Band 48, Heft 2

In clinical practice, increased serum γ-glutamyltransferase (GGT) activity is usually interpreted as a marker of alcohol abuse and liver dysfunction. The knowledge of the GGT's physiological functions has expanded and several important epidemiological associations have been reported. This review examines evidence for an association of high normal serum GGT enzyme activity, mostly within the reference range, with the risk of mortality and major vascular (i.e., cardiovascular morbidity and mortality) and non-vascular outcomes (i.e., incident type 2 diabetes, chronic kidney disease and cancer), independent of alcohol consumption and other prognostic factors. Clin Chem Lab Med 2010;48:147–57.

Background: Back propagation (BP) artificial neural networks are a distribution-free method for data analysis based on layers of artificial neurons that transduce imputed information. It has been recognized as having a number of advantages compared to traditional methods including the possibility to process imperfect data, and complex non-linear data. The objective of this study was to review the principles, procedures, and limitations of BP artificial neural networks for a non-mathematical readership. Methods: A real data sample of weight, height and measured body surface area from 90 individuals was used as an example. SPSS 17.0 with neural network add-on was used for the analysis. The predicted body surface from a two hidden layer BP neural network was compared to the body surface calculated by the Haycock equation. Results: Both the predicted values from the neural network and from the Haycock equation were close to the measured values. A linear regression analysis with neural network as predictor produced an r 2 -value of 0.983, while the Haycock equation produced an r 2 -value of 0.995 (r 2 >0.95 is a criterion for accurate diagnostic testing). Conclusions: BP neural networks may, sometimes, predict clinical diagnoses with accuracies similar to those of other methods. However, traditional statistical procedures, such as regression analyses need to be added for testing their accuracies against alternative methods. Nonetheless, BP neural networks have great potential through their ability to learn by example instead of learning by theory. Clin Chem Lab Med 2010;48:159–65.

Background: Alkaline phosphatase (ALP) is a widely used marker for skeletal and hepatobiliary disorders, but its activity is also increased in atherosclerosis and peripheral vascular disease. It is an inflammatory marker like C-reactive protein (CRP). We therefore analyzed its relationship with CRP in the United States National Health and Nutrition Examination Survey (NHANES) 2005–2006. Methods: The analysis included 4155 men and non-pregnant women over the age of 20 years. The relationship between log-transformed ALP and plasma CRP was analyzed using univariate and multivariate models. Results: ALP activity was significantly correlated with age, waist circumference, body mass index, blood pressure, exercise, alcohol, triglycerides, and other liver enzymes after adjusting for age, gender and ethnicity (p<0.001). ALP was significantly associated with a higher frequency of cardiovascular disease (p=0.02), hypertension (p=0.01) hypercholesterolemia (p=0.04), and diabetes (p=0.02). Compared to the lowest quartile of ALP, the adjusted odds ratio (OR) associated with the highest quartile were 1.9 [95% confidence intervals (CI) 1.1–3.5], 1.6 (95% CI 1.0–2.5), 1.5 (95% CI 1.1–2.1) and 1.7 (95% CI 1.0–2.4) for cardiovascular disease, hypertension, hypercholesterolemia, and diabetes, respectively. In multivariate analysis, log ALP was an independent predictor of log CRP (p=1.0×10 −6 ). A multivariate model that included log ALP, ethnicity, glycohemoglobin, waist circumference, albumin, apolipoprotein B, γ-glutamyltransferase and uric acid explained 40% of the variance in log CRP. Conclusions: ALP is a marker of cardiometabolic risk, but it needs to be tested as part of a multivariate model in prospective studies. Clin Chem Lab Med 2010;48:167–73.

