A rapid urine creatinine assay by capillary zone electrophoresis

Determination of creatinine in urine and blood serum human samples by CZE-UV using on-column internal standard injection

Creatinine is a well-stablished biomarker for kidney malfunctions and for normalization parameter of urinary quantitative information. Recently, metabolic studies have been discovering other functionalities for creatinine tests in human urine and blood serum. In this work we present an enhanced capillary electrophoresis (CE) based protocol for determination of creatinine. CE is a high-throughput separation technique that have been getting attention through the last decades and might be considered to be adopted as an analytical instrumentation for clinical purposes. In the proposed method, we performed a short injection program with on-column addition of internal standard. Additionally, the method allows a simultaneous screening of non-proteinogenic amino acids that could be considered for metabolomics purposes. We design a pilot study that successfully estimated the creatinine value in 100 urine samples with (2.85 ± 1.78) mg dL^-1 LOD; (8.24 ± 5.93) mg dL^-1 LOQ and 82.4% accuracy. Considering that serum creatinine is also included in the clinical laboratory routines for estimated Glomerular Filtration Rate dosage, the method was complementary applied to 10 blood serum samples, which resulted in a model with (0.4 ± 0.2) mg dL^-1 LOD; (2.0 ± 0.6) mg dL^-1 LOQ and 83.8% of accuracy. All results were in agreement with reference values. The proposed method promotes a great analytical frequency and reproducibility with enhanced specificity compared with the ongoing protocol by Jaffe's reaction, thereby proving to be useful as an alternative for creatinine exams that might help complete a diagnosis of a series of health-related issues.

Fluorescence photobleaching of urine for improved signal to noise ratio of the Raman signal - An exploratory study

Urine analysis is an important clinical test routinely performed in pathology labs for disease diagnosis and prognosis. In recent years, near-infrared Raman spectroscopy has drawn considerable attention for urine analysis as it can provide rapid, reliable, and reagent-free analysis of urine samples. However, one important practical problem encountered in such Raman measurements is the orders of magnitude stronger spectral background preventing one to utilize the full dynamic range of the detector which is required for the measurement of Raman signal with good signal-to-noise ratio (SNR). We report here the results of an exploratory study carried out on human urine samples to show that the photobleaching, which is a major disadvantage during the fluorescence measurement, could be utilized for suppressing the measured background to improve the SNR of the Raman peaks. It was found that once the photobleaching reached its plateau, there were improvements by ~67% and ~47% in the SNR and the signal to background ratio (SBR), respectively, of the Raman signals as compared to the spectra measured at the start of acquisition. Further, the reduced background also allowed us to utilize the full dynamic range of the detector at increased integration time without saturating the detector indicating the possibility of obtaining an improved detection limit.

Microfluidic chip-capillary electrophoresis device for the determination of urinary metabolites and proteins

Microfluidic chip-CE (MC-CE) devices have caught recent attention for diagnostic applications in urine. This is due to the successes reported in handling real urine samples by integrating microfluidic chips (MC) with analyte enrichment and sample cleanup to CE with high separation efficiency and sensitive analyte detection. Here, we review the determination of urinary metabolites and proteins by MC-CE devices within the past 7 years. The application scope for MC-CE integrated devices was found to exceed the use of either technique alone, showing comparable performance to laser-induced fluorescence detection using less sensitive UV detectors, offering the flexibility to handle difficult urine samples with on-chip dilution and online standard addition and delivering enhanced performance as compared with commercial microfluidic chip electrophoresis chips.

Two low-cost digital camera-based platforms for quantitative creatinine analysis in urine

In clinical analysis creatinine is a routine biomarker for the assessment of renal and muscular dysfunctions. Although several techniques have been proposed for a fast and accurate quantification of creatinine in human serum or urine, most of them require expensive or complex apparatus, advanced sample preparation or skilled operators. To circumvent these issues, we propose two home-made platforms based on a CD Spectroscope (CDS) and Computer Screen Photo-assisted Technique (CSPT) for the rapid assessment of creatinine level in human urine. Both systems display a linear range (r(2) = 0.9967 and 0.9972, respectively) from 160 μmol L(-1) to 1.6 mmol L(-1) for standard creatinine solutions (n = 15) with respective detection limits of 89 μmol L(-1) and 111 μmol L(-1). Good repeatability was observed for intra-day (1.7-2.9%) and inter-day (3.6-6.5%) measurements evaluated on three consecutive days. The performance of CDS and CSPT was also validated in real human urine samples (n = 26) using capillary electrophoresis data as reference. Corresponding Partial Least-Squares (PLS) regression models provided for mean relative errors below 10% in creatinine quantification.

