The problems of proteinuria measurement in urine with presence of Bence Jones protein.

OBJECTIVES: Protein concentration measurement in the urine can be problematic in the presence of Bence Jones protein. We have carried out an external quality control assessment with the participation of 79 clinical biochemistry laboratories from the Czech Republic and Slovakia. DESIGN AND METHODS: The laboratories received a reference urine sample obtained from a patient with multiple myeloma and lambda free light chain proteinuria and were asked to type the paraprotein using immunofixation and to measure total urinary protein using their established method, most commonly turbidimetry, pyrogallol red assay, and biuret assay. RESULTS: There was a very wide inter-laboratory variability in the protein concentration readouts with up to three-fold difference in some cases. High-resolution two-dimensional electrophoresis and linear mass spectrometry showed that a high proportion of the urinary paraprotein was composed of lambda light chain fragments with molecular weight of 12kDa. CONCLUSIONS: Our results highlight the challenges of reliable and reproducible measurement of urinary protein concentration in the presence of Bence Jones protein.

International Staging System required standardization of biochemical laboratory testing in multiple myeloma.

The standardization of biochemical measurement procedures in multiple myeloma is necessary for reliable prognostic stratification of patients in multicentric trials. The new prognostic index International Staging System for multiple myeloma uses only two laboratory markers, albumin and beta-2 microglobulin. Our study compared results of albumin, beta-2 microglobulin and monoclonal immunoglobulin measurements from six centers which provide treatment for multiple myeloma in the Czech Republic and attempted to standardize the analytic procedures. We have found that the measurement of albumin is well standardized and the results from all laboratories were comparable. The measurement of beta-2 microglobulin achieved comparability only after a partial unification of analytical methods. The determination of monoclonal immunoglobulin concentration provided comparable results for concentrations higher than 20 g/l with higher variability for lower values.

Trueness verification in European external quality assessment schemes: time to care about the quality of the samples.

An external quality assessment (EQA) survey on 14 fresh-frozen, single-donation sera assigned with reference measurement procedure (RMP) values revealed a mean bias of + 5.2% and + 3.7% for the cholesterol oxidase and the photometric glucose oxidase procedure groups, respectively. Conversely, on lyophilized sera, the same procedure groups showed almost bias-free results, the differences from the RMP values being only -0.8% for cholesterol and + 0.7% for glucose. These data, which are in fairly good agreement with the literature, suggest the existence of artificial matrix effects in processed materials. Therefore they indicate that, currently, assessment of trueness is hampered in many European EQA schemes, as most of them use lyophilized sera. This approach may give a false impression about the trueness of laboratory results as well as carrying the risk that laboratories calibrated on the RMP values of the survey samples could make errors in patient testing. Consequently, if European EQA is willing to fulfil a post-market vigilance function of the performance of in vitro diagnostic medical devices, then the time has come to tackle the problem of the quality of the survey samples. EQA organizers urgently need to make an effort to seek out materials that analytically behave like authentic clinical specimens. In the meantime, alternative approaches should be used. Although not ideal, the special survey described in this article is one of the possibilities. Naturally, it implies logistic problems and increased costs for the individual EQA schemes. However, both can be overcome with the cooperation of the predominantly nationally organized schemes.

[Diagnostic value of carbohydrate-deficient transferrin, gamma-glutamyltransferase and mean erythrocyte volume as laboratory markers of chronic alcohol abuse]. / Diagnostická výteznost karbohydrát deficitního transferinu, gama-glutamyltransferázy a stredního objemu erytrocytu jako laboratorních markeru chronického abúzu alkoholu.

INTRODUCTION: Our research aimed at finding out values of carbohydrate-deficient transferin (CDT), gamma-glutamyltransferase (GGT) and mean corpuscular volume (MCV) for the purposes of future etiological diagnostics of alcohol neuropathy in thin fibres. METHODS: We examined the serum of 80 control subjects (50 women and 30 men), and the serum of 33 alcoholics (20 men and 13 women) with the daily consumption of more than 60 g alcohol in the course of the last four weeks. CDT was determined with the use of microcolumn separation after iron saturation followed by turbidimetric immunoassay (ChronoAlcoI. D., Sangui Biotech, Inc.) on Cobas-Mira analyser. CDT is expressed as a percentage of the total transferin. Senzitivity, specificity, positive likelihood ration (+LR), ROC and the area under the ROC curve were determined using statistical program MedCalc. RESULTS: The senzitivity, specificity and positive likelihood ratio (+LR) for CDT-%, respectively, were 82.6, 96.7 and 24.8 for men (cut off 2.2%), and 60.0, 88.0 and 5.0 for women (cut off 2.5%). The respective values for GMT were 95.7, 90.0 and 9.6 for men (cut off 0.64 mu kat/l), and 90.0, 80.0 and 4.5 for women (cut off 0.38 mu kat/l); for MCV 82.6, 96.7 and 24.8 for men (cut off 95.0 fL), and 80.0, 100.0 and 20.0 for women (cut off 97.2 fL). The area under the ROC curve for CDT-%, GMT and MCV, respectively, were 0.940, 0.964 and 0.896 for men, and 0.829, 0.917 and 0.906 for women. CONCLUSION: In men, CDT-% and MCV showed the same values of the statistical parameters studied. GGT was more sensitive and less specific. In women, all the parameters studied presented a lesser diagnostic value, except for MCV with 100% specificity and +LR 20.0.

