Lack of transferability between two automated immunoassays for serum IGF-I measurement.

BACKGROUND: IGF-I is a clinically relevant protein in the diagnosis and monitoring of treatment of growth disor- ders. The Growth Hormone Research Society and the International IGF Research Society have encouraged the adoption of a universal calibration for immunoassays to improve standardization of IGF-I measurements, but currently commercial assays are calibrated either against the old WHO IRR 87/518 or the new WHO 02/254. We compared two IGF-I immunochemiluminescent assays: IMMULITE® 2000 (Siemens) and LIAISON® (DiaSorin), which differ in their standardization, and verified their precision according to quality specifications based on biological variation and their linear range. METHODS: 62 patient serum samples were analyzed for both assays and compared according to standards of the Clinical and Laboratory Standards Institute (CLSI), EP9-A2-IR. Precision was verified according to CLSI EP15- A2. Optimal coefficient of variation (CVo) and desirable coefficient of variation (CVd) for IGF-I assays were calculated as quality specifications based on the biological variability, in order to assess if the interassay analytical CV (CVa1) in the two methods were appropriate. Two dilution series using the 1st WHO International Standard (WHO IS) for IGF-I 02/254 were used to verify and compare the linearity range. RESULTS: The regression analysis showed constant and proportional differences for serum samples (slope b = 0.8115 (CI 95% CI; 0.7575-0.8556); intercept a = 33.6873 (95% CI: 23.3613-44.0133) between assays and similar pro- portional differences for WHO IS 02/254 standard dilutions series (slope b = 0.8024 (CI 95% CI; 0.7560-0.8616); intercept a = 6.9623 (95% CI: -2.0819-18.4383) between assays. Within-laboratory coefficients of variation for low and high levels were 2.82% and 3.80% for IMMULITE® 2000 and 3.58% and 2.14% for LIAISON®, respecttively. CONCLUSIONS: IGF-I concentrations measured by both assays are not transferable. The results emphasize the need to express IGF-I concentrations in standard deviation score (SDS) according to a matched normal population of the same age and gender. Within-laboratory precision in both methods met quality specifications derived from biological variation.

Uromodulin and α(1)-antitrypsin urinary peptide analysis to differentiate glomerular kidney diseases.

BACKGROUND/AIMS: Glomerular kidney disease (GKD) is suspected in patients based on proteinuria, but its diagnosis relies primarily on renal biopsy. We used urine peptide profiling as a noninvasive means to link GKD-associated changes to each glomerular entity. METHODS: Urinary peptide profiles of 60 biopsy-proven glomerular patients and 14 controls were analyzed by combining magnetic bead peptide enrichment, MALDI-TOF MS analysis, and ClinProTools v2.0 to select differential peptides. Tentative identification of the differential peptides was carried out by HPLC-MS/MS. RESULTS: The HPLC-MS/MS results suggest that uromodulin (UMOD; m/z: 1682, 1898 and 1913) and α(1)-antitrypsin (A1AT; m/z: 1945, 2392 and 2505) are differentially expressed urinary peptides that distinguish between GKD patients and healthy subjects. Low UMOD and high A1AT peptide abundance was observed in 80-92% of patients with GKD. Proliferative forms of GKD were distinguished from nonproliferative forms, based on a combination of UMOD and A1AT peptides. Nonproliferative forms correlated with higher A1AT peptide levels - focal segmental glomerulosclerosis was linked more closely to high levels of the m/z 1945 peptide than minimal change disease. CONCLUSION: We describe a workflow - urinary peptide profiling coupled with histological findings - that can be used to distinguish GKD accurately and noninvasively, particularly its nonproliferative forms.

Proteomic approach to the study of statin pleiotropy in kidney transplant patients.

