Volume 46, Issue 11

Background : All of the recent guidelines now endorse the use of troponin as the biomarker or choice for the diagnosis of acute myocardial infarction (AMI). Methods : Review of the recent guidelines criteria. Results : Rising and/or falling values of troponin in patients who appear to have ischemic heart disease will result in the diagnosis of AMI. The recent guidelines emphasize the use of the 99th percentile value for troponin and suggest it should be measurable with a high level of precision. They also suggest how to operationalize determining a significant change for patients who appear to have recurrent infarction and classify AMI into five subtypes. Conclusions : Understanding these criteria will be important to a consistent approach to the diagnosis of AMI in the future. Clin Chem Lab Med 2008;46:1485–8.

Troponin quality specifications describing the pre-analytical, analytical and post-analytical performance of cardiac troponin (cTn) assays are important for both manufacturers of cTn assays and laboratories that routinely test for cTn. Pre-analytical requirements refer not only to acceptable sample type for analysis and the stability of cTn but also to the proper handling of specimens prior to analysis to avoid pre-analytical false positive results. Analytical issues that may contribute to differences between cTn assays include analytical sensitivity and imprecision at low cTn concentration, antibody specificity and immunoreactivity of plasma cTn forms, assay specificity and the presence of falsely positive and negative interferences, and for cTnI the lack of standardised measurement, all which may impact on patient cTn results. Current second generation cTnI and fourth generation cTnT assays generally have an imprecision of around 20% coefficient of variation (CV) at the 99th percentile of the reference population, which is greater than the recommended imprecision of 10% CV. As the next generation of more analytically sensitive cTn assays are developed it can be anticipated that cTn upper reference limits will decrease by approximately 10-fold. Monitoring assay imprecision at ultra low cTn concentrations will require that the laboratory uses a quality control close to this level and a negative control to monitor baseline drift. Establishment of cTn reference ranges will require reference populations to be cardio-healthy to enable differentiation from community populations who are at increased cardiovascular risk. Close collaboration between the laboratory and local clinicians is required to ensure adequate clinical validation of more sensitive cTn assays. Clin Chem Lab Med 2008;46:1489–500.

Standardization of cardiac troponin I (cTnI) measurement is important because of the central role for diagnosis of myocardial infarction. In blood, cTnI is present as a heterogeneous mixture of different molecular species. The analytical problem caused by this heterogeneity may be circumvented by recognition of a unique, invariant part of the molecule that is common to all components of the mixture. Antibodies used for the development of cTnI assays should selectively recognize epitopes within this invariant part, leading to a consequential increase in the homogeneity of immunoassay reactivity. This should be associated with the use of a reference material that represents the natural and major antigen in blood after tissue release, i.e., the troponin complex. Although a primary reference material for cTnI is available, studies indicate that cTnI assays remain without harmony after recalibration using this material. To achieve closer comparability of cTnI values between assays, the use of a secondary reference material, consisting of a panel of human serum pools, is proposed for use by manufacturers to calibrate their assays. To assign true cTnI concentration values to this secondary reference material, establishment of a reference measurement procedure for cTnI is required. A practical approach to the development of a reference procedure could be to design an immunochemical assay with well-characterized specificity to the invariant part of the cTnI molecule and calibrated using the primary reference material. Clin Chem Lab Med 2008;46:1501–6.

