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Articles by J. C Lieske
Total Records ( 3 ) for J. C Lieske
  J. C Seegmiller , D. R Barnidge , B. E Burns , T. S Larson , J. C Lieske and R. Kumar
 

Background: Urinary albumin excretion is a sensitive diagnostic and prognostic marker for renal disease. Therefore, measurement of urinary albumin must be accurate and precise. We have developed a method to quantify intact urinary albumin with a low limit of quantification (LOQ).

Methods: We constructed an external calibration curve using purified human serum albumin (HSA) added to a charcoal-stripped urine matrix. We then added an internal standard, 15N-labeled recombinant HSA (15NrHSA), to the calibrators, controls, and patient urine samples. The samples were reduced, alkylated, and digested with trypsin. The concentration of albumin in each sample was determined by liquid chromatography–tandem mass spectrometry (LC-MS/MS) and linear regression analysis, in which the relative abundance area ratio of the tryptic peptides 42LVNEVTEFAK51 and 526QTALVELVK534 from albumin and 15NrHSA were referenced to the calibration curve.

Results: The lower limit of quantification was 3.13 mg/L, and the linear dynamic range was 3.13–200 mg/L. Replicate digests from low, medium, and high controls (n = 5) gave intraassay imprecision CVs of 2.8%–11.0% for the peptide 42LVNEVTEFAK51, and 1.9%–12.3% for the 526QTALVELVK534 peptide. Interassay imprecision of the controls for a period of 10 consecutive days (n = 10) yielded CVs of 1.5%–14.8% for the 42LVNEVTEFAK51 peptide, and 6.4%–14.1% for the 526QTALVELVK534 peptide. For the 42LVNEVTEFAK51 peptide, a method comparison between LC-MS/MS and an immunoturbidometric method for 138 patient samples gave an R2 value of 0.97 and a regression line of y = 0.99x + 23.16.

Conclusions: Urinary albumin can be quantified by a protein cleavage LC-MS/MS method using a 15NrHSA internal standard. This method provides improved analytical performance in the clinically relevant range compared to a commercially available immunoturbidometric assay.

  J. C Seegmiller , B. E Burns , A. H Fauq , N Mukhtar , J. C Lieske and T. S. Larson
 

Background: Glomerular filtration rate (GFR) can be determined by measuring renal clearance of the radiocontrast agent iothalamate. Current analytic methods for quantifying iothalamate concentrations in plasma and urine using liquid chromatography or capillary electrophoresis have limitations such as long analysis times and susceptibility to interferences. We developed a liquid chromatography–tandem mass spectrometry (LC-MS/MS) method to overcome these limitations.

Methods: Urine and plasma samples were deproteinized using acetonitrile and centrifugation. The supernatant was diluted in water and analyzed by LC-MS/MS using a water:methanol gradient. We monitored 4 multiple reaction monitoring transitions: m/z 614.8–487.0, 614.8–456.0, 614.8–361.1, and 614.8–177.1. We compared the results to those obtained via our standard capillary electrophoresis (CE-UV) on samples from 53 patients undergoing clinical GFR testing.

Results: Mean recovery was 90%–110% in both urine and plasma matrices. Imprecision was ≤15% for the m/z 614.8–487.0 and 614.8–456.0 transitions over a 10-day period at 1 mg/L. Method comparison for 159 patient samples (53 clearances) provided the following Passing–Bablok regressions: plasma iothalamate LC-MS/MS (y) vs CE-UV (x), y = 0.99x + 0.36; urine iothalamate LC-MS/MS vs CE-UV, y = 1.01x + 0.31; corrected GFR LC-MS/MS vs CE-UV, y = 1.00x + 0.00. Interfering substances prevented accurate iothalamate quantification by CE-UV in 2 patients, whereas these samples could be analyzed by LC-MS/MS.

Conclusions: Iothalamate can be quantified by LC-MS/MS for GFR measurement. This method circumvents potential problems with interfering substances that occasionally confound accurate GFR determinations.

  E. C Lorenz , T. J Vrtiska , J. C Lieske , J. J Dillon , M. D Stegall , X Li , E. J Bergstralh and A. D. Rule
 

Background and objectives: Management of incidental renal artery and kidney abnormalities in patients undergoing computed tomography scans is a clinical challenge because their frequency in healthy subjects has not been precisely estimated. Therefore, the prevalence and management of these abnormalities were determined among a large cohort of potential kidney donors undergoing protocol evaluations.

Design, setting, participants, & measurements: All patients at the Mayo Clinic who underwent computed tomographic angiography and urography as part of their kidney donor evaluation between 2000 and 2008 were identified. Radiographic reports were abstracted for abnormalities of the renal arteries and kidneys. The prevalence of radiographic abnormalities was stratified by age and gender, and the effect on approval for kidney donation was determined.

Results: Among 1957 potential kidney donors, the mean ± SD age was 43 ± 12 years, and 58% were women. The most common abnormalities were kidney stones (11%), focal scarring (3.6%), fibromuscular dysplasia (2.8%), and other renal artery narrowing or atherosclerosis (5.3%). Fibromuscular dysplasia, focal scarring, parenchymal atrophy, and upper tract dilation were more common in women. Renal artery narrowing, focal scarring, and indeterminate masses increased with age. Overall, 25% of potential donors had at least one abnormality. However, these incidental radiographic abnormalities contributed to exclusion from donation in only 6.7% of potential donors.

Conclusions: Incidental radiographic abnormalities of the renal arteries and kidneys are common. The majority of imaging findings are not perceived to be harmful enough to prevent kidney donation, but future studies are needed to determine their clinical relevance.

 
 
 
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