Point of care creatinine measurement for diagnosis of renal disease using a disposable microchip

A point-of-care device for the determination of elevated creatinine levels in blood is reported. This device potentially offers a new and simple clinical regime for the determination of creatinine that will give huge time savings and removal of several steps of determination. The test employs a disposable prefilled microchip and the handheld Medimate Multireader®. By optimizing the analytical conditions it was found that the LOD of the proposed method was 87 μM creatinine, close to the normal human serum levels that are in the range of 60 to 100 μM. A statistical analysis of the residual shows a normal distribution, indicating the absence of systematic errors in the proposed method. The test can be used to distinguish patients with renal insufficiency (creatinine levels >100 μM) from healthy persons. Long-term monitoring could furthermore distinguish between acute renal failure and chronic kidney disease by the rate of creatinine concentration rise.

Quantification of creatinine in biological samples based on the pseudoenzyme activity of copper-creatinine complex

Glomerular filtration rate (GFR), the marker of chronic kidney disease can be analyzed by the concentration of cystatin C or creatinine and its clearance in human urine and serum samples. The determination of cystatin C alone as an indicator of GFR does not provide high accuracy, and is more expensive, thus measurement of creatinine has an important role in estimating GFR. We have made an attempt to quantify creatinine based on its pseudoenzyme activity of creatinine in the presence of copper. Creatinine in the presence of copper oxidizes paraphenylenediamine dihydrochloride (PPDD) which couples with dimethylamino benzoicacid (DMAB) giving green colored chromogenic product with maximum absorbance at 710 nm. Kinetic parameters relating this reaction were evaluated. Analytical curves of creatinine by fixed time and rate methods were linear at 8.8-530 μmol L(-1) and 0.221-2.65 mmol L(-1), respectively. Recovery of creatinine varied from 97.8 to 107.8%. Limit of detection and limit of quantification were 2.55 and 8.52 μmol L(-1) respectively whereas Sandell's sensitivity and molar absorption coefficient values were 0.0407 μg cm(-2) and 0.1427×10(4) L mol(-1) cm(-1) respectively. Precision studies showed that within day imprecision was 0.745-1.26% and day-to-day imprecision was 1.55-3.65%. The proposed method was applied to human urine and serum samples and results were validated in accordance with modified Jaffe's procedure. Wide linearity ranges with good recovery, less tolerance from excipients and application of the method to serum and urine samples are the claims which ascertain much advantage to this method.

LC-MS-MS Measurements of Urinary Creatinine and the Application of Creatinine Normalization Technique on Cotinine in Smokers' 24 Hour Urine

A simple and sensitive high performance liquid chromatography-tandem mass spectrometry (HPLC-ESI-MS-MS) method was developed and validated for the quantification of creatinine in human urine. The analysis was carried out on an Agilent Zorbax Eclipse XDB-C18 column (2.1 × 150 mm, 3.5 μm). The mobile phase was 0.1% formic acid in water and 0.1% formic acid in acetonitrile (50/50, v/v). Linear calibration curves were obtained in the concentration range of 1-2000.0 ng/mL, with a lower limit of quantification of 0.99 ng/mL. The intra- and interday precision (RSD) values were below 3%. The method was successfully applied to a bioequivalence study of creatinine in Chinese smokers and nonsmokers. The total cotinine in 24 h urine and cotinine : creatinine ratio were also positively associated (Pearson R = 0.942, P < 0.0001). However, cotinine : creatinine ratio varied significantly across smoking groups for the difference of individual. 24 h urinary cotinine was more appropriate for expressing correlation with tar than cotinine : creatinine ratio.

Assay for the simultaneous determination of guanidinoacetic acid, creatinine and creatine in plasma and urine by capillary electrophoresis UV-detection

Guanidinoacetic acid (GAA) measurement has recently become of great interest for the diagnosis of creatine (Cn) metabolism disorders, and research calls for rapid and inexpensive methods for its detection in plasma and urine in order to assess a large number of patients. We propose a new assay for the measurement of GAA by a simple CZE UV-detection without previous sample derivatization. Plasma samples were filtered by Microcon-10 microconcentrators and directly injected into the capillary, while for urine specimens a simple water dilution before injection was needed. A baseline separation was obtained in less than 8 min using a 60.2 cm x 75 microm uncoated silica capillary, 75 mmol/L Tris-phosphate buffer pH 2.25 at 15 degrees C. The performance of the developed method was assessed by measuring plasma creatinine and Cn in 32 normal subjects and comparing the data obtained by the new method with those found with the previous CE assay. Our new method seems to be an inexpensive, fast and specific tool to assess a large number of patients both in clinical and in research laboratories.