Background : The discovery of the cardiac endocrine function more than 25 years ago was a breakthrough for the implementation of a routine laboratory marker of heart failure. The heart secretes two different natriuretic peptides with similar biological effects. B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) emerged as the superior diagnostic markers compared to circulating A-type natriuretic peptide (ANP) and proANP derived peptide forms. However, the biochemistry with the processing and metabolism of proBNP, NT-proBNP and BNP with their impact on BNP quantification are still incompletely understood. Methods : Published data and own results were used. Results : This review shows that the present understanding of the biochemistry of BNP and its circulating forms is far from complete. The regulation of BNP secretion occurs mainly at the level of gene transcription with only minor stores of proBNP and processed BNP 1–32 within cardiomyocytes. proBNP is believed to be split into BNP 1–32 and NT-proBNP 1–76 mainly upon secretion, although limited amounts of processed BNP have also been described in the secretory granules of atrial cardiomyocytes. proBNP can be also detected in the circulation and exists as a monomer. There is no evidence for relevant processing of proBNP into BNP 1–32 and NT-proBNP in the circulation. Only small amounts of the intact hormone BNP 1–32 appear to circulate in plasma, there are no known BNP binding proteins. The major circulating BNP forms appear to be split products of BNP 1–32, but are still not sufficiently characterized. Dipeptidyl-peptidase IV degrades BNP 1–32 to BNP 3–32 at its N-terminal end. NT-proBNP appears to be rapidly truncated at both ends as well. proBNP and NT-proBNP are glycosylated to a variable degree. BNP and NT-proBNP are extracted by the kidneys to a comparable extent. In contrast to BNP, the biological half-life of NT-proBNP in humans is still not known. The current commercial BNP assays do not significantly cross-react with NT-proBNP and vice versa. However, BNP as well as NT-proBNP assays cross-react with proBNP to a varying extent. Conclusions : The better characterization of circulating proBNP, BNP, and NT-proBNP forms is necessary to define the relevant standard for assay standardization. Until then, assays should be designed to detect the total amount of the circulating analyte to achieve optimal sensitivity. The identification of possible disease effects on proBNP, BNP, and NT-proBNP metabolism could pave the way for the development of more disease specific assays in the clinical setting. Clin Chem Lab Med 2008;46:1507–14.

There is evidence that natriuretic peptide (namely atrial and/or B-type natriuretic peptides) plasma concentration may be elevated in many clinical conditions besides cardiovascular diseases, the most frequent being lung diseases, renal and liver failure, acute cerebrovascular events, acute and chronic inflammatory diseases and certain metabolic and endocrine disorders. In general, increased circulating levels of natriuretic peptides (compared to the normal range of a healthy population) may be considered expression of activation of the neuro-endocrine system, which can be the cause or consequence of cardiac stressor events. Furthermore, some variables, such as gender and obesity, may affect natriuretic peptide secretion and plasma concentration by completely extra-cardiac mechanisms. Increased expression of the natriuretic peptide system, counteracting neuro-hormonal and immunological activation, may occur in many clinical conditions, as witnessed by the considerable number of diseases in which the natriuretic peptide system has been found to be altered. Several studies have demonstrated that higher circulating levels of natriuretic peptides represent a strong independent risk factor for major cardiovascular complications and/or death, even in extra-cardiac diseases. Because several of these diseases may be present in patients with left ventricular dysfunction, the possible influence on diagnostic and prognostic accuracy of natriuretic peptides in heart failure will be discussed. Clin Chem Lab Med 2008;46:1515–23.

Background : B-natriuretic peptide (BNP) and aminoterminal proBNP (NT-proBNP) are clinically useful for the diagnosis of decompensated heart failure and for prognosis in heart failure and acute coronary syndromes. Clinical use of these biomarkers in critically ill patients being treated in intensive care is not well established. Methods : This is a narrative review of evidence identified searching MEDLINE with the strategy [(BNP OR NT-proBNP) AND (critical illness AND intensive care)]. Seven primary reports and two narrative reviews were retrieved. For completeness, literature from each of the following searches was reviewed: [(BNP OR NT-proBNP) AND (critical illness)] and [(BNP OR NT-proBNP) AND (intensive care)]. Results : Primary literature used BNP and NT-proBNP for diagnosis, prognosis and monitoring. For diagnosis of acute lung injury in unselected intensive care patients and for diagnosis of heart failure in trauma patients, the biomarkers had low sensitivity and are of modest use. BNP and NT-proBNP were found to have a significant ability to prognosticate adverse outcomes in critically ill patients. A single paper examined the use of BNP as a non-invasive replacement for pulmonary capillary wedge pressure, finding little value. The impact of renal insufficiency on the markers was noted as a confounder in most studies. In the secondary searches, some preliminary data suggested a possible role for the natriuretic peptides in exclusion of a cardiac cause for certain conditions among intensive care unit (ICU) patients. However, the general findings were that the performance of BNP and NT-proBNP is unimpressive among ICU patients. Conclusions : Currently, utilization of BNP and NT-proBNP does not appear to provide much useful information or have a substantial role in the care of critically ill patients in intensive care. Clin Chem Lab Med 2008;46:1524–32.