Background: Increased uric acid is associated with the metabolic syndrome, conditions linked to oxidative stress and insulin resistance. Non-alcoholic fatty liver disease (NAFLD) is now considered a hepatic manifestation of insulin resistance. However, little has been written regarding the association between uric acid and NAFLD. Methods: We examined the association between uric acid and the presence of NAFLD in 3768 Koreans (2133 men, 1635 women; aged 20–75 years) in a health examination program. Uric acid quartiles were categorized separately as follows: Q1: ≤291.5, Q2: 291.6–333.1, Q3: 333.2–380.7, and Q4: ≥380.8 μmol/L for men; Q1: ≤202.2, Q2: 202.3–232.0, Q3: 231.1–267.7, and Q4: ≥267.8 μmol/L for women. Hepatic steatosis was diagnosed based on abdominal ultrasonographic findings by hyperechogenicity of liver tissue, difference of echogenicity between the liver and diaphragm, and visibility of vascular structures. The odds ratios (ORs) and 95% confidence intervals (CIs) for NAFLD were calculated across each quartile of serum uric acid. Results: The prevalence of NAFLD was 25.8% (32.2% in men and 17.4% in women). After adjustment for age, body mass index (BMI), smoking, regular exercise, blood pressure, fasting plasma glucose (FPG), triglycerides, and high-density lipoprotein (HDL) cholesterol, the ORs (95% CIs) for NAFLD according to each quartile of uric acid were 1.00, 1.55 (1.13–2.14), 1.77 (1.30–2.41), and 2.01 (1.45–2.78) for men and 1.00, 0.69 (0.40–1.20), 1.12 (0.67–1.88), and 1.94 (1.21–3.13) for women. Conclusions: Serum uric acid is independently associated with the presence of NAFLD, and uric acid may be a useful additional measure in assessing the risk of NAFLD in the clinical setting. Clin Chem Lab Med 2010;48:175–80.

Background: It has been previously reported that plasma osteopontin (OPN) concentrations are increased in cardiovascular disorders. The goal of the present study was to determine plasma OPN concentrations in healthy pregnant women and preeclamptic patients, and to investigate their relationship to the clinical characteristics of the study subjects and to markers of inflammation [C-reactive protein (CRP)], endothelial activation [von Willebrand factor antigen (VWF:Ag)] or endothelial injury (fibronectin), oxidative stress [malondialdehyde (MDA)] and trophoblast debris (cell-free fetal DNA). Methods: Forty-four patients with preeclampsia and 44 healthy pregnant women matched for age and gestational age were involved in this case-control study. Plasma OPN concentrations were measured with ELISA. Serum CRP concentrations were determined with an autoanalyzer using the manufacturer's reagents. Plasma VWF:Ag was quantified by ELISA, while plasma fibronectin concentrations were measured by nephelometry. Plasma MDA concentrations were estimated by the thiobarbituric acid-based colorimetric assay. The amount of cell-free fetal DNA in maternal plasma was determined by quantitative real-time PCR analysis of the sex-determining region Y ( SRY ) gene. For statistical analyses, non-parametric methods were applied. Results: Serum levels of CRP, as well as plasma concentrations of VWF:Ag, fibronectin, MDA and cell-free fetal DNA were significantly higher in preeclamptic patients than in healthy pregnant women. There was no significant difference in plasma OPN concentrations between controls and the preeclamptic group. However, preeclamptic patients with plasma fibronectin concentrations in the upper quartile had significantly higher plasma OPN concentrations than those below the 75th percentile, as well as healthy pregnant women [median (interquartile range): 9.38 (8.10–11.99) vs. 7.54 (6.31–9.40) and 7.40 (6.51–8.80) ng/mL, respectively, p<0.05 for both]. Furthermore, in preeclamptic patients, plasma OPN concentrations showed a significant positive linear association with plasma fibronectin (Spearman R=0.38, standardized regression coefficient (β)=0.41, p<0.05 for both). Conclusions: Plasma OPN concentrations are increased in preeclamptic patients with extensive endothelial injury. However, further studies are warranted to explore the relationship between OPN and endothelial damage. Clin Chem Lab Med 2010;48:181–7.

Background: Fabry disease is an X-chromosomally inherited lysosomal storage disorder leading to accumulation of glycosphingolipids, mainly globotriaosylceramide (ceramide-trihexoside, Gb3). Concentrations of Gb3 in plasma and urine have been used to diagnose Fabry disease and to monitor enzyme replacement therapy with recombinant α-galactosidase. Methods: Gb3 was purified from plasma or urine by combined liquid extraction/protein precipitation and solid-phase extraction, and was detected by flow-injection analysis electrospray mass spectrometry (MS) using multi-reaction-monitoring. Calibration was performed via standard addition using C17-Gb3 as internal standard. The most abundant isoforms were monitored for calculation of total Gb3. Results: A MS-based assay for quantification of Gb3 in plasma and urine was established and validated. Intra- and inter-assay coefficient of variation (CV) of the method were ≤12%. However, at low concentrations the CV was 16%. The linear range covers roughly two orders of magnitude, down to 0.54 mg/L in plasma and 0.07 mg/L in urine. Careful adjustment of tuning parameters was necessary to obtain identical isoform intensities and quantitative results on different mass spectrometers. Gb3 concentrations in healthy controls were <4 mg/L in EDTA-plasma and <10 μg/mmol creatinine in urine. Significantly increased Gb3 concentrations were found in plasma and urine from male and female patients with Fabry disease. Conclusions: An improved MS protocol for Gb3 quantification has been developed, validated, and shown to be suitable for diagnosis and monitoring of Fabry patients. Clin Chem Lab Med 2010;48:189–98.