Effect of prolonged physical exercise on urinary proANP1-30 and proANP31-67

Dynamic exercise strongly affects atrial natriuretic peptides (ANP), in particular the mature bioactive alphaANP and the proANP fragments, namely proANP1-98, proANP1-30 and proANP31-67. The proANPs influence kidney functions and their plasma levels increase after physical exercise. We measured urinary proANP1-30 and proANP31-67 levels before and at the end of physical exercise in 28 well-trained male cyclists. For the first time, the proANP1-30 and proANP31-67 urinary levels in athletes before and at the end of a prolonged agonistic bicycle race were measured. Urinary creatinine and total proteins were also measured. The urinary proANP31-67, creatinine and total protein levels were significantly higher at the end of exercise than before. In contrast, proANP1-30/protein and proANP31-67/protein ratios decreased after exercise. Even proANP1-30/creatinine and proANP31-67/creatinine ratios were lower after exercise. A significant correlation between proANP1-30 and proANP31-67 urinary levels at the end of exercise was found. The proANP31-67/creatinine ratio before and after exercise also showed a significant correlation. The variation of urinary proANP fragments confirmed their possible role in physical exercise. In particular, it could be interpreted as a response of the body or kidney to renal impairment occurring during exercise.

Capillary electrophoretic determination of triamterene, methotrexate, and creatinine in human urine

A capillary zone electrophoresis (CZE) method using a fused-silica capillary (60.2 cm x 75 microm ID) was investigated for the determination of triamterene (TRI), methotrexate (MTX), and creatinine (CREA) in human urine. The separation was performed using a hydrodynamic injection time of 7 s (0.5 psi), a voltage of 25 kV, a capillary temperature of 30 degrees C, and 40 mM phosphoric acid adjusted to pH 2.25 by addition of triethanolamine as separation electrolyte. Under these conditions, analysis takes about 15 min. A linear response over the 0.5-15.0 mg L(-1) concentration range was found for TRI and MTX, and 0.5-80.0 mg L(-1) for CREA. Dilution of the sample (water:urine, 1:1 for TRI and MTX, and 1:25 for CREA determination) was the only step necessary prior to analysis by electrophoresis. The developed method is easy, rapid, and sensitive and has been applied to determine triamterene,methotrexate, and creatinine in urine samples with satisfactory results.

Determination of creatinine in urine by tandem mass spectrometry

BACKGROUND

Electrospray tandem mass spectrometry (TMS) is a very powerful tool that enables one to perform high sample throughput analysis. This paper describes a method to determine creatinine in urine by tandem mass spectrometry with direct sample infusion into an ion source.

METHODS

Samples (50 microl) were diluted with internal standard (IS) (450 microl of 0.667 mmol/l deuterated creatinine). Diluted samples were introduced into mass spectrometer with no prior pretreatment and after purification on ion-exchange 96-column cartridge. Tandem mass spectrometry analyses were performed in selected reaction monitoring mode. Creatinine and creatinine-d(3) were monitored using precursor and product ion settings (m/z 114 to 86 and m/z 117 to 89, respectively). The time of an analysis was 3.015 min. Both TMS methods were compared mutually and with the results obtained by enzymatic and Jaffe method.

RESULTS

Linearity was obtained in the range 0.06-60 mmol/l. Detection limit was 0.2 mumol/l and recoveries were in the range 95.1-98.3% for both the assays with and without ion-exchange column. Results of both assays are in good agreement with those obtained by enzymatic and Jaffe method based on log-transformed Bland-Altman plots. Electrospray tandem mass spectrometry method utilizing both approaches with and without ion-exchange column is acceptable according to CLIA criteria.

CONCLUSION

Tandem mass spectrometry allows rapid, sensitive and selective determination of creatinine in untreated urine.