The evaluation of cardiac endocrine function by means of automated robust assays has permitted the introduction of a cheap and powerful clinical tool. Plasma concentration of B-type-related natriuretic peptides is a marker of either hemodynamic or neurohormonal stress on the heart and has been validated within the diagnostic and prognostic domain in patients with suspected or ascertained heart failure, mostly in the in-hospital setting. Evidence is growing, supporting an out-of-hospital use, namely in primary care. Its implementation in this setting in screening programs and diagnostic algorithms might contribute to decrease the apparent disparity between the general practitioner and the specialist approach to disease management. Clin Chem Lab Med 2008;46:1533–42.

Acutely dyspneic patients are challenging, because their symptoms can be due to cardiac, pulmonary or other diseases. B-type natriuretic peptide testing offers higher diagnostic accuracy (85%–90%) than clinical assessments for identifying heart failure as the cause of dyspnea. On the other hand, the high clinical sensitivity and negative predictive value of natriuretic peptides permit to rule out heart failure with an accuracy >90%. Natriuretic peptides are the most powerful, single prognostic markers of complications associated with acute dyspnea and permit the early recognition of high-risk patients. It has been shown that systematic natriuretic peptide testing reduces the economic expenses associated with clinical management of acutely dyspneic patients. Finally, whether these biomarkers could be used to guide heart failure therapy in the acute setting remains to be elucidated. Clin Chem Lab Med 2008;46:1543–9.

Reactive oxygen species (ROS) are widely considered to be a causal factor in aging and in a number of pathological conditions, such as atherosclerosis, carcinogenesis and infarction. Their role in bone metabolism is dual, considering their effects under physiological or pathological conditions. Under physiological conditions, the production of ROS by osteoclasts helps accelerate destruction of calcified tissue, thus assisting in bone remodeling. In pathological conditions, when a bone fractures, e.g., radical generation is remarkably high. However, though the increases in osteoclastic activity and ROS production are linked in many skeletal pathologies, it remains to be clarified whether increased ROS production overwhelms antioxidant defenses, leaving the individual open to hyperoxidant stress. Clin Chem Lab Med 2008;46:1550–5.

Total plasma homocysteine (tHcy) concentration is elevated in elderly patients with mental illness compared to control subjects. There are many different determinants of plasma tHcy concentration, including the presence of vascular disease. The presence of vascular disease may contribute to cognitive impairment. Clarification of the role of vascular risk factors in mental illness is important because most are modifiable, in contrast to other risk factors, such as age and genetics. In this review, we summarize the findings of our investigations of vascular disease and plasma tHcy level in elderly patients with mental illness. Elevated plasma tHcy concentration in elderly patients with mental illness was mainly associated with the presence of vascular disease and was not related to the specific psychogeriatric diagnosis. Furthermore, it seems possible that the control of conventional vascular risk factors could be guided by the level of plasma tHcy, serum cystatin C, serum N-terminal pro-brain natriuretic peptide, and serum C-reactive protein. Clin Chem Lab Med 2008;46:1556–61.