Background: Exercise in humans augments the mobilization of circulating hematopoietic progenitor cells (CD34 + ) from the bone marrow. We investigated the effect of inflammation on erythroid marrow activity by mobilization of erythroid progenitor cells (EPs) along with soluble markers of erythropoiesis. Methods: Ten healthy athletes who participated in an ultradistance foot race participated in the study. Peripheral blood mononuclear cells were isolated, before (phase I), at the end (phase II), and at 48 h post-race (phase III). EPs were detected as burst colony forming units (BFU-e) and colonies were scored at day 14. Markers of inflammation (C-reactive protein, serum amyloid-A, interleukin-6, ferritin and S100B) and bone marrow activity (erythropoietin, soluble transferrin receptor and lipocalin-2) were assessed. Results: An approximately three-fold decrease in BFU-e number was observed at phase II. sTfR concentrations were also decreased at phase II and remained decreased at phase III. However, EPO and lipocalin-2 concentrations reached a maximum value at phase II, with a tendency to decrease at phase III. Conclusions: These findings indicate that exercise-induced inflammation modulates bone marrow homeostasis leading to an increase in leukocyte turnover and a decrease in erythroid compartment. It appears that lipocalin-2 is the main factor that regulates the production and mobilization of EPs. Clin Chem Lab Med 2010;48:199–203.

Background: Commercially available prolactin immunoassays detect macroprolactin to variable degrees. Best practice requires laboratories to assess the cross-reactivity of their prolactin assay with macroprolactin, and where appropriate, introduce a screen for the presence of macroprolactin. Our policy has been to reanalyse hyperprolactinaemic samples following polyethylene glycol (PEG) precipitation and to report the resultant value as the monomeric prolactin content of the sample. The goal of this study was to determine the need to continue PEG precipitation when prolactin measurements with the Wallac AutoDELFIA were replaced by the Beckman DxI 800. Methods: A total of 317 apparently hyperprolactinaemic samples were analysed for prolactin using the Beckman DxI 800 and results compared with those determined with the PEG screening technique on the Wallac AutoDELFIA. Any samples demonstrating a discordance of >25% were re-analysed using gel filtration chromatography (GFC) for a definitive result. Results: The results indicate the Beckman DxI overestimates the prolactin concentration in 1%–2% of hyperprolactinaemic samples. PEG precipitation prior to analysis with the Wallac AutoDELFIA resulted in a 1% false negative diagnosis of hyperprolactinaemia. Conclusions: Prolactin results can be reported directly from the DxI. When results are discordant with the clinical presentation, prolactin should be measured using GFC. Clin Chem Lab Med 2010;48:205–8.

Background: The cerebrospinal fluid/serum glucose ratio (CSF/S glu ) and CSF lactate measurements are part of the routine CSF work-up. The in-vitro stability of both metabolites in CSF has not been formally investigated. Methods: Following collection, CSF/S glu and CSF L-lactate concentrations were measured repeatedly at five time points (baseline, 1 h, 2 h, 4 h and 24 h) in CSF and whole blood specimens stored at 4°C. Results: CSF glucose and lactate concentrations were stable over 24 h in samples with both normal and increased CSF cell counts. The CSF cell count did not influence CSF glucose concentrations, but correlated significantly with CSF lactate concentrations. The CSF/S glu increased significantly over time due to glucose consumption. Conclusions: Glucose and L-lactate are stable in CSF specimens at 4°C over 24 h. The CSF/S glu seems to be more reliable than CSF lactate because it is independent of the cell count. Falsely increased CSF/S glu may be corrected by the rate of consumption of blood glucose. Clin Chem Lab Med 2010;48:209–12.

