Band 45, Heft 1

The appropriate development of hemostasis encompasses a delicate equilibrium between anti- and prothrombotic forces developing during three distinct phases (primary hemostasis, coagulation and fibrinolysis) that are closely linked to each other and precisely regulated to close vessel wounds, promote vascular healing and maintain vessel patency. Imbalance in each of these systems produces either hemorrhagic or thrombotic disorders. Inherited bleeding disorders, caused by quantitative or qualitative alterations of either platelets or plasma proteins involved in blood coagulation and fibrinolysis, may lead to serious and lifelong bleeding conditions, the severity of which is inversely associated with the degree of the underlying defect. Rapid and reliable identification of these pathologies is worthy of focus to allow the adoption of appropriate substitutive or supportive antihemorrhagic therapies. Evaluation of the hemorrhage-prone patient requires careful recording of the medical history, attention to pertinent physical findings and the discretionary use of laboratory resources. Owing to the low diagnostic efficiency of clinical history and examination, an appropriate and reliable laboratory approach, encompassing first- and second-line testing, is essential to screen, diagnose and monitor patients with bleeding diatheses. As both the analytical sensitivity and responsiveness of traditional coagulation assays to different abnormalities differ widely, each laboratory should establish individual guidelines based on field experience and on reagent and instrument characteristics. Emerging evidence indicates that the implementation of global coagulation tests, such as the thrombin generation assay and clot waveform analysis, would provide additional information for clinical decision-making for patients with inherited bleeding disorders. Clin Chem Lab Med 2007;45:2–12.

Transfer of automated laboratory data collected during routine clinical care from the laboratory information system into a database format that enables linkage to other administrative (e.g., patient characteristics) or clinical (e.g., medication, diagnoses, procedures) data provides a valuable tool for clinical epidemiological research. It allows the investigation of biochemical characteristics of diseases, therapeutic effects and diagnostic and/or prognostic markers for disease with easy access and at relatively low cost. To this end, the Utrecht Patient Oriented Database (UPOD), an infrastructure of relational databases comprising data on patient characteristics, laboratory test results, medication orders, hospital discharge diagnoses and medical procedures for all patients treated at the University Medical Centre Utrecht since January 2004, was established. Current research within UPOD is focused on the innovative linkage of laboratory and medication data, which, for example, makes it possible to assess the quality of pharmacotherapy in clinical practice, to investigate interference between laboratory tests and drugs, to study the risk of adverse drug reactions, and to develop diagnostic and prognostic markers or algorithms for adverse drug reactions. Although recently established, we believe that UPOD broadens the opportunities for clinical pharmacoepidemiological research and can contribute to patient care from a laboratory perspective. Clin Chem Lab Med 2007;45:13–9.

Background : Cardiovascular diseases (CVDs) are the leading cause of death in most countries of the world. In this study, associations between CVDs and polymorphisms of angiotensin-converting enzyme ( ACE ), atrial natriuretic peptide ( ANP ), β 2 -adrenal receptor ( B2AR ) and endothelial nitric oxide synthase ( ENOS ) genes were explored in a community-based setting. Methods : Between March and May 2001, 1740 subjects ≥35 years from the Matsu area in Taiwan were recruited to this study, representing 71.6% of the target population in Matsu. After informed consent was obtained during an interview, physical examination, resting ECG, serum biochemical profile and a questionnaire survey were used to obtain information. Genomic DNA was also collected and analyzed. Owing to technical limitations, 1186 samples were analyzed. Genetic polymorphisms of the genes in question were investigated using PCR and restriction fragment length polymorphism (RFLP). The distribution of allele frequencies for these genes was derived for stroke, coronary artery disease, hypertension, diabetes, hypercholesterolemia, hypertriglyceridemia and overweight subgroups. Results : The ENOS Glu298Asp polymorphism was associated with hypercholesterolemia (odds ratio 0.658, 95%CI 0.460–0.940; p=0.025) and the ACE D/I variant was associated with hypertriglyceridemia (odds ratio 0.722, 95%CI 0.536–0.973; p=0.033). Polymorphisms of the other genes were not associated with any of the disease groups. Conclusions : This community-based study reveals that genetic factors might play a role in the metabolism of lipids. The genetic risk for CVDs needs further investigation. Clin Chem Lab Med 2007;45:20–5.

