Diagnostic potential of urinary enzymes and beta 2-microglobulin in acute urinary tract infection

What is the Diagnostic Accuracy of Novel Urine Biomarkers for Urinary Tract Infection?

Background

Urinary tract infection (UTI) affects half of women at least once in their lifetime. Current diagnosis involves urinary dipstick and urine culture, yet both methods have modest diagnostic accuracy, and cannot support decision-making in patient populations with high prevalence of asymptomatic bacteriuria, such as older adults. Detecting biomarkers of host response in the urine of hosts has the potential to improve diagnosis.

Objectives

To synthesise the evidence of the diagnostic accuracy of novel biomarkers for UTI, and of their ability to differentiate UTI from asymptomatic bacteriuria.

Design

A systematic review.

Data Sources and Methods

We searched MEDLINE, EMBASE, CINAHL and Web of Science for studies of novel biomarkers for the diagnosis of UTI. We excluded studies assessing biomarkers included in urine dipsticks as these have been well described previously. We included studies of adult patients (≥16 years) with a suspected or confirmed urinary tract infection using microscopy and culture as the reference standard. We excluded studies using clinical signs and symptoms, or urine dipstick only as a reference standard. Quality appraisal was performed using QUADAS-2. We summarised our data using point estimates and data accuracy statistics.

Results

We included 37 studies on 4009 adults measuring 66 biomarkers. Study quality was limited by case-control design and study size; only 4 included studies had a prospective cohort design. IL-6 and IL-8 were the most studied biomarkers. We found plausible evidence to suggest that IL-8, IL-6, GRO-a, sTNF-1, sTNF-2 and MCR may benefit from more rigorous evaluation of their potential diagnostic value for UTI.

Conclusions

There is insufficient evidence to recommend the use of any novel biomarker for UTI diagnosis at present. Further evaluation of the more promising candidates, is needed before they can be recommended for clinical use.

Biomarkers in urinary tract infections - which ones are suitable for diagnostics and follow-up?

Introduction: Urinary tract infections (UTIs) are one of the most common infections worldwide. Under special circumstances, clinicians must rely on laboratory findings, which might have a weak predicting value, misguiding the practitioners and leading to incorrect diagnosis and overuse of antibiotics. Therefore, there is an urgent need for reliable biomarkers in UTIs. Methods: We performed a literature search for biomarkers used in UTIs from January 1999 until May 2020. We used "urinary tract infection" and "biomarker" as the main key words in the PubMed, Medline and Cochrane databases. After peer review, we excluded the duplicates and identified the suitable articles, from which we collected the data and divided the available biomarkers into 5 groups: i) conventional markers; ii) promising, thoroughly studied biomarkers; iii) promising biomarkers that need further studies; iv) biomarkers of unknown significance; v) controversial, not useful markers. Results: We found 131 articles, mostly from the paediatric population. Neutrophil gelatinase-associated lipocalin (NGAL) and interleukins (IL) have a leading role in diagnosing and differentiating UTIs based on a lot of observational, comparative trials. Heparin Binding Protein (HBP), Lactoferrin (LF), Heat-Shock Protein-70 (HSP-70), Human Defensin-5 (HD-5), Lipopolysaccharide Binding Protein (LBP) and mass spectrometry studies are promising, but confirming data are lacking. The measurable components of the innate immune system and local host cell response could be appropriate biomarkers, but their significance is currently unknown. Conclusions: Conventional biomarkers for UTIs have low specificity. The use of urinary NGAL and interleukins could improve the sensitivity and specificity of laboratory diagnosis of UTIs.

Detection of PCT and urinary β2 -MG enhances the accuracy for localization diagnosing pediatric urinary tract infection

OBJECTIVE

The purpose of this article was to investigate whether the combination of urinary beta 2 microglobulin (urinary β₂ -MG) and procalcitonin (PCT) diagnosis could enhance the localization diagnostic precision of pediatric urinary tract infection comparing with single diagnosis.

METHODS

A study was conducted in the Nephrology Department of Wuhan women and children's health care centre. This study incorporated 85 participants, including 35 children who were diagnosed as upper urinary tract infection (UUTI) with the symptom of fever and 50 children who conducted lower urinary tract infection (LUTI). Levels of PCT and urinary β₂ -MG in both UUTI and LUTI patients were measured and compared.