Micellar electrokinetic chromatographic and capillary zone electrophoretic methods for screening urinary biomarkers of human disorders: a critical review of the state-of-the-art

Human urine plays a central role in clinical diagnostic being one of the most-frequently used body fluid for detection of biological markers. Samples from patients with different diseases display patterns of biomarkers that differ significantly from those obtained from healthy subjects. The availability of fast, reproducible, and easy-to-apply analytical techniques that would allow identification of a large number of these analytes is thus highly desiderable since they may provide detailed information about the progression of a pathological process. From among the variety of methods so far applied for the determination of urinary metabolites, capillary electrophoresis, both in the capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) modes, represents a robust and reliable analytical tool widely used in this area. The aim of the present article is to focus the interest of the reader on recent applications of MEKC and CZE in the field of urinary biomarkers and to discuss advantages and/or limitations of each mode.

Urinary insulin-like growth factor-I measurement in an actual sport competition, an additional approach in laboratory antidoping tests

BACKGROUND

The insulin-like growth factor hormone (IGF-I) is an important protein hormone under investigation with physical exercise and for doping detection. Urinary IGF-I level in fact represents a relevant measurement when the postexercise proteinuria is under analysis. To verify the IGF-I level variation in the circulation and in urinary excretion in the occasion of a competition, the plasma and urine IGF-I in athletes before and after an actual competitive event were measured.

METHODS

Twenty well-trained cyclists took part in a competition (102 km) and concluded the intense physical exercise in approximately 2(1/2) h. Urine and blood samples were collected from each athlete 10-20 min before and at the end of the competition. Plasma and urine total IGF-I (pIGF, uIGF), total urinary proteins (uPr), and creatinine (uCr) concentrations were measured.

RESULTS

The uIGF [from 76.2+/-15.8 to 256.9+/-29.1 ng/l (p<0.001)], uPr [from 29.4+/-6.7 to 325.9+/-95.1 mg/l (p<0.005)], and uCr [from 6.3+/-1.0 to 10.0+/-0.8 mmol/l (p<0.005)] significantly increased. The pIGF was 262.6+/-14.3 and 247.3+/-11.8 microg/l before and end-exercise, respectively. A statistical correlation between uIGF and uPr was demonstrated (p<0.001). The pIGF/uIGF ratio was significantly (p<0.05) decreased comparing the end with before the competition.

CONCLUSIONS

The pIGF/uIGF significantly decreased at the end, compared with before the competition, suggesting a changed uIGF excretion. This increment appeared to be increased, although not significantly, considering the ratio with uCr.

Capillary electrophoresis with laser-induced fluorescence detection for laboratory diagnosis of galactosemia

Galactosemia, a metabolic disorder associated with the intolerance to dietary galactose due to an inherited enzymatic deficiency, is indicated by heightened levels of galactose in urine (galactosuria). In this report, capillary electrophoresis (CE) with laser-induced fluorescence detection was evaluated for its ability to screen urinary carbohydrates, particularly galactose. Neonatal urine samples with normal and abnormal levels of galactose were analyzed with galactose concentrations quantitated relative to urinary creatinine concentrations to account for variable urinary dilution. Analysis of nine samples by CE in a single-blind manner defined four as negative (normal) and five as positive for galactosuria with galactose levels as high as 146.8 +/- 5.9 mM. Galactosuria was correlated with clinical galactosemia diagnoses for four of the positive samples, while the remaining positive was associated with a patient diagnosed with Hurler's syndrome.

High-performance capillary zone electrophoretic assay for markers of diabetic nephropathy in plasma and urine

A new high-performance capillary zone electrophoretic assay for creatine (Cr), creatinine (Cn), urea (U) and uric acid (Ua), markers of human diabetic nephropathy, both in plasma and urine has been developed with UV detection at 200 nm. The plasma sample was deproteinized with trichloroacetic acid and centrifuged at 10 000 rpm for 10 min. The urine sample was diluted 20-fold with buffer before analysis. The optimum separation conditions for the markers was investigated with respect to the concentration of the buffer, the pH, the voltage and the capillary temperature. Baseline separation was achieved in 25 mmol/L phosphate buffer (pH 3.45) using a 21 cm x 75 microm I.D. fused-silica capillary at 40 degrees C with an electric field of 1190 V/cm. The calibration curves showed good linearity in the range 3.5-1000, 0.18-700, 500-5000 and 2-800 microM (r2 min > 0.998) for Cr, Cn, U and Ua, respectively. The proposed method also has a high reproducibility (peak area RSD max < 3%) and has been successfully applied to the determination of clinical samples.

