Band 48, Heft 1

After a break of 41 years, 2009 saw the first influenza pandemic of the 21st century caused by a triple-reassortant influenza A (H1N1) virus. The current estimated case fatality rate is lower than that of previous influenza pandemics, but this may change as the pandemic evolves. Illness frequently occurs in previously healthy, young adults with a wide range of clinical presentations. The majority of circulating pandemic viruses remain susceptible to neuraminidase inhibitors, although all strains are intrinsically resistant to the adamantanes. Monovalent vaccines against the pandemic strain are available in both live attenuated and inactivated forms. This review aims to summarise important virological, epidemiological and clinical aspects of the pandemic influenza A (H1N1) virus for physicians and other clinical personnel. Clin Chem Lab Med 2010;48:11–21.

Occult hepatitis B virus (HBV) infection is characterized by the presence of HBV DNA in serum and/or in the liver of patients negative for hepatitis B surface antigen (HBsAg). Occult infection may impact in several different clinical contexts including the risk of HBV transmission with transfusion or transplantation, and endogenous viral reactivation. The gold standard test for detection of occult infection is the amplification of HBV DNA. However, the serological assay for the long-lasting antibody response to the highly immunogenic HBV core antigen (anti-HBc) represents a qualified candidate as a surrogate for DNA amplification, or for increasing overall sensitivity when assessing the risk of occult hepatitis in peripheral blood. The risk of occult hepatitis associated with anti-HBc seropositivity has been demonstrated extensively, and the presence of antibody response to HBc can be considered a sentinel marker of occult HBV infection. Clin Chem Lab Med 2010;48:23–9.

ISO 15189's particular requirements for quality management in medical laboratories provide guidance for (a) relating performance specifications to the intended use of a test or examination procedure, (b) designing internal quality control (IQC) procedures to verify the attainment of the intended quality of test results, as well as (c) determining the uncertainty or results, where relevant and possible. This guidance has particular implications for analytical quality management, specifically for validating method performance relative to quality goals or requirements (intended use), designing statistical quality control procedures on the basis of the quality required for a test and the precision and bias observed for a method, and characterizing the quality achieved in practice by calculating measurement uncertainty. There already exists an error framework that provides practical tools and guidance for managing analytical quality, along with an existing concept of total error that can be used to characterize the quality of laboratory tests, thus there is considerable concern and debate on the merits and usefulness of measurement uncertainty. This paper argues that total error provides a practical top-down estimate of measurement uncertainty in the laboratory, and that the ISO/GUM model should be primarily directed to and applied by manufacturers. Clin Chem Lab Med 2010;48:31–40.

On May 28–29, 2009, a number of medical laboratory opinion leaders, pathologists and biochemists met in Sitges, Spain to discuss issues of interest to medical laboratory professionals. The meeting was sponsored by Bio-Rad Laboratories Inc. (Hercules, CA). Over 40 persons representing Austria, Belgium, Czech Republic, Finland, Germany, Great Britain, Israel, Italy, Netherlands, Portugal, South Africa, Spain, Sweden and the US participated in the 1.5 days meeting. The intended purpose of the convocation was to give medical laboratory professionals from different countries and backgrounds an opportunity to share ideas, concerns and experiences in five areas of interest of the sponsor. These areas of interest included: • a requirement for medical laboratory accreditation across Europe • uncertainty of measurement in a clinical laboratory setting • application of Six Sigma values to characterize laboratory quality • effects of analytical errors on patient care and outcomes • harmonization of allowable total error (TEa) specifications The convocation began with a keynote speech by Dr. James Westgard on “Managing quality vs. measuring uncertainty in the medical laboratory”. Dr. Westgard's presentation was thought provoking and called into question the utility and practicality of using uncertainty in a medical laboratory setting. This journal contains a companion article written by Dr. Westgard on this topic. After the keynote speech, the meeting adjourned into five discussion groups and reconvened the next day to hear the outcomes of the discussions by each of the working groups. This article provides a synopsis of the reports from each working group. Clin Chem Lab Med 2010;48:41–52.