Background : The aim of our study was to determine the frequency of anti-thyroid-stimulating hormone (TSH) receptor antibodies (TRAb) in Tunisian patients with Graves' disease (GD) and to compare the validity of TRAb to that of thyroperoxidase (TPO-Ab) and thyroglobulin antibodies (TG-Ab). Methods : ELISA was used to determine the frequency of TRAb, TPO-Ab and TG-Ab in sera of 190 patients with GD. Patients were divided into four groups: those with untreated active GD (group A, n=71), those receiving treatment with anti-thyroid drugs (group B, n=85), those in relapse (group C, n=15) and those in remission (group D, n=19). Sera of 100 healthy blood donors served as controls. Results : The sensitivity of TRAb for the diagnosis of GD (95.8%) was significantly higher than that of TPO-Ab (73.2%) and TG-Ab (42.2%) (p=0.0005 and p<10 –7 , respectively). The positive rate for TRAb was lower in group B than in group A (70.6% and 95.8%, respectively; p=0.0001). The levels of TRAb were significantly higher in group A than in group B (mean 30.1 and 14.2 IU/L, respectively; p=0.006). Conclusions: TRAb, but neither TPO-Ab nor TG-Ab, is valuable in the diagnosis and management of patients with GD. Clin Chem Lab Med 2007;45:26–9.

Background : Pancreatic cancer is an aggressive malignancy of the gastrointestinal tract and one of the most lethal human cancers. It has been shown that endogenous cytokines, produced aberrantly in many malignancies, including pancreatic cancer, may act as autocrine growth factors or as indicators of the immune response to tumors. Granulocyte-colony stimulating factor (G-CSF) and macrophage-colony stimulating factor (M-CSF) are hematopoietic growth factors (HGFs), i.e., cytokines that induce proliferation of hematopoietic and cancer cells. Methods : Serum levels of G-CSF, M-CSF, carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9) were determined using immunoenzymatic assays in 62 patients with pancreatic cancer before and 30 days after surgery, and in 65 healthy controls. Results : Cancer patients had significantly higher levels of all parameters measured compared to healthy subjects, especially in non-resectable tumors. Higher values of diagnostic parameters [specificity, sensitivity and area under receiver operating characteristic (ROC) curve] were observed for M-CSF than G-CSF, and for combined use of M-CSF with CA 19-9. Based on Cox analysis, elevated preoperative serum M-CSF was a significant prognostic factor for patient survival, although not independent of tumor stage. Conclusions : Our findings suggest the usefulness of M-CSF as a tumor marker for pancreatic cancer, especially in combination with CA 19-9. Clin Chem Lab Med 2007;45:30–4.

Background : There are few data on the impact of insulin resistance on the recently defined categories of prehypertension (PHT) and prediabetes (PDM). The aim of this study was to examine associations of surrogate markers of insulin resistance with PHT/PDM. Methods : Subjects included 554 individuals who underwent a 75-g oral glucose tolerance test (OGTT). They were classified into four groups using a severity score for high blood pressure and glucose tolerance. Insulin resistance was measured using the homeostasis model assessment of insulin resistance (HOMA-R) and three surrogate markers obtained from 75-g OGTT values (ISI-composite, Stumvoll index, and OGIS index). Results : HOMA-R increased significantly, but the other three surrogate indices decreased with increasing severity score. Of these markers, the OGIS index was mostly associated with prevalent PHT/PDM and the odds ratio for insulin resistance was 3.61 (95% CI 1.68–7.76, p=0.001) for subjects with either PHT or PDM and 29.98 (12.81–70.18, p<0.001) for subjects with both PHT and PDM. Conclusions : PHT and PDM frequently coexist in relatively lean Japanese subjects. Decreased insulin sensitivity may contribute to the underlying status of PHT/PDM. Among the surrogate markers of insulin resistance, the OGIS index is the most sensitive for assessment of PHT/PDM status. Clin Chem Lab Med 2007;45:35–9.