Microfabricated electrophoresis chip for bioassay of renal markers

A novel capillary electrophoresis chip-based detection system for simultaneous measurements of the renal markers creatine, creatinine, p-aminohippuric acid, and uric acid is described. Fluid control is used for mixing the sample with the enzymes creatininase (CA), creatinase (CI), and sarcosine oxidase (SOx) and for separating the neutral hydrogen peroxide end product from the anionic p-aminohippuric and urate species. The 'total' (creatinine and creatine) signal was measured with the running buffer containing all three enzymes, while the creatine signal alone was recorded by mixing the sample with the CI-SOx solution. Creatinine concentrations are measured by comparing the response in the presence and absence of CA. The peroxide product and the oxidizable p-aminohippuric and uric acids are detected electrochemically at a downstream gold-coated thick-film amperometric detector. The four renal markers are readily measured within 5 min, while creatinine/creatine within less than 2 min. Factors influencing the performance, including the level of three enzymes, separation voltage, and detection potential, are optimized. Applicability to urine samples is demonstrated. Such a multianalyte microchip detection device would allow renal function testing to be performed more rapidly, easily, and economically in the point-of-care setting.

Effects of Acute, Heavy-Resistance Exercise on Urinary Peptide Hormone Excretion in Humans

To examine physical exercise-related changes in urinary excretion of protein/peptide hormones and to correlate modifications with the general increase in post-exercise proteinuria, urine C-peptide, insulin and insulin-like growth factor-I (IGF-I) and their plasma concentrations were measured. Plasma and urinary C-peptide, insulin and IGF-I before (Bex) and at the end (Eex) of physical exercise (a 2.5-hour competition, 102 km) were analysed in 20 young cyclists. At Eex compared with Bex, concentration of urinary C-peptide decreased slightly but significantly (21.3 +/- 2.7 vs. 13.5 +/- 1.7 nmol/l), but urinary insulin and urinary IGF-I concentrations significantly increased at Eex (92.5 +/- 4.2 vs. 131.4 +/- 15.7 pmol/l and 10.0 +/- 2.1 vs. 33.6 +/- 3.8 pmol/l, respectively). Plasma insulin and plasma C-peptide significantly decreased, whereas plasma IGF-I was unchanged. Urinary concentrations of total proteins and creatinine significantly increased. Both Eex urinary C-peptide/urinary protein and urinary C-peptide/urinary creatinine ratios were significantly reduced. The correlation between C-peptide and insulin in plasma was confirmed at Bex as well as Eex, but in urine only at Bex. An increased renal tubular reabsorption of C-peptide at the end of exercise might be suggested, but the expected values considering creatinine excretion were almost three times less. The Eex urinary insulin concentration was higher than expected, considering the circulation levels, but lower when compared with the expected concentration considering creatinine excretion. Physical exercise proteinuria, related to an increased protein filtration and a saturation of the mechanisms responsible for the reabsorption, does not appear similar for all peptide hormones.

Urinary insulin-like growth factor I in athletes, before and after physical exercise, and in sedentary subjects

BACKGROUND

Insulin-like growth factor I (IGF-I), like growth hormone (GH), is excreted in urine in a smaller fraction than the concentration found in blood. Exercising subjects undergo post-exercise proteinuria. The present work aims to propose a method for urinary IGF-I analysis (uIGF-I) by defining urinary concentration in sedentary individuals and athletes before and after strenuous exercise.

METHODS

Urine samples were collected from 30 sedentary healthy male individuals during the morning and from 30 well-trained cyclists, before and after a competition of about 3 h (150 km). uIGF-I was measured in undiluted acidified urine by radioimmunoassay (RIA) method using a purified polyclonal rabbit antibody, human 125I-IGF-I and a second anti-rabbit antiserum. The acidification of the urine samples and the excess of IGF-II addition in the incubation medium of the assay were used to dissociate the binding and to block the interference from IGF binding proteins (IGFBPs). Urinary growth hormone (uGH), total protein (utPr) and creatinine (ucr) concentrations were also measured by immunoradiometric assay (IRMA), colorimetric and capillary electrophoresis methods, respectively.

RESULTS

The analysis range was 0-2500 ng/l (0-327 pmol/l), the intra- and inter-assay coefficients of variations (CVs) ranged from 2.3% to 7.8%, respectively. The detection limit was 0.6 pg/tube. The uIGF-I/creatinine (cr) ratio in healthy subjects was 70 +/- 8 pg/mg cr. The uIGF-I/creatinine ratio (pg/mg cr) was different (p<0.001) in athletes before vs. after competition 93 +/- 27 vs. 136 +/- 13. Athletes' [uIGF-I/total proteins] ratio (ng/mg tPr) before and post-exercise was 2.3 +/- 0.5 and 2.5 +/- 0.3, respectively.

