Band 40, Heft 2

This document reviews the scientific evidence expected to persuade clinical laboratories to substitute pancreatic amylase measurement for total amylase in cases of suspected pancreatic pathology. A substantial evidence is now available to support such change. The measurement of pancreatic amylase in serum is: 1. more sensitive and specific for the detection of pancreatic tissue damage than that of the total enzyme activity, 2. easy and quick to perform in emergency conditions, 3. analytically precise in relation to its clinical application, 4. suitable for easy transfer and comparison of results from different care delivery units, and 5. characterized by welldefined decision limits for the diagnosis of acute pancreatitis.

The non-forage feeding of dairy cows rich in fast absorption carbohydrates, the low value of their euglycemic-hyperinsulinemic clamp suggest a dysregulation of carbohydrate metabolism able to produce neurodegenerative disorders. Comparisons between Alzheimer's disease developed in diabetes mellitus and bovine spongiform encephalopathy (BSE) direct the discussion of the origin of BSE not only towards a contamination by prion proteins.

Patients undergoing long-term hemodialysis (HD) exhibit increased levels of oxidative stress, likely contributing to the increased rate of cardiovascular disease. The present study represents a critical evaluation of some of the most widely used oxidative indicators, as applied to the monitoring of hemodialysis-associated oxidative stress. Total plasma antioxidant capacity was determined by two independent procedures, the total antioxidant status (TAS) and the ferric reducing ability of plasma (FRAP) methods. Plasma lipid peroxidation was assessed by determining the peroxidation products malonaldehyde and 4-hydroxynonenal (MDA-4HNE) as well as lipid hydroperoxides (“Fox-2” and “ d -ROMs” methods). Total plasma thiols and plasma b-tocopherol were also determined. MDA-4HNE levels were higher in HD patients and decreased following HD, possibly due to passive diffusion across dialysis filters. d -ROMs were also higher in HD patients but exhibited a further increase following the dialysis procedure. Serum α-tocopherol did not show any significant differences. Plasma thiols were lower in HD patients and were restored following HD. Plasma total antioxidant capacity determined with either method was unexpectedly higher in HD patients compared to controls, and decreased following HD. These data indicate that, of the biomarkers studied, d -ROMs level is the one more accurately reflecting the oxidative alterations taking place in HD patients, while determination of MDA-4HNE fails to detect oxidation occurring during the HD sessions. In addition, our findings point out that the determination of total antioxidant capacity in HD patients is severely affected by the concomitant fluctuations in plasma urate levels and therefore needs careful interpretation.

We have examined the effects of propofol, taurine, and the combination of propofol and taurine on amino acid profiles and the immune function markers superoxide anion (O 2 − ), hydrogen peroxide (H 2 O 2 ), and released myeloperoxidase (MPO) activity in neutrophils (PMN). Propofol led to significant changes in the dynamic PMN-free amino acid pool. Exogenous taurine significantly reduced PMN neutral amino acid and α-aminobutyrate (α-aba) as intracellular taurine increased. Incubation with propofol plus taurine resulted in lower intracellular taurine levels and elevated α-aba and neutral amino acid concentrations compared to propofol alone. Concerning PMN immune function markers, propofol significantly decreased O 2 − -and H formation and released MPO. Taurine led to an increased release of MPO and concomitant significantly reduced O 2 − and H 2 O 2 levels. When propofol and taurine were applied together they appeared to act additively with regard to superoxide and hydrogen peroxide formation. In the case of MPO, taurine neutralized propofol's effects, supporting the idea that MPO activity may be regulated by taurine. We believe therefore that taurine is important for strengthening PMN host defense capability, although the mechanisms are not yet clear. Moreover, taurine appears to act primarily by altering the PMN osmotic balance, while propofol seems to affect PMN amino acid metabolism and/or uptake and release.

Comparative analysis of the hemochromatosis-associated mutations C282Y, H63D and S65C in the HFE gene in 51 patients using three different methods is reported. One PCR-RFLP method was based on general primers, whereas another employed mutation-specific mismatched primers. The third method was a new PCR-based reverse hybridisation line probe assay (LiPA), comprising DNA amplification by general primers followed by a single step reverse hybridization to specific probes, immobilized on a nitrocellulose strip. Forty-eight (94%) of the 51 samples yielded identical results by all three methods. Three discrepant results were obtained, caused by polymorphisms in the primer binding region, resulting in no amplification at all or selective amplification, leading to misinterpretation of the HFE genotype by PCR-RFLP. The design of the assay and the stringency of the reaction conditions used are crucial to obtain a correct HFE genotype. PCR-LiPA offers an easy and reliable alternative to currently used conventional methods.