Background : Italian air force acrobatic pilots are occupationally susceptible to oxidative stress damage that can lead to overt signs and symptoms of hypoxia. We propose erythrocyte glycohydrolases as new, sensitive markers to assess oxidative stress. Methods : We measured erythrocyte concentrations of β-D-glucuronidase (GCR), hexosaminidase, O-β-N-acetyl-D-glucosaminidase (O-GlcNAcase), plasma membrane fluidity and plasma hydroperoxides from 19 pilots and compared these to 40 matched healthy subjects. Results : Plasma hydroperoxide concentrations and the erythrocyte ghosts' fluorescence anisotropy were significantly lower in the pilots. Concentrations of GCR, O-GlcNAcase and hexosaminidase in pilots were significantly different from controls, being lower, higher and higher, respectively. Conclusions : Pilots, in spite of their oxidative stress, are better protected than controls, probably as a result of their physical training and proper diet. Our results confirm that erythrocytes, with their 120-day life span, are a useful model for investigating physiopathological conditions, and glycohydrolases are good markers for monitoring oxidative stress, even in healthy people. Clin Chem Lab Med 2010;48:213–6.

Background: Squamous cell carcinoma antigen-immunoglobulin M (SCCA-IgM) is a useful biomarker for the risk of development of hepatocellular carcinoma (HCC) in patients with cirrhosis due to its progressive increase associated to HCC evolution. In patients with cirrhosis, other assays have been affected by interfering reactivities of IgM. In this study, the analytical specificity of the SCCA-IgM assay was assessed by evaluating SCCA-IgM measurement dependence on different capture phases, and by measuring the recovery of SCCA-IgM reactivity following serum fractionation. Methods: Serum samples from 82 patients with cirrhosis were analyzed. SCCA-IgM was measured using the reference test (Hepa-IC, Xeptagen, Italy) that is based on rabbit oligoclonal anti-squamous cell carcinoma antigen (SCCA) and a dedicated ELISA with a mouse monoclonal anti-SCCA as the capture antibody. Results: SCCA-IgM concentrations measured with the reference assay (median value=87 AU/mL) were higher than those measured with the mouse monoclonal test (median value=78 AU/mL). However, the differences in the SCCA-IgM distribution were not statistically significant (p>0.05). When SCCA-IgM concentrations measured with both tests were compared, a linear correlation was found (r=0.77, p<0.05). Fractionation of the most reactive sera by gel-filtration chromatography showed that total recovery of SCCA-IgM reactivity was seen only in the fractions corresponding to components with a molecular weight higher than IgM and SCCA (>2000 kDa) with both tests. Conclusions: The equivalence of both SCCA-IgM assays and the absence of reactivity not related to immune complexes support the analytical specificity of SCCA-IgM measurements. The results validate the assessment of SCCA-IgM for prognostic purposes in patients with cirrhosis. Clin Chem Lab Med 2010;48:217–23.

Background: Anti-cyclic citrullinated peptide (CCP) antibody is emerging as an important diagnostic marker for rheumatoid arthritis (RA). We evaluated the analytical and diagnostic performance of the ARCHITECT anti-CCP (Abbott Diagnostics), a new fully automated chemiluminescent microparticle immunoassay. Methods: Serum samples from 69 patients with RA and 86 non-RA patients were used to evaluate the performance of the ARCHITECT anti-CCP assay, and the results were compared with those of EliA CCP (Phadia). The optimal cut-off value was calculated using receiver operating characteristic (ROC) curve analysis. Results: Within-run and total imprecision (%CV) of the ARCHITECT anti-CCP were <6% and good linearity was observed over the claimed range. The areas under the ROC curves for the ARCHITECT anti-CCP and EliA CCP were 0.90 and 0.89, respectively. The sensitivity and specificity were 76.8% and 95.3% for the ARCHITECT anti-CCP and 78.3% and 95.3% for EliA CCP using the manufacturer's cut-off thresholds. Both assays showed sensitivity of 84.1% and specificity of 94.2% using the optimal cut-off values. Conclusions: The analytical performance of the ARCHITECT anti-CCP was satisfactory and diagnostic performance was comparable to that of EliA CCP. The use of optimal cut-off thresholds can yield higher sensitivity with minimal loss of specificity. Clin Chem Lab Med 2010;48:225–30.

