Volume 48, Issue 5

Defects in primary hemostasis typically lead to a bleeding diathesis and include several disorders, such as von Willebrand disease and various platelet function defects that may arise because of failure of membrane receptors, deficiencies in internal storage organelles, and/or signal transduction problems. The laboratory identification of a primary hemostasis defect including platelet function defects now involves a multi-step process. These processes begin with a full blood count to assess platelet count and size, progressing, if necessary, to platelet aggregation studies, and leading to further specific testing including flow cytometry, electron micro-scopy and/or genetic testing. This review outlines the sequential process of platelet function investigations, and discusses each of the essential components in some detail. Clin Chem Lab Med 2010;48:579–98.

Preparing for a natural disaster starts with a thorough understanding of the geography of your particular location, as well as its weather patterns. Early planning must also look beyond the disaster to examine the possible consequences of such a disaster. While no disaster/emergency preparedness planners like to think of the bleakest outcome (i.e., mass fatalities), building in solutions at the outset of a plan alleviates having to figure them out in the middle of an earthquake, a fire, or a hurricane. January's earthquake in Haiti holds lessons for anyone who is part of a first responder or healthcare profession, and those lessons have been hard ones for the world to learn. Clin Chem Lab Med 2010;48:599–602.

Several drug candidates for Alzheimer's disease are being evaluated in clinical trials, with the goal of finding a drug with disease-modifying effects. When such a drug finally reaches the market, there will be a demand for accurate diagnostic tools useful for early detection of disease and for monitoring biochemical effects. The core cerebrospinal fluid (CSF) biomarkers amyloid peptides (Aβ42), total-tau and phospo-tau are promising in this respect. However, inter-center variation (caused by pre-analytical, analytical and post-analytical factors), and inter-laboratory variation (caused by analytical factors), particularly for CSF Aβ42, lowers their utility in multicenter studies. Here, we discuss the causes of these variations, and present a global quality control program to overcome them. Clin Chem Lab Med 2010;48:603–7.

The hemoglobin A1c (HbA1c) assay provides a reliable measure of chronic glycemia and correlates well with the risk of long-term diabetes complications, so that it is currently considered the test of choice for monitoring and chronic management of diabetes. Recently, HbA1c testing has been included within the diagnostic criteria recommended for diagnosis of diabetes in nonpregnant individuals by the American Diabetes Association (ADA). The emerging concept that HbA1c can be used rather than blood glucose in the diagnosis of diabetes is highly appealing for a variety of reasons, including less sensitivity to preanalytical variables, lower within subject biological variablity, little to null interference from diurnal variations, acute stress and common drugs which are known to influence glucose metabolism, as well as the fact that one single measurement might provide information for both diagnosing diabetes and tracking glycemic control. On the other hand, the use of HbA1c for screening and diagnosing diabetes also carries some limitations, including the worse diagnostic performance in different populations (i.e., pregnancy, elderly and non-Hispanic blacks), the risk of overdiagnosis in subjects with iron deficiency anemia, in subjects genetically predisposed to hyperglycation, and in those with increased red blood cell turnover. There is also a higher risk of misdiagnosis in patients with end-stage renal disease and heavy alcohol consumption. Finally, HbA1c testing might be biased due to the interference from several hemoglobin variants, is characterized by a higher imprecision than blood glucose measurement, and is more expensive. This paper will critically summarize the potential advantages and limitations of HbA1c as a recommended test for diagnosing diabetes. Clin Chem Lab Med 2010;48:609–14.

The primary reference measurement procedures (PRMPs) for the international standardization of catalytic concentration measurements of α-amylase, alanine aminotransferase, aspartate aminotransferase (AST), creatine kinase (CK), γ-glutamyltransferase and lactate dehydrogenase have been performed in reference laboratories for several years. The IFCC Committee on Reference Systems for Enzymes and two reference laboratories, with official accreditation for the PRMPs, have collected useful information on some of the steps of the reference procedures that require special attention. This document comprises errata corrige for minor mistakes in published PRMPs for AST and CK. Several notes on the PRMPs are emphasized. This includes details that are very important for improved standardization, and general suggestions for reducing measurement uncertainty. Clin Chem Lab Med 2010;48:615–21.

