Band 54, Heft 8

Matrix metallo-proteinases (MMPs) are a family of zinc-dependent endopeptidases, capable of degrading all the molecular components of extracellular matrix. A class of MMPs is gelatinases which includes gelatinase A or MMP-2 (72 kDa) and gelatinase B or MMP-9 (92 kDa), which have been shown to play critical roles in pathophysiology of many human disease and, in particular, cancer progression. For these reasons they obtained a great interest as potential non-invasive biomarker in providing useful clinical information in cancer diagnosis and therapy. A sensitive and unexpensive method for analysis of gelatinases is the gelatine zymography, which allows to measure the relative amounts of active and inactive enzymes in body fluids and tissue extracts. The procedure involves the electrophoretic separation of proteins under denaturing but non reducing conditions through a polyacrylamide gel containing a synthetic substrate (gelatin). The aim of this mini-review has been to describe the general principles of gelatine zymography technique, underling the main advantages and disadvantages. Even though an improvement of this method is necessary for a better applicability in laboratory medicine, gelatine zymography represents the most convenient method to detect the activity of the different gelatinases from a wide range of biological samples.

The performance of all measurement procedures used in routine clinical laboratories shall be verified; a minimum is to verify the precision and trueness of the results. This is well established and adequate recommendations and procedures are available. Conveying this information in a form that is adequate and understandable for the practical end-user in the health care sector is still a much debated issue. By tradition, since several decades, the “total error” (TE) is presented, a quantity that is the linear sum of an imprecision and bias. Since any combination of the two can yield the same TE it may not be very helpful in finding and correcting a root-cause for an unacceptable value. Also, an acceptable TE may hide an unacceptable level of its constituents. An alternative is the measurement uncertainty (MU), which is recommended by accreditation and standardizing bodies The MU separates the imprecision and bias and expresses an interval around a best estimate within which the true value is expected with a certain probability. We describe the reporting the best estimate of a measurement result and describe how the uncertainty of the result, can be calculated, using simple custom-made software.

A recent issue in this journal revisited performance specifications since the Stockholm conference. Of the three recommended methods, two use total error models to establish performance specifications. It is shown that the most commonly used total error model – the Westgard model – is deficient, yet even more complete models fail to capture all errors that comprise total error. Moreover, total error models are often set at 95% of results, which leave 5% of results as unspecified. Glucose meter performance standards are used to illustrate these problems. The Westgard model is useful to asses assay performance but not to set performance specifications. Total error can be used to set performance specifications if the specifications include 100% of the results.

The uncertainty of a measurement result is a fundamental concept in metrology indicating the range within the “true” value of a measurement should lie. Although not commonly reported with results, the calculation of measurement uncertainty (MU) has become common in routine clinical laboratories. Interpretation of numerical pathology results is made by comparison with data from other measurements. As MU is aimed at assisting with result interpretation, it should be related to the specific comparison being made. There are three basic type of comparators: a previous result from the same patient, a population reference interval, or a clinical decision point. For each comparison, the “true” value is that which would have been obtained from the instrument used to make the comparator measurements if it was measured without uncertainty. The MU is the range of likely deviations from this true value due to the method used to produce the result under interpretation. For patient monitoring, if the two measurements were made on the same analyzer, the uncertainty is the imprecision of the assay over the relevant time frame. In comparing with a manufacturer-specific reference interval, the MU is deviation from the manufacturer’s master calibrator. For clinical decision points produced with the assays traceable to international references, the MU is related to deviation from that reference standard. For optimal use of MU in the clinical laboratory, it may be necessary to consider the use of the test result and the concept of a single MU for each result may need to be revised.

There appears to be a growing debate with regard to the use of “Westgard style” total error and “GUM style” uncertainty in measurement. Some may argue that the two approaches are irreconcilable. The recent appearance of an article “ Quality goals at the crossroads: growing, going, or gone ” on the well-regarded Westgard Internet site requires some comment. In particular, a number of assertions which relate to ISO 15189 and uncertainty in measurement appear misleading. An alternate view of the key issues raised by Westergard may serve to guide and enlighten others who may accept such statements at face value.