Background: The new swine influenza (H1N1) requires fast and accurate diagnosis. Currently, there are few reports about the diagnostic performance of influenza antigen tests with regard to the H1N1 virus infection. We evaluated the reactivity of eight commercially available rapid antigen tests in samples from confirmed infected patients. Methods: From 23 patients tested positive by polymerase chain reaction (PCR), parallel testing with the antigen tests QuickVue Influenza A+B (Quidel Corporation), Binax NOW Flu A and B (Binax), Clearview Exact Influenza A and B (Inverness medical), TRUFLU (Meridian Bioscience), Directigen EZ Flu A+B (Becton Dickinson), Influenza A and B (Diagnostik Nord), Xpect Flu A and B (remel) and Influenza Antigen Quick (Generic Assays) was performed. Results: Only few antigen tests showed positive reactivity in six of the 23 samples. The virus load of the reactive samples as indicated by the PCR cycle threshold was high. Negative results of rapid influenza tests do not rule out infection with the new influenza A (H1N1) virus. Their analytical sensitivity with reference to the virus load is low and not reproducible. Conclusions: As reliable laboratory results during a pandemic are essential, the diagnostic use of rapid influenza tests seems to be questionable. Clin Chem Lab Med 2010;48:53–6.

Background: Laboratory performance can be measured using a set of model key performance indicators (KPIs). The design and implementation of KPIs are important issues. KPI results from 7 years are reported and their implementation, monitoring, objectives, interventions, result reporting and delivery are analyzed. Methods: The KPIs of the entire laboratory process were obtained using Laboratory Information System (LIS) registers. These were collected automatically using a data warehouse application, spreadsheets and external quality program reports. Customer satisfaction was assessed using surveys. Nine model laboratory KPIs were proposed and measured. Results: The results of some examples of KPIs used in our laboratory are reported. Their corrective measurements or the implementation of objectives led to improvement in the associated KPIs results. Conclusions: Measurement of laboratory performance using KPIs and a data warehouse application that continuously collects registers and calculates KPIs confirmed the reliability of indicators, indicator acceptability and usability for users, and continuous process improvement. Clin Chem Lab Med 2010;48:57–61.

Background: Efficient laboratory service is the cornerstone of modern health care systems. Scientific innovations have contributed to substantial improvements in the field of laboratory science, but errors still prevail. These errors are classified as preanalytical, analytical and postanalytical, depending upon the time of presentation. Methods: The data for 67,438 routine venous blood specimens were scrutinized, and errors were documented over the period of 1 year in the clinical biochemistry laboratory of Govind Ballabh Pant Hospital in Delhi, India. Results: Preanalytical errors were most common, with a frequency of 77.1% followed by postanalytical 15% and analytical 7.9%, respectively. Conclusions: Our study illustrates the importance of proper venipuncture procedures, analytical expertise and correct transcription of numerical data for precise and accurate reporting of results to clinicians. There is an urgent need for close inter-departmental cooperation to meet the goal of ensuring patient well being. Clin Chem Lab Med 2010;48:63–6.

Background: The goal of this study was to validate the DiaSorin Liaison BAP OSTASE, a new method for measurement of bone alkaline phosphatase (BAP), and to compare this method with the Beckman-Coulter Access Ostase. We also wanted to establish the reference range for BAP in adults and children. Methods: We determined the precision, functional sensitivity, recovery, linearity and measurement uncertainty, accuracy profile and β-expectation limits. We defined an adult reference interval using individuals with 25-OH vitamin D >80 nmol/L, parathormone <58 ng/L, and normal calcium, phosphorous and estimated glomerular filtration rate. Each adult subclass (men/non-menopausal women/menopause women) contained 120 individuals. We also determined the 2.5th and 97.5th percentiles from a population of 450 children, stratified according to age and gender. Results: The results of the validation showed: precision <6%, functional sensitivity <0.74 μg/L, mean recovery 98.8±4.2% and good linearity. Relative uncertainty ranged from 9.0% to 12.9%, and the risk of one result falling out of the ±15% acceptance limits was <5% for concentrations between 7 and 94 μg/L. The Bland-Altman plot showed no systematic bias between the two methods. In adults, we did not find any statistical difference between the different subclasses. The upper limit of normality observed in the entire population (n=360) was 21.3 μg/L (90% CI: 18.3–24.2 μg/L). Conclusions: The Liaison BAP OSTASE is a robust method, and is completely validated between 7 and 93 μg/L: in this range, 95% of the values obtained will be within ±15% of the true value. Clin Chem Lab Med 2010;48:67–72.