This document is issued by the Italian Society of Clinical Biochemistry and Clinical Molecular Biology (SIBioC) and a number of other National Scientific Societies and Associations in order to promote a coordinated plan for implementing the standardization of glycated hemoglobin (HbA 1c ) measurement in Italy according to the recommendations by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). Changes in reporting HbA 1c results, new units, how to relate old and new units, a timeline for changes and definition of the analytical goals are the main issues discussed. Clin Chem Lab Med 2010;48:623–6.

Background: Gene copy number variations (CNVs) are increasingly recognized to play important roles in the expression of genes and hence on their respective enzymatic activities. This has been demonstrated for a number of drug metabolizing genes, such as UDP-glucuronosyltransferases 2B17 ( UGT2B17 ) and sulfotransferase 1A1 ( SULT1A1 ), which are subject to genetic heterogeneity, including CNV. Quantitative assays to assess gene copy number are therefore becoming an integral part of accurate genotype assessment and phenotype prediction. Methods: In this study, we evaluated a microfluidics-based system, the Bio-Rad Experion system, to determine the power and utility of this platform to detect UGT2B17 and SULT1A1 CNV in DNA samples derived from blood and tissue. UGT2B17 is known to present with 0, 1 or 2 and SULT1A1 with up to 5 gene copies. Results: Distinct clustering (p<0.001) into copy number groups was achieved for both genes. DNA samples derived from blood exhibited less inter-run variability compared to DNA samples obtained from liver tissue. This variability may be caused by tissue-specific PCR inhibitors as it could be overcome by using DNA from another tissue, or after the DNA had undergone whole genome amplification. Conclusions: This method produced results comparable to those reported for other quantitative test platforms. Clin Chem Lab Med 2010;48:627–33.

Background: Variability of cytochrome P450 (CYP) in humans is largely related to the pharmacological and toxicological effects of drugs and chemicals. Identification of single nucleotide polymorphisms (SNPs) could be important for knowing their involvement in many drugs metabolism. The goal of this study was to analyze the genotype frequency of 10 SNPs related to mirtazapine metabolism [CYP3A4*17, CYP3A4*18, CYP3A5*3A, CYP1A2*1F, pregnane/steroid X receptor (PXR) (rs3814055, rs38114057, rs3814058) and constitutive androstane receptor (CAR) (rs4073054, rs2307424, rs2502815)]. Methods: The study was carried out in 207 healthy Spanish volunteers that had participated in phase I clinical trials. Other studies were performed: Hardy-Weinberg equilibrium, haplotype estimation and linkage disequilibrium. Results: No mutation related to CYP3A4*17 and CYP3A4*18 was found. Therefore, we analyzed data for the other eight SNPs. Allele frequencies were in equilibrium with the Hardy-Weinberg equation. Six haplotypes were determined for three PXR SNPs, and four for CAR SNPs. Tests for linkage disequilibrium showed a high association between PXR (rs38114057) and PXR (rs3814058) (p= 0.001), and between the three CAR SNPs (p=0.001), which could be useful for identification of tag SNPs. Conclusions: In the present study, the genotype frequencies of some SNPs related to mirtazapine metabolism in Spaniards were analyzed and showed that our study population is representative of HapMap European population. The results obtained could be analyzed with pharmacokinetic parameters of mirtazapine to elucidate the genotype-phenotype relationship, the involvement of these SNPs in metabolic reactions, drug interactions, and prediction of treatment response. Clin Chem Lab Med 2010;48:635–9.

Background: Venipuncture is an invasive procedure to obtain whole blood in order to obtain high quality and sufficient amounts of genomic DNA. Obtaining DNA from non-invasive sources is preferred by patients, medical doctors and researchers. Saliva collected with cotton swabs (Salivette ® ) is increasingly being used to study chemical compounds, and it can also be a source of DNA. However, extracting DNA from Salivettes is very laborious and time consuming. Therefore, we developed a protocol for automated genomic DNA extraction from saliva collected in Salivette ® using the QIAxtractor. Methods: Saliva (0.1–2.0 mL) was collected by chewing on a Salivette ® for 1–2 min. A total of 70 samples, collected from healthy volunteers, were extracted with the QIAxtractor robot and a Qiagen DX reagent pack. Quantity and quality was assessed using UV spectrometry and real-time polymerase chain reaction (PCR) (substitution at position –729 in the CYP1A2 gene). Results: The average DNA concentration from the saliva samples was 6.0 μg/mL (95% CI 5.4–6.6 μg/mL). In 100% of the saliva samples, PCR products were detected with an average cycle threshold of 23.1 (95% CI 22.6–23.6). Conclusions: DNA can be extracted in sufficient amounts from Salivette ® with a fully automated system with a short turnaround time. Real-time PCR can be performed with these samples. Clin Chem Lab Med 2010;48:641–3.

