Timothy S Larson

Mayo Foundation for Medical Education and Research, Scottsdale, AZ, USA

Are you Timothy S Larson?

Claim your profile

Publications (63)359.73 Total impact

  • Article: Identification and Characterization of Kidney Transplants With Good Glomerular Filtration Rate at 1 Year but Subsequent Progressive Loss of Renal Function.
    [show abstract] [hide abstract]
    ABSTRACT: BACKGROUND: After the first year after kidney transplantation, 3% to 5% of grafts fail each year but detailed studies of how grafts progress to failure are lacking. This study aimed to analyze the functional stability of kidney transplants between 1 and 5 years after transplantation and to identify initially well-functioning grafts with progressive decline in allograft function. METHODS: The study included 788 adult conventional kidney transplants performed at the Mayo Clinic Rochester between January 2000 and December 2005 with a minimum graft survival and follow-up of 2.6 years. The modification of diet in renal disease equation for estimating glomerular filtration rate (eGFRMDRD) was used to calculate the slope of renal function over time using all available serum creatinine values between 1 and 5 years after transplantation. RESULTS: Most transplants demonstrated good function (eGFRMDRD ≥40 mL/min) at 1 year with positive eGFRMDRD slope between 1 and 5 years after transplantation. However, a subset of grafts with 1-year eGFRMDRD ≥40 mL/min exhibited strongly negative eGFRMDRD slope between 1 and 5 years suggestive of progressive loss of graft function. Forty-one percent of this subset reached graft failure during follow-up, accounting for 69% of allograft failures occurring after 2.5 years after transplantation. This pattern of progressive decline in estimated glomerular filtration rate despite good early function was associated with but not fully attributable to factors suggestive of enhanced antidonor immunity. CONCLUSIONS: Longitudinal analysis of serial estimated glomerular filtration ratemeasurements identifies initially well-functioning kidney transplants at high risk for subsequent graft loss. For this subset, further studies are needed to identify modifiable causes of functional decline.
    Transplantation 10/2012; · 4.00 Impact Factor
  • Article: Analytic and clinical validation of a standardized cystatin C particle enhanced turbidimetric assay (PETIA) to estimate glomerular filtration rate.
    [show abstract] [hide abstract]
    ABSTRACT: Abstract Background: Cystatin C is an alternative biomarker for assessing glomerular filtration rate (GFR), yet lack of standardization could hinder its widespread use. In this study we analytically and clinically validated a newer cystatin C particle-enhanced turbidimetric assay (PETIA) traceable to a certified reference material and compared it to the more commonly used particle-enhanced nephelometric assay (PENIA). Methods: Samples from four patient cohorts at the Mayo Clinic were studied: 1) clinical convenience samples (n=50); 2) samples from patients undergoing iothalamate urinary clearance testing for clinical indications (n=101); 3) volunteers without kidney disease (n=292); 4) samples from 1999-2000 with previous cystatin C measurements. Results: The cystatin C PETIA was analytically robust between 0.15 mg/L and 8.36 mg/L. PETIA cystatin C values were 27.5% higher than PENIA results. Furthermore, PENIA results were 12.9% lower in 2010 than in 2000. PETIA cystatin C values and existing equations performed reasonably well to estimate GFR with an overall -7.4% bias for all patients analyzed. Age and gender specific reference intervals were established for the PETIA cystatin C. Conclusions: Cystatin C can be precisely measured by PETIA traceable to the international reference material, ERM-DA471/IFCC, using a routine chemistry autoanalyzer. There are important biases between this assay and the widely employed Siemens PENIA. This study highlights the importance of assay standardization if cystatin C is to be widely used to estimate GFR.
    Clinical Chemistry and Laboratory Medicine 09/2012; 50(9):1591-6. · 2.15 Impact Factor
  • Article: Urinalysis is more specific and urinary neutrophil gelatinase-associated lipocalin is more sensitive for early detection of acute kidney injury.