RESULTS

The level of PCT and β₂ -MG were both significantly higher in UUTI group compared with in LUTI group. AUC of urinary β₂ -MG ROC (sensitivity of 71.4%, specificity of 90.0%) was significantly smaller than that of PCT ROC (sensitivity of 77.1%, specificity of 96.0%) in the single diagnosis. Although in the combined diagnosis, the sensitivity and specificity increased to 88.6% and 98%, respectively.

CONCLUSIONS

Both PCT and β₂ -MG could be used to localize the UTI. Introducing urinary β₂ -MG into PCT diagnosis could increase the sensitivity and specificity of UTI lesion diagnosis in clinical practice.

Preclinical perspective of urinary biomarkers for the detection of nephrotoxicity: what we know and what we need to know

The assessment of kidney damage is a challenge and must incorporate assessment of the functional capacity of the kidney, as well as a comprehensive understanding of the kidney's role. Multiple parameters have been used for many years to measure renal functionality to assess renal damage. It is astonishing that, beside histopathology, the most common traditional parameters are serum based. However, urine is also used to obtain additional information regarding the health status of the kidneys. Since 2008, several novel urinary protein biomarkers have been qualified by the US FDA and the European Medicines Agency in conjunction with the Predictive Safety Testing Consortium in a specially developed qualification process. Subsequently, the Pharmaceuticals and Medical Devices Agency accepted the qualification of these seven urinary biomarkers. This review will give an overview of the state-of-the-art detection based on urinary biomarkers, which will enhance toxicological research in the future. In addition, the qualification process that leads to acceptance of these biomarkers will be described because of its uniqueness and importance for the field of biomarker research.

The Diagnostic Value of N-Acetyl-β-D-Glucosaminidase and Microalbumin Concentrations in Rheumatoid Arthritis

The purpose of this research was to compare the diagnostic values of laboratory variables, to present quantitative evaluations of the diagnostic sifted test with reference to sensitivity and specificity, the predictive value of the positive and negative test and precision of the test for N-acetyl-β-D-glucosa-minidase (NAG), microalbumin, rheumatoid factor (RF), Creactive protein (CRP), DAS 28 index, in early diagnosis of untreated rheumatoid arthritis (RA), and to define the effect of untreated rheumatoid arthritis on glomerular and tubular function. Using a colorimetric assay for the determination of Nacetyl-β-D-glucosaminidase and an immunoturbidimetric assay for the determination of urinary albumin, the samples of serum and urine have been examined in 70 participants (35 RA who were not treated, 35 healthy controls). RF was defined with the test for agglutination (Latex RF test) in the same participants. Out of 35 examined patients with RA, in 13 we found the presence of NAG enzymuria (sensitivity of the test 37.14%), while microalbuminuria appeared in 4 patients (sensitivity of the test 11.42%). RF appeared in 17 patients (sensitivity of the test 48.57%). Four patients were NAG and RF positive, while 3 patients were microalbuminuria and RF positive. Among 18 RF negative patients, 9 patients were NAG positive, and 1 patient presented with microalbuminuria. Among 17 RF positive RA, the presence of NAG was found in 4 patients, and the presence of microalbuminuria in 3 patients. Among 18 RF negative RA, NAG enzymuria appeared in 9 patients. Microalbuminuria was present in 1 patient. In the healthy control group, 8 patients were NAG positive, 2 patients were positive for microalbuminuria. RF appeared in 2 patients. NAG has higher sensitivity than microalbuminuria in the detection of asymptomatic renal lesions in untreated RA.