Background: The Belgian External Quality Assessment Scheme for Flow Cytometry evaluates the long-term analytical performance of participating laboratories by calculating a regression line between the target and reported values of each parameter for each laboratory during the past 3 years. This study aims to develop a method to find laboratories with aberrant variability or bias using robust techniques and to obtain robust estimates of the variability. Methods: A method is proposed to find outliers with respect to the individual regression line, followed by a step to find regression lines with excessive variability and finally a step to find regression lines with high bias. Results: The model was applied to the results obtained by 52 laboratories for CD4%. From the 1340 data points, 35 were determined to be regression outliers. The second step revealed one regression line with excessive variability; the third step detected three regression lines with exceeding bias. Conclusions: The methodology allows assessment of the long-term performance of laboratories, taking into account samples with different target values. Outliers in the first step indicate accidental mistakes, outliers in the second and third step point to high analytical variability or bias. Clin Chem Lab Med 2010;48:645–50.

Background: Obtaining a suitable specimen for analysis in a timely manner is pivotal in clinical chemistry service provision. Serum is recognized as the preferred specimen for most assays, but because of time constraints for completion of clotting and an increasing number of patients on anti-coagulant therapy, latent clotting or no clotting is an outcome which can lead to errors and delay in delivery of critical results. Although lithium heparin plasma has unique problems, it has become an alternative in hospital-based laboratories. Methods: The Becton-Dickinson (BD) rapid serum tube (RST) was evaluated in a hospital environment using a total of 53 participants, both healthy and anticoagulated, for 31 analytes against BD PST II and BD SST II tubes measured with Beckman DxC800 and DxI800 analyzers. Results: Most results from the RST tube were comparable with those from the SST II tube. Potassium results were closer to the PST II plasma concentrations. Incomplete and latent clotting was encountered in the RST specimens from participants (cardiac and dialysis) who had received a total of >7000 units of heparin [activated partial thromboplastin time (APTT) >150 s], warfarin/heparin combination, and specimens from cardiac surgery patients who had received a total of >25,000 units of heparin (APTT >200 s) at the time of collection of specimens. Conclusions: The RST tube provides a suitable alternative to lithium heparin plasma tubes for most patients in a hospital environment. However, latent clotting continued to occur in specimens collected from participants who had received high concentrations of anticoagulants. Clin Chem Lab Med 2010;48:651–7.

Background: Neuromyelitis optica (NMO, Devic syndrome) is an inflammatory disorder of the central nervous system of putative autoimmune etiology that primarily affects the optic nerves and spinal cord. NMO is frequently associated with immunoglobulin G (IgG) antibodies to aquaporin-4 (AQP4-IgG), which are thought to be involved in the patho-genesis of the disease. The frequency and diagnostic relevance of immunoglobulin M (IgM) antibodies to aquaporin-4 (AQP4-IgM) in patients with NMO is essentially not known. Testing for AQP4-IgM may be of importance since 20%–30% of patients with NMO are negative for AQP4-IgG. Moreover, IgM antibodies are more potent activators of complement compared with IgG, and are detectable at NMO lesional sites. Methods: Serum samples from 42 patients with NMO spectrum disorders (NMOSD) and from 66 controls were tested for IgM AQP4-Ab using a cell-based assay employing HEK293 cells transfected with human full length AQP4. To control for possible interactions between IgG and IgM, serum was depleted of IgG prior to testing by indirect immunofluorescence. Results: IgM AQP4-Ab were detectable in 4/42 samples from patients with NMOSD, but in none of the 66 control samples. In three patients, titers were higher following depletion of total IgG from the samples. One sample was positive only after precipitation of total IgG. Conclusions: AQP4 antibodies of the IgM class exist in almost 10% of patients with NMO and might contribute to lesion pathology. Routine testing for AQP4-IgM appears to not be justified, as all AQP4-IgM positive patients were also positive for AQP4-IgG, and none of the AQP4-IgG negative samples were positive for AQP4-IgM. Clin Chem Lab Med 2010;48:659–63.