CONCLUSIONS

uIGF-I assay appears to be an effective way of monitoring IGF-I excretion. In the cyclists, in the pre-exercise state, uIGF-I was comparable with that measured in sedentary healthy individuals. In the cyclists, after strenuous exercise, the increased uIGF-I/cr and uGH/cr ratios suggested a relation with the post-exercise proteinuria. In conclusion, proteinuria physiologically obtained, such as post-exercise proteinuria, might be a new approach in IGF-I system investigation.

The measurement of insulin-like growth factor-I (IGF-I) concentration in random urine samples

The aim of the present study was to assess a suitable expression of the urinary concentration of a protein/ peptide hormone such as insulin-like growth factor-I (IGF-I), measured in the urine of healthy individuals when the specimen collection is executed randomly. One hundred and twenty male subjects were divided by age into four groups, namely healthy sedentary young (SYA) and older (SOA) adults, older (OC) and young (YC) children. In a single urine specimen, randomly collected during the morning from each individual, total urinary IGF-I was measured by immunoradiometric method, and urinary creatinine (uCr) and total proteins (utPr) were measured by capillary electrophoresis and spectrophotometric methods, respectively. The urinary IGF-I concentrations were not significantly different in all groups investigated and they were (mean +/- SD): 82.7 +/- 82.8 ng/l, 103.5 +/- 83.3 ng/l, 80.4 +/- 64.4 ng/l in OC, SYA and SOA, respectively; only in the YC group there was a tendency to higher values (125.2 +/- 93.2 ng/l) compared with the other groups. utPr ranged from 26 to 40 mg/l and did not demonstrate significant differences between groups. The urinary IGF-I correlated with uCr and utPr, and statistical significance was observed in all measurements. The measurement of urinary IGF-I in random urine and its ratio to utPr is an innovative, useful way of investigation of urinary protein/peptide hormones.

Electrophoretically mediated microanalysis with small molecules: the Jaffé method for creatinine carried out in a capillary tube

An eletrophoretically mediated microanalysis (EMMA) approach, used to perform online chemistry between two small molecules, has been characterized and optimized. The "plug-plug" type EMMA method involved electrophoretic mixing and subsequent reaction of nanoliter plugs of creatinine-containing samples and alkaline picrate (Jaffe reaction) within the confines of the capillary column, which acts as a microreactor. Analyses were performed by pressure injecting a plug of picrate followed by a plug of the creatinine-containing sample. A potential was then applied to electrophoretically mix the two reactants, and an incubation time of up to 6 min allowed the reaction to proceed prior to the application of a 27 kV separation potential with absorbance detection at 485 nm. The use of a 50 microm inner diameter(ID) extended light path capillary (150 microm pathlength) was found to be adequate for determining elevated levels of creatinine in human blood sera, but could not be used to quantify normal levels. Quantification of both normal and elevated levels of creatinine in sera was possible with a 75 microm ID high-sensitivity cell (1200 microm pathlength). Calibration plots using the latter for creatinine in human blood sera spanned the expected clinical range and were linear between 40 microM and 1.2 mM (r2 = 0.996) with an estimated limit of detection of 17 microM (signal-to-noise ratio S/N = 3). A quantitative comparison of results obtained with the reported EMMA method and accepted clinical methodology correlated very well (slope = 1.001).

High-throughput multi-analyte screening for renal disease using capillary electrophoresis

End-state renal disease (ESRD) affects 300000 people in the United States each year. A large percentage of these individuals (approximately 20%) die within the first year after diagnosis. Current methods of determining renal function rely on the measurement of a single marker using slow and frequently non-specific colorimetric methods. In this report, capillary zone electrophoresis was used to perform a multi-analyte assay for markers of renal function in urine. This method tested for creatinine (Cr), creatine (Cn), uric acid (UA), and p-aminohippuric acid (PAH) levels. The limits of detection (S/N=3) were found to be 5 microM for Cr, 0.75 microM for Cn, and 1.5 microM for UA and PAH. Linear ranges were determined to be 5-500 microM for Cr, 0.75-500 microM for Cn, and 1.5-250 microM for UA and PAH. These ranges included the expected concentrations of the markers in human urine after 50-fold dilution. This screening method proved to be a simple and fast way to perform a high throughput analysis for multiple renal function indicators.