Comparison of different immunoassays for CA 19-9.

We compared six routinely employed immunoassay kits: Architect i2000 and AxSYM, Abbott Laboratories; Elecsys 2010, Roche Diagnostics; ELSA, CIS-BioInternational; Immulite 1, Diagnostic Products Corporation; and IRMA-mat, Byk-Sangtec Diagnostica. Using all analytical systems, we measured identical groups of clinical samples completed with selected control samples. The repeatability of measurements (coefficient of variation) ranged from 2.1% (Elecsys 2010) to 6.7% (ELSA). The parameters of Passing-Bablok regression show significant systematic differences among analytical systems. Data from a Bland-Altman diagram suggest that these differences project onto other, still more significant individual differences among individual samples. Though the cut-off values differ between various systems, no similar clinical efficacy appears to be attained. The behavior of individual systems is quite different for identical control materials and does not necessarily duplicate the calibration for biological samples. The results of determining CA 19-9 cannot be extrapolated from one analytical technique to another, even in cases where the same monoclonal antibody is used. Standardization of CA 19-9 measurement systems is necessary to allow use of the results for the purposes of evidence-based medicine.

[Heterogeneity of the frequency of the apolipoprotein E-epsilon 4 allele in the European population]. / Heterogenita frekvence alely apolipoprotein E-epsilon 4 v evropské populaci.

BACKGROUND: Apolipoprotein E (apo E) is one of the most important constituents of plasma lipoproteins. A genetic polymorphism in the 4th exon of the apo E gene determines the existence of epsilon 2, epsilon 3 and epsilon 4 alleles in human population coding for three common isoforms of apo E: apo E2, apo E3, and apo E4. The aim of the study is to present the heterogeneity of the epsilon 4 allele frequency in the European region. METHODS AND RESULTS: The mean frequency of the epsilon 4 allele is 13.6% in the whole European population (95%) confidence interval: 7.2-20.0%; 45 evaluated studies, 19940 subjects). Frequency of the epsilon 4 is 17.7% in Northern Europe (12.0-23.4%; 11 studies, 4564 subjects), 15.5% in Western Europe (10.9-20.0%; 21 studies, 11,615 subjects), 12.8% in Central Europe (9.1-16.5%; 5 studies, 939 subjects), and 8.0% in Southern Europe (3.2-12.8%; 8 studies, 2822 subjects). The mean frequency of epsilon 4 allele established preliminary in two localities (Prague, Hradec Králové) in the Czech Republic is 15.7% (15.5-15.9; 2 studies, 95 subjects). CONCLUSIONS: The study confirmed an apo E-epsilon 4 frequency heterogeneity in the European population. The occurrence of epsilon 4 allele decreases from the North to the South in Europe. The highest frequency of epsilon 4 allele is in Finland (mean 22.1%), the lowest in Sardinia (5.2%).

Survey of serum potassium reference measurements.

We compared the quality of reference measurements for serum potassium in four reference laboratories from three different European countries, using a panel of 60 native patients' samples. The reference methods were based on either ion chromatography (one laboratory) or flame atomic emission spectrometry (three laboratories). Performance specifications for serum potassium measurements were defined as a maximum overall coefficient of variation (CV) of 1.5%, a maximum bias of 0.65% and a maximum total error of 3.0%. The overall imprecision for all laboratories was in the range of 0.7 to 1.3%, and was thus below the proposed specification of 1.5%. However, two laboratories reported 12 and 13 quadruplicates with CVs exceeding this limit. The mean bias (expressed as deviation from the overall mean of all laboratories) for all reference laboratories was < 0.65%. In the lower concentration range, however, one laboratory exceeded this limit. No laboratory measured samples with a total error above 3.0%. From these results, it can be concluded that the reference measurements, and, thus, also the reference methodologies, based on ion chromatography and flame atomic emission spectrometry were equivalent, and able to satisfy current analytical specifications for serum potassium measurements.

"Ocean-to-Ocean Project": a transcontinental external quality assessment trial in clinical chemistry realized throughout Eurasia.

More than 800 diagnostic laboratories situated throughout the Eur-Asian continent--from the Pacific Coast up to the North Sea littoral--were involved in a common survey of External Quality Assessment (EQA). It consisted of the simultaneous measurement of up to 30 analytes of 'general' clinical chemistry using the same batch of control material. The laboratories were associated in four EQA institutions: SKZL (The Netherlands), OQUASTA (Austria), SEKK (Czech Republic) and BKKSystem (Community of Independent States). The results demonstrated the feasibility of such a large-scale survey and provided a realistic idea about the state-of-the-art of laboratory diagnosis in these countries: Besides some local specific problems, such as poor quality of water or the forced use of reagents and calibrators from different sources, there are general problems hindering an efficient process of 'harmonization' in laboratory medicine, namely, the high methodological dispersion especially in the case of enzymes and of some organic analytes. At the same time there is a potential necessity for more concentrated implementation of internal quality assessment into the routine work of laboratories.