Background: Allowable total error is usually derived from data on biological variation or from state-of-the-art of measuring technology. Here we present a new principle for evaluating allowable total error when the concentration of the analyte (the measurand) is used for prediction: What are the predictive consequences of allowable total errors in terms of errors in the estimate of the hazard ratio (HR)? Methods: We explored the effect of analytical measurement errors on Cox regression estimates of HR. Published data on Cox regression coefficients were used to illustrate the effect of measurement errors on predicting cardiovascular events or death based on serum concentration of cholesterol and on progression of chronic kidney disease to kidney failure based on serum concentrations of albumin, bicarbonate, calcium and phosphate, and urine albumin/creatinine-ratio. Results: If the acceptable error in the estimate of the HR is 10%, allowable total errors in serum cholesterol, bicarbonate and phosphate are approximately the same as allowable total error based on biological variation, while allowable total error in serum albumin and calcium are a little larger than estimates based on biological variation. Conclusions: Evaluating allowable total error from its effect on the estimate of HR is universally applicable to measurands used for prediction.

Background: In this study, we analyzed frozen sera with known commutabilities for standardization of serum electrolyte measurements in China. Methods: Fresh frozen sera were sent to 187 clinical laboratories in China for measurement of four electrolytes (sodium, potassium, calcium, and magnesium). Target values were assigned by two reference laboratories. Precision (CV), trueness (bias), and accuracy [total error (TE a )] were used to evaluate measurement performance, and the tolerance limit derived from the biological variation was used as the evaluation criterion. Results: About half of the laboratories used a homogeneous system (same manufacturer for instrument, reagent and calibrator) for calcium and magnesium measurement, and more than 80% of laboratories used a homogeneous system for sodium and potassium measurement. More laboratories met the tolerance limit of imprecision (coefficient of variation [CV a ]) than the tolerance limits of trueness (bias a ) and TE a . For sodium, calcium, and magnesium, the minimal performance criterion derived from biological variation was used, and the pass rates for total error were approximately equal to the bias (<50%). For potassium, the pass rates for CV and TE were more than 90%. Compared with the non homogeneous system, the homogeneous system was superior for all three quality specifications. Conclusions: The use of commutable proficiency testing/external quality assessment (PT/EQA) samples with values assigned by reference methods can monitor performance and provide reliable data for improving the performance of laboratory electrolyte measurement. The homogeneous systems were superior to the non homogeneous systems, whereas accuracy of assigned values of calibrators and assay stability remained challenges.

Background: Monoclonal (M) components can interfere with the direct bilirubin (D-Bil) assay on the AU Beckman Coulter instrumentation and produce spurious results, such as D-Bil values greater than total bilirubin (T-Bil) or very low/negative D-Bil values. If properly detected, this interference may uncover undiagnosed patients with monoclonal gammopathy (MG). Methods: We investigated the interference rate on the D-Bil AU assay in serum samples known to contain M proteins along with their isotype and described the protocol set up in our laboratory to help with the diagnosis of MG based on D-Bil spurious results as first indication. Results: During a period of 4 years, 15.4% (345 of 2235) of serum samples containing M immunoglobulins produced erroneous D-Bil results, although no clear relationship between the magnitude or isotype of the M component and interference could be found. In total 22 new patients were diagnosed with MG based on the analytical artefact with the D-Bil as first indication. Conclusions: The D-Bil interference from MG on the Beckman AU analysers needs to be made known to laboratories in order to prevent clinical confusion and/or additional workup to explain the origin of anomalous results. Although this information may not add to the management of existing patients with serum paraproteins, it can benefit patients that have not been diagnosed with MG by triggering follow up testing to determine if M components are present.

