Uric Acid Monitoring Research Articles

Serum uric acid as a surrogate marker of favorable response to bevacizumab treatment in patients with metastatic colon cancer.

Bevacizumab is a monoclonal antibody which is a vascular endothelial growth factor inhibitor. It obscures vascularization of tumor tissue and damages intratumoral microcirculation. The damaged intratumoral microcirculation leads to tissue hypoxia and results in increase of uric acid level. The main aim of our study was to investigate the relationship between uric acid change and response to bevacizumab therapy. This study included a total of 158 patients with metastatic colorectal cancer who had received bevacizumab therapy. The number of male patients was 100 (63.3%) while female patients number was 58 (37.7%). The median age was 61 (29-83). There was relationship between increase of uric acid level of third month uric acid level and stable disease (p<0.001). There was a significant overall survival increased in the group with increased uric acid level (p<0.001). The decline of CEA level was related to uric acid level (p<0.022). In conclusion, this study is the first showing significant increases of serum uric acid in patients with metastatic colorectal cancer who favorably responded to chemotherapy with bevacizumab. But further studies are justified to test whether monitoring uric acid levels might predict clinical outcomes of patients with metastatic colorectal cancer.

Uric acid in Type 2 Diabetes mellitus with nephropathy

Introduction: Uric acid is an important antioxidant that contributes for around 60% of free radical scavenging capacity of serum. Its role has been controversial in type 2 diabetes mellitus. Earlier studies have reported that renal disease leads to elevation of uric acid in DM, but recently high uric acid levels are reported to be risk factor for the development of diabetes mellitus. Aim of our study is to compare uric acid in type 2 DM with renal disease with non-diabetics and also to compare its levels among patients in different stages of diabetic nephropathy. Methodology: The case control study was conducted in medical college hospital in coastal Karnataka. Data of serum uric acid, renal profile and demographic profiles of 89 type 2 diabetes mellitus patients was collected from the clinical biochemistry laboratory in the year 2016. Data of 80 non-diabetic controls was taken. Transasia XL-640 was used for the estimation.Estimated GFR (eGFR) was calculated using MDRD formula. Results: We found an elevation in uric acid and creatinine levels, extremely significantly lower eGFR in diabetics (P = 0.0195, P=0.0078 and P =0.0001respectively).Odd’s ratio was 3.128 between uric acid and diabetic nephropathy. A highly significant (P < 0.0016) differences was observed in uric acid levels among patients of different stages of diabetic nephropathy. Conclusion: Hyperuricemia was found in diabetic nephropathy patients. There was a significant difference in uric acid was observed among different stages of nephropathy. However causal relationship is inclusive. Prospective studies need to be designed with a serial monitoring of uric acid, GFR and microalbunuria in diabetics till the development of nephropathy to establish which the cause is and which is effect among these two factors (uric acid and diabetic nephropathy. Keywords: Uric acid, eGFR, Diabetes mellitus, Nephropathy

Noninvasive Uric acid Monitoring Device using Near-Infrared Spectroscopy

The prevalence of gout in the United States has risen over the last twenty years and gout now affects 8.3 million Americans. Currently, gout is diagnosed either by extracting a fluid sample from the joint to look for formation of uric acid crystals or by drawing blood to measure the level of uric acid. Both of these methods are invasive, cumbersome, and time-consuming. The purpose of this study is to prevent gout attack with a novel approach called noninvasive infrared uric acid monitoring. This approach utilizes a cost-effective and portable near-infrared (NIR) spectroscopybased device that can offer quick, noninvasive, and preventative way to monitor the patient's uric acid level. By using uric acid infrared spectroscopy characteristics, infrared wavelengths between 1400 to 1700nm are emitted on uric acid samples and detector senses non-absorbed Infrared light. The detected NIR signal gets amplified and filtered to maintain a high signal to noise ratio (SNR) over the wavelengths of interest. A linear regression algorithm is used to distinguish and predict the uric acid concentration among other biomarkers in the sample. Finally, a digital signal processing was used to process the data. Based on the Beer-Lambert's law, a linear relationship between the light absorbance and uric acid concentration is expected. Minimum detectable change in uric acid level was analyzed and a mathematical model was compared to the measured data. Another potential benefit of this approach is its versatility. By modifying infrared wavelength and the calibration system in the DSP chip, other biomarkers can be measured.