    [show abstract] [hide abstract]
    ABSTRACT: BACKGROUND: Neutrophil gelatinase-associated lipocalin (NGAL) protein is a promising biomarker to detect acute kidney injury (AKI). Earlier detection of AKI could facilitate evaluation of novel therapeutic strategies.METHODS: Random and 24-h urine samples were prospectively obtained from 125 normal volunteers for analytic validation of a urinary enzyme-linked immunosorbent assay for NGAL. For clinical validation of the test, urine from 363 emergency department patients admitted to the hospital was obtained for NGAL enzyme-linked immunosorbent assay and urinalysis and AKI was determined by the use of Acute Kidney Injury Network (AKIN) criteria.RESULTS: NGAL was stable in urine for 7 days when ambient, 4°C or frozen (-20 or -70°C). The assay was linear between 0.24 and10 000 ng/mL with a limit of quantitation of 0.24 ng/mL. Intra- and inter-assay precision were excellent (coefficient of variation <5%); however, urinary white blood cells were associated with increased NGAL levels. The 95th percentile reference value for NGAL in females is ≤65.0 and ≤23.4 ng/mL in males. Urinary NGAL levels increased with AKI stage but had only fair sensitivity (65%) and specificity (65%) to differentiate no AKI versus Stages 1, 2 or 3 (area under the curve 0.70). Urinalysis with microscopy was very specific (91%) but not very sensitive (22%) with an area under the curve of 0.57.CONCLUSIONS: NGAL can be reliably measured in clinical urine samples, although pyuria is an important potential confounder. In our cohort, increased urinary NGAL was associated with AKI by the AKIN criteria; however, the sensitivity and specificity were only fair, in part because patients with pre-renal causes are not excluded by AKIN criteria. Conversely, findings on microscopic urinalysis are very specific for AKI.
    Nephrology Dialysis Transplantation 04/2012; · 3.40 Impact Factor
  • Source
    Article: Relative performance of the MDRD and CKD-EPI equations for estimating glomerular filtration rate among patients with varied clinical presentations.
    [show abstract] [hide abstract]
    ABSTRACT: The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation was developed using both CKD and non-CKD patients to potentially replace the Modification of Diet in Renal Disease (MDRD) equation that was derived with only CKD patients. The objective of our study was to compare the accuracy of the MDRD and CKD-EPI equations for estimating GFR in a large group of patients having GFR measurements for diverse clinical indications. A cross-sectional study was conducted of patients who underwent renal function assessment for clinical purposes by simultaneous measurements of serum creatinine and estimation of GFR using the MDRD and CKD-EPI equations and renal clearance of iothalamate (n = 5238). Bias compared with measured GFR (mGFR) varied for each equation depending on clinical presentation. The CKD-EPI equation demonstrated less bias than the MDRD equation in potential kidney donors (-8% versus -18%) and postnephrectomy donors (-7% versus -15%). However, the CKD-EPI equation was slightly more biased than the MDRD equation in native CKD patients (6% versus 3%), kidney recipients (8% versus 1%), and other organ recipients (9% versus 3%). Among potential kidney donors, the CKD-EPI equation had higher specificity than the MDRD equation for detecting an mGFR <60 ml/min per 1.73 m(2) (98% versus 94%) but lower sensitivity (50% versus 70%). Clinical presentation influences the estimation of GFR from serum creatinine, and neither the CKD-EPI nor MDRD equation account for this. Use of the CKD-EPI equation misclassifies fewer low-risk patients as having reduced mGFR, although it is also less sensitive for detecting mGFR below specific threshold values used to define CKD stages.
    Clinical Journal of the American Society of Nephrology 08/2011; 6(8):1963-72. · 5.23 Impact Factor
  • Article: Importance of cystatin C assay standardization.
    Clinical Chemistry 06/2011; 57(8):1209-11. · 7.91 Impact Factor
  • Article: The effect of coronary angiography on renal function in preemptive renal transplant candidates.