Background: The aim of the study was to promote the establishment and implementation of quality indicators (QIs) in clinical laboratories, catch up with the state of art, and provide preliminary quality specifications for established QIs. Methods: Clinical laboratories from different provinces in China were included in this QIs survey in 2015. All participants were asked to collect data related to QIs and complete QIs questionnaires. Defect percentages and sigma values were calculated for each QI. The 25th percentile, median, and the 75th percentile of defect percentages and TATs were calculated as optimum, desirable and minimum quality specifications. While 25th, median, and 75th of sigma values were calculated as minimum, desirable and optimum quality specifications, respectively. Results: Five thousand seven hundred and fifty-three clinical laboratories from 28 provinces in China participated in this survey. Median defect percentages of pre-examination QIs varied largely from 0.01% (incorrect sample container) to 0.57% (blood culture contamination) with sigma values varied from 4.0σ to 5.1σ. Median defect percentages of examination phase QIs were all really high. The most common problem in examination phase was test uncovered by inter-laboratory comparison (86.67%). Defect percentages of critical values notification and timely critical values notification were all 0.00% (6.0σ). While the median of defect percentages of incorrect laboratory reports was only 0.01% (5.4σ). Conclusions: Improvements are needed in all phases of total testing process (TTP) in laboratories in China, especially in examination phase. More attention should be paid when microbiology specimens are collected and results are reported. Quality specifications can provide directions for laboratories to make effort for.

Background: In this study, we provide a short analytical evaluation of the new Fujirebio Lumipulse ® G non-competitive immunoassay for 25(OH)D. Clinical performance was compared with three commercial competitive automated immunoassays against a Vitamin D Standardization Program (VDSP)-traceable liquid chromatography-tandem mass spectrometry (LC-MS/MS) in six different clinically relevant populations. Methods: Lumipulse ® G 25(OH)D precision, measurement uncertainty, recovery, limit of quantification were assessed, as well as 25(OH)D2 and C3-epimer recovery. For method comparison, 250 serum samples obtained in healthy Caucasians and Africans, osteoporotic, hemodialyzed and intensive care patients and 3rd trimester pregnant women were analyzed by all methods. Correlation was studied using Passing-Bablok and Bland-Altman analysis. Concordance correlation coefficient (CCC) was calculated to evaluate agreement between immunoassays and the LC-MS/MS. Results: The Lumipulse ® G 25(OH)D assay presented interesting analytical features and showed excellent correlation to the LC-MS/MS results (y=1.00×–1.35 ng/mL), as obtained in healthy Caucasian individuals. In the other special populations, Lumipulse ® G presented a concordance with LC-MS/MS which was generally higher than competitors, even if all methods significantly under-recovered 25(OH)D in hemodialyzed patients. Intra-assay CV ranged from 12.1% at 9.6 ng/mL to 2.1% at 103.7 ng/mL and inter-assay CV ranged from 16.2 to 3.7% at the same concentrations, respectively. Measurement uncertainty, with a probability of 95%, were respectively 33.1 and 7.6% at these concentrations. LOQ was found to be at 4.6 ng/mL. Mean (95% CI) 25(OH)D2 revovery was 77% (74–81) and no cross-reactivity was observed with C3-epimer. Conclusions: Fujirebio Lumipulse ® G 25-OH Vitamin D Total assay is therefore considered suitable for assessment of vitamin D status in clinical routine.

Background: Faecal (f-) calprotectin is a widely used marker for intestinal inflammation. However, extraction procedure is time consuming and cumbersome. The main aim of this study was to evaluate patient-performed extraction of f-calprotectin compared to extraction performed in the laboratory. Methods: A total of 81 adult patients with an established diagnosis of inflammatory bowel disease provided two samples from the same bowel movement, one conventional faeces sample and one sample with a patient administered extraction device. A laboratory technician extracted the conventional faeces sample with the same extraction device. Results: F-calprotectin results from the laboratory-performed extraction and the patient-performed extraction correlated significantly, with a Spearman rank correlation coefficient of 0.92. Method comparison showed a slope of 1.20 (95% confidence interval 1.08–1.36) with intercept of –0.30 (95% confidence interval –9.00 to 4.62). This demonstrates a small proportional difference between the results from the home extracted samples and the results from the laboratory extracted samples, where the home extracted samples are slightly higher. However, six of the 81 patients had made obvious mistakes in the extraction process and their samples were excluded from the study. Conclusions: Patient administered extraction of f-calprotectin can be a realistic alternative for selected patients. However, instructions must be very precise to avoid mistakes.