Background: The Freelite™ system for nephelometric or turbidimetric measurement of serum free light chains (FLCs) has been available since 2001. It has been valuable for the management of patients with oligosecretory myeloma, light chain myeloma and AL amyloidosis. However, there are several limitations of the method. The goal of this study was to evaluate the analytical performance of the FLC assay. Methods: Titrated controls and clinical serum specimens were used to determine precision and post-dilution recovery. Results: As reported elsewhere, we found that the assay had several limitations, including poor post-dilution linearity and overestimation by nephelometry. Conclusions: These data demonstrate that the results of the FLC assay must be interpreted jointly by the clinician and the biologist, taking into account the individual patient's clinical and biological characteristics. Clin Chem Lab Med 2010;48:73–9.

Bakground: The goal of our study was to test the relative stability of urine, unconjugated, free catecholamines and the methyl derivatives. We measured the change in concentrations in commercially available urines after storage at various pH values, temperatures and time, from days up to 10 weeks. Methods: Samples of commercial control urines were adjusted to pH 2.0, 4.0, 6.0 and 8.0 and aliquots stored at ambient temperature (20–26°C), 4°C and –18 o C. The free catecholamines (cats) and the free methyl derivatives (mets) were measured after 1, 2, 3 and 6 days and 1, 2, 3 and 10 weeks using the automated sample trace enrichment dialysis (ASTED) procedure with reversed phase ion pair high performance liquid chromatography (HPLC) and coulometric detection. Results: Free catecholamines were relatively stable, with <15% loss of concentration, when stored at pH 6.0 or less for at least 4 days and up to 10 weeks at pH 2.0 at either 4 o C or –18 o C. At pH 8.0, the concentration fell to <60% after 48 h and at a pH of 6.0 or 8.0, up to 90% was lost within the first week at 4 o C and 25 o C. More than 40% of free normetadrenaline and metadrenaline were lost after 1–2 weeks when stored at 20–25 o C and pH 8.0. After 10 weeks at pH 4.0, 6.0 and 8.0, up to 90% loss was observed at 25 o C. Free cats were stable at pH 2.0 and 4.0 at –18 o C and the free mets were stable at –18 o C over the entire time period studied and at all pHs. Conclusions: In the analysis of free catecholamine and the free methyl derivatives, urine samples should be acidified to a pH range 2.0–3.0 to ensure stability and hence the correct analysis. Clin Chem Lab Med 2010;48:81–7.

Background: Nitric oxide (NO) is known to be a signaling molecule with many physiogical functions including apoptotic process regulation. Since apoptosis may contribute to the pathophysiology of schizophrenia, this study was undertaken to determine the plasma concentrations of NO in schizophrenics. Methods: Nitrite/nitrate (NO 2 – /NO 3 – ) concentrations were measured in plasma from 40 patients with schizophrenia, and 36 age- and gender-matched healthy persons using a colorimetric test. Results: Plasma NO 2 – /NO 3 – concentrations were significantly higher in patients with schizophrenia (102.8±34.7 μmol/L, p<0.0001) than in controls (69.2±13.2 μmol/L). Also, mean NO 2 – /NO 3 – values in female patients and controls were significantly higher (118.2±44.7 μmol/L, p<0.001; 74.8±16.1 μmol/L, p<0.05, respectively) compared to males (94.7±25.3 μmol/L, 67.6±10.8 μmol/L). Significant correlation was seen between plasma NO 2 – /NO 3 – concentrations and heredity, number of episodes and peripheral blood mononuclear cell (PBMC) caspase-3 activity, which was significantly higher in patients than in controls (p<0.05). There was no significant difference in NO 2 – /NO 3 – concentrations between patients with different Positive and Negative Syndrome Scale (PANSS) scores or between patients treated with haloperidol (97.2±31.2 μmol/L) and those treated with other atypical antipsychotic drugs (109.8±33.7 μmol/L). Both parameters showed no significant differences between smokers and non-smokers. Conclusions: This study showed that plasma NO 2 – /NO 3 – concentrations were significantly increased in patients with schizophrenia, being significantly higher in female than male patients, and showing a significant correlation with heredity, number of episodes and PBMC caspase-3 activity. These results suggest that NO could be considered an inducer or regulator of apoptosis in patients with schizophrenia. Clin Chem Lab Med 2010;48:89–94.