    [show abstract] [hide abstract]
    ABSTRACT: Increasing numbers of patients undergo preemptive renal transplantation. Obtaining cardiac catheterizations prior to transplantation to screen for coronary artery disease is controversial because of the perceived risk of inducing contrast nephropathy and the need for dialysis in patients with marginal renal function. We sought to examine the true impact of cardiac catheterization on time to dialysis in a cohort of preemptive renal transplant candidates. From a cohort of 376 transplant candidates evaluated preemptively at our program between 2/2001 and 4/2005, 34 patients had positive dobutamine stress echocardiograms. We reviewed the subsequent need for dialysis in these patients. Among candidates undergoing angiography, 8.7% required dialysis within 14 d of contrast administration and 26% eventually needed dialysis prior to transplantation at 5.3 ± 3.7 months after their pre-transplant evaluation. Among patients who did not undergo angiography, 27% needed dialysis prior to transplantation at 2.4 ± 1.8 months after pre-transplant evaluation. Our results demonstrate a low risk of hastening the need for dialysis after coronary angiography in preemptive renal transplant candidates. Undergoing angiography had no effect on the ultimate need for or timing of dialysis initiation. These findings support completion of full cardiac evaluation as indicated for high-risk preemptive renal transplant candidates.
    Clinical Transplantation 11/2010; 25(4):594-9. · 1.67 Impact Factor
  • Article: Serum sodium, renal function, and survival of patients with end-stage liver disease.
    [show abstract] [hide abstract]
    ABSTRACT: Serum creatinine, a component of the model for end-stage liver disease (MELD), is an important prognostic indicator in patients with end-stage liver disease (ESLD). In addition, serum sodium has recently been recognized as an important predictor of mortality in patients with ESLD. We investigate the role of serum creatinine and sodium, and glomerular filtration rate (GFR) as determinants of survival in patients with ESLD. A prospective database was utilized to identify all adults listed for primary liver transplantation (LTx) at the Mayo Clinic, Rochester, between 1990 and 1999. GFR was measured by iothalamate clearance. Among 837 patients listed for LTx, 660 had complete data including measured GFR. There was a significant association between GFR and survival after adjustment for MELD, with a linear rise in the risk of death as GFR decreased between 60 and 20ml/min/1.73m(2). Multivariable models showed that GFR is superior to creatinine in predicting mortality - a model consisting of total bilirubin (hazard ratio (HR)=2.17, p<0.01), INR (HR=3.26, p<0.01) and GFR (HR=0.42, p<0.01) was superior to MELD (chi-square 65.6 vs. 59.4, c-statistic 0.792 vs. 0.780). Serum sodium did not contribute to survival prediction when accurately measured GFR data were available. Serum concentrations of creatinine and sodium in patients with end-stage liver disease reflect a reduction in renal function, the underlying event that decreases survival.
    Journal of Hepatology 02/2010; 52(4):523-8. · 9.26 Impact Factor
  • Article: Iothalamate quantification by tandem mass spectrometry to measure glomerular filtration rate.
    [show abstract] [hide abstract]
    ABSTRACT: 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. 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. Mean recovery was 90%-110% in both urine and plasma matrices. Imprecision was <or=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. 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.
    Clinical Chemistry 02/2010; 56(4):568-74. · 7.91 Impact Factor
  • Article: Comparison of urinary albumin quantification by immunoturbidimetry, competitive immunoassay, and protein-cleavage liquid chromatography-tandem mass spectrometry.