BACKGROUND/AIMS: Statins are prescribed in kidney transplant recipients in order to manage dyslipidemia, a common complication in these patients. The efficacy of statins in reducing cholesterol levels has been accompanied by pleiotropic effects. Fifty-four kidney transplant patients were included in the present study, the objective of which was to ascertain the effect of 12 weeks of atorvastatin therapy (10 mg/day) on the patients' lipid profile, renal function, markers of inflammation and plasma peptide profile. METHODS: Biochemical variables were determined with a routine clinical laboratory analyzer, and the proteomic approach was based on magnetic particle-assisted sample processing coupled to mass spectrometry readout. RESULTS: Atorvastatin therapy improved the lipid profile of patients and caused significant changes in their plasma peptide profile; peptides with m/z 1063 and 1898 decreased after treatment and were identified as fragments derived from molecules involved in vascular inflammation, i.e. high-molecular-weight kininogen and complement factor C4, respectively. CONCLUSION: These findings may contribute to the growing body of evidence of the anti-inflammatory actions attributed to statins, by which these drugs could improve these patients' clinical status.

Pretransplant inflammation: a risk factor for delayed graft function?

BACKGROUND: Inflammation plays an important role in the pathogenesis of ischemic acute kidney injury (IAKI). In this study, we hypothesize that transplant recipients with pretransplant inflammation may have a greater chance of developing delayed graft function (DGF), an example of IAKI. PATIENTS AND METHODS: We analyzed 178 patients who had undergone their first transplant using cadaveric donors. Blood samples were extracted from transplant recipients prior to transplantation. C-reactive protein (CRP) (nephelometry); interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) (automatized enzyme chemiluminescence immunometric assay); and pregnancy-associated plasma protein A (PAPP-A) (enzyme-linked immunosorbent assay) were determined using the pretransplant blood samples. The risk factors analyzed included cold ischemia, type and time of dialysis, donor and recipient age and HLA compatibility. RESULTS: Sixty-one patients (34.3%) developed DGF. Pretransplant TNF-alpha (9.31 +/- 2.57 vs. 10.56 +/- 3.82 pg/mL; p=0.039) and PAPP-A (1.25 +/- 0.74 vs. 1.90 +/- 1.56 mU/L; p=0.002) were significantly elevated in the group of patients with DGF. Univariate analysis showed that PAPP-A, TNF-alpha, cold ischemia, type of dialysis (hemodialysis) and donor age were associated with DGF. Multivariate analysis showed that PAPP-A (p=0.006), cold ischemia (p=0.009) and type of dialysis (p=0.046) were independent risk factors for DGF. CONCLUSIONS: Pretransplant inflammation (TNF-alpha, PAPP-A) in transplant recipients could be a risk factor for the development of DGF.

Ghrelin, glucose homeostasis, and carotid intima media thickness in kidney transplantation.

BACKGROUND: Abnormalities in glucose homeostasis (AGH) frequently occur in kidney transplantation and favor vascular lesions. The purpose of this study was to analyze whether C-reactive protein (CRP), adiponectin, and ghrelin are markers of AGH and indicators of carotid atherosclerosis in kidney transplant patients with fasting plasma glucose below 126 mg/dL. METHODS: This was a cross-sectional study of 85 kidney transplant patients (59 men; mean age: 52.4 +/- 11.6 years; median posttransplant follow-up 31 (range 3-61) months). All patients underwent an oral glucose tolerance test. Abnormalities in glucose homeostasis were diagnosed following American Diabetes Association criteria. CRP, adiponectin, and ghrelin levels were determined. Doppler ultrasound of the carotid artery was performed to determine intima media thickness (IMT) and atheromatous plaque. RESULTS: A total of 50.5% of patients had AGH (12.9% were diagnosed with new-onset diabetes mellitus after transplantation and 37.7% had impaired glucose tolerance or impaired fasting glucose), whereas 49.4% were normoglycemic. Patients with AGH were older (P=0.002), had greater carotid IMT (P=0.022), and lower ghrelin concentrations (P=0.017) than normoglycemic patients. Logistic regression analyses showed ghrelin to be an independent marker for AGH (P=0.012) and AGH to be related to greater IMT (P=0.041). No differences in adiponectin or CRP were found in relation to AGH or atherosclerosis; however, there was a positive correlation between adiponectin levels and prednisone dose (r=0.240; P=0.044). CONCLUSIONS: A total of 50.5% of the study patients had abnormalities in glucose homeostasis. Patients with AGH had a higher percentage of preclinical atherosclerosis (greater carotid IMT). Ghrelin is an independent marker for abnormalities in glucose homeostasis.