Activity and isoenzyme profile of N-acetyl-beta-D-glucosaminidase in urine from workers exposed to cadmium

The urinary excretion of N-acetyl-beta-D-glucosaminidase (U-NAG) and urinary Cadmium (U-Cd) concentration, a measure of the metal load in the body, were evaluated in 28 workers exposed to Cd, to determine the relation between the two parameters. In urine from 22 exposed workers with U-Cd<2 microg/g creatinine (Cr) there was no significant difference in U-NAG value (0.98+/-0.59 U/gCr) compared to non-exposed (0.73+/-0.48 U/gCr). In the six workers with 2 microg/gCr < or =U-Cd<10 microg/gCr the U-NAG (2.32+/-0.61 U/gCr) was statistically (P<0.05) higher than in other workers. In both the U-Cd intervals examined there were no altered values of beta2-microglobulin from urine of exposed workers compared to non-exposed (<0.30 mg/l). The U-NAG isoenzymes were separated by DEAE-cellulose chromatography from urine of non-exposed subjects and exposed workers. The U-NAG isoenzyme profile in urine of non-exposed subjects showed a high percentage (about 95%) of the A (acid) form, a much lower percentage (about 4.5%) of B (basic) form and a negligible percentage (about 0.5%) of I (intermediate) form. In the urine of 22 exposed workers with U-Cd<2 microg/gCr, the percentages of U-NAG isoenzymes were not different from non-exposed. In the urine of six workers with 2 microg/gCr< or =U-Cd<10 microg/gCr the percentage (8.34+/-0.91) of isoenzyme B (U-NAG-B), a marker of lesional enzymuria, was statistically increased (P<0.05) compared to non-exposed (4.42+/-0.56). These results suggest that adopting a biological limit for U-Cd equal to 10 microg/gCr might not be sufficiently protective. The increase in U-NAG-B content at 2 microg/gCr<U-Cd</=10 microg/gCr is probably due to a lesion of the proximal tubule caused by the metal which might follow an induction of the apoptotic process.

Polymorphonuclear elastase as a diagnostic marker of acute pyelonephritis in children

OBJECTIVE

Experimental evidence suggests that neutrophils and their metabolites play an important role in the pathogenesis of pyelonephritis. The aim of this study was to investigate the diagnostic value of polymorphonuclear elastase-a(1)-antitrypsin complex (E-a(1)-Pi) for the detection of acute pyelonephritis in children.

METHODS

Eighty-three patients, 29 boys and 54 girls, 25 days to 14 years of age, with first-time symptomatic urinary tract infection were prospectively studied. Fifty-seven healthy children served as controls. Dimercaptosuccinic acid (DMSA) scan and voiding cystourethrography were performed in all patients. Plasma and urinary E-a(1)-Pi, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), neutrophil count, urinary N-acetyl-beta-glucosaminidase (NAG), N-acetyl-beta-glucosaminidase b (NAG b), and creatinine levels were measured in all patients on admission and 3 days after the introduction of antibiotics. The same markers were also measured in the control subjects.

RESULTS

Planar DMSA scintigraphy demonstrated changes of acute pyelonephritis in 30 of 83 children (group A). It was normal in the remaining 53 children (group B). The sex and age distributions were not significantly different between the 2 groups, as well as between the patients and the control subjects (group C). Nineteen of the 53 children with a normal DMSA had body temperature >/=38 degrees C, whereas all but 4 children with abnormal DMSA had temperature >/=38 degrees C. Therefore, the temperature was significantly different between these 2 groups. The sensitivity and specificity of fever (>/=38 degrees C) as an indicator of renal involvement based on isotopic findings were 86% and 64%, respectively. Given the significant number of the febrile children with normal DMSA scintiscans, group B was subdivided into B(1) with 19 febrile children (14 boys and 5 girls) and B(2) with 34 children whose body temperature was below 38 degrees C (8 boys and 26 girls). The sex and age distribution was significantly different between groups B(1) and B(2). The mean age of group B(1) was.78 years (range: 28 days to 9 years; median:.25 years; standard deviation: 2.1). All but 1 child in this group were younger than 1 year of age. In contrast, in group B(2), there were only 4 infants, the remaining 30 children were older than 2.5 years (mean age: 6 years; median: 7 years; standard deviation: 3.5; range: 34 days to 12 years). The mean duration of fever before hospital admission was 2.8 days for group A and 1.8 days for group B(1). This difference was not statistically significant. Similarly, body temperature was not significantly different between these 2 groups. The distribution of plasma E-a(1)-Pi values was normal in the control subjects. The sensitivity and specificity of plasma E-a(1)-Pi, as an indicator of renal involvement, were 96% and 50%, respectively, taking the 95th percentile of the reference range as a cutoff value. However, considering as a cutoff value the level of 72 microg/dL (95th percentile of group B(2)), its sensitivity and specificity were 74% and 86%, respectively. Plasma E-a(1)-Pi levels were significantly elevated in group A compared with group B and in both groups, the plasma E-a(1)-Pi values were significantly higher than in the control subjects. A significant difference also was noticed between group A and each of the subgroups B(1) and B(2) and also between the subgroups themselves. Plasma E-a(1)-Pi concentrations correlated significantly with neutrophil count in groups A (r =.3), B (r =.4), and B(2) (r =.46), but the correlation was not significant in group B(1.) ESR levels showed, among the different groups, similar differences with those of E-a(1)-Pi values. Unlike E-a(1)-Pi, CRP levels were comparable between groups A and B(1), which both consisted of febrile children. Neutrophil count was not significantly different between subgroups B(1) and B(2). (ABSTRACT TRUNCATED)