    [show abstract] [hide abstract]
    ABSTRACT: Increased urinary albumin excretion is a well-documented diagnostic and prognostic biomarker for renal disease. Urinary albumin is typically measured in clinical settings by immunoassay methods. However, neither a reference method nor a urine albumin calibration reference material is currently available. We quantified urinary albumin in patient samples by using 3 commercially available reagent systems: DiaSorin SPQ and Beckman Coulter LX 20 (immunoturbidimetric), and Siemens Immulite (competitive immunoassay). Results were compared to values obtained by protein-cleavage liquid chromatography-tandem mass spectrometry (LC-MS/MS). In general, results from the 3 immunoassays agreed with results from LC-MS/MS. However, the SPQ results showed a negative bias across all ranges of albuminuria [(0-200 mg/L, y = 0.91x - 3.74 (CI 0.86-0.96); > 200 mg/L, y = 0.88x - 40.30 (CI 0.76-1.00)], whereas the LX 20 showed minimal bias in the 0-200 mg/L range [y = 0.97x - 88 (CI 0.92-1.02)] and the Immulite assay showed positive bias in the 0-200 mg/L range [y = 1.15x - 4.38 (CI 1.09-1.20)]. These results showed a reasonable quantification of urinary albumin by representative polyclonal and monoclonal immunoassays compared to an LC-MS/MS assay. In addition, the results do not suggest the presence of nonimmunoreactive albumin in urine. However, differences in analytic performance between assays support the need for a reference calibration material and reference method to standardize clinical laboratory measurements of urinary albumin.
    Clinical Chemistry 09/2009; 55(11):1991-4. · 7.91 Impact Factor
  • Article: Kidney transplantation for primary focal segmental glomerulosclerosis: outcomes and response to therapy for recurrence.
    [show abstract] [hide abstract]
    ABSTRACT: For a subset of adults and children with primary focal segmental glomerulosclerosis (FSGS), proteinuria and renal dysfunction recur after kidney transplantation (KTx). Predicting recurrence and response to plasmapheresis (PP) or other interventions remains problematic. The prevalence, recurrence rate, outcomes, and treatment responses of patients with FSGS were determined among 1573 KTx recipients. Although 5.0% carried some diagnosis of FSGS, only 1.9% (n=30) met strict diagnostic criteria for primary FSGS including biopsy-proven FSGS, lack of secondary factors, negative family history, and progression to end-stage renal disease within 10 years. Of these, 47% had recurrent FSGS compared with 8% of those not meeting strict criteria (P<0.001). Recurrence was more common in children compared with adults (86% vs. 35%, P=0.01). Graft survival was lower for recipients with primary FSGS compared with all others and inferior graft survival was attributable to recurrent FSGS. Fourteen patients received PP preemptively (pre-KTx) or therapeutically (post-KTx) for recurrent disease. Four pediatric patients additionally received anti-CD20 (rituximab) therapy. Of the different treatment approaches, only PP combined with rituximab was associated with prolonged remission of proteinuria. The results indicate that patients at high risk for FSGS recurrence can be identified and may benefit from carefully planned peritransplant interventions.
    Transplantation 05/2009; 87(8):1232-9. · 4.00 Impact Factor
  • Article: Quantification of urinary albumin by using protein cleavage and LC-MS/MS.
    [show abstract] [hide abstract]
    ABSTRACT: 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). 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, (15)N-labeled recombinant HSA ((15)NrHSA), 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 (42)LVNEVTEFAK(51) and (526)QTALVELVK(534) from albumin and (15)NrHSA were referenced to the calibration curve. 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 (42)LVNEVTEFAK(51), and 1.9%-12.3% for the (526)QTALVELVK(534) peptide. Interassay imprecision of the controls for a period of 10 consecutive days (n = 10) yielded CVs of 1.5%-14.8% for the (42)LVNEVTEFAK(51) peptide, and 6.4%-14.1% for the (526)QTALVELVK(534) peptide. For the (42)LVNEVTEFAK(51) peptide, a method comparison between LC-MS/MS and an immunoturbidometric method for 138 patient samples gave an R(2) value of 0.97 and a regression line of y = 0.99x + 23.16. Urinary albumin can be quantified by a protein cleavage LC-MS/MS method using a (15)NrHSA internal standard. This method provides improved analytical performance in the clinically relevant range compared to a commercially available immunoturbidometric assay.