Background: We compared the Elia CTD Screen (ECS), a fluoroenzymeimmunoassay incorporating 17 human antinuclear antigens (ANA), with indirect immunofluorescence (IIF) on Hep-2 cells in order to determine the clinical utility of the ECS in additon to or without IIF. Methods: We examined 1708 consecutive serum samples submitted for ANA testing using the ECS and IIF in parallel. Positive screen results were further examined by quantitative fluoroenzymeimmunoassays and/or immunoblots for antibody identification. The medical records were evaluated for systemic rheumatic disorders. Results: Concordance between ECS and IIF was observed in 1344 (78.8%) samples. ECS had a better detection rate for anti-dsDNA, -SSA/Ro, -SSB/La, -U1RNP and -Jo-1 antibodies, whereas IIF was superior in the detection of anti-CENP-B antibodies as well as anti-histone, -nucleosome and -Pl-12 antibodies, which are not included in the ECS antigen panel. ECS had a 100% sensitivity for Sjögren’s syndrome, systemic sclerosis and Sharp syndrome. The sensitivity for Sjögren’s syndrome was slightly higher for ESC than for IIF (94%). IIF had a higher diagnostic sensitivity for systemic lupus erythematosus, indeterminated connective tissue disease, Raynaud’s syndrome and limited scleroderma, compared to ESC (100% vs. 80%, 100 vs. 75%, 89 vs. 57%, 100 vs. 88.9%). Conclusions: Our results suggest that the ECS represents an appropriate diagnostic tool for ANA screening. However, since some antigens are not incorporated in the ECS panel, and some ANA can also be missed by IIF, sequential or parallel screening with ECS and IIF may be reasonable when the clinical suspicion for connective tissue disease is high.

Background: The utility of ghrelin as a biomarker may be different depending on gender. The aim of this study was to assess ghrelin levels in a population-based sample of adolescents, and to evaluate their association with obesity and obesity-related parameters depending on sex. Methods: The studied population included 601 randomly selected 14-to 16-year-old children. Anthropometrical data were measured and body mass index (BMI) and waist to hip ratio calculated. Body composition was assessed using an impedance body composition analyzer. Total serum ghrelin levels were determined using a multiplexed bead immunoassay. Serum leptin and adiponectin levels were determined by ELISA and insulin by RIA. Results: Ghrelin levels were significantly higher in girls than in boys. Serum ghrelin concentrations were significantly lower (p<0.01) in obese than in normal weight (NW) girls, but showed no differences by weight category in boys. Ghrelin showed a significant negative relationship with waist circumference (WC), waist to hip ratio and fat mass (p<0.05) in both genders, and with weight and BMI (p<0.01) in girls, and insulin (p<0.01) and HOMA (p<0.05) in boys. Ghrelin also correlated negatively with leptin levels in girls (p<0.01). Conclusions: Our study describes serum ghrelin levels in adolescents, showing a sexual dimorphism in ghrelin levels in these 14-to 16-year-old children, and a different association of ghrelin levels with obesity by gender that suggests a different appetite and energy expenditure control depending on sex at this age.