Background: Measurement of some haemostatic factors and products formed during activation of haemostasis seems to be promising in the determination of hypercoagulability. Methods: The fibrinolytic variables euglobulin clot lysis time, tissue-type plasminogen activator, plasminogen activator inhibitor-1 and the haemostasis activation markers prothrombin fragment 1+2, thrombin-antithrombin complex and D-dimer were determined in 101 apparently healthy men and women aged 20–92 years (58±18 years, mean±SD) to establish variability due to several demographic, behavioural and metabolic factors. Results: None of the fibrinolytic variables were affected by smoking, while tissue-type plasminogen activator antigen was significantly lower in women compared to men. Multiple regression analysis revealed several independent associations between tissue-type plasminogen activator, plasminogen activator inhibitor, body mass index and lipid levels, describing up to 40% of the variance in fibrinolytic variables. For haemostasis activation markers, no gender difference or effect of smoking was observed. Only D-dimer was independently associated with age. The haemostasis activation markers determined proved to be extremely sensitive to blood sampling procedure and were significantly higher in samples obtained by an untrained nurse compared to a trained nurse. Conclusions: Fibrinolytic variables are predominantly modulated by age, body mass index and blood lipids, while haemostasis activation markers are mainly un-influenced by these factors. Clin Chem Lab Med 2007;45:40–6.

Background : Recently, homocysteine production was observed in tumour cell lines and homocysteine was proposed as a tumour marker. Furthermore, homocysteine production by activated immunocompetent cells was demonstrated. Methods : In this study, homocysteine metabolism and immune activation status were investigated in 128 patients suffering from various types of cancer (haematological disorders, lung cancer, gastrointestinal tumours, gynaecological cancer and tumours of other localisation) and healthy age-matched controls. Results : A high percentage of patients (39.1%) showed moderate hyperhomocysteinaemia, while cysteine, folate and vitamin B 12 concentrations were within reference ranges. Most patients were found to have elevated concentrations of the immune activation and inflammation markers neopterin and C-reactive protein (CRP), as well as a higher erythrocyte sedimentation rate (ESR). Patients of different cancer groups differed significantly regarding vitamin B 12 and neopterin concentrations; higher B 12 levels were also associated with tumour progression. Univariate regression analysis showed that CRP, ESR and neopterin were suited best to predict death. In multivariate analysis, neopterin was best suited to predicting death, while homocysteine and B vitamins were not associated with patient outcome. Homocysteine concentrations were correlated with folate and cysteine levels. Higher neopterin concentrations coincided with lower folate concentrations, but higher vitamin B 12 concentrations. Conclusions : Associations between neopterin and folate concentrations may indicate that cellular immune activation might partly contribute to the development of folate deficiency in cancer patients, thus possibly also impairing homocysteine remethylation. Clin Chem Lab Med 2007;45:47–53.

Background : Hyperhomocysteinemia has been associated with vascular disease in many epidemiological studies. However, the pathophysiology is unclear. It is postulated that increased levels of homocysteine induce an inflammatory response in endothelial cells, mediated by pro-inflammatory cytokines and chemokines. The aim of this study was to investigate whether plasma concentrations of interleukin-6, interleukin-8, C-reactive protein, and monocyte chemoattractant protein-1 are increased with higher plasma homocysteine concentrations and whether decreasing homocysteine by vitamin supplementation decreases the concentration of these markers. Methods : Plasma homocysteine, interleukin-6, interleukin-8, C-reactive protein, and monocyte chemoattractant protein-1 concentrations were measured in 230 volunteers before and after 8 weeks of multivitamin supplementation (folic acid, B 6 , and B 12 ). Results : At baseline, plasma homocysteine concentration was weakly associated with interleukin-8, but not with interleukin-6, C-reactive protein or monocyte chemoattractant protein-1. Vitamin supplementation resulted in a significant decrease in homocysteine concentration, but no effect on interleukin-6, interleukin-8, C-reactive protein or monocyte chemoattractant protein-1 was observed. Conclusions : At baseline homocysteine was only weakly correlated with interleukin-8, but not with interleukin-6, C-reactive protein or monocyte chemoattractant protein-1. Vitamin supplementation affected homocysteine concentration, but not cytokine levels. The hypothesis that hyperhomocysteinemia increases arteriosclerotic or thrombotic risk through vascular inflammation was not supported by this study. Clin Chem Lab Med 2007;45:54–8.