Background : Poster presentations at major meetings serve to rapidly present and share study results with the scientific community. On the other hand, full-text publication of abstracts in peer-reviewed journals provides dissemination of knowledge. The purpose of this study was to evaluate the publication rate of abstracts presented at the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Meeting, to assess the factors influencing publication and determine the impact factor of these journals. Methods : All poster abstracts presented at the 2002 IFCC Meeting were included in the study. A Medline search was performed to identify a matching journal article. Topics, country of origin, study type, study center and publication year were tabulated. Journals and impact factors of publication were noted. Results : Out of 900 presented abstracts, 125 (13.9%) were published as full-text articles. Publication rates according to topics of the meeting, country of origin and university affiliation demonstrated significant differences. Abstracts from multi-centered studies had higher publication rates, and the journals they were published in had higher impact factors than single center studies. The median impact factor of the journals was 2.093. According to regression analysis, the major predictors for publication were interventional research and university affiliation (odds ratios 2.916 and 1.782, respectively; p<0.05). Conclusions : The publication rate for abstracts of this clinical chemistry meeting was lower than rates from other fields of medicine. Factors leading to failure require elucidation. Encouraging authors to submit their presentations for full-text publication might improve the rate of publication. Clin Chem Lab Med 2008;46:1562–7.

Background : Transition from communications (abstracts) of an Argentinean congress and their publication as full papers was analyzed. No similar report was found for clinical laboratory in Latin America. Methods : A total of 388 communications from five congresses were identified, and searches were performed on the internet to find the publications. Pairs were established (1 communication, 1 publication), and characteristics were analyzed. Results : In total, 10.8% of the communications were published. Mean time elapsed was 2±1.0 years . A total of 62% of the publications appeared in Argentinean journals and 38% in foreign journals (5 in Spanish, 11 in English). Mean author number was 4.8±2.4 for communications and 5.1±2.3 for publications. In total, 59.5% of the publications changed the number and order of authors. Clinical Chemistry was the main topic (45.4% for communications, 38.1% for publications), followed by Microbiology (21.1%, 23.8%). Universities participated in 217 communications (55.9%) and 32 publications (76.2%), while other institutions participated in 171 communications (44.1%) and 10 publications (23.8%). Conclusions : Publication index was lower than for other congresses. Time elapsed was consistent with others. Preference for Argentinean journals may indicate a focus on local readers but also limitations in language skills. Variations in authorship arise from modifications of individual participation in the final work. More publications from all institutions are desirable. Differences of content were below those reported by others. Clin Chem Lab Med 2008;46:1568–74.

Background : The incidence of variant angina in oriental patients is higher than in patients from the Western world. Endothelin-1 (ET-1) seems to be associated with coronary vasospasm in variant angina, suggesting that ET-1 gene variants may be important in coronary vasospasm in variant angina. We wanted to assess potential association between Korean variant angina and three polymorphisms of the ET-1 gene, which include the +138delA polymorphism in exon 1, G8002A polymorphism in intron 4 and Lys198Asn polymorphism in exon 5. Method : A total of 97 patients with variant angina and 111 healthy controls were studied. Analyses of the +138delA , G8002A and Lys198Asn polymorphisms were carried out by polymerase chain reaction-restriction fragment length polymorphism and haplotype techniques. Results : The frequency of mutant 138delA allele was lower in the angina group than in controls [p=0.003, odds ratio (OR)=0.42] and the frequencies of A8002 or Asn198 were significantly higher in the variant angina group than in controls (p=0.005, OR=2.17 or p=0.009, OR=1.75, respectively). According to haplotype analysis, 4A/A8002/Asn198 haplotype was significantly associated with the disease (p=0.0162, OR=2.33) and 3A/G8002/Lys198 haplotype was protective against the disease (p=0.0043, OR=0.54). Conclusions : The ET-1 gene polymorphisms, such as +138delA , G8002A and Lys198Asn polymorphisms, seem to be associated with variant angina in Korean patients. Clin Chem Lab Med 2008;46:1575–80.