Background: Recent literature suggests a role for apolipoprotein L (apoL) aberrations in the pathogenesis of schizophrenia. ApoL is almost exclusively associated with apolipoprotein A-I in high-density lipoproteins (HDLs). The objective of this study was to examine the correlation between symptom scores and serum HDL in antipsychotic-naive schizophrenia patients. Methods: In this cross-sectional study, 60 antipsychotic-naive schizophrenia patients were systematically examined for their symptom scores, with good inter-rater reliability. Concurrently, an overnight fasting serum lipid profile from these patients was assessed. Results: Serum HDL had a significant inverse correlation with a total negative syndrome score (ρ=−0.43; p=0.001). Conclusions: The study observation supports the potential role for HDL abnormalities in the genesis of negative symptoms in schizophrenia. Clin Chem Lab Med 2010;48:95–8.

Background: Biological variation data for free plasma amino acids are lacking from the more comprehensive databases. Therefore, we determined the intra- and inter-individual components of variation in healthy subjects. These data were used to define desirable goals for imprecision, bias and total error, indices of individuality and reference change values. Methods: Plasma samples were collected from 11 volunteers at weekly intervals over 5 weeks. Free plasma amino acids were analyzed by reversed-phase HPLC and analytical and biological variation data were derived using ANOVA. Results: Intra-individual coefficients of variation ranged from 9.5% to 46.4%, with lower values among the essential amino acids. The mean inter-individual coefficient of variation was 46.6% and was higher than intra-individual values for all amino acids. Thus, indices of individuality were below 0.8. Reference change values ranged from 30.9% to 128.4% and total error values ranged from 15.2% to 61.0%. Conclusions: Plasma amino acids exhibit relatively low intra-individual coefficients of variation, with essential amino acids showing tighter homeostatic control. Analytical quality goals can be reasonably achieved with current methods. Reference intervals are of limited value in the detection of unusual results in an individual. Therefore, comparison of serial results by means of the reference change values is recommended. Clin Chem Lab Med 2010;48:99–104.

Background: It has been suggested that potassium concentrations may vary between different geographical regions, possibly reflecting ethnic differences in potassium status. This study compared the serum potassium concentrations of three Asian ethnicities in a single geographical location. Methods: Details of simultaneous serum potassium, creatinine, cholesterol, triglyceride and serum index measurements for samples from polyclinics and health screening were extracted for multivariable linear regression. Haemolysed and duplicate patient samples were excluded. Separate analysis was performed based on measurement platform (Roche or Beckman-Coulter) and patient location. Results: Eighty-five thousand nine hundred and ninety-seven records met the inclusion criteria. When controlled for age, gender, serum creatinine, cholesterol and triglyceride, the average serum potassium concentration in Indians was 0.13–0.16 mmol/L higher than in Malays, who in turn had average serum potassium concentrations 0.05–0.06 mmol/L higher than Chinese when controlled for age, gender, serum creatinine, cholesterol and triglyceride concentrations. For patients undergoing health screening, the average serum potassium concentration in Indians and Malays was 0.12 mmol/L higher than in Chinese. Conclusions: Chinese individuals have lower average serum potassium concentrations than Indians and Malays. This may have clinical implications in relation to the high occurrence of thyrotoxic hypokalaemic paralysis and the aetiology of sudden unexplained death syndrome (SUDS) in Asians. Clin Chem Lab Med 2010;48:105–8.

Background: The free β subunit of human chorionic gonadotropin (free β-hCG) is an important serum marker for biochemical screening. Its weekly median value varies with ethnicity. Most of the fluorometers for lanthanide chelates are designed for the detection of signals from europium (Eu 3+ ) chelates only. Methods: We developed a two-site, one-step assay using two monoclonal antibodies (MAbs) against free β subunit and β subunit with Eu 3+ chelates as labels. Using the present assay, we evaluated 24,634 normal serum samples in Chinese pregnant women during 8–20 weeks of gestation. Results: The detection limit using this assay was <0.05 ng/mL. The within-run and between-run imprecision was <6.0% and 7.0% using control material. Free β-hCG concentrations measured using the current assay in 999 maternal serum samples correlated well with those obtained by samarium (Sm 3+ )-labeled DELFIA free hCGβ assay (r=0.987). The medians for 8–20 weeks for maternal serum free β-hCG were higher in the women from mainland China compared to reports from other countries. Conclusions: The present assay is suitable for use in biochemical screening of women in mainland China. Our study on the median concentrations of free β-hCG will help establish reference values that are specific for ethnic populations from the Chinese mainland. These will be useful for studying the importance of ethnic factors in biochemical screening. Clin Chem Lab Med 2010;48:109–14.