Evaluation of an electrochemical biosensor for uric acid measurement in human whole blood samples

BackgroundUric acid measurement has become increasingly important, and electrochemically modified detection method based portable devices hold a dominant position in the market for point of care and self-monitoring of uric acid blood levels. However, there has been a lack of detailed performance evaluation of the electrochemical detection devices that are currently being used in professional health care facilities and for home self-monitoring of uric acid. MethodsA commercially available uric acid monitoring system that is chemically modified to reduce interference was evaluated via clinical evaluation for its performance and interference as compared to a centralized laboratory instrument. ResultsPrecision was within ±3.1% for 3 levels of control solutions and whole blood samples. A range from 30 to 55% was acceptable for the measurement of hematocrit levels in whole blood samples. There was no interference for the potential substances at their high therapeutic levels. Hemolyzed samples of up to 75g/l showed no interference with test results obtained by the BeneCheck system, while a −45.9% bias% was obtained during testing of the same samples by a spectrophotometer. Clinical evaluation showed that >95% of tests were within ±20% bias% compared to a centralized instrument in hospitals. ConclusionThe uric acid monitoring system was suitable for use in monitoring or screening uric acid concentration for home users or professionals.

Association between serum uric acid level and microalbuminuria to chronic vascular complications in Thai patients with type 2 diabetes

AimsTo investigate an association between serum uric acid/microalbuminuria and chronic micro/macro-vascular complications in type 2 diabetic patients. MethodsThis cross-sectional study enrolled 608 patients with type 2 diabetes. All subjects were examined and basic information on health of the subjects was recorded for inclusion criteria. Several chemical parameters (fasting plasma glucose, triglyceride, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, uric acid, and microalbuminuria), and related chronic vascular complications were measured and recorded in data forms. ResultsLogistic regressions were used to analyse odds ratios between uric acid/microalbuminuria levels and several chronic vascular complications. Prevalence of chronic vascular complications in T2DM patients, namely coronary arterial disease, cerebrovascular disease, diabetic nephropathy, diabetic retinopathy, and diabetic peripheral neuropathy was significantly correlated with increase of uric acid level [2.29 (1.01–5.2), 16.01 (4.74–54.09), 9.99 (4.4–22.8), 4.43 (1.3–15.1), 4.37 (1.5–12.9)], and of microalbuminuria level [7.0 (3.6–13.8), 3.2 (1.2–8.7), NA, 14.7 (5.1–42.7), 7.2 (2.9–17.7)]. ConclusionBoth elevated uric acid and microalbuminuria levels were significantly associated with diabetic chronic micro/macro-vascular complications. Monitoring of uric acid and microalbuminuria levels provides a predictive value for a presence of chronic micro/macro-vascular complications in patients with type 2 diabetes.

Laser patterned carbon–polyethylene mesh electrodes for wound diagnostics

Carbon loaded polyethylene films were selected as the base substrate for a mechanically flexible and conductive sensing material for use wound monitoring technologies. The films were processed using laser ablation of the surface to increase the effective surface area of the electrode and then subject to an oxidative electrochemical etch to improve the electron transfer kinetics. The surface morphology of the resulting films was analysed and the electrode performance in relation to monitoring uric acid, a key wound biomarker, was optimized. A prototype smart bandage was designed, based on interfacing the mesh to a portable potentiostat, and the response to urate and potential interferences assessed.

Carbon Fibre Composites: Integrated Electrochemical Sensors for Wound Management

The applicability of employing a carbon fibre mesh as an electrochemical sensing substructure for assessing urate transformations within wound exudates is evaluated. Prototype sensor assemblies have been designed and their response characteristics towards uric acid and other common physiological components are detailed. Modification of the carbon fibre sensor through surface anodization and the application of cellulose acetate permselective barriers have been shown to lead to optimized responses and much greater sensitivity (1440% increase) and specificity. These could enable the accurate periodic monitoring of uric acid in wound fluid. The performance characteristics of the composite sensors in whole blood, serum and blister fluid have been investigated.