Background : It has been suggested that an increase in oxidative stress in individuals with Down syndrome (DS) may cause adverse effects in the cell membranes through the oxidation of polyunsatured fatty acids. Methods : We examined erythrocyte malondialdehyde (MDA) levels in 100 individuals of both sexes (34 males and 66 females) with DS, aged from newborn to 29 years. The cytogenetic analysis revealed 90 individuals with regular trisomy 21, four individuals with trisomy 21 by Robertsonian (Rb) translocation, and six individuals with mosaic trisomy 21. DS individuals were divided into six age groups. The control group consisted of 100 healthy individuals of both sexes (40 males and 60 females) who were age-matched with DS subjects. Results : No significant differences were found in erythrocyte MDA levels between the sexes in any of the age groups for the DS group and the control group. We confirmed significantly higher erythrocyte levels of MDA in individuals with DS compared to the control group. A significant difference was observed in erythrocyte MDA levels between DS individuals with trisomy and controls for all age groups, and in individuals with DS due to Rb translocation trisomy. However, in DS individuals with mosaicism, MDA levels depended on the percentage of diploid and trisomy cells. Conclusions : Our results confirm an increase in lipid peroxidation in patients with DS. Clin Chem Lab Med 2007;45:59–62.

Background : Pregnancy-associated plasma protein A (PAPP-A) was recently described as a new marker of cardiovascular events and of inflammation in uremic patients. The aim of this study was to determine levels of PAPP-A in chronic dialysis patients and its possible relationships with renal osteodystrophy. Methods : A total of 99 adult chronic hemodialysis patients, 14 peritoneal dialysis patients and 41 control subjects were included in the study. Serum PAPP-A, intact parathormone (iPTH), calcium, phosphorus and alkaline phosphatase (ALP) were measured. The correlations between PAPP-A and iPTH, calcium, phosphorus and ALP were determined. Results : PAPP-A levels were significantly higher in peritoneal dialysis [4.5 (3.2–6.7) mU/L, median (interquartile range)], and hemodialysis patients [4.7 (3.8–6.5) mU/L] in comparison to control subjects [3.4 (3.0–5.0) mU/L] (p<0.05). In hemodialysis patients, post-dialysis PAPP-A levels [6.2 (4.7–9.4) mU/L] were significantly higher than pre-dialysis levels [4.7 (3.8–6.5) mU/L] (p<0.05). There was a weak but statistically significant positive correlation between serum PAPP-A and iPTH (r=0.216; p=0.041) and ALP (r=0.205; p=0.044) in the hemodialysis group. Correlation between the duration of dialysis therapy and PAPP-A levels was also significant (r=0.267; p=0.008) in the hemodialysis group. Conclusions : PAPP-A levels are elevated in acute coronary syndromes and are closely related to inflammation and oxidative stress. We conclude that PAPP-A levels are increased in dialysis patients and may reflect a greater degree of chronic inflammation than osteodystrophy in uremic patients. Clin Chem Lab Med 2007;45:63–6.

Background : L-Cysteine (L-Cys) is implicated in the reduction of free radical production. The aim of this study was to investigate whether L-Cys supplementation prevents modulation of the activities of erythrocyte membrane acetylcholinesterase (AChE), Na + ,K + -ATPase and Mg 2+ -ATPase induced by free radicals in basketball players during training. Methods : Blood was obtained from 10 basketball male players before (group A) and after a game (group B) and after 1 week of L-Cys (0.5 g/24 h orally) supplementation before (group C) and after training (group D). Lactate, pyruvate and total antioxidant status (TAS) were measured using commercial kits and the enzyme activities were determined spectrophotometrically. Results : Both lactate and pyruvate levels remarkably increased after exercise. In contrast, TAS levels significantly decreased in group B, increased in group C and then declined (group D), reaching those of group A. AChE activity was statistically increased post-exercise (3.98±0.04 × mg protein) compared with pre-training (2.90±0.05 × mg protein, p<0.01). Na + ,K + -ATPase activity was also higher post-exercise (1.27±0.05 μmol Pi/h×mg protein) than that pre-exercise (0.58±0.04 μmol Pi/h×mg protein, p<0.001). When the players were supplemented with L-Cys, both AChE and Na + ,K + -ATPase activities remained unaltered post-exercise. Mg 2+ -ATPase activities were unchanged in all groups studied. Conclusions : L-Cys supplementation may protect the enzyme activities studied against stimulation induced by free radical production during training in athletes by ameliorating their total antioxidant capacity. Clin Chem Lab Med 2007;45:67–72.