    Clinical Chemistry 04/2009; 55(6):1100-7. · 7.91 Impact Factor
  • Source
    Article: Do we need another equation to estimate GFR from serum creatinine in renal allograft recipients?
    Andrew D Rule, Timothy S Larson
    Nephrology Dialysis Transplantation 08/2008; 23(7):2427-8; author reply 2428. · 3.40 Impact Factor
  • Article: Comparison between immunoturbidimetry, size-exclusion chromatography, and LC-MS to quantify urinary albumin.
    [show abstract] [hide abstract]
    ABSTRACT: The accurate and precise measurement of urinary albumin is critical, since even minor increases are diagnostically sensitive indicators of renal disease, cardiovascular events, and risk for death. To gain insights into potential measurement biases, we systematically compared urine albumin measurements performed by LC-MS, a clinically available immunoturbidimetric assay, and size-exclusion HPLC. We obtained unused clinical urine samples from 150 patients who were stratified by degrees of albuminuria (<20 mg/L, 20-250 mg/L, >250 mg/L) as determined by the immunoturbidimetric assay used in our clinical laboratory (Roche Hitachi 912). Urine albumin was then remeasured via LC-MS and HPLC (Accumin) assays. The immunoturbidimetric assay, calibrated using manufacturer-supplied serum-derived calibrators (Diasorin), underestimated albumin compared with LC-MS. After calibration with purified HSA, this immunoturbidimetric assay correlated well with LC-MS. HPLC overestimated albumin compared with both LC-MS and immunoturbidimetry. The current LC-MS and HPLC assays both performed poorly at concentrations <20 mg/L. Efforts are needed to establish gold-standard traceable calibrators for clinical assays. LC-MS is a specific method to quantify albumin in native urine when concentrations exceed 20 mg/L, and therefore could be employed for standardization among assays.
    Clinical Chemistry 07/2008; 54(9):1504-10. · 7.91 Impact Factor
  • Article: Kidney transplant histology after one year of continuous therapy with sirolimus compared with tacrolimus.
    [show abstract] [hide abstract]
    ABSTRACT: Analysis of 1-year surveillance biopsies was carried out for kidney transplant recipients participating in a randomized trial comparing tacrolimus- and sirolimus-based immunosuppression. The analysis was restricted to recipients remaining on assigned regimen throughout the first posttransplant year. Biopsies from 57 of 84 (68%) tacrolimus-randomized recipients were compared with 38 of 81 (47%) of sirolimus-randomized recipients, the discrepancy being explained by a higher rate of sirolimus discontinuation for non-graft-related complications. Included recipients from the two groups did not differ for baseline characteristics or 1-year iothalamate clearance. Histologic analysis indicated no differences between the groups for glomerular, arterial/arteriolar, or acute interstitial abnormalities. There were, however, significantly higher mean scores in the tacrolimus group for interstitial fibrosis and tubular atrophy with a trend toward higher estimated percent interstitial fibrosis. The results indicate that sirolimus may be associated with reduced early graft fibrosis compared with tacrolimus. This potential benefit is offset by lower success rate in maintaining the regimen and was not accompanied by superior glomerular filtration rate at 1 year.
    Transplantation 05/2008; 85(8):1212-5. · 4.00 Impact Factor
  • Article: Diurnal blood pressure changes one year after kidney transplantation: relationship to allograft function, histology, and resistive index.