Functional parameters and 99mtechnetium-dimercaptosuccinic acid scan in acute pyelonephritis

The diagnostic value of 99mtechnetium-dimercaptosuccinic acid (DMSA) scintigraphy, ultrasonography and renal functional parameters [urine N-acetyl-beta-D-glucosaminidase (NAG)/creatinine and urine albumin/creatinine quotients] in acute pyelonephritis (APN) were studied in 39 children (28 girls, 11 boys, median age 9 months, range 2 weeks to 9.4 years, 28 patients < 1 year, 11 patients > 1 year) with first-time urinary tract infection. Ultrasonography of the urinary tract was performed on admission and together with DMSA scintigraphy (< 10 days from admission). Urine NAG/creatinine and urine albumin/creatinine quotients were measured daily and after 6-8 weeks. Ultrasonography revealed abnormalities in 12 of 39 (31%) patients [11/32 patients (34%) with positive DMSA scintigraphy], while DMSA uptake defects were present in 32 of 39 (82%) patients [21/28 < 1 year (75%), 11/11 > 1 year (100%), P = 0.08]. Urine NAG/creatinine and urine albumin/creatinine quotients were significantly higher in children < 1 year with APN, as well as in non-renal fever controls, than in older children. However, in both age groups the urine NAG/creatinine and urine albumin/creatinine quotients were significantly higher in APN than in non-renal fever. The urine NAG and albumin excretion decreased rapidly after the initiation of antimicrobial therapy and had normalized at 6-8 weeks. The size and grade of the DMSA uptake defect (DMSA score) did not correlate with duration of disease at admission, maximum C-reactive protein or maximum fever. The urine NAG/creatinine quotient in the children < 1 year showed, however, a significant correlation with the DMSA score (r = 0.58, P < 0.05), while no correlation was found in the older children. We conclude that DMSA scintigraphy is a sensitive method to confirm the clinical diagnosis of APN, although a substantial number of infants appear to have normal scans. Early determination of the urine NAG/creatinine and albumin/ creatinine quotients may further improve the diagnostics in the infant.

Determination of urinary N-acetyl-beta-glucosaminidase in patients with hypertension and renal artery stenosis

The purpose of the study was to measure the urinary excretion of N-acetyl-beta-glucosaminidase (U-NAG) in patients suspected of having renovascular hypertension and to compare the enzyme excretion before and after active intervention with operation or percutaneous transluminal renal angioplasty (PTRA). Eighty-one patients with severe, therapy-resistant hypertension were examined with regard to renal artery stenosis (RAS). At least one significant renal artery stenosis was found in 61 patients, whilst the remaining 20 patients were classified as having essential hypertension. Enzyme levels were found to be significantly higher in RAS patients as compared with patients with severe hypertension lacking significant renal artery stenosis, 0.66 (0.41-0.91, median value, 1st and 3rd quartiles) versus 0.35 (0.27-0.54); P < 0.01. Both groups of patients had significantly higher U-NAG values than a healthy reference population (0.2, 0.13-0.27; P < 0.01). Forty of the RAS patients were randomized to surgery or PTRA and followed prospectively for 2 years. After either renal vascular surgery or PTRA a significant rise in U-NAG excretion was observed 7-10 days after treatment. Urinary NAG excretion remained elevated during long-term follow-up. It is suggested that U-NAG should be determined in patients with therapy-resistant hypertension with suspicion of renal artery stenosis.