Background: In accordance with an ongoing activity for worldwide harmonization based on traceability in laboratory methods, the goal of this study was to validate the applicability of recommended “common” reference intervals for serum creatinine concentrations using a specific enzymatic method to the Croatian population. Methods: The reference group consisted of 240 healthy subjects (120 males and 120 females), between 18 and 74 years of age (median 57 years), who were selected in accordance with the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) recommendations. Creatinine in serum was measured using the creatinine enzymatic assay (Olympus OSR61204) that was standardized to the isotopic dilution mass spectrometry (IDMS) method and National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 967. In addition, creatinine was measured using a kinetic Jaffe method (Olympus OSR6178) standardized to NIST SRM 909b level 2 standard. Results: Method comparison between enzymatic creatinine (x) and the Jaffe kinetic method (y) gave the following P/B equation for the entire group (n=240): y=1.00x+17.00; r=0.968. Reference intervals for serum creatinine (central 95th percentiles) obtained using the enzymatic creatinine method ranged from 54 to 107 μmol/L for males and from 50 to 93 μmol/L for females. The IFCC recommended common reference intervals for global applications are 64–104 μmol/L and 49–90 μmol/L for males and females, respectively. Conclusions: Comparability of obtained results confirmed the applicability of recently recommended “common” reference intervals to the Croatian population for all laboratories measuring serum creatinine concentrations using enzymatic methods traceable to the IDMS method and NIST SRM 967. Clin Chem Lab Med 2010;48:231–5.

Background: Physiological changes during pregnancy may affect laboratory parameters. Reference values based on samples from non-pregnant women are not necessarily useful for clinical decisions during pregnancy. There is a need to establish reference values during pregnancy in order to recognize pathological conditions. Methods: Eight hundred and one women with expected normal pregnancies were included in the study. Of these, 391 had no complications during pregnancy, delivery, or the early postpartum period. Blood samples were obtained at gestational weeks 13–20, 21–28, 29–34, 35–42, at labor, and 1 and 2 days postpartum. Reference intervals were calculated for 36 tests as recommended by the International Federation of Clinical Chemistry and Laboratory Medicine. Results: Many tests showed such large variations indicating that gestational age-specific reference intervals were necessary. Other tests had different but stable values when compared to non-pregnant women. A minor decrease in albumin levels was observed. This was not only due to pregnancy-associated hemodilution, since other components with the same or a larger molecular diameter did not show a similar decrease. Many tests exhibited a broad distribution around vaginal delivery and in the early postpartum period. Conclusions: Only a few parameters were unaffected during uncomplicated pregnancy, delivery, and the early postpartum period suggesting that implementation of gestational age-specific reference intervals is necessary. Clin Chem Lab Med 2010;48:237–48.

Background: A reliable early marker is required for diagnosis of cobalamin deficiency. We calculated an appropriate holotranscobalamin (HoloTC) cut-off point for identifying cobalamin deficiency using an immunoenzymatic assay. Methods: Determination of the cut-off threshold and correlation between HoloTC and the other diagnostic parameters routinely used for vitamin B 12 deficiency [total vitamin B 12 (tB 12 ), folate, homocysteine] were measured in 250 routine blood specimens from 107 men (mean age 59.0±18.8 years) and 143 women (mean age 54.2±23.1 years). The inclusion criterion was serum tB 12 concentration ≤221 pmol/L. Results: Analytical performance results agreed with those reported by others. A weak correlation (R=0.42) was found between HoloTC and tB 12 . A 40 pmol/L cut-off threshold was chosen for HoloTC and the associated sensitivity and specificity was 0.86 and 0.66, respectively. Out of 250 tested samples, 126 showed tB 12 concentrations 139–221 pmol/L (gray zone, GZ) and 124 had tB 12 concentrations <139 pmol/L (low, L). Values less than the cut-off for HoloTC were present in 68.2% and 37.9% of cases in the GZ and L group, respectively (p<0.01), and in 53.2% of subjects. Conclusions: Our results confirmed the analytical reliability of the AxSYM HoloTC assay. The method is adequate for routine use and a cut-off threshold of 40 pmol/L is appropriate for assessing cobalamin deficiency in populations with reduced tB 12 values. Clin Chem Lab Med 2010;48:249–53.

Background: Automated hematological analyzers have contributed to more precise and faster results. They also make it possible to measure several blood cell parameters automatically. Among the parameters provided, platelet indices are probably the most ignored by clinical laboratories due to the difficulty of standardization, as well as being affected by a range of methodological problems. It has been suggested that each laboratory determines its own reference intervals with the equipment used. Methods: Our goal was to determine the reference range of platelet distribution width (PDW) in venous blood samples from 231 patients using the Pentra 120 ABX hematology analyzer. Results: The PDW median was 13.3%, with a reference range of 10.0%–17.9% for the 5th–95th percentiles, with a confidence interval of 95%. Conclusions: Among all indices, the PDW has been receiving attention due to its usefulness for distinguishing between reactive thrombocytosis and thrombocytosis associated with myeloproliferative disorder. Determination of the PDW reference range is fundamental, and the association of this parameter with the platelet number and mean platelet volume may be used for the diagnosis and differentiation of several pathologies. Clin Chem Lab Med 2010;48:255–7.