Integrated urate sensors for detecting wound infection

The applicability of employing a carbon fibre mesh as the sensing element within a “smart bandage” for assessing urate transformations within wound exudates is evaluated and a novel strategy for the detection of bacterial contamination presented. Prototype sensor assemblies have been designed and their response characteristics towards the periodic monitoring of uric acid within whole blood, serum, blister fluid and microbial culture has been evaluated. The rapid and selective metabolism of urate by Pseudomonas aeruginosa, the bacteria responsible for most adventitious wound infections, has been investigated. A preliminary evaluation of the efficacy of utilizing the microbial response to endogenous wound urate as means of detecting the onset of infection is presented.

Determination of uric acid and p-aminohippuric acid in human saliva and urine using capillary electrophoresis with electrochemical detection : Potential application in fast diagnosis of renal disease

The monitoring of uric acid (UA) and p-aminohippuric acid (PAH) levels in biological samples is routinely carried out in clinical laboratories as an indication of renal disease. With the aim of investigation of the correlation between the trace amounts of UA and PAH in human saliva or urine and renal diseases, we carried out the determination of UA and PAH in human saliva and urine by using capillary electrophoresis with electrochemical detection (CE-ED) in this work. Under the optimum conditions, UA, PAH and three coexisting analytes could be well separated within 21 min at the separation voltage of 14 kV in 80 mmol/L borax running buffer (pH 9.2). Good linear relationship was established between peak current and concentration of analytes over two orders of magnitude with detection limits ( S/ N = 3) ranged from 5.01 × 10 −7 to 2.00 × 10 −6 mol/L for all analytes. The result shows that this proposed method could be successfully applied for the study on the correlation between the levels of UA and PAH in human saliva and urine and renal diseases, and provide an alternative and convenient method for the fast diagnosis of renal disease.

A disposable single-use electrochemical sensor for the detection of uric acid in human whole blood

We report here a non-enzymatic detecting electrode strip for fast monitoring of uric acid in human whole blood. A single-use amperometric uric acid sensor strip, incorporating a three-electrode configuration, has been fabricated on a polypropylene substrate using low cost screen-printing (thick-film) technology. Both the working and counter electrodes were prepared by screen-printing commercial carbon ink. The integration on the same support of pseudo-reference electrode was obtained by screen-printing a commercial silver ink and subsequent electrochemical pretreatment. Simply by placing a 20 μl human whole blood drop on the strip is enough for uric acid analysis by square-wave voltammetry. Real human whole blood samples were analyzed by this method and compared to the phosphotungstic acid clinical test procedure with satisfactory results.

An evaluation of clinical accuracy of the EasyTouch blood uric acid self-monitoring system

Objectives: Self-monitoring blood uric acid device is an important tool for patients to efficiently monitor their blood uric acid concentrations. The objective of the present study was to evaluate the accuracy of EasyTouch uric acid monitoring system. Design and methods: Capillary blood uric acid concentrations measured using EasyTouch and the reference values obtained from COBAS MIRA were performed in the Department of Laboratory Medicine, Wei-Gong Memorial Hospital. Results were evaluated using (1) linear regression analysis, (2) percentage of readings within a defined range of deviation from the reference value, and (3) coefficients of variation (CVs) calculated from 60 measurements in series. Results: The window of the 177 EasyTouch readings covered a wide range from 0.1785 to 0.6367 mmol/L (3–10.7 mg/dL). Linear regression analysis yielded a regression slope of 0.975, an intercept of 0.0118 mmol/L and an R 2 of 0.8966. Of the EasyTouch readings, 64 (36.2%), 61 (34.5%), 34 (19.2%), 9 (5.08%), and 9 (5.08%) were within the intervals of <5%, 5–10%, 10–15%, 15–17%, and >17%, respectively, of the reference values. Further analysis for the performance of each lot of strips showed that both coefficients of correlation and the percentages of readings within the CLIA's criterion (±17%), respectively, were in a narrow range from 0.8777 to 0.9541 and from 92.1% to 100%. The CVs for the seven lots of strips (lot 1 to lot 7) ranged from 2.93% to 6.33%, 3.2% to 5.9%, 3.64% to 7.0%, 2.84% to 7.6%, 2.68% to 5.42%, 3.03% to 6.93%, and 3.18% to 5.17%, respectively. Conclusion: EasyTouch is an acceptable diagnostic device which provides accurate uric acid measurements.