Background: Thyroid function tests are frequently assessed during pregnancy to evaluate thyroid dysfunction or to monitor pre-existing thyroid disease. However, using non-pregnant reference intervals can lead to misclassification. International guidelines recommended that institutions should calculate their own pregnancy-specific reference intervals for free thyroxine (FT4), free triiodothyronine (FT3) and thyroid-stimulating hormone (TSH). The objective of this study is to establish gestation-specific reference intervals (GRIs) for thyroid function tests in pregnant Turkish women and to compare these with the age-matched non-pregnant women. Methods: Serum samples were collected from 220 non-pregnant women (age: 18–48), and 2460 pregnant women (age: 18–45) with 945 (39%) in the first trimester, 1120 (45%) in the second trimester, and 395 (16%) in the third trimester. TSH, FT4 and FT3 were measured using the Abbott Architect i2000SR analyzer. Results: GRIs of TSH, FT4 and FT3 for first trimester pregnancies were 0.49–2.33 mIU/L, 10.30–18.11 pmol/L and 3.80–5.81 pmol/L, respectively. GRIs for second trimester pregnancies were 0.51–3.44 mIU/L, 10.30–18.15 pmol/L and 3.69–5.90 pmol/L. GRIs for third trimester pregnancies were 0.58–4.31 mIU/L, 10.30–17.89 pmol/L and 3.67–5.81 pmol/L. GRIs for TSH, FT4 and FT3 were different from non-pregnant normal reference intervals. Conclusions: TSH levels showed an increasing trend from the first trimester to the third trimester, whereas both FT4 and FT3 levels were uniform throughout gestation. GRIs may help in the diagnosis and appropriate management of thyroid dysfunction during pregnancy which will prevent both maternal and fetal complications.

Background: SOX17 belongs to the high-mobility group-box transcription factor superfamily and down-regulates the Wnt pathway. The aim of our study was to evaluate the prognostic significance of SOX17 promoter methylation in circulating tumor DNA (ctDNA) in plasma of non-small cell lung cancer (NSCLC) patients. Methods: We examined the methylation status of SOX17 promoter in 57 operable NSCLC primary tumors and paired adjacent non-cancerous tissues and in ctDNA isolated from 48 corresponding plasma samples as well as in plasma from 74 patients with advanced NSCLC and 49 healthy individuals. SOX17 promoter methylation was examined by Methylation Specific PCR (MSP). Results: In operable NSCLC, SOX17 promoter was fully methylated in primary tumors (57/57, 100%), and in corresponding ctDNA (27/48, 56.2%) while it was detected in only 1/49 (2.0%) healthy individuals. In advanced NSCLC, SOX17 promoter was methylated in ctDNA in 27/74 (36.4%) patients and OS was significantly different in favor of patients with non-methylated SOX17 promoter (p=0.012). Multivariate analysis revealed that SOX17 promoter methylation in ctDNA was an independent prognostic factor associated with OS in patients with advanced but not operable NSCLC. Conclusions: Our results show that SOX17 promoter is highly methylated in primary tumors and in corresponding plasma samples both in operable and advanced NSCLC. In the advanced setting, SOX17 promoter methylation in plasma ctDNA has a statistical significant influence on NSCLC patient’s survival time. Detection of SOX17 promoter methylation in plasma provides prognostic information and merits to be further evaluated as a circulating tumor biomarker in patients with operable and advanced NSCLC.

Background: Plasma 3-methoxytyramine (3-MT), a metabolite of dopamine, is elevated in up to 28% of patients with head and neck paragangliomas (HNPGLs). As free dopamine is incorporated in circulating platelets, we determined dopamine concentration in platelets in patients with a HNPGL. Methods: A single center cohort study was performed between 2012 and 2014. Thirty-six patients with a HNPGL were compared to healthy controls (68 for dopamine in platelets and 120 for plasma 3-MT). Results: Dopamine concentration in platelets was elevated in HNPGL patients compared to healthy controls (median [interquartile ranges] 0.48 [0.32–0.82] pmol/10 9 platelets vs. 0.31 [0.24–0.47] pmol/10 9 platelets; p<0.05), whereas plasma 3-MT concentration did not differ between both groups (0.06 [0.06–0.08] nmol/L vs. 0.06 [0.06–0.06] nmol/L; p=0.119). Based on 68 healthy controls, the reference interval for dopamine concentration in platelets was 0.12–0.97 pmol/10 9 platelets. Six (16.7%) patients with a HNPGL demonstrated an increased dopamine concentration in platelets compared to three (8.3%) patients with an increased plasma 3-MT level (p=0.053). The sensitivity and specificity were 16.7% and 98.5% for platelet dopamine and 8.3% and 97.5% for plasma 3-MT concentration (p=0.37). Conclusions: Dopamine concentration in platelets is elevated in patients with a HNPGL compared to healthy subjects, and may be a novel biomarker for dopamine producing paraganglioma.