Background: To date, no prospective epidemiological data are available, particularly in women, on mean leukocyte telomere length as a risk predictor. Methods: Using leukocyte DNA samples collected at baseline in a prospective cohort of over 28,000 initially healthy women, we examined the relationship between mean leukocyte telomere repeat copy number to single gene copy number (TSR) in 134 incident cases of colorectal carcinoma (CRC), and 357 matched controls; all were Caucasian. Results: The observed log e -transformed TSRs were similar between cases and controls (p=0.79). Using an adjusted analysis, we found no evidence for an association of the log e -TSRs with CRC risk [adjusted odds ratio (OR)=0.943, 95% confidence interval (CI)=0.647–1.376, p=0.762]. Stratified analysis by median follow-up time, or postmenopausal status also showed similar null findings. Conclusions: In concordance with our previous findings in Caucasian men, the present study in Caucasian women found no evidence for an association of mean leukocyte telomere length with risk of incident CRC, further suggesting that leukocyte telomere length may not be a useful indicator for risk assessment. Clin Chem Lab Med 2010;48:259–62.

Background: In a previous study, we found that heat shock protein 27 (HSP27) was over-expressed in gastric adenocarcinoma (GA) tissue. In this study, our goal was to further verify the expression profile of HSP27 in patients with GA. Methods: Western blot and immunohistochemistry were employed to determine HSP27 expression in 50 paired tumor and adjacent normal tissue. ELISA was used to quantify serum HSP27 concentrations in the same 50 GA patients and 50 healthy individuals. Results: Compared to adjacent normal tissues, HSP27 was over-expressed in 25 (50%, p=0.000) and 24 (48%, p=0.000) cases of GA tissue by Western blot and immunohistochemistry, respectively. ELISA revealed significantly higher serum concentrations of HSP27 in patients with GA patients (mean=986 pg/mL) compared to healthy individuals (mean=573 pg/mL) (p=0.003). In addition, infection with Helicobacter pylori (HP) in healthy individuals was associated with increased expression of HSP27 in both gastric mucosa and serum. Conclusions: These data suggest that HSP27 is over-expressed in GA tissue and serum concentrations of HSP27 are increased in patients with GA. Over-expression of HSP27 may indicate a gastric malignant/infectious process. The detection of serum HSP27 concentrations by ELISA may be useful for screening for GA. Clin Chem Lab Med 2010;48:263–9.

Background: There is a need to identify reliable markers for malignant mesothelioma. Soluble mesothelin related peptides (SMRP) and osteopontin (OPN) have gained interest in recent years for this purpose. Methods: SMRP (Fujirebio Diagnostics Inc.) and OPN (R&D Inc.) ELISA methods were evaluated for multiple parameters. Concentrations were measured in blood from patients with mesothelioma, normal healthy volunteers, and patients with other (non-mesothelioma) cancers. In silico analysis was performed using the GeoProfiles database. At the protein level, SMRP and OPN were measured in cell culture supernatants, and values were compared in patients pre- and post-extrapleural pneumonectomy. Results: The SMRP assay demonstrates intra-assay CVs of 2.3% and 3% (at 4.6 nM and 13.7 nM, respectively), and inter-assay CVs of 3.5% and 3.7% at the same concentrations. The limit of detection (LOD) is 0.182 nM. The OPN assay demonstrates intra-assay CVs of 5.8%, 4.1%, and 5.2% (at 1.9, 5.1, and 11.1 ng/mL, respectively), and inter-assay CVs of 8.5%, 8.4%, and 12.1% at the same concentrations. The LOD is 0.032 ng/mL. Both SMRP and OPN in mesothelioma patients were significantly higher than in patients with other (non-mesothelioma) cancer and in healthy volunteers. The two markers do not appear to correlate with each other and exhibit different tissue expression patterns. Protein concentrations of these markers are highest in different sets of cell lines. Finally, SMRP but not OPN concentrations were decreased in five of seven consecutive patients after extrapleural pneumonectomy, compared to their respective pre-operative values. Conclusions: These assays provide reliable and reproducible quantitation of SMRP and OPN proteins. Both are increased in mesothelioma patients compared to non-mesothelioma controls. However, the two analytes do not correlate with each other and show distinct expression profiles and protein expression. Concentrations of SMRP but not OPN are decreased in post-surgical samples. Our results further characterize these markers, establish assay performance characteristics, and lay the groundwork for further studies to measure these markers in blood. Clin Chem Lab Med 2010;48:271–8.