Background: We evaluated the body fluid (BF) mode on the new Sysmex XE-5000 analyzer. Methods: Red (RBC) and white blood cell (WBC) (differential) counts of BFs (139 patient samples and 87 normal samples) were measured and compared to the Fuchs-Rosenthal chamber and stained cytospin slides. Results: Extended cell counting using the BF mode was noted to have an improved WBC detection limit (CV 20 %) of 10×10 6 /L. Excellent agreement with the manual method was observed for most BFs [mean bias +2 to 6×10 6 /L for cerebrospinal fluid (CSF) and –1 to 12×10 6 /L for other fluids]. In CSF, the BF-mode counted more WBC (polymorphic nuclear cells) compared with the manual method (mean bias +5 to 6×10 6 /L), especially in samples with low cell counts (<20×10 6 /L). Carry over was negligible (mostly <0.17%) and linearity was excellent (mean bias <5%). The reference ranges for CSF (n=87) were RBC 0×10 6 /L, WBC and mononuclear <7×10 6 /L, and polymorph nucleated cells <3×10 6 /L. Conclusions: The BF mode on the Sysmex XE-5000 offers rapid and accurate RBC and WBC (differential) counts in clinically relevant concentration ranges in CSF and other fluids. In addition, the exclusion of high fluorescent cells, such as mesothelial cells and macrophages from WBC counting may reduce the number of manual analyses in pleural fluids and ascites. Clin Chem Lab Med 2010;48:665–75.

Background: The quality of blood-pack units in perioperative blood salvage was studied with respect to the presence of extracellular haemoglobin (Hb) and in terms of oxidative stress and the mechanical properties of red blood cells (RBC). Methods: The study was performed on blood-pack units and patients' blood after retransfusion. Results were compared to those obtained in patients prior to autotransfusion. Free Hb, non-protein thiols (as antioxidant marker) and markers of oxidative stress (conjugated dienes, thiobarbituric reactive substances and protein carbonyl content) were measured. The mechanical properties of RBC were evaluated by their osmotic fragility, membrane fluidity by measuring the fluorescence anisotropy of an extrinsic probe and permeability by measurement of extracellular K + and lactate dehydrogenase. Results: Despite washing, extracellular Hb concentrations remained high (up to 0.7 g/L in blood-pack units) and was associated with a decrease of haptoglobin in patients, despite a concomitant inflammatory syndrome. In blood-pack units, we observed a decrease in antioxidant markers along with an increase in oxidative stress markers in association with an alteration of RBC membrane properties. Conclusions: Haemolysis must be limited during perioperative blood salvage in order to prevent exposure to oxidative stress and improve the efficiency of autotransfusion. Clin Chem Lab Med 2010;48:677–83.

Background: Celiac disease (CD) antibodies, immunoglobulin A (IgA) anti-tissue transglutaminase (anti-tTG), IgA endomysium antibody (EMA), IgA and IgG anti-gliadin antibodies (IgA and IgG AGA) are first-line diagnostic tools used in selecting patients for duodenal biopsy. The goal of this study was to evaluate the diagnostic quality of serological testing for CD. Methods: CD serological tests (IgA and IgG AGA, anti-tTG and EMA) from 11,915 individuals were measured. Data were combined with clinical data and results of duodenal biopsy using a unique Danish personal identification number. Results: The positive predictive value (PPV) varied according to different combinations of positive CD antibodies, being highest when all antibodies were positive (97.6%). The anti-tTG concentration correlated strongly with EMA positivity, number of additional positive antibodies, and higher PPV. A logistic regression model predicted the probability of later biopsy-proven CD in relation to concentrations of IgA AGA and anti-tTG at initial serological screening. Conclusions: The anti-tTG concentration at initial serological CD screening was highly informative in relation to EMA positivity, number of additional CD specific antibodies and PPV. Furthermore, in the high-risk group of patients investigated, the concentrations of anti-tTG and IgA AGA at initial serological screening could accurately predict the probability of future biopsy-proven CD. Clin Chem Lab Med 2010;48:685–91.

