Dirk Bernard

Reevaluation of Formulas for Predicting Creatinine Clearance in Adults and Children, Using Compensated Creatinine Methods

In clinical practice, glomerular filtration rate (GFR) is the most important marker for evaluation of renal function (1). Dosages of drugs that are eliminated by glomerular filtration are often based on GFR. At present, the most reliable methods for accurate assessment of overall GFR require intravenous administration of exogenous compounds and are both cumbersome and expensive. In clinical practice, creatinine clearance (CrCl) is widely accepted as a simple measure of GFR. However, CrCl systematically overestimates GFR because creatinine is freely filtered by the glomerulus and is also secreted by the proximal tubule. In the earliest methods, serum creatinine was assayed by the Jaffe reaction after deproteinization, eliminating the pseudo-chromogen effect of proteins (2). Similarly, the first automated methods used dialysis membranes to prevent interference from plasma proteins. Today, however, analyzers use undiluted serum and plasma, making them subject to the so-called “protein error” (3). This produces a positive difference of ∼27 μmol/L creatinine compared with HPLC methods (4)(5)(6)(7). Because urine contains relatively little or no protein, the protein error affects only creatinine determinations in serum. Therefore, CrCl is underestimated when creatinine methods affected by protein error are used. This underestimation has been stated to be compensated by the overestimation attributable to tubular secretion of creatinine. However, studies confirming this statement are lacking. In compensated Jaffe methods, the values assigned to the calibrator set point are adjusted to minimize the pseudo-creatinine contribution of proteins. The result is that compensated methods produce lower creatinine values. Alternatively, the protein error can be avoided by use of enzymatic creatinine methods. Collection of timed urine for CrCl is often a major source of error; therefore, simple formulas have been introduced to estimate GFR based on serum creatinine concentration, age, gender, body weight, and body length (8)(9) …

The effect of supplementation with an antioxidant preparation on LDL-oxidation is determined by haptoglobin polymorphism

Abstract The genetic polymorphism of haptoglobin (Hp) is an independent risk factor in the pathogenesis of atherosclerosis, a condition in which decreased resistance to in vitro oxidation of LDL-cholesterol is observed. We hypothesised that the Hp polymorphism is one of the factors modulating the resistance to Cu2+-induced oxidation of LDL during antioxidant supplementation. In this study, 74 middle-aged subjects with increased oxidative stress were allocated to either matched placebo or oral antioxidative treatment (Quatral®) once daily for 16 weeks. Study parameters were increase of lag phase (ΔLAG) and the ratio of lag phase during treatment period versus baseline (relative oxidation resistance, ROR), measured by Cu2+-induced oxidation of isolated LDL. Hp phenotypes were determined by starch gel electrophoresis. A significant and persistent increase of ΔLAG (P < 0.05) and ROR (P < 0.01) were observed after 16 weeks of active treatment versus placebo. Interindividual differences in both parameters were significantly associated with the Hp polymorphism: in the active treatment group, ΔLAG and ROR were significantly higher in Hp 1-1 subjects (P < 0.01) compared to Hp 2-1 and 2-2. Our data demonstrate that Hp phenotype is one of the modulating factors determining the increased resistance to Cu2+-induced oxidation of LDL during antioxidative treatment.

Distribution of Lymphocyte Subsets in Bone Marrow and Peripheral Blood Is Associated with Haptoglobin Type. Binding of Haptoglobin to the B-Cell Lectin CD22

Haptoglobin is an acute phase protein showing a genetic polymorphism with 3 major types: Hp 1-1, Hp 2-1, and Hp 2-2. In this study, flow cytometric analysis demonstrated that all three haptoglobin types bind to CD22 on human B-lymphocytes with equal affinity. Comparison of reference values for lymphocyte subsets in peripheral blood and bone marrow showed significant differences between haptoglobin types. Haptoglobin 2-2 is associated with higher peripheral B-lymphocyte counts (P < 0.001) and CD4+ T-lymphocyte counts (P < 0.05). In bone marrow, CD4+ T-cell percentages were highest (P < 0.001) but B-cell percentages were lowest (P < 0.001) in haptoglobin 2-2 type. A negative correlation between serum haptoglobin 1-1 concentration and peripheral B-cell counts was observed (r = -0.663). Our results suggest that haptoglobin is involved in lymphocyte distribution. The present findings are a potential cause of over- or underestimation of lymphocyte subset counts in the clinical staging of immunodeficiency diseases.