Background: The objective of the present study was to calculate age- and gender-specific reference ranges for serum insulin-like growth factor I (IGF-I) and insulin-like growth factor binding protein 3 (IGFBP-3) concentrations using quantile regression. Methods: From the Study of Health in Pomerania (SHIP), 1798 men and women aged 25–85 years were recruited. Serum IGF-I and IGFBP-3 concentrations were determined using a chemiluminescent immunometric assay on an Immulite 2500 ® analyzer. Quantile regressions were performed to calculate the 2.5th and 97.5th percentiles. Results: The reference ranges identified 43 (4.6%) women and 41 (4.8%) men with serum IGF-I concentrations, and 47 (5.0%) women and 42 (5.0%) men with serum IGFBP-3 concentrations outside the reference range. Conclusions: The use of quantile regression results in accurate calculation of age- and gender-specific reference ranges for serum IGF-I and IGFBP-3. Clin Chem Lab Med 2010;48:115–20.

Background: N-terminal-pro brain natriuretic peptide (NT-proBNP) is a useful cardiac marker that is also influenced by renal dysfunction. It was our objective to assess the relationship between NT-proBNP concentrations in plasma and worsening renal function, and to attempt adjustment of NT-proBNP for renal dysfunction in a prospective, stratified multi-center study. Methods: We stratified 203 male patients according to their cardiac status and the estimated glomerular filtration rate (eGFR). Cardiac disease was assessed by medical history, physical examination and standardized echocardiography. Patients were stratified according to the following: absence of cardiac history and abnormalities (control, CTRL, n=66), cardiac history without left ventricular hypertrophy (LVH) or left ventricular systolic dysfunction (LVD) (history, n=30), LVH without systolic dysfunction (LVH, n=68), and LVD [ejection fraction (EF) <40%, LVD, n=39]. Renal disease was stratified according to the eGFR: 15–30 mL/min (n=52), 31–75 mL/min (n=99), and >75 mL/min (n=52). Results: NT-proBNP was correlated with eGFR in the entire study population and for all levels of cardiac disease (all p<0.01). Regression analysis allowed adjustment of NT-proBNP for eGFR in a continuous manner, and this adjustment significantly improved the predictive value (receiver operating characteristic curve for symptomatic LVD from 0.80 to 0.86, p<0.01; sensitivity from 74% to 83% and specificity from 68% to 79%). Conclusions: NT-proBNP correlates inversely and significantly with eGFR throughout all levels of cardiac strata. We propose for the first time a continuous adjustment algorithm which markedly improves the predictive values of NT-proBNP in male patients with impaired renal function. Clin Chem Lab Med 2010;48:121–8.

Background: Total plasma homocysteine (tHcy) concentration is increased in elderly patients with mental illness. Also, patients with vascular disease have significantly higher plasma tHcy concentration compared with patients without vascular disease. Apolipoprotein E (apoE) status is associated with cardiovascular disease and a major genetic risk factor is inheritance of the e4 allele. In the present study, we investigated the association between plasma tHcy and apoE status. Methods: The relation between apoE status, plasma tHcy and vascular disease was investigated in a cohort of consecutively enrolled elderly patients with mental illness (n=328). Results: Plasma tHcy concentrations were increased (p<0.01) in carriers of APOE4 (13.6 μmol/L; 9.2–21.7 μmol/L) compared to non-carriers (12.4 μmol/L; 8.3–19.9 μmol/L). The proportion of patients with vascular disease was significantly (p<0.001) increased among carriers (61%) compared to non-carriers (42%). An increased percentage (p<0.001) of APOE4 carriers was observed in patients with Alzheimer's disease (AD) with (71%) or without vascular disease (42%), and in patients with vascular dementia (VaD) (54%) compared to a reference group (34%). Conclusions: Since carriers of APOE4 showed an increased likelihood of vascular disease, these patients need more intensive control of other modifiable vascular risk factors. Furthermore, the association between plasma tHcy and the presence of APOE4 might be attributed to an increased proportion of vascular disease in APOE4 carriers. Clin Chem Lab Med 2010;48:129–35.