    [show abstract] [hide abstract]
    ABSTRACT: Loss of circadian BP change has been linked to target organ damage and accelerated kidney function loss in hypertensive patients with and without chronic kidney disease. Ambulatory BP-derived data from 119 consecutive kidney transplant recipients who presented for the first annual evaluation were examined in relation to allograft function, histology, and ultrasound findings. A total of 101 (85%) patients were receiving antihypertensive medications (median 2), and 85 (71%) achieved target awake average systolic BP (SBP) of <135 mmHg. A day-night change in SBP by 10% or more (dippers) was detected in 29 (24%). Dipping status was associated with younger recipient age, lack of diabetes, low chronic vascular score, and low resistive index. Nondippers and reverse dippers had lower GFR compared with dippers (P = 0.04). For every 10% nocturnal drop in SBP, GFR increased by 4.6 ml/min per 1.73 m(2) (R = 0.3, P = 0.003). Nondippers and reverse dippers were equally common in recipients with normal histology and in those with pathologic findings on surveillance biopsy. On multivariate analysis, percentage of nocturnal fall in SBP and elevated resistive index independently correlated with GFR. This study indicates that lack of nocturnal fall in SBP is related to poor allograft function, high chronic vascular score, and high resistive index irrespective of allograft fibrosis. Further studies are needed to determine whether restoration of normal BP pattern will confer better allograft outcome.
    Journal of the American Society of Nephrology 05/2007; 18(5):1607-15. · 9.66 Impact Factor
  • Source
    Article: A liquid chromatography-mass spectrometry method for the quantification of urinary albumin using a novel 15N-isotopically labeled albumin internal standard.
    Clinical Chemistry 04/2007; 53(3):540-2. · 7.91 Impact Factor
  • Article: Comparison of low versus high tacrolimus levels in kidney transplantation: assessment of efficacy by protocol biopsies.
    [show abstract] [hide abstract]
    ABSTRACT: The use of calcineurin inhibitors is generally guided by drug blood levels. However, those levels are chosen based on clinical experience, lacking adequate titration studies. In these analyses, we compared clinical and histologic endpoints in two groups of kidney transplant recipients: in the first (HiTAC, January 2000 to June 2002, n=245) tacrolimus levels were significantly higher than in the second (LoTAC, July 2002 to September 2004, n=330). This change in drug levels (15% reduction) was made in an attempt to reduce the incidence of polyoma virus nephropathy (PVAN). Other immunosuppressive medications were unchanged during these two time periods. The recipient and donor demographics were not statistically different between the two groups. Compared to HiTAC, at one year posttransplant LoTAC had: 1) lower incidence of PVAN (10.5% vs. 2.5%, P<0.0001); 2) lower fasting glucose levels; 3) higher iothalamate glomerular filtration rate (52+/-19 vs. 59+/-17 ml/min/m, P<0.0001); and 4) on protocol one-year biopsies, lower incidence and severity of interstitial fibrosis (67% vs. 45%, P=0.003) and tubular atrophy (82% vs., 66%, P=0.01). The incidence and severity of acute rejection episodes was similar between both groups (7.8% versus 7.6%). Modest reductions in tacrolimus exposure early posttransplant are associated with significant beneficial effects for the patient and the allograft without an increased immunologic risk.
    Transplantation 02/2007; 83(4):411-6. · 4.00 Impact Factor
  • Article: Effects of analytic variations in creatinine measurements on the classification of renal disease using estimated glomerular filtration rate (eGFR).
    [show abstract] [hide abstract]
    ABSTRACT: This study uses the Isotope Dilution Mass Spectrometer-Traceable Modification of Diet in Renal Disease (MDRD) equation to evaluate the effects of analytic variation of serum creatinine on estimated glomerular filtration rate (eGFR). The equation was inverted to provide critical creatinine levels corresponding to eGFRs equal to 15, 30, and 60 mL/min/1.73 m(2). eGFRs were calculated for two populations of patients representing clinic outpatients and hospitalized inpatients. Simulation studies evaluated the effects of analytic bias for these populations. Differences between creatinine tests ordered on consecutive blood draws were analyzed for within-subject eGFR variation. Finally, propagation of error techniques established the relationship between creatinine imprecision and eGFR imprecision. eGFR of 60 mL/min/1.73 m(2) corresponds to creatinine levels of 80-156 micromol/L. A 20-micromol/L negative shift of creatinine approximately doubles the percentage of patients classified in various stages of decreased renal function, whereas a positive shift approximately halves the percentage. The central 95% limits for within-subject variation of eGFR are 33% for outpatients, 38% for inpatients and 40% across the groups. eGFR imprecision is approximately 15%-20% higher than creatinine imprecision. Small analytic changes in serum creatinine create major shifts in the distributions of eGFR, which can cause large differences in the classification of patients. The within-subject variations in eGFR over time, especially between hospital and clinic measurements, can be large. Therefore, tight control of laboratory analysis is important.