Different approaches have been proposed for the enrichment of fetal nucleated red blood cells (NRBC) from maternal blood as an alternative way to obtain fetal tissue for non-invasive prenatal diagnosis. The main purpose of this study was to compare two of our monoclonal antibodies (2E11.3 and 2B7.4 mAbs) with the most widely used commercial anti-CD71 mAb, in terms of their ability to isolate NRBC from maternal blood by magnetic activated cell sorting (MACS). Peripheral blood samples were obtained from 60 pregnant women at a mean gestational age of 16 weeks (range: 10–19 weeks). The number of NRBC isolated by our antibodies (median: 68, range: 0–2102) was significantly higher than that obtained by the commercial antibody (median: 38, range: 0–2165) in the same samples. However, in the final preparations, contamination by maternal nucleated blood cells was lower when the commercial antibody was used. Since fetal NRBC are rare in maternal blood, the improved NRBC recovery achieved by our non-commercial antibodies should facilitate the non-invasive detection of fetal aneuploidies in maternal blood.

It seems likely that the neuropeptide Y (NPY)-leptin axis is involved in the regulation of energy expenditure in man. The purpose of this study was to observe the effect of a model of intense prolonged exercise-mediated energy expenditure (25 km swim race in 6.9–10.5 hours) on leptin and NPY concentrations in male longdistance swimmers. Sixteen long-distance swimmers (mean age 25, range 18–45 years) who took part in a 25 km sea swimming competition (Toroneos golf, Chalkidiki, Greece) participated in the study. Mean competition time was 8.5 hours (range 6.5–10.5). The participants were allowed food and beverage intake ad libitum before and throughout the 25 km race. Venous blood samples were taken prior and immediately after the race for the measurement of serum leptin and plasma NPY. Non-esterified free fatty acids (NEFFA) and glycerol levels were determined as indicators of adipose tissue lipids mobilization. Results showed that leptin levels after marathon swimming were significantly reduced (p<0.001) in all athletes. There was a statistically significant negative correlation (r=−0.812, p<0.01) between the values of leptin and glycerol just after the termination of swimming. Blood serum glycerol and free fatty acid levels were significantly increased (p<0.001) in all swimmers. Plasma NPY levels were also increased (p<0.01) in 81.2% of the swimmers. Linear regression analysis revealed a significant negative correlation between the values of leptin and NPY (r=−0.789, p<0.01). In conclusion, these data support our initial hypothesis that appropriate changes in leptin and NPY take place during marathon swimming to compensate for the negative energy balance produced due to this prolonged effort. This indicates the NPY-leptin axis involvement in the regulation of energy expenditure in man.

It has been suggested that hyperhomocysteinemia observed in patients with occlusive vascular disease is caused by reduced renal function secondary to renovascular disease. We have therefore used serum cystatin C, a new sensitive marker for glomerular filtration, in 59 patients with acute coronary syndromes and high plasma homocysteine (tHcy) concentration to measure renal function. Samples were also obtained from 34 patients with low-normal plasma tHcy and 50 control subjects. The patients with low-normal plasma tHcy concentration showed decreased concentrations of serum cystatin C and serum creatinine and increased concentrations of blood folate and serum cobalamin compared to the controls and to the patients with high plasma tHcy. There was a large overlap in cystatin C concentrations between patients with high and low-normal plasma tHcy. None of the parameters investigated except plasma tHcy were significantly different in the group of patients with high plasma tHcy concentration compared to the control group. In order to further demonstrate the importance of renal impairment, a subgroup of the patients with high plasma tHcy was supplemented daily with folic acid 5 mg, pyridoxine 40 mg and cyancobalamin 1 mg for 3 months. Vitamin therapy reduced plasma tHcy from 18.3±4.6 μmol/l to 9.6±2.2 μmol/l (p<0.0001). However, vitamin treatment did not strengthen the correlation between cystatin C and plasma tHcy concentrations. These findings do not support the hypothesis that subtle renal dysfunction is an important cause of high plasma tHcy concentration in patients with acute coronary syndromes.