Background: The sensitivity and selectivity of traditional methods limits ultramicro detection of proteins. Bio-barcode amplification detection methods based on nanotechnology enables ultramicro detection of protein. However, bio-barcode amplification detection depends on the oligonucleotides being fixed on a glass chip. It also requires specialized equipment, which limits its application. We introduce a nano-nucleic acid barcode dot detection technology to determine ultramicro concentrations of protein. The method is simple, quick and accurate. Methods: Magnetic probe (IgG-M) and dual-labeled gold nanoparticle bio-probe (IgG-Au-DNA) were prepared. Protein was captured using a sandwich assay technique and magnetic separation was used. The DNA barcode was released with dithiothreitol (DTT) and detected directly without the requirement for polymerase chain reaction (PCR). Serum prostate-specific antigen (PSA) from 135 patients was detected with this method and compared with enzyme linked immunosorbent assay (ELISA) and radioimmunoassay (RIA). Results: Each IgG-Au-DNA could be covered with 138±47 oligonucleotides and 11±3 antibodies. The IgG-M could bind 118 μg of antibody per mg. The sensitivity of nano-nucleic acid barcode dot detection technology might allow detection of 1 fg/mL. There were no significant differences in serum PSA from 135 patients when comparing the three methods (compared with ELISA, r=0.950; and with RIA, r=0.967). Conclusions: The nucleic acid barcode dot method does not require special equipment or complex procedures, but its detection limit is 2–3 orders of magnitude lower than ELISA. Clin Chem Lab Med 2010;48:279–83.

Background: The goal of this study was to evaluate the clinical impact of using the same total prostate-specific antigen (tPSA) and free PSA (fPSA) assays calibrated with World Health Organization (WHO) materials or with Hybritech Tandem-R calibrator. Methods : From the initial correlation study that included 150 patients, the clinical impact of the WHO calibration was simulated using a large cohort (n=4548) of referred patients. Interim reports of the European Study of Screening for Prostate Cancer (ERSPC) were used to evaluate the clinical outcomes of patients and the risk of prostate cancer (PCa). Results: WHO calibration of tPSA assays leads to a reduction of about 20% in measured results (tPSA WHO=0.81 tPSA Hybritech+0.04; fPSA WHO=0.78 fPSA Hybritech+0.00; %fPSA WHO=0.92 %fPSA Hybritech+0.00). The simulation showed that the WHO calibration is associated with a risk of missing 15% of PCa. Conclusions: The discrepancies between the two calibrations lead to significant clinical misinterpretation with decreased detection of PCa if tPSA cut-off thresholds are not adjusted. Clin Chem Lab Med 2010;48:285–8.

Background: Cultures for urinary tract infections (UTI) constitute a large workload in the clinical microbiology laboratory, although up to 80% are usually negative. Several automated methods are available to screen urines for UTI, one being the flow cytometry-based Sysmex ® UF-100. Methods: The performance of the UF-100 was evaluated over a 16-month period using urine culture as the reference method. Results: During this period, a total of 5356 urine samples were studied (469 children; 3229 women and 1658 men), of which 706 were culture positive (593 grew Gram negative bacilli). Receiver operating characteristics (ROC) curve analysis showed an area under the curve (AUC) of 0.83 for leukocytes and 0.85 for bacterial count. Applying cut-off values reported in the literature gave sensitivities ranging from 75% to 90%, resulting in 73–174 false negatives (FN). Using a logical combination (leukocytes ≥15×10 6 /L OR bacteria ≥500×10 6 /L) gave a sensitivity of 98%. However, the specificity dropped to 25%, resulting in 15 FN. Conclusions: Screening urine samples for UTI detects a large number of culture positive samples. However, the rather large number of FN observed precludes the use of the UF-100 as a routine screening method to exclude urine samples from culture. Clin Chem Lab Med 2010;48:289–92.