Background : Behçet's disease is a multysystemic immunoinflammatory disease with a wide variety of clinical manifestations, whereas recurrent aphthous stomatitis is a local oral disease. The aim of this study was to examine the distribution of homocysteine levels in patients with active Behçet's disease, possible association of homocysteine with nitric oxide and neopterin levels, and to characterize the differences between patients with Behçet's disease and those with recurrent aphthous stomatitis in terms of these parameters compared with healthy controls. Methods : A total of 23 patients with active Behçet's disease, 25 patients with recurrent aphthous stomatitis as positive controls, and 21 healthy subjects were included in this study. Serum homocysteine and neopterin levels were measured flourimetrically by HPLC. Serum nitric oxide production was assayed by measuring total nitrite levels with Griess reagent. Results : Significantly higher homocysteine (12.9±3.3 μmol/L) and lower nitric oxide (41.5±10.9 μmol/L) and neopterin (6.4±1.0 nmol/L) levels were observed in patients with Behçet's disease compared with healthy controls (10.7±2.0 μmol/L, 49.7±16.2  μmol/L, 8.7±2.2 nmol/L, respectively) (p<0.03 for neopterin, p<0.04 for homocysteine and nitric oxide). However, homocysteine, nitric oxide, biopterin and neopterin levels and the neopterin/biopterin ratio for recurrent aphthous stomatitis patients were not significantly different compared to healthy controls. A significant positive correlation was observed between serum homocysteine and serum neopterin/biopterin ratio in patients with Behçet's disease (r=0.975, p<0.005). Conclusions : In contrast to recurrent aphthous stomatitis, there is a higher prevalence of hyperhomocysteinemia in Behcet's disease. Homocysteine may have deleterious effects on the pathology of Behcet's disease by decreasing nitric oxide levels and interfering with the immune system. Clin Chem Lab Med 2007;45:73–7.

Background : The aim of the current study was to investigate levels of adenosine deaminase in plasma of patients with hydatidiform mole. Methods : Plasma adenosine deaminase levels were determined in 17 women with normal pregnant course, in 17 women with hydatidiform mole, and in 17 non-pregnant healthy volunteers. Results : Mean adenosine deaminase activity in the hydatidiform mole group was 121.5±24.8 U/L, significantly higher than in the pregnant control (7.8±6.5 U/L; p<0.0001) and non-pregnant control groups (6.4±7.4 U/L; p<0.0001). A cutoff level of 40.5 U/L was found, with both sensitivity and specificity of 100%. Conclusions : Adenosine deaminase may play a role in the development of hydatidiform mole. Clin Chem Lab Med 2007;45:78–81.

Background : Classification and regression tree (CART) analysis is a non-parametric technique suitable for the generation of clinical decision rules. We have studied the performance of CART analysis in the separation of pleural exudates and transudates. Methods : Basic demographic, radiologic and laboratory data were retrospectively evaluated in 1257 pleural effusions (204 transudates and 1053 exudates, according to standard clinical criteria) and submitted for CART analysis. The model's discriminative ability was compared with that of Light's criteria, in both the original formulation and an abbreviated version, i.e., deleting the pleural fluid (PF)/serum lactate dehydrogenase (LDH) ratio from the triad. Results : A first CART model built starting from all available data identified PF/serum protein ratio and PF LDH ratios as the two best discriminatory parameters. This algorithm achieved a sensitivity of 96.8%, slightly lower than that of classical Light's criteria (98.5%) and comparable to that of the abbreviated Light's criteria (97.0%), and significantly better specificity (85.3%) compared to both classical (74.0%) and abbreviated (79.4%) Light's criteria. A second CART model developed after excluding serum measurements selected PF protein and PF LDH as the most discriminatory variables, and correctly classified 97.2% of exudates and 77.0% of transudates. Conclusions : CART-based algorithms can efficiently discriminate between pleural exudates and transudates. Clin Chem Lab Med 2007;45:82–7.