Microdialysis sampling and monitoring of uric acid in vivo by a chemiluminescence reaction and an enzyme on immobilized chitosan support membrane

A new detection system based on microdialysis sampling and chemiluminescence (CL) reaction was developed for in vivo monitoring of uric acid (UA) with high sensitivity, selectivity and accuracy. The uric acid is indirectly monitored by CL detection of enzymatic reaction product formation (H 2O 2), catalyzed by Uricase. A microprobe was modified and coated with immobilized enzyme through a Streptavidin–biotin mediated linker by using a chitosan support membrane, polyurethane trapped ferrocene film is employed to protect the probe surface and diminish the interference from reductant molecules, which often are present in the blood (e.g. ascorbic acid). The earlier mentioned probe and the constructed sensor can detect uric acid in the range of 0.01–1 mM with detection limit (3 σ) of 5 μM. Finally, the system is used to monitor uric acid (UA) variation through an acute myocardial infarction (AMI) model. Following AMI-induced oxidative stress, the UA level decreases continuously, thus suggesting that UA plays a protective role as a substitute antioxidant. Furthermore, the in vivo monitoring results show good agreement with those obtained by a standard method, and the procedure is recommended for in vivo and real time monitoring of UA. In addition, the proposed method can be more accurate since the UA may be potentially oxidized by in vitro exposure to oxygen in the presence of a catalyst.

Miniaturized graphite sensors doped with metal-bathophenanthroline complexes for the selective potentiometric determination of uric acid in biological fluids.

Miniaturized poly(vinyl chloride) matrix membrane sensors in an all-solid-state graphite support, responsive to urate anion, were developed. The membranes incorporate lipophilic ion-pair complexes of urate anion with ruthenium(III), iron(II), nickel(II) and copper(I) bathophenanthroline (4,7-diphenyl-1,10-phenanthroline) counter cations. The sensors demonstrate a near-Nernstian response to urate over the concentration range 1 x 10(-2)-1 x 10(-5) mol l-1 and have micromolar detection limits and good selectivity properties. The response is virtually unaffected by pH changes in the range 7-10 and the response times are 5-10 s in aqueous solutions and in human serum and urine samples. A flow injection detector incorporating an iron(II) bathophenanthroline-urate graphite sensor was used for continuous monitoring of uric acid. The minimum detectable concentration was approximately 8 micrograms ml-1 and the sample throughput was approximately 120 h-1. Direct potentiometric determination of uric acid in the static and hydrodynamic modes of operation over the range 15 micrograms ml-1-1.5 mg ml-1 showed average recoveries of 98.7 and 97.8% with RSDs of 0.6 and 0.7%, respectively. Application of the method to the determination of uric acid in human serum and urine gave results that compared favourably with those obtained by the standard spectrophotometric method.

Bi-enzyme reactor for electrochemical detection of low concentrations of uric acid and glucose

An enzyme-based flow-injection amperometric analysis system (FIA) for monitoring of uric acid and glucose is described. The oxidase and peroxidase enzymes are physically coimmobilised in a sandwich-type reactor and ferrocene serves as a mediator. The assays are based on the measurement of a reduction current resulting from the enzymatic reactions, at a glassy carbon electrode held at 0.00 mV (vs. Ag/AgCl). The high selectivity (ascorbic acid did not interfere) is coupled to high sensitivity (a detection limit of 30 and 60 nmol/l for uric acid and glucose, respectively; signal/noise = 3) and good stability (the enzymes remained active for more than 6 weeks at 30(C). The usefulness of the assay in clinical chemistry is illustrated by the measurement of human serum uric acid and glucose concentration. The results obtained were in fairly good agreement with those obtained using conventional hospital laboratory methods.