Impact of creatinine production on the agreement between glomerular filtration rate estimates using cystatin C-derived, and 4- and 6-variable Modification of Diet in Renal Disease (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations.

BACKGROUND: It has recently been reported that patient selection has a strong impact on the agreement between glomerular filtration rate (GFR) estimates from serum cystatin C and creatinine. The aim of our study was to evaluate the effect of creatinine production rate (CPR) on this subject. MATERIAL AND METHODS: GFR was estimated from serum cystatin C and from creatinine using the 4- and 6-variable Modification of Diet in Renal Disease (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations in 50 healthy subjects, 43 patients with renal failure, 794 kidney and 104 liver transplant recipients, 61 patients with heart failure, 59 patients with biliary obstruction, and 113 critically ill patients. RESULTS: In the 295 patients with impaired CPR (< 900 mg/24 h/1.73 m(2)), discordances of more than 40% between GFR(MDRD4) and GFR(cystatinC) were observed in 38% of cases, between GFR(MDRD6) and GFR(cystatinC) in 22%, and between GFR(CKD-EPI) and GFR(cystatinC) in 27% (in all cases due to GFR overestimation from creatinine). In the 929 patients with maintained CPR (> 900 mg/24 h/1.73 m(2)), greater discordances than 40% between GFR(MDRD4) and GFR(cystatinC) were observed in 8% of cases, between GFR(MDRD6) and GFR(cystatinC) in 9%, and between GFR(CKD-EPI) and GFR(cystatinC) in 7% (in the major part of cases due to GFR overestimation from cystatin C). CONCLUSION: The main source of differences of more than 40% between GFR estimates from serum creatinine and cystatin C is a GFR overestimation in patients with low CPR and GFR underestimation in patients with high CPR by the creatinine-derived equations.

Association between butyrylcholinesterase activity and low-grade systemic inflammation.

BACKGROUND: Pro-inflammatory cytokine production is directly inhibited by acetylcholine (ACh), and a relationship between total circulating ACh hydrolytic capacity and inflammatory reactions has been previously reported. Butyrylcholinesterase (BChE) is the major ACh hydrolyzing enzyme in plasma, and the aim of our study was to evaluate its association with low-grade systemic inflammation. MATERIAL AND METHODS: A total of 4,077 patients clinically managed in the Cardiology, Hypertension, and Digestive Medicine Units were included in our study. Three subclinical chronic inflammatory degrees were established in accordance with the high-sensitivity C-reactive protein (hsCRP) concentrations proposed, for low (< 1 mg/L), average (1-3 mg/L), and high (> 3-10 mg/L) cardiovascular disease risk estimation. RESULTS: In male patients with subclinical chronic inflammation and hsCRP concentrations < 1 mg/L, a significant positive correlation was observed between BChE and hsCRP (p < 0.02); however, for hsCRP concentrations > 3 mg/L, the correlation between these variables in both sexes becomes significantly negative (p < 0.001), as in patients with acute inflammation (hsCRP > 10 mg/L). In all cases significant positive correlations were obtained between the BChE activities and albumin concentrations (p < 0.001). CONCLUSIONS: The liver production of BChE and albumin occurs in a coupled fashion, and these biochemical variables may be considered as negative inflammatory reactants, whose serum levels are inversely associated with the increasing degree of subclinical inflammation.

Determination of everolimus in blood samples from kidney and liver transplant recipients using the sirolimus chemiluminescence magnetic microparticle immunoassay (CMIA) on the Architect-i1000® system.

BACKGROUND: There is significant immunoassay cross-reactivity between everolimus and sirolimus, and their routine determination using a common method may reduce the reagent costs. METHODS: In 122 blood samples from kidney (n = 30) and liver (n = 92) transplant recipients, everolimus concentrations were determined using the Abbott IMx® microparticle enzyme immunoassay (MEIA) as previously described, and the Abbott sirolimus chemiluminescence magnetic microparticle immunoassay (CMIA) on the Architect-i1000® system. RESULTS: A high correlation coefficient (r = 0.981, p < 0.001) and a linear regression MEIA = 0.73CMIA + 0.55, with an acceptable standard error of the estimate (ma68 = 0.32 ng/mL), were obtained, indicating the transferability of the results produced by both immunoassays. CONCLUSIONS: The newly-developed sirolimus CMIA assay on the Architect® platform may be a valid alternative to other immunoassays for the routine therapeutic monitoring of everolimus.

Interference of circulating endogenous antibodies on the Dimension® DGNA digoxin immunoassay: elimination with a heterophilic blocking reagent.

Only two cases have been previously described about circulating endogenous antibodies interference on the immunochemical determination of digoxin. In an elderly patient with history of social cat handling was observed a moderate positive interference (about 0.8 ng/mL) on the Dimension® DGNA digoxin immunoassay (capture rabbit antibody), which was eliminated treating the serum samples with a heterophilic blocking reagent. The Architect® immunoassay was not affected.