We present data on the changes of the bone formation markers osteocalcin (OC), bone-specific alkaline phosphatase (bone ALP) and bone sialoprotein (BSP), as well as the resorption markers pyridinoline (PYD), deoxypyridinoline (DPD), C- and N-terminal telopeptide cross-linked collagen type I (CTX, NTX), and tartrateresistant acid phosphatase type 5b (TRACP) at five time points during the course of two years in healthy premenopausal, perimenopausal and early postmenopausal women. The prospective study showed that CTX ( p <0.001), NTX ( p =0.001) and TRACP ( p =0.001), as well as bone ALP ( p =0.009) and OC ( p =0.052), were significantly increased already in the transition period from peri- to postmenopause. The pyridinium crosslinks indicated an increased collagen degradation rate already in the perimenopause (PYD, p =0.017; DPD, p =0.054). Significant inverse correlations with the two years changes of the bone mineral density were found for bone ALP, CTX, OC and DPD in the perimenopausal group. The measurement of a comprehensive panel of biochemical bone markers clearly shows that metabolic changes in bone metabolism appear pronounced in the perimenopause, a period still presenting satisfactory estrogen supply. Thus, the perimenopause is an important phase for a contingent development of osteoporosis.

The purpose of the work was to establish a reliable procedure for blood sampling from central venous catheters with a minimal loss of blood. Based on previous studies of potassium measurements, the routine procedure had been to discard 12 ml of blood. In order to clear the catheter from substances from the infusion including potassium, the catheters were first flushed with 5 ml of saline. Repeated samples in fractions of 3 ml for hematological analyses (ethylenediaminetetraacetic acid plasma; seven patients), coagulation tests (citrate plasma; seven patients) and for serum measurements (eight patients) showed that a discarded volume of 3 ml corresponding to at least six times the dead-space of the catheters was sufficient after initial flushing with saline.

Following up previous experience with External Quality Assessment (EQA) and Proficiency Testing Programs (PTP) on drugs of abuse (DoA) testing in Italy and in other European countries, the government of the Lombardy Region, first among Italian regions, established in 1995 a compulsory EQA scheme for laboratories authorized to perform these tests. The purpose of the present work is the description of the program and the overall evaluation of the results obtained in the first three annual cycles (1995–1998). During each annual cycle laboratories received 22 urine samples; some samples were collected from patients (“real samples”) and some were “spiked” urine samples. Both types of samples could contain the following substances/classes of substances: opiates, cocaine, cannabinoids, methadone, buprenorphine, benzodiazepines, barbiturates. Type A laboratories used an immunological screening method; they expressed the results as concentrations. Type B laboratories, authorized to perform screening methods followed by confirmatory techniques, searched for and identified single substances and provided an interpretation on possibly taken drugs. During the study period the laboratories produced about 21 000 analytical results. Among them, falsenegative results were 0.9% of true positives, and falsepositive results were 0.7% of true negatives. Performance using the spiked samples was better than using real samples, and performance of type B laboratories better than that of type A. The results obtained during the program are consistent with those of other quality control programs. This program, in addition, has provided information on the status of DoA testing in the Lombardy region's laboratories, in particular on their analytical performance, on the quality of interpretation of results and on a degree of improvement achieved during the program.

The objective of this study was to establish reference intervals for thyroid stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), total thyronine (TT4) and total triiodothyronine (TT3) on the Architect i2000 analyser (Abbott). Serum samples were obtained from apparently healthy adults (n=217, age 18–90 years) excluding individuals taking oral contraceptives or under hormone replacement therapy. The second group were ambulatory euthyroid patients (n=323) excluding those with a history of thyroid disorders. We also investigated thyroid hormones in sera from euthyroid hospitalised patients (n=490) excluding those with severe non-thyroidal illness. The reference intervals for the healthy adults were for TSH 0.17–4.23 mIU/l, for FT4 11.24–26.86 pmol/l, for FT3 2.56–6.36 pmol/l, for TT4 55.8–155.1 nmol/l and for TT3 0.90–2.54 nmol/l. TSH and TT3 concentrations were similar in males and females. However, FT4, FT3 and TT4 levels exhibited significant differences between females and males. No significant differences were observed between the concentrations of TSH, FT3, TT3, FT4 and TT4 in healthy subjects and in euthyroid ambulatory patients aged 18–90 years. TSH levels in healthy subjects were the same in younger and older individuals. In contrast, in outpatients and in hospitalised patients TSH concentrations were significantly lower (20%) in subjects older than 50 years compared to those younger than 50 years. For FT3 and TT3 we consistently observed in all three study groups 6–7% and 8–12% higher concentrations in the younger (<50 years) compared to the older (>50 years) subjects. For FT4 and TT4 no consistent pattern of correlation with age was detectable when the three study groups were analysed independently. The reference intervals for thyroid hormones determined in this study differ considerably from values found in other European and non-European countries. This underlines the need for population-specific reference ranges.