Background : To evaluate the extent of interlaboratory variation and accuracy in hemoglobin A 2 (HbA 2 ) assays, a pilot study of external quality assessment was organized among 48 Italian laboratories routinely measuring HbA 2 . As part of the study, a survey was also performed by sending a questionnaire concerning some important analytical aspects related to the determination of HbA 2 . Methods : The trial specimens consisted of three whole blood samples (A, B and C) with normal, pathological and borderline HbA 2 content, respectively. All laboratories used HPLC analyzers from the same manufacturer (Bio-Rad Laboratories). Results : Normal and pathological samples were clearly differentiated by all laboratories, while data for the borderline sample partially overlapped those for the other samples. The overall interlaboratory coefficient of variation was 8.0%, 6.0% and 7.9% for samples with low, high and intermediate HbA 2 levels, respectively. To assign HbA 2 target values to the samples, the median of the laboratory group was used. The accuracy of HbA 2 results was evaluated on the basis of allowable total error. The proportion of laboratories reporting unacceptable results was 31.9% (15 out of 47) for sample A, 17.0% (8 out of 47) for sample B, and 31.9% (15 out of 47) for sample C. No abnormalities in the chromatographic separation pattern were reported by any of the laboratories. Conclusions : We conclude that quality in the measurement of HbA 2 should be improved. Clin Chem Lab Med 2007;45:88–92.

Background : Quantification of viral load (VL) is standard for monitoring HIV-1 therapy and is crucial before deciding whether to switch or to continue a current antiretroviral regimen. Methods : We compared the performance of the four most widely used commercial viral-load assays, COBAS Amplicor Monitor v1.5, Versant HIV-1 RNA 3.0, Abbott RealTime HIV-1 and Cobas AmpliPrep/Cobas TaqMan HIV-1 (CAP/CTM), in terms of intra- and inter-assay variability, as well as hands-on-time, specificity and ability to quantify group M subtypes. Results : Although linearity and correlation were confirmed for the assays and comparable sensitivity and specificity were verified for genetically diverse HIV-1 subtypes, demonstrating suitability for monitoring of HIV group M isolates, the viral loads obtained showed variations, with a mean difference of 0.1–0.4 log, depending on the system used. Conclusions : Although sensitivity and precision were confirmed for all the systems, differences between them should be taken into account when viral load monitoring of the same person is performed using different systems. Clin Chem Lab Med 2007;45:93–9.

Background : CA 19-9 is a marker principally related to pancreatic and gall bladder cancer. Although its determination has no value in screening for these malignancies, it is used in post-operative monitoring and during chemotherapeutic treatment of confirmed disease. Measurements during follow-up must be comparable and must be performed with standard, validated methods. Methods : We compared four routinely used analytical systems for CA 19-9 determination: the Architect i2000 and AxSYM systems from Abbott Laboratories, the Elecsys 1010 from Roche Diagnostics, and the KRYPTOR system from Brahms Diagnostics. We evaluated the analytical performance of the four systems and compared measurements of CA 19-9 values, which covered the whole analytical range. Results : The analytical performance and accuracy of the four systems were fairly good, but Passing-Bablok regression and mountain plots showed significant differences in CA 19-9 values measured with the four platforms. Conclusions : Our data indicate that during tumor follow-up, the use of the same system is appropriate to avoid the risk of a variation due to the method rather than the disease. Moreover, whenever a change in analytical equipment is required, careful analysis of CA 19-9 results must be undertaken. Clin Chem Lab Med 2007;45:100–4.

We performed analytical validation of the new version of the Liaison N-Tact PTH (parathormone) assay according to NCCLS guidelines and compared this new generation of reagent with the Roche Elecsys PTH assay. We showed that this new version is a sensitive and precise method with good recovery. Significant carryover was observed, but with limited clinical implications. We demonstrated that the new version of the Liaison PTH is in reasonably good agreement with the Roche Elecsys PTH assay, and as we observed no differences in a hemodialyzed population, moving from one method to the other should not affect the daily follow-up of patients. However, one should be cautious with the highest values (>500 pg/mL). We established reference intervals of 12–54 pg/mL for the Liaison and 14–52 pg/mL for the Elecsys assay. Clin Chem Lab Med 2007;45:105–7.