Background: The interference of ascorbic acid in the determination of plasma uric acid concentrations, by decreasing the formation of chromophore in Trinder's reaction, is well known. By contrast, the effects of other antioxidant vitamins, such as retinol and α-tocopherol have not been investigated. Knowledge of the analytical interaction of these antioxidants in the uric acid assay would be useful. Methods: The effect of a mix of vitamins (Cernevit ® ) on uric acid analysis in a patient hospitalized in a neurological intensive care unit was observed. The effects of the different antioxidant components of the mixture (retinol, α-tocopherol and ascorbic acid) on the concentration of uric acid from a pool of plasma were also tested. Results: Among the different combinations of vitamins tested, only retinol potentiated the antioxidant effect of ascorbic acid. The most marked effect was observed with 80 IU/mL of retinol and 5.7 mmol/L of ascorbic acid. Conclusions: We demonstrate for the first time the synergistic interference of ascorbic acid and retinol on the measurement of uric acid in plasma. We established that ascorbic acid interference is potentiated by regeneration of reduced ascorbic acid by retinol. Such interference must be kept in mind to avoid misinterpreting low plasma uric acid concentrations in patients in whom this analyte is critical. Clin Chem Lab Med 2010;48:693–5.

Background: In order to assess the reference intervals for B-type natriuretic hormone (BNP) in the first days of life, we measured peptide concentrations using the fully automated Access platform. Methods: Plasma BNP was measured in 188 apparently healthy newborns and infants throughout the first month of extra-uterine life, as well as in 245 healthy infants ranging from 1 month to 12 years of age. Results: BNP showed the highest concentrations in the first 2 days of life, with a progressive decline afterwards. Moreover, BNP values in the first week of life were significantly higher (p<0.0001) than values observed in the next periods. As a result, a significant negative correlation was found between BNP and age values when considering all 433 samples (ρ=–0.816, p<0.0001 by the Spearman rank correlation test). There was no significant difference between BNP values found in males and females. Conclusions: According to this data, our study indicates that at least two reference intervals should be used for newborns and infants. The first, with higher BNP values for neonates in the first week of extra-uterine life, and the other, with lower BNP values for infants aged 2 weeks to 12 years. Clin Chem Lab Med 2010;48:697–700.

Background: Serum tryptase measurements are increasingly being used in clinical practice. However, there is a paucity of studies focused on factors that influence tryptase concentrations. We investigated the relationships between total tryptase concentrations and age, gender, atopy, alcohol consumption, smoking, and common metabolic abnormalities in adults. Methods: This was a cross-sectional study of a random sample from an adult population (n=420, age 18–92 years, 45% males) from a single municipality. Serum total tryptase was measured using a fluoro-enzyme immunoassay. Results: The median tryptase concentration was 5.1 μg/L (range, <1–30.7 μg/L). There was a significant (p<0.0001) continual increase in tryptase with age; the median concentrations were 4.0 μg/L in 18–30 years old and 6.6 μg/L in those >80 years. Female gender and heavy ethanol use were negatively and independently associated with tryptase concentrations. Tryptase was higher in individuals that were non-atopic, overweight, or had metabolic syndrome compared to individuals that were atopic, normal weight, or did not have the metabolic syndrome. However, these associations were attenuated after adjusting for age. Conclusions: Serum total tryptase concentrations in adults are not significantly modified by atopy status, but may be modified by lifestyle factors, such as alcohol consumption and gender. Serum total tryptase concentrations are particularly dependent on age. Clin Chem Lab Med 2010;48:701–6.

Background: Adipocytokines play an important role in controlling energy homeostasis, and in various metabolic processes related to obesity. The aim of this study was to describe serum leptin and adiponectin concentrations in a sample of pubertal Spanish children and to evaluate their association with anthropometric parameters and body composition. Methods: The study included 833 pubertal boys and girls. Serum leptin and adiponectin concentrations were determined by ELISA. Results: Leptin concentrations were significantly higher (p<0.0001) in obese or overweight (OW) children compared with children with normal weight (NW). Adiponectin was significantly lower (p<0.01) in obese or OW girls compared with girls of NW, although these findings were not the same for boys. Weight, body mass index (BMI), waist circumference (WC), hip circumference (HC), and waist to hip ratio were significantly correlated (p<0.01) with leptin concentrations in both genders. Correlation of leptin with fat mass and % fat mass was strong, particularly in boys. The association of adiponectin concentrations with anthropometric variables was weaker in both genders. No significant correlations were found between adiponectin concentrations and fat mass or % fat mass. Conclusions: In summary, our study showed that, in pubertal children, leptin is related to weight, BMI, WC and HC and correlates even more strongly with % fat mass. However, adiponectin was weakly related to anthropometric variables and was not correlated with body fat. Clin Chem Lab Med 2010;48:707–11.