Background : The excretion of cholesterol from liver and intestine is regulated by ATP-binding cassette half-transporters ABCG5 and ABCG8. Polymorphisms in their genes have been related to higher levels of plasma lipids. Thus, the aim of the present study was to evaluate the possible association between the 1950C>G ( ABCG5 ) and the 251A>G ( ABCG8 ) polymorphisms and the presence of hypercholesterolemia (HC) in Chilean subjects. Methods : A total of 118 non-related individuals with HC (total cholesterol, TC ≥6.2 mmol/L) and 104 normolipidemic subjects (controls, TC ≤5.17 mmol/L), aged 18 to 65 years old, were included in this study. The ABCG5 1950C>G and ABCG8 251A>G genotypes were assessed by polymerase chain reaction-restriction fragment length polymorphism. Results : The genotype distribution of the ABCG5 / ABCG8 polymorphisms was in Hardy-Weinberg equilibrium in both groups. The frequency of CC homozygous genotype for ABCG5 1950C>G polymorphism was higher in HC patients than in controls (42% vs. 10%, p<0.001). On the other hand, no significant differences for the 251A>G polymorphism of the ABCG8 gene were observed (p=NS). Nevertheless, HC subjects carrying the GG genotype for the 251A>G variant exhibited higher values of high-density lipoprotein cholesterol when compared to other genotypes (p=0.020). Conclusions : Our data showed that the ABCG5 1950C>G polymorphism is associated with HC in the studied population. Nevertheless, this study is limited by its sample size. Clin Chem Lab Med 2008;46:1581–5.

Background : A paternity disagreement analyzed with 15 autosomal microsatellite markers indicated allele sharing between the mother, questioned child and the alleged father generating an inconclusive paternity result. Design and methods : In total, 15 autosomal and 17 Y tandem repeat loci were analyzed using AmpF l STR Identifiler, AmpF l STR ® Y-filer™ kits followed by six microsatellite markers on X chromosome in DNA extracted from peripheral blood samples of the mother, questioned child and alleged father. Results : Microsatellite analysis examined with 15 autosomal short tandem repeats (STRs) indicated at least one allele sharing at 14 loci between the mother, questioned child and alleged father except for the TPOX locus where a paternal-child allele mismatch was observed. Y chromosome investigations using 17 repeat markers signified the case as non-paternity (exclusion). A complete match of the six X chromosome loci in the questioned child with the mother was observed. Conclusions : Our investigations on inconclusive paternity due to atypical allele sharing in autosomal microsatellites were resolved with X- and Y-chromosome STR analyses confirming the case as non-paternity. Clin Chem Lab Med 2008;46:1586–8.

Background : Fatty acid metabolites play a key role in numerous physiological and pathological processes. A rapid liquid chromatography-mass spectrometry assay for the simultaneous determination of prostanoids, isoprostane and lipoxygenase (LOX) derived fatty acid metabolites in a small biological sample of only 20 μL was developed. Methods : Human plasma samples were applied to a filter spot, extracted without prior derivatization and analyzed within 13 min. Detection of metabolites was performed on a triple quadrupole mass spectrometer in negative multiple-reaction monitoring detection mode. Application of this assay to various biological matrices was performed. Results : The validated assay was linear over the concentration range of 5–500 nmol/L for prostanoids and isoprostane, 50–5000 nmol/L for LOX-derived metabolites and 400–40,000 nmol/L for fatty acids. Limits of quantitation were 0.4–233 nmol/L, depending on the metabolite. Plasma samples from diabetic patients and controls showed significant increases in (±)9-HODE and 15(S)-HETE with p-values of 0.019 and 0.024, respectively. Conclusions : The small amount of 20 μL sample volume used in this assay and the demonstrated application to various sample types makes it an ideal routine analysis method for fatty acid metabolites. The resulting values for LOX-derived metabolites in diabetes mellitus type 2 samples support earlier findings about the role of lipid oxidation products in diabetes. Clin Chem Lab Med 2008;46:1589–97.