Background: There is little information on the reproducibility of measurement of cytokine levels in sputum obtained from cystic fibrosis (CF) patients. Our aim was to investigate whether assay of cytokine levels in CF sputum is reproducible or is hampered by proteolytic degradation. Methods: Interleukin-8 (IL-8) and tumor necrosis factor-α (TNF-α) levels were measured in native and spiked samples (fresh or after freezing for 15 and 23 days at −70°C) obtained from nine CF patients using an immunometric assay with chemiluminescent substrate run on a IMMULITE analyzer. Results: For both cytokines, linearity was >0.98 for dilutions up to 1:32. After storage, cytokine concentrations in native samples varied between −2.9% and −5.6% for IL-8 and between 0.4% and 3.0% for TNF-α. In spiked samples, concentrations increased by 5.8%–12.6% for TNF-α and decreased by 3.8%–14.3% for IL-8 after 15 and 23 days of storage. In samples spiked with cytokines, the mean recovery rates for IL-8 and TNF-α were 109.4% and 106.3%, respectively. Conclusions: Measurement of IL-8 and TNF-α in CF sputum is reproducible and is not hampered by freezing and thawing of samples. Clin Chem Lab Med 2007;45:108–11.

Background : Among other methods, trichloroacetic acid precipitation is used to quantify total protein in cerebrospinal fluid (CSF). Methods : We analyzed the influence of hemoglobin on total protein concentration assayed by the trichloroacetic acid method and compared the results to the benzethonium chloride method. Results : Four CSF samples were spiked with different amounts of hemoglobin, leading to overestimation of protein concentration when assayed by the trichloroacetic acid method. Using the benzethonium chloride method, measurement of protein concentration was minimally disturbed. In addition, albumin and total protein concentrations were measured in 135 clinical samples. The total protein/albumin ratio remained constant when protein was measured with the benzethonium chloride method, while ratios increased when protein was assayed by the trichloroacetic acid method. Conclusions : Strong interference by hemoglobin leads to overestimation of the total protein concentration in CSF when assayed by the trichloroacetic acid method and may lead to false conclusions when evaluating the blood-brain barrier. Clin Chem Lab Med 2007;45:112–3.

The influence of interference by hemolysis, icterus and lipemia on the results of routine chemistries may lead to wrong interpretations. On Synchron LX-20 instruments (Beckman Coulter) serum or plasma indices can be used as reliable semi-quantitative measures of the magnitude of such interference. In an article recently published in this journal, we presented the results of a multicenter study carried out in Dutch hospitals in which we determined cutoff indices for analytes above which analytically significant interference exists. Clinically significant interference cutoff indices were also derived for these analytes. In this article, we describe the handling of patient samples with clinically significant interference by hemolysis, icterus or lipemia. We investigated several possible approaches for correction of the result: dilution of the interference; mathematical correction in the case of hemolysis; treatment with ferrocyanide to destroy bilirubin; and removal of lipids in lipemic patient samples. We concluded, that mathematical correction of potassium or lactate dehydrogenase results in hemolytic samples can only be carried out if intravascular hemolysis is ruled out. Hemoglobin quantification in serial patient samples, combined with measurement of haptoglobin, represents a useful tool to rule out in vivo hemolysis. We derived an algorithm for this situation. We do not simply recommend mathematical correction, unless it is clinically acceptable. We present formulas for potassium and lactate dehydrogenase: corrected potassium=measured potassium–(hemolytic index increment×0.14); corrected lactate dehydrogenase=measured lactate dehydrogenase–(hemolytic index increment×75). The dilution studies indicated that dilution is only applicable for bilirubin, C-reactive protein and iron. The results of treatment with ferrocyanide were poor, and we do not recommend this method. Removal of lipids using high-speed centrifugation or LipoClear (StatSpin Inc.), a non-toxic and non-ionic polymer, is a very effective approach, although C-reactive protein, creatine kinase-MB (CK-MB) and cholesterol cannot be removed using LipoClear. For all interferants (hemoglobin, bilirubin, lipids), relatively simple algorithms are derived that can easily be implemented in the clinical laboratory. Clin Chem Lab Med 2007;45:114–9.