Background: Serum γ-glutamyltransferase activity (GGT), even when within its normal reference range, catalyzes low density lipoprotein oxidation in vitro and predicts cardiovascular events. Of the four GGT fractions (b-GGT, m-GGT, s-GGT, and f-GGT) recently identified in blood, only b-GGT is found within atherosclerotic plaques. Our goal was to identify the determinants of the GGT fractions (b-, m-, s-, and f-GGT) and their association with established cardiovascular risk factors in healthy subjects. Methods: Multiple linear regression analysis was applied to estimate the association of fractional GGT with gender, age, body mass index, arterial pressure (AP), plasma glucose, alanine aminotransferase (ALT), high and low density lipoproteins (LDL-C) cholesterol (HDL-C), triglycerides (TG) and C-reactive protein (CRP) in 200 healthy subjects. Results: All GGT fractions were associated with ALT; b-GGT with AP, TG, and CRP; m-GGT with LDL-C, TG and CRP; s-GGT with TG and CRP, and f-GGT only with LDL-C, whereas gender was associated with s-GGT and f-GGT only. Conclusions: In healthy individuals, cardiovascular risk factors are associated with high molecular weight GGT fractions, namely with b-GGT, the only form present within the plaque. This finding adds to the present knowledge concerning the relevance of GGT, within its reference range, for atherosclerosis-related events. Clin Chem Lab Med 2010;48:713–7.

Background: Survivin is a member of the family of inhibitor of apoptosis proteins that is overexpressed in several human tumors. Previous studies have found that overexpression of survivin in cancer cells induces an antibody response. Methods: We compared 232 serum samples from colorectal cancer (CRC) patients and 365 samples from healthy volunteers using an in vitro enzyme-linked immunosorbent assay to evaluate the survivin autoantibody response in patients. Results: The sensitivity of the anti-survivin response from patients with CRC was 56.9%, and the specificity was 64.1%. When a cut-off value of 5.0 ng/mL was chosen for carcinoembryonic antigen (CEA) in these same serum samples, the values for sensitivity and specificity were 40.9% and 86.6%, respectively. Combined detection using survivin autoantibodies and CEA produced better sensitivity (51.3%) and specificity (89.9%) compared to the sensitivity of CEA (40.9%) and the specificities of the individual markers (64.1% and 86.6%, respectively). The area under a receiver operating characteristic curve was 0.617 for survivin autoantibodies, 0.630 for CEA and 0.694 for both markers together. Conclusions: A positive association between autoantibodies against survivin and preoperative CEA concentrations in sera of patients with CRCs was established. Our results suggest that analysis of both parameters would assist in screening patients with CRC. Clin Chem Lab Med 2010;48:719–25.

Background: Over the last 20 years, high dose therapy followed by hemopoietic stem cell transplantation has been employed in patients with multiple myeloma (MM). During 16 years of follow-up, the degree of tumor response and survival in 238 patients with autologous stem cell transplantation (ASCT) and changes in the serum protein electrophoretic pattern were analyzed. Methods: Agarose gel electrophoresis with densitometric analysis and immunofixation were performed to evaluate serum monoclonal protein. IgM, IgA, IgG and β 2 -microglobulin (β2M) were quantitated. Urine protein electrophoresis with IF was performed on cellulose acetate gel using colloidal silver staining without concentrating. Results: After 34 months of follow-up (range 1–160 months), eight patients (3.4%) showed a distinct monoclonal protein band that was different from their original isotype switch. This was observed to be a transient phenomenon (22.2 months). Thirty-seven patients (15.5%) developed oligoclonal bands (OB) between the first and the twentieth month after ASCT (mean 4.4 months), which persisted for 7.9 months (1–36 months). The mean overall survival time was statistically different (p<0.05) between the group with OB and the group without them. Mean values of serum albumin, β2M, and non-involved immunoglobulins did not show statistical differences. Conclusions: The occurrence of OB could be a potential favorable prognostic marker after transplantation due to the prolonged survival observed. Close follow-up of anomalous protein bands, either in serum or urine, is essential due to the additional difficulty in interpretation when the therapeutic response and evolution are evaluated. Clin Chem Lab Med 2010;48:727–31.