Background : The aim of this study was to provide an improved outline of the patterns and correlates of changes in plasma bilirubin after partial hepatectomy. Methods : A large series of blood measurements and complementary variables were prospectively collected from 85 patients undergoing liver resection, and bilirubin correlations were assessed by regression analysis. Results : Early postoperatively, the best simultaneous correlates of increasing bilirubin were the preoperative value, the duration of surgery, and the number of blood transfusions (r 2 =0.74, p<0.001). Subsequently, increasing bilirubin became related to the number of resected liver segments, the duration of intraoperative liver ischemia, the use of continuous vs. intermittent ischemia, and the presence of sepsis (r 2 =0.82, p<0.001); these were also the best simultaneous correlates of peak bilirubin. This pattern was characterized by prominently conjugated hyperbilirubinemia, hypocholesterolemia, and moderately increased alkaline phosphatase, and occurred in the absence of obstructive cholestasis. Conclusions : Major hepatectomy, parenchymal ischemia, and sepsis have similar and synergistic impacts as determinants of prominently conjugated hyperbilirubinemia after liver resection. This is likely related to impaired hepatocellular bilirubin transport and occurs in the absence of obstructive components. Clin Chem Lab Med 2008;46:1598–601.

Background : The offspring of individuals with a history of premature myocardial infarction are at increased risk of premature coronary attacks. The aim of this study was to determine parent/offspring associations of coronary risk factors in families affected by premature myocardial infarction and to compare these to corresponding control families. Methods : The cohort of cases consisted of 71 male survivors of myocardial infarction and their 128 descendants (aged 7–18 years). As control families, 85 randomly selected healthy males with their 66 descendants were investigated. Besides traditional risk factors, serum high sensitive C-reactive protein (hsCRP), apolipoprotein (apo) E phenotypes and lipoprotein(a) were analyzed. Results : In the offspring of the patients, fibrinogen and atherogenic lipoprotein parameters were higher than in the corresponding controls, but hsCRP, lipoprotein(a) and anthropometric data did not differ between the groups. The adult-offspring positive correlations were detected in fibrinogen and in almost all measured lipoprotein fractions in the affected families; amongst the controls, the association was observed only for triglyceride levels. Multiple logistic regression analysis demonstrated independent association of offspring apoB, apoA-I and fibrinogen levels with a family history of premature myocardial infarction. Conclusions : The most informative predictors of future coronary attacks during childhood are apoB-100 and apoB/apoA-I ratio; serum hsCRP and lipoprotein(a) do not have predictive value in childhood. Clin Chem Lab Med 2008;46:1602–8.

Background : We investigated the expressions and ratios of type 1 T helper cell (Th1) cytokines interferon-γ (IFN-γ) and interleukin-2 (IL-2), as well as type 2 T helper cell (Th2) cytokines interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-13 (IL-13) and interleukin-10 (IL-10) in pelvic inflammatory disease (PID) patients. Methods : The human cytokine LINCOplex multiplex bead array was used to measure the plasma levels of Th1 and Th2 cytokines in 50 healthy controls, as well as in 41 PID patients before and after routine protocol treatment. Results : Significantly increased expressions of Th1 cytokine IFN-γ (p=0.004), as well as Th2 cytokine IL-5 (p=0.001), and dramatically increased IL-10 (p=0.0001), but significantly decreased expression of Th1 cytokine IL-2 (p=0.029) in PID patients were found after comparison to the control group. The ratio of IFN-γ to IL-13 showed a significant increase, but the ratios of IFN-γ to IL-10 and IL-2 to IL-10 was significantly decreased in PID patients before treatment compared to after treatment and controls. Conclusions : The results indicate that the imbalance and cross-regulation between Th1 and Th2 cytokines pathways is probably contributed to the mechanism of PID. Clin Chem Lab Med 2008;46:1609–16.