Evolution of Haptoglobin Concentration in Serum during the Early Phase of Acute Myocardial Infarction

Haptoglobin (Hp) is a haemoglobin-binding acute phase protein with three genetic types: Hp 1-1, Hp 2-1, Hp 2-2. We investigated 45 patients during the first 48 hours of acute myocardial infarction, and studied determinant factors and clinical correlates. Upon hospital admission, serum haptoglobin concentration was increased (1.95 +/- 0.94 g/l, mean +/- SD, P < 0.001) versus the reference population (0.97 +/- 0.46 g/l, n = 107), independent of haptoglobin type: 1.84 +/- 0.64 g/l (Hp 1-1, n = 11) (P < 0.01), 1.98 +/- 0.79 g/l (Hp 2-1, n = 25) (P < 0.001), 1.98 +/- 1.58 g/l (Hp 2-2, n = 9) (P < 0.001). Moreover, during the first hours of hospitalization, a temporal lowering of haptoglobin was observed suggesting acute haemolysis, independent of the haptoglobin type. Minimal serum haptoglobin was reached 9.6 +/- 5.8 hours after admission. The amplitude of the haptoglobin decrease correlated with initial serum haptoglobin (r = 0.78) and was more pronounced (P < 0.05) in men (0.53 +/- 0.57 g/l) than in women (0.18 +/- 0.17 g/l). Decrease of serum haptoglobin did not correlate with infarct size (based on creatine kinase-MB release). Out of the other acute phase proteins measured upon admission, only C-reactive protein was significantly increased (P < 0.05). During the next 36 hours, haptoglobin increased as a result of the acute phase response to myocardial injury. Our findings suggest that acute myocardial infarction is also preceded by an acute phase response, characterized by an initial high haptoglobin and followed by a temporal haptoglobin decrease due to haemolysis.

Neurohumoral and inflammatory activation in patients with coronary artery disease treated with statins

Inflammation plays an important part in the pathophysiology of coronary artery disease (CAD).1 High sensitive C reactive protein (hsCRP) reflects activation of the inflammatory system and independently predicts risk of first coronary events at all levels of low density lipoprotein (LDL)-cholesterol and a full spectrum of Framingham risk categories.2 Recent trials indicate that statins reduce inflammation.3,4 This leads to a better clinical outcome and reduces the rate of atherosclerosis progression independently of the reduction in cholesterol levels. The reasons why patients with raised levels of C reactive protein (CRP) have a worse outcome are, however, not clear. The inflammatory biomarkers interleukin 6 (IL6), soluble tumour necrosis factor receptors (sTNFr) 1 and 2 have proinflammatory and procoagulant properties. Our first aim was to evaluate whether high levels of hsCRP in patients with stable CAD receiving standard statin treatment are associated with activation of these biomarkers. Our second aim was to evaluate whether hsCRP and cytokine levels are determined by LDL-cholesterol or by neurohumoral activation measured by levels of N-terminal pro-B type natriuretic peptide (NT-proBNP). We analysed a subgroup of an ongoing prospective study comprising 153 statin treated patients with stable CAD. They were evaluated >6 months from myocardial infarction or cardiac revascularisation, and were free from infection, inflammatory diseases, malignancy and anti-inflammatory treatment. …

Difficulties in evaluating urinalysis following combined pancreas-kidney transplantation.

Combined pancreas–kidney transplantation has been introduced in the treatment of patients with type 1 diabetes and renal failure 20 years ago. By 1985 374 combined pancreas–kidney transplantations had been reported to the International Pancreas Transplant Registries.1 Surgical drainage of the transplanted exocrine pancreas into the urinary bladder solves most of the postoperative problems encountered with the exocrine secretions. Furthermore, monitoring of pancreatic enzyme (amylase) activity in urine has been shown to be useful in diagnosis of rejection of the pancreatic graft.2 However, little attention has been paid to the biochemical consequences of high activities of proteolytic pancreatic enzymes on the determination of urinary proteins. The present case illustrates the difficulties in interpreting proteinuria in patients with combined pancreas–renal transplant with pancreaticocystostomia. In the propositus, interpretation of the urinary protein electrophoresis is hampered by the presence of pancreatic juice proteins and peptides originating from digestion of proteins by activated pancreatic enzymes. Results of immunochemically determined marker proteins ([micro]albumin, transferrin, β2-microglobulin) are unreliable due to digestion by pancreatic enzymes.

Alterations in Serum Haptoglobin Concentration During the Early Phase of Myocardial Infarction

Haptoglobin (Hp) is a haemoglobin-binding protein involved in the acute- phase reaction. Acute myocardial infarction (AMI) is characterised by inflammation and haemolysis. The aim of this study was to monitor the changes in Hp and free haemoglobin concentration during AMI as part of an investigation into the possible role of Hp in the pathogenesis of this disorder.