Oxidative stress, inflammation and cardiovascular mortality in haemodialysis--role of seniority and intravenous ferrotherapy: analysis at 4 years of follow-up.

BACKGROUND: Cardiovascular disease is the principal cause of morbidity and mortality in haemodialysis patients. The classic risk factors do not account for all cases of elevated cardiovascular disease in this patient population and it is becoming increasingly clear that other cardiovascular risk factors are implicated. The objective of this study was to analyse whether or not C-reactive protein (CRP) and plasma copper oxidized anti-lipoprotein (oxLDL) antibody titre are risk factors for cardiovascular mortality during 4 years of follow-up. METHODS: A prospective follow-up study was carried out in 94 stable, chronic haemodialysis patients for 48 months (July 1999-July 2003) (gender: 50 males and 44 females; mean age: 67+/-14 years). Eighty-four per cent of these patients were receiving intravenous erythropoietin and 63% were receiving intravenous ferrotherapy (iron gluconate). Basal markers of inflammation and oxidative stress were determined at the beginning of the study. CRP levels were determined by chemiluminescent enzyme-labelled immunometric assay. The oxLDL antibody titre was measured by enzyme-linked immunosorbent assay using native LDL and oxLDL as antigens. RESULTS: Fifty deaths occurred during the study, 66% (n = 33) of which were due to cardiovascular disease. Patients presented with basal CRP and oxLDL levels indicative of chronic inflammation and elevated oxidative stress [CRP median: 5.16 mg/l (25-75% percentile: 0.35-88.7 mg/l); oxLDL antibodies median: 153 (optical density at 495 nm x 1000) (25-75% percentile: 112-214)]. A positive correlation was found between CRP and age (r = 0.33, P = 0.003). Study of the risk factors demonstrated that age (P = 0.007), oxLDL antibody titre (P = 0.04) and albumin (P = 0.02) were the only predictors of cardiovascular mortality at 4 years of follow-up in this patient population. The Cox proportional hazards model for cardiovascular mortality showed that of the markers studied, oxLDL antibody titre was an independent risk factor for cardiovascular mortality. CONCLUSIONS: Oxidative stress (oxLDL antibody titre) is one of the principal risk factors for cardiovascular mortality in this population of haemodialysis patients. Intravenous ferrotherapy, due to its pro-oxidant properties, probably favours oxidative stress. Serum concentration of CRP was not a good predictive factor of cardiovascular mortality during 4 years of follow-up, possibly because of the slight positive correlation that exists between CRP and age.

"New" cardiovascular risk factors in patients with chronic kidney disease: role of folic acid treatment.

Cardiovascular disease (CVD) is the principal cause of mortality in patients with chronic renal disease undergoing hemodialysis. In addition to the CVD risk factors, a new hypothesis has recently been aroused related to "new" factors involved in the development of atherosclerosis in the uremic patient; worthwhile mentioning are the homocysteine, inflammation, and oxidative stress, among others. The potential utility of the folic acid in the hyperhomocysteinemia control is well known, although its mechanism of action, either as antioxidant or anti-inflammatory, has not been established. Our results confirm that the patients undergoing dialysis demonstrate hyperhomocysteinemia, an increased inflammatory status, and an increase of the lipid peroxidation markers. The administration of IV folinic acid induces a reduction of homocysteine levels subordinate to the inflammatory status of the patient. Additionally, although no inflammatory effects were shown, the results provide evidence for the antioxidant effect of IV folinic acid administration by reducing the lipid peroxidation marker levels. The statistic analysis demonstrates no correlation among the 3 markers, in spite of its higher levels in these particular patients. Homocysteine does not independently predict mortality in patients taking oral folic acid. Nevertheless, the PCR (an inflammation marker) and the antibody antioxidative-LDL (a lipidic peroxidation marker) show a good prediction of mortality at the 24-month follow-up analysis. The knowledge of these "new" CV risk factors, as well as the factors that influence them, could be useful to prevent the development of atherosclerosis in patients with chronic renal disease.