Elevated urinary beta-hexosaminidase in patients with stroke

Urinary beta-hexosaminidase is a sensitive indicator of renal damage. The urinary excretion of this enzyme was measured in 31 patients with ischaemic stroke in the acute phase and in 126 patients 21-43 weeks after their stroke. Both immediately and after 21-43 weeks the patients showed a similar and a significantly increased level of urinary beta-hexosaminidase. This indicates the presence of renal injury in the stroke patients, which in turn might reflect a generalized vascular disease.

The pathobiology of subclinical pyelonephritis--an experimental evaluation

Clinical studies have demonstrated a poor correlation between localization tests, which are designed to determine the site of urinary tract infection, and symptoms of upper urinary tract infection. One explanation is that microorganisms may be present in the kidney but not initiate an inflammatory response with associated symptoms. An animal model has been developed to obtain quantitative information on the comparative pathobiology of lesion-inducing and non-lesion-inducing infections. In this model, non-manipulated kidneys had acquired a persistent microbial flora within 48 hours of the lower urinary tract becoming infected. This bacterial invasion was not associated with gross or histologic changes within the renal parenchyma, but minor foci of inflammatory cells were seen beneath the epithelium lining the calyces. Ureteric urines from such kidneys contained many leukocytes and high numbers of bacteria. These results showed that the kidneys were infected, rather than colonized, and the term "subclinical" infection was appropriate. Antimicrobial agents were variably successful at eradicating the infection. These experimental observations support the concept of subclinical pyelonephritis and may explain the absence of symptoms in the clinically equivalent situation in humans.

Renal function of children receiving long-term parenteral nutrition

Renal function was assessed in 13 children at a mean (+/- SD) age of 9 +/- 4.9 years who had been receiving total parenteral nutrition for 7.9 +/- 4.1 years. All children had normal blood pressure, urinary sediment, and serum creatinine concentrations (58.3 +/- 1.0 mumol/L). Glomerular filtration rate was measured by plasma clearance of diethylenetriaminepentaacetic acid labeled with indium 111. All 13 children had decreased glomerular filtration rate (65.5 +/- 11.9 ml/min per 1.73 m2; range 49.5 to 83.7). Creatinine clearance was 69.1 +/- 10.9 ml/min per 1.73 m2. No tubular damage, as assessed by beta 2-microglobulinuria, was detectable. Renal ultrasonography showed normal architecture with no evidence of nephrocalcinosis in all subjects. The kidney size was normal in seven children; six had reduced (less than -1 SD) size. No relationship was seen between the true glomerular filtration rate and diagnosis, number of episodes of infections, or antibiotics used. The duration of total parenteral nutrition was inversely correlated with the true glomerular filtration rate (r = -0.66, p less than 0.01). The decrease in glomerular filtration rate was not related to the underlying disease or to the nephrotoxic drugs used; the mechanism was not identified. We conclude that long-term total parenteral nutrition is associated with a decrease in glomerular filtration rate.

N-acetyl-beta-D-glucosaminidase in the localisation of urinary tract infection in patients with spinal cord injury

This study evaluates the pattern of urinary N-acetyl-beta-D-glucosaminidase (NAG) isoenzyme excretion in patients with spinal cord injury (SCI) and its use as a diagnostic tool in localising the site of urinary tract infection (UTI). NAG-B excretion in 27 control SCI patients (mean 207.78 units) was significantly higher than in 10 normal controls (mean 12.6 units) p less than 0.001). The relative isoenzyme distribution as represented by NAG-B/Total NAG percentage is however similar in both groups, 24.27 and 20.38% respectively. NAG-B excretion in 6 SCI patients with upper UTI was not significantly higher than in 12 SCI patients with lower UTI. NAG-B/Total NAG percentage was significantly different between these two groups (35.3% and 24.98% respectively, p less than 0.05). There was no significant difference in NAG-B excretion or NAG-B/Total NAG percentage between control SCI patients and those with lower UTI. The results indicate that there is a non-selective increase in urinary NAG excretion in control SCI patients and those with lower UTI. In SCI patients with upper urinary UTI there is a selective increase in NAG-B excretion. The overlap in enzyme values between the different groups suggests that the test may not be clinically useful in localising the site of UTI.