    Clinical Chemistry and Laboratory Medicine 02/2007; 45(6):737-41. · 2.15 Impact Factor
  • Article: Preemptive living donor kidney transplantation: do the benefits extend to all recipients?
    [show abstract] [hide abstract]
    ABSTRACT: Preemptive kidney transplantation (prior to the institution of dialysis) avoids the morbidity and mortality of dialysis; however, detailed studies of high-risk patients are lacking. The aim of the current study was to compare recent outcomes of preemptive (P) versus nonpreemptive (NP) living donor kidney transplantation with an emphasis on high-risk recipients. We retrospectively analyzed 438 sequential solitary living donor kidney transplants at our institution between January 2000 and December 2002. In all, 44% were preemptive. NP recipients were dialyzed for 21+/-36 months (range 1-312 months). Overall, three-year patient survival was similar in the NP and P groups. When stratified by diabetes and age >65 years, P and NP recipients again showed similar survival. Death-censored three-year graft survival was better in the P group (97% vs. 90%, P=0.01), but was not significant by multivariate analysis. Delayed graft function was more frequent in NP vs. P (10% vs. 4%; P=0.01), but other early complications were similar including: acute rejection, 16% vs. 11% (P=0.11); primary nonfunction, 3% vs. 2% (P=0.38); and wound complications, 19% vs. 17% (P=0.54). Glomerular filtration rate at three years was similar in the two groups (53+/-23 preemptive vs. 52+/-20 ml/min nonpreemptive; P=0.37). With prompt referral and workup, preemptive kidney transplantation can be performed successfully in a large percentage of renal allograft recipients. Preemptive transplantation avoids unnecessary dialysis and should be emphasized as initial therapy for many patients with end-stage renal disease.
    Transplantation 01/2007; 83(2):144-9. · 4.00 Impact Factor
  • Source
    Article: Modeling chronic glycemic exposure variables as correlates and predictors of microvascular complications of diabetes.
    [show abstract] [hide abstract]
    ABSTRACT: The degree to which chronic glycemic exposure (CGE) (fasting plasma glucose [FPG], HbA1c [A1C], duration of diabetes, age at onset of diabetes, or combinations of these) is associated with or predicts the severity of microvessel complications is unsettled. Specifically, we test whether combinations of components correlate and predict complications better than individual components. Correlations and predictions of CGE and complications were assessed in the Rochester Diabetic Neuropathy Study, a population-based, cross-sectional, and longitudinal epidemiologic survey of 504 patients with diabetes followed for up to 20 years. In multivariate analysis, A1C and duration of diabetes (and to a lesser degree age at onset of diabetes but not FPG) were the main significant CGE risk covariates for complications. A derived glycemic exposure index (GE(i)) correlated with and predicted complications better than did individual components. Composite or staged measures of polyneuropathy provided higher correlations and better predictions than did dichotomous measures of whether polyneuropathy was present or not. Generally, the mean GE(i) was significantly higher with increasing stages of severity of complications. A combination of A1C, duration of diabetes, and age at onset of diabetes (a mathematical index, GE(i)) correlates significantly with complications and predicts later complications better than single components of CGE. Serial measures of A1C improved the correlations and predictions. For polyneuropathy, continuous or staged measurements performed better than dichotomous judgments. Even with intensive assessment of CGE and complications over long times, only about one-third of the variability of the severity of complications is explained, emphasizing the role of other putative risk covariates.
    Diabetes Care 11/2006; 29(10):2282-8. · 8.09 Impact Factor