This study was undertaken to evaluate the feasibility of using commercial control materials in a regional external quality assessment scheme (EQAS) for serum carcinoembryonic antigen (CEA) measurement. We have assessed the commutability of 12 commercial control materials using five automated immunochemical systems. We compared the intermethod behavior of the materials with that of 12–14 patient serum pools. In a total of 48 comparisons (12 materials × 4 pairs of analytical systems), seven instances of noncommutability were apparent, as shown by normalized residuals falling outside the ±3 interval. The use of non-commutable materials generates two negative effects. In EQAS, the interlaboratory variation recorded is not representative of the variation expected in the assay of patient sera; in interlaboratory harmonization programs, recalibration with non-commutable materials increases, instead of decreasing, the interlaboratory variation. Both these effects were shown to occur in CEA measurement with the tested materials and systems. The materials planned to be used in our EQAS turned out to be commutable: this gave us the guarantee of measuring realistic interlaboratory variation values, although the check for commutability should be extended to all the analytical systems used by the participants in the scheme.

Simulation can be a means for the laboratory management to investigate the effects of proposed changes in the laboratory. Also, when specifications of analyzers are available one can investigate which analyzer should be purchased to fulfill existing needs. The potential of simulation is shown here by simulating the turn-around time of batched samples under several conditions. Three routine analyzers (DAX, AXON and Immuno-1) were modeled. The temporal pattern of the arrival of the samples at the different analyzers was determined. The impact of these patterns and the two batching methods on the turn-around time was investigated. Simulation proved to be a useful method to study the effects of batching and arrival patterns on the turn-around time.

The Immediate Response Mobile Analyzer (IRMA) is a selective and portable point-of-care testing (POCT) blood gas, electrolyte and hematocrit (Hct) analyzer. The overall analytical performance was evaluated in a two-center study involving two Italian hospital laboratories, following the guidelines suggested by the manufacturer (based on the NCCLS protocol), after a preliminary evaluation of their formal validity. The IRMA was compared to the analyzers used in the routine laboratory as reference. The considered parameters were pH, pO 2 , pCO 2 , Na + , K + , ionized calcium and Hct. When using the aqueous quality control material provided by the manufacturer most of the parameters showed good precision, with the exception of pCO 2 and pO 2 that showed high CVs on two of the three levels of the aqueous control. We could demonstrate that this imprecision was material-related and was reduced when using a different material (blood equilibrated by tonometry). With tonometred blood for pO 2 and pCO 2 and the aqueous material for the remaining parameters the CVs were all below 5%, ranging from 0.08% to 2.8%. The IRMA results correlated adequately with the comparison instruments, with the exception of sodium and ionized calcium where contradictory results were obtained in the two centers.

The painter Johannes Vermeer (1632–75) worked in the town of Delft in the Dutch Republic. This article focuses on associations between his painting method and the expertise in optics available in Delft at the time. His art represents an extraordinary combination of technical prowess and poetic expression.

The European Communities Confederation of Clinical Chemistry has been actively engaged in raising the level of clinical chemistry in the European Union. Closer contacts between the national societies for clinical chemistry have resulted in more comparable programs for postgraduate training of clinical chemists, closer similarity of contents and practice of the profession in the different countries, and the official registration of professionals. This article reviews some of the characteristics of professional organisation, practice, and regulation in the fifteen European Union countries. Many similarities appear. In half of the countries microbiology, blood-banking and transfusion medicine fall within the domain of clinical chemistry. The minimum number of years for training (university and postgraduate) is eight, but in practice this will extend to 10 or more years. Official regulation of the profession by law exists in a minority of countries. Continuing education and re-registration have not been officially instituted yet in any country, but these issues will be the next steps forward. In those countries that prepare themselves for entering the European Union, training and practice of clinical chemistry are moving towards the common standards of the European Communities Confederation of Clinical Chemistry.