Association between fever and reduced renal concentrating capacity

The renal concentrating capacity was assessed in 18 adult patients with febrile infections of non-renal origin. Urine osmolatity was determined after overnight fluid deprivation for 10 hours followed by subcutaneous administration of 4 micrograms of desmopressin. All patients had a transient reduction of the concentrating capacity as compared to a subsequent test performed one month later (p less than 0.001). During the febrile disease, 12 of 18 patients could not achieve a maximal urine osmolality above the lower limit (-2 SD) of an age-related reference interval. These results suggest that in febrile patients with bacteriuria, a reduced renal concentrating capacity does not necessarily mean that the infection is localised to the kidneys but may rather be explained by fever per se.

Renal concentration capacity in adult patients with urinary tract infections

The maximal urine concentration capacity was studied in patients with acute pyelonephritis and in patients with clinically diagnosed acute cystitis. In the former group renal concentration ability was reduced in 16 of 22 patients and improved in all but two patients. Among patients with symptoms of acute cystitis 6 of 22 had a concentration capacity below 2 SD of normal values. Several of these patients had raised acute phase proteins and increased their urine osmolality at follow-up indicating that cases of acute pyelonephritis could have been included. It is concluded that the wide overlap between the groups makes the maximal urinary concentration capacity a method of limited value for level diagnosis in acute UTI infection. The test should be reserved for follow-up to reveal permanent renal damage.

Ureteric catheterization in the diagnosis of pyelonephritis--an experimental evaluation

Experimental models of renal infections have been used to determine the accuracy with which the cellular and microbiologic components of ureteric and voided urine reflected the pathologic status of the kidney in pyelonephritis. In acute pyelonephritis, the composition of the ureteric urine reflected the pathologic status of the kidney, although in a few cases ureteric samples were either sterile or cell free. Animals with chronic pyelonephritis in which the lesions were either infected or sterile commonly had sterile ureteric urine. Pyuria, however, was demonstrable in both these situations. In subclinical pyelonephritis, ureteric samples from infected kidneys were variably culture positive, although pyuria was a common observation. Discriminate function analysis based on actual renal status and ureteric data gave an overall correct classification rate of 67% and demonstrated at least 80% agreement in four of the five classification groups.

Enzymuria in workers exposed to inorganic mercury

Urinary excretion of beta-hexosaminidase (NAG = N-acetyl-beta-glucosaminidase) and albumin was examined in 41 chlor-alkali workers exposed to inorganic mercury and 41 age-matched controls. Either U-HG or B-Hg levels for these workers were available dating from the 1960s to the present. Increased U-NAG was seen in workers with a U-Hg today of more than 4 micrograms/mmol creat (about 50 micrograms/l: 35 ug/g creat). Multiple linear regression analysis showed that U-NAG was correlated to U-Hg and integrated dose but not to the present B-Hg level. No albuminuria (detection limit 12.5 mg/l) was found in any of the subjects. In a longitudinal study, no decrease in U-NAG levels was seen in 15 chlor-alkali workers after their vacation (means = 20d). In five workers followed for ten months after a short exposure period, no definite time trend could be seen. The results show that there is a slight effect on renal tubules even at rather low levels of exposure to mercury vapour. The clinical significance of the enzymuria levels found here is, however, debatable.

Association between fever and the antibody response to Tamm-Horsfall protein in urinary tract infection

The usefulness of measuring serum antibodies to Tamm-Horsfall protein (THP) for diagnosing the level of acute urinary tract infections in adult women was evaluated. There was a significant (p less than 0.001) elevation of IgG and IgA anti-THP in pregnant and non-pregnant women with acute pyelonephritis compared to women with acute cystitis. The changes in anti-THP antibody titre among patients with acute pyelonephritis varied considerably, limiting the value of determining such antibodies for diagnostic purposes. Patients with febrile infections of non-renal origin demonstrated an antibody response comparable to the pyelonephritis patients. One explanation for these results could be that fever is associated with transient rental tubular damage, thus exposing THP to the immune system. Polyclonal antibody activation seems less likely since neither an IgM antibody response to THP, nor an increase in antibody titre to poliovirus could be demonstrated.