Background : The A1C-Derived Average Glucose (ADAG) study was commenced to gain a better understanding of the relationship between HbA 1c and average blood glucose and to investigate if HbA 1c could be expressed in the same units as day-to-day glucose monitoring. Owing to the impact of the outcome of this study it was very important to determine HbA 1c values with a minimum of uncertainty and as close as possible to the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) primary reference method, which is the only valid anchor of HbA 1c standardization. Methods : Approximately 2300 samples were analyzed with four IFCC secondary reference methods. Additional off-line calibration with IFCC secondary reference material with assigned IFCC values was performed to improve the uncertainty in the HbA 1c value determination. Results : Additional off-line calibration improved the 95% confidence interval between the four different HbA 1c methods at HbA 1c of 6.00% from ±0.28% (5.72%–6.28%) to ±0.20% (5.80%–6.20%) and at HbA 1c of 9.00% from ±0.43% (8.57%–9.43%) to ±0.24% (8.76%–9.24%). Conclusions : The HbA 1c results used in the ADAG study were determined with the lowest uncertainty technically feasible by using four certified IFCC secondary reference methods and additional off-line calibration with IFCC secondary reference material. Clin Chem Lab Med 2008;46:1617–23.

Background : Biogenic amine, adrenaline, noradrenaline, dopamine and 5-hydroxy-tryptamine (5-HT) levels are related to interleukin-6 (IL-6) plasma concentrations and endurance exercise. The aim of our study was to investigate the effect of the mode of delivery on maternal-neonatal IL-6, biogenic amine and their precursor amino acid levels. Methods : Some women with normal pregnancy (n=56) were divided into two groups: group A (n=26) with normal labor and vaginal delivery, and group B (n=30) with scheduled cesarean section. Blood was obtained from the mothers at the beginning of labor and immediately after delivery (pre- vs. post-delivery), as well as from the umbilical cord (CB). Total antioxidant status (TAS) and IL-6 levels were measured with commercial kits, the precursor amino acids, tyrosine and tryptophan with tandem mass spectrometry and the biogenic amine blood levels with HPLC methods, respectively. Results : TAS, IL-6, biogenic amine and their precursor amino acid blood levels were similar in the two groups of mothers pre-delivery. TAS levels were reduced, whereas the amino acids, the catecholamine, 5-HT and IL-6 levels were increased post-delivery and in the CB of group A and unaltered in group B at the same time of the study. Conclusions : During a vaginal delivery process, the low TAS, the increased levels of the studied amino acids, the catecholamines, 5-HT and IL-6 may be due to the activation of the neuroendocrine system and the participation of skeletal and uterine muscles. The mode of delivery may be taken into account when IL-6 plasma levels are evaluated as an anti-inflammatory index perinatally. Clin Chem Lab Med 2008;46:1624–30.

Background : Sirolimus is an immunosuppressant used in solid organ transplantation. Due to variable individual pharmacokinetics and narrow therapeutic ranges, therapeutic drug monitoring (TDM) is critical to the success of post-transplantation patient care. We developed a rapid method quantifying whole blood sirolimus using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with an automated online extraction technology. Methods : Whole blood (100 μL) was mixed with a precipitation solution containing internal standard (32-desmethoxyrapamycin) and centrifuged at 15,634× g for 10 min. The supernatant (50 μL) was injected onto a turbulent flow preparatory column and then a C18 analytical column. The mass spectrometer was set for positive electrospray to monitor the ammonium adducts. Results : Analytical time was 4 min/injection. Inter- and intra-assay variation coefficients across three concentration levels ranged from 2.3% to 7.4%. The method was linear from 1.0 to 100.0 ng/mL with an accuracy of 93.3%–100.0%. No carryover was detected from samples at 313.6 ng/mL. There was no obvious ion suppression from patient samples or interference from other commonly used immunosuppressants. Good correlation with an in-house commercial LC-MS was observed. Conclusions : The LC-MS/MS method coupled with turbulent flow technology is rapid and efficient in TDM of whole blood sirolimus. Clin Chem Lab Med 2008;46:1631–4.

