitored included serum concentrations of blood urea nitrogen (BUN), creatinine, uric acid, glucose, total protein, albumin, cholesterol, triglyceride, calcium, magnesium and inorganic phosphorus were determined using assay kits provided by Abbott Laboratories. Blood samples were collected from all subjects before and after treatment. Serum was obtained by centrifugation of blood samples 2000 rpm for 15 minutes. The results were to compare according to the children references results in Tietz (5).
Additionally, urinary b-NAG (Boehringer-Mannheim); Beta-2-microglobulin (Diagnostic Product Corp.); microalbumin (Behring) were used according to the manufacturers instruction.
Urine samples (24 hour collections) were collected before and after treatments and subjected to analysis for the following parameters: protein, creatinine, N-acetyl-beta-D-glucosaminidase (NAG), b-2 microglobulin (b-2M) and microalbumin. For analysis of NAG and microalbumin urine samples were stored at -200C until analysis could be performed. To urine samples used for analysis of b-2M, 0.1 NaOH was added to make the pH 6-8 and the mixture frozen at -200C until day of the analysis.
In addition to biochemical analysis, urine samples were analyzed microbiologically to determine the presence of any organism(s).
In this study the average age of the patients was (7.7 + 3.7 years), 89.3% were girls and 14.3% were boys. The pediatric patient demographics and urine culture results are shown in Table 1. Organisms cultured out of the urine demonstrated 71.4% was caused by E,.coli, 13.4% Enterobacter ssp. and P.mirabilis, respectively. None of the UTIs were caused by multiple organisms.
Biochemical parameters were within the normal range before and after treatment (data not shown). Table 2 shows the level of NAG, b-2M and microalbumin in the control group (n=10). Table 3 shows the urine level of biochemical parameters including NAG, b-2M and microalbumin. NAG and b-2M showed significant results before and after treatment. NAG concentrations before treatment were elevated compared to control patients without UTI (UTI patient 6.94 + 4.08 and control patients 1.85 + 0.03 U/L; p<0.001). Additionally, NAG was significantly reduced after treatment (before treatment 6.94 + 4.08, after treatment 4.03 + 1.94 U/L; p < 0.05). Beta-2M (b-2M) was also significantly elevated in UTI patients compared to controls (120.23 + 80.2 compared to 21.05 + 4.5 ng/ml; p < 0.001). Treatment also significantly reduced b-2M (before treatment 120.23 + 80.2 after treatment 33.71 + 15.46 ng/ml; p < 0.05). All patients showed WBCs in urinary sedimentation analysis.
Evaluation of the urinary level of enzymes is considered an important test for determining renal function (6,7). Among the enzymes, NAG has played an important role in detecting kidney damage. This enzyme has a high molecular weight and is found in the lysosomes of proximal tubular cells (7). The stability of this enzyme and lack of diurnal variation makes this enzyme important for monitoring purposes.
The importance of increased urinary levels of tubular epithelial cell enzymes, in early diagnosis of tubular damage has been reported in the literature. N-acetyl-beta-D-glucosaminisade (NAG), alanine amino peptidase (AAP), and b-2 microglobulin (b-2M) have been used in the diagnosis of renal proximal tubular damage(8,9). In patients with UTIs before treatment, the level of NAG expressed as U/L or U/g urine creatinine compared to the control group are 3.75 times and 6.5 times higher, respectively. Additionally, the concentrations of b-2M before treatment compared to the control group were 5.59 times and 8.39 times higher when expressed as ng/ml or ng/mg urine creatinine, respectively.
Other biochemical parameters in UTI patients showed no significant changes compared to control patients and this indicated that other biochemical parameters are insufficient for early diagnosis and follow up of UTI patients.
Our results are in according with literature. Dance et al (10) showed an increase of 10-35 times of NAG in urine relative to control in different kidney disease. The NAG level expressed as u/g ratio to creatinine was carried out to prevent any error that might come from changes in urinary flow.
Welwood et al. (11) reported a 10-fold and 40-fold an increase in the level of NAG expressed as u/g urine creatinine relative to control in acute glomerulonephritis (AGN) and nephrotic syndrome (NS), respectively. Tucker et al. (12), also reported an increased in NAG level in acute tubular necrosis and AGN relative to control group. Belli et al. (13) studied 96 patients 1 to 8 years old and considered that NAG excretion could distinguish cystitis from pyelonephritis. Their results demonstrate that urinary NAG levels are elevated in children with pyelonephritis in the presence or absence of urinary tract abnormality.
An increased level of b-2M in 24 hr urine samples is evident in upper urinary tract infection, in shock, where nephrotoxic agents caused tubular necrosis and pyelonephritis were reported in the literature (4,14,15,16). This parameter can play an important role in early diagnosis of these diseases.
Asami et al. (17), showed the early detection of renal tubular disorder and glomerular dysfunction in insulin-dependent diabetes mellitus in children, NAG is more effective than b-2M and microalbumin.
N-acetyl-beta-D-glucosaminidase (NAG), b-2 microglobulin (b-2M) are good indicators for early diagnosis and monitoring of patients with urinary tract infections. Due to the lack of diurnal variations and stability of NAG this parameter is considered as a better indicator than b-2M.
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Table 1. Demographics and Urine Culture Results
of Pediatric Patients with UTIs
F___ 3_____ 11______ E. Coli
F___ 3.5_____8______ P.mirabilis
F___ 4_____ 14______ Enterobacter ssp.
F___ 4_____ 16______ E.Coli
F___ 5_____ 17______ E.Coli
F___ 5_____ 16______ E.Coli
F___ 5_____ 16______ E.Coli
F___ 6_____ 16.5_____Enterobacter ssp.
F___ 7_____ 19______ E.Coli
F___ 7_____ 30______ E.Coli
F___ 8_____ 23.5_____E.Coli
F___ 8_____ 21______ E.Coli
F___ 9.5____23______ E.Coli
F__ 10_____ 25______ E.Coli
F__ 10_____ 26______ E.Coli
F__ 11_____ 34______ P.mirabilis
F__ 12_____ 36______ E.Coli
M__13_____ 48______ E.Coli
M__14_____ 58______ P.mirabilis
M__14_____ 32______ E.Coli