Abstract Background: Quantification of monoclonal immunoglobulin free light chains (FLCs) in serum is used increasingly in clinical practice for the diagnosis, prognostic assessment, and treatment monitoring of monoclonal gammopathies. It is used as an adjunct to standard serum protein electrophoresis and immunofixation. However, methods for FLC quantification need further standardization and validation. Methods: The Czech Myeloma Group and the Czech Society of Clinical Biochemistry have initiated an interlaboratory study where six laboratories collaborating with the primary myeloma treatment centres measured FLC concentrations in 12 serum samples from patients with monoclonal gammopathies. Results: Repeatability of the measurements in five laboratories was calculated based on differences between the results of duplicate measurements. We found that repeatability depended more on the laboratory than on the device used for measurement. Conclusions: The study revealed several weak points in the methodology, including the need for a uniform sample dilution procedure. Interlaboratory reproducibility was comparable with values achieved in the NEQAS programme. Because the κ/λ ratio cannot be measured with high precision, κ and λ FLC concentrations should be used where possible. Due to its impact on the clinical management of patients with gammopathy, FLC quantification needs to become a part of the regular quality control cycle in myeloma centres.
The aim of this opinion is to summarize and to comment the consensus of the European Atherosclerosis Society and European Federation of Clinical Chemistry and Laboratory Medicine, which covers two main areas: 1) whether it is necessary / required to be fasting or non-fasting before blood sampling for lipids measurement, and what are the changes in the concentration of blood lipids during the day; 2) What decision limits (cut off value) of lipids and lipoproteins should be reported from laboratories and what is the recommended procedure for people with extreme / critical blood lipid values. Following parameters are discused: total cholesterol, LDL cholesterol, HDL cholesterol, non-HDL cholesterol, triglycerides, apolipoprotein A1, apolipoprotein B, lipoprotein(a). This opinion should be the object of interest both for professionals in clinical laboratories and for physicians in hospitals and out-patients departments.Key words: apolipoproteins - blood collection - cholesterol - laboratory testing - lipoprotein(a) - cut off limits - triglycerides.
For most patients with a monoclonal immunoglobulin, measuring
FLC is unlikely to have additional benefit for monitoring of
disease activity with the notable exception of those with
nonsecretory/oligosecretory myeloma. FLCs monitoring could
identify patients with resistance to current therapy regimens
more quickly than M-Ig determination. Conversely the most
rapidly responding patients may have a worse outcome. FLCs
measurement can help us also in patients with early relapse
still on chemotherapy or in case of free light chains escape
phenomenon. Because of the kappa/lambda FLC ratio calculation
is strongly influenced by measurement errors, therefore we
recommend the preferential use of relevant FLC concentration
values.
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.
Cil: V ramci externi kontroly kvality SEKK, Gamapatie GP2/08
obdrželo 64 ceských klinických laboratoři a 15 slovenských
laboratoři vzorek moci od nemocne mnohocetným myelomem s Bence
Jonesovou bilkovinou typu lambda. Metody: Laboratoře provedly
typizaci paraproteinu v moci imunofixaci a stanoveni celkove
koncentrace bilkoviny v moci různými metodami, předevsim
turbidimetrii, metodou s pyrogallovou cerveni a s biuretovým
cinidlem. Výsledky: Ziskane výsledky byly významně rozdilne.
Metodou vysokorozlisovaci dvourozměrne elektroforezy s
nasledným westernblottingem byly ve zkoumane moci prokazany
předevsim fragmenty lehkých řetězců lambda o molekulove
hmotnosti 12 000 Da. Zavěr: Stanoveni koncentrace celkove
bilkoviny v moci je z různých důvodů poměrně obtižne. Tato
skutecnost je jestě zvýrazněna při přitomnosti fragmentů Bence
Jonesovy bilkoviny v moci, jak prokazala i tato prace.
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.