Background : Urine microscopic analysis is hampered by its lack in standardisation and semi-quantitative reports, resulting in limited reliability. Automation of urinalysis could overcome these problems. Methods : We compared the performance of the iQ200 with traditional microscopy and strip analysis in routine urinalysis. A total of 1482 routine samples, positive in dipstick testing, were evaluated for erythrocytes, leukocytes, casts, dysmorphic erythrocytes and bacteria using the iQ200 and traditional microscopy. The results of 320 of these samples were linked to underlying urological pathology as well as results from bacterial culturing. Results : Analytically, the iQ200 surpasses traditional microscopy. The identification of casts and dysmorphic erythrocytes in routine samples improves when using the iQ200, although the sub-classification of casts required well-trained technicians. The auto-classification of particles was least reliable for yeast and bacterial cocci. The quantitative reports, and therefore the use of precise cut-off points allowed earlier and improved detection of urinary tract pathology. Conclusions : The performance of the iQ200 is equal to traditional microscopy, but it strongly improves the reliability of urinalysis by standardisation, quantitative reports and improved workflow. From a clinical point of view, renewed attention and improvement of routine urinalysis aids in the efficient detection of renal and urinary tract pathology. Clin Chem Lab Med 2008;46:1635–40.

Background : Blood alcohol determination plays an important role in laboratory medicine and forensic medicine. Nowadays, many methods are being used for alcohol measurement, but these methods are time-consuming and complex to perform laborious sample pre-treatment. The disposable amperometric biosensor, due to its portability, low cost and potential for fabrication, should be readily applicable for blood alcohol determination. Methods : The biosensor was fabricated by immobilizing alcohol dehydrogenase and nicotinamide adenine dinucleotide coated by Nafion combined with gold nanoparticles onto the surface of screen-printed electrode modified with Meldola's blue. Evaluations of biosensor performance were performed according to the relevant National Committee for Clinical Laboratory Standards standard. Results : The biosensor response for serum alcohol presents good linearity, precision, stability, accuracy, and specificity. Conclusions : The biosensor exhibits the capability of detecting blood alcohol concentration in the clinical laboratory and in forensic medicine, unnecessarily performing laborious sample pre-treatment. Clin Chem Lab Med 2008;46:1641–7.

Background : Total error (TE) in analytical measurement is calculated as systematic error (SE) plus z-times random error (RE). The z-multiplier is typically chosen at the 95% probability level, being 1.96 in the absence of SE (two-sided 95% probability) and 1.645 when SE is of considerable magnitude (one-sided 95% probability). Up to now, no SE/RE ratio dependent z-values have been considered. Here, we present z-values for SE/RE ratios ranging from 0 to 1. Methods : The z-multiplier (95% probability level) was empirically obtained by modulation of the standard normal distribution with the EXCEL NORMDIST function (Microsoft EXCEL ® 2002). In total, five distributions representing SE/RE ratios between 0 and 1 were calculated, so that the total probability outside a TE boundary ±1.96 σ was in the order of 5.013%. Results : For distributions with SE/RE ratios ranging from 0 to 1 that satisfy the aforementioned total probability outside a TE boundary ±1.96 σ, we found that the associated z-multipliers exhibit values from 1.96 (SE/RE=0), 1.769 (SE/RE=0.25), 1.68 (SE/RE=0.5), 1.651 (SE/RE=0.75) to 1.645 (SE/RE=1). The respective probability values beyond ±1.96 σ were 2.5%/2.5%, 1.165%/3.849%, 0.368%/4.645%, 0.081%/4.934%, and 0.013%/5% for the SE/RE ratios of 0, 0.25, 0.5, 0.75, and 1. Conclusions : The results show that at SE/RE ratios >0.75 the one-sided 95% probability level is practically reached. The results allow a refined calculation of TE at specified SE/RE ratios and a general understanding of the relevance of two- and one-sided probabilities at different SE/RE ratios. Clin Chem Lab Med 2008;46:1648–9.