Rolf Kruse

Quality control in urinary stone analysis: results of 44 ring trials (1980-2001).

Abstract Urinary stone analysis is the most important diagnostic step after stone removal from the body. The methods employed for these analyses are based on diverse analytical principles. Chemical methods are used for detecting individual ions. Infrared spectroscopy is used for examining molecular structures, and X-ray diffraction for determination of the crystalline structure of a substance. Since 1980, a twice-yearly ring trials quality control survey has been on offer to examine the quality of urinary stone analyses. A summary of the results of 44 ring trials (1980–2001) has been compiled for individual pure substances and binary (two-component) mixtures. On average, 100 laboratories have participated in these ring trials. Initially, over 80% of the participants carried out their analyses using chemical methods. In 2001, this figure decreased to a mere 13%. In contrast, a progressive increase in the use of infrared spectroscopy was observed, up to 79% of all participants employed this method. X-Ray diffraction was only employed in a small number of specialised laboratories (5–9%). The chemical methods produced a very high proportion of errors (6.5–94%) with both the pure substances and binary mixtures, whereas high error rates for infrared spectroscopy and X-ray diffraction were confined to individual substances only. Due to the poor results in the ring trials, the majority of laboratories stopped using chemical analysis, which is now considered to be obsolete. Regarding mixtures, error rates of over 10% also occurred with infrared spectroscopy and X-ray diffraction. Ring trials are indispensable for the quality management of urinary stone analysis.

Trueness verification of actual creatinine assays in the European market demonstrates a disappointing variability that needs substantial improvement. An international study in the framework of the EC4 creatinine standardization working group

Abstract Background: The European In Vitro Diagnostics (IVD) directive requires traceability to reference methods and materials of analytes. It is a task of the profession to verify the trueness of results and IVD compatibility. Methods: The results of a trueness verification study by the European Communities Confederation of Clinical Chemistry (EC4) working group on creatinine standardization are described, in which 189 European laboratories analyzed serum creatinine in a commutable serum-based material, using analytical systems from seven companies. Values were targeted using isotope dilution gas chromatography/mass spectrometry. Results were tested on their compliance to a set of three criteria: trueness, i.e., no significant bias relative to the target value, between-laboratory variation and within-laboratory variation relative to the maximum allowable error. Results: For the lower and intermediate level, values differed significantly from the target value in the Jaffe and the dry chemistry methods. At the high level, dry chemistry yielded higher results. Between-laboratory coefficients of variation ranged from 4.37% to 8.74%. Total error budget was mainly consumed by the bias. Non-compensated Jaffe methods largely exceeded the total error budget. Best results were obtained for the enzymatic method. The dry chemistry method consumed a large part of its error budget due to calibration bias. Conclusions: Despite the European IVD directive and the growing needs for creatinine standardization, an unacceptable inter-laboratory variation was observed, which was mainly due to calibration differences. The calibration variation has major clinical consequences, in particular in pediatrics, where reference ranges for serum and plasma creatinine are low, and in the estimation of glomerular filtration rate. Clin Chem Lab Med 2008;46:1319–25.

Modifications of haematology analyzers to improve cell counting and leukocyte differentiating in cerebrospinal fluid controls of the Joint German Society for Clinical Chemistry and Laboratory Medicine.

Flow cytometry (FCM) is used with haematology analyzers (HAs) to count cells and differentiate leukocytes in cerebrospinal fluid (CSF). To evaluate the FCM techniques of HAs, 10 external DGKL trials with CSF controls were carried out in 2004 to 2008. Eight single platform HAs with and without CSF equipment were evaluated with living blood leukocytes and erythrocytes in CSF like DGKL controls: Coulter (LH750,755), Abbott CD3200™, CD3500™, CD3700™, CD4000™, Sapphire™, ADVIA 120® CSF assay, and Sysmex XE‐2100®. Results were compared with visual counting of native cells in Fuchs‐Rosenthal chamber, unstained, and absolute values of leukocyte differentiation, assayed by dual platform analysis with immune‐FCM (FACSCalibur™, CD45, CD14) and the chamber counts. Reference values X were compared with HA values Y by statistical evaluation with Passing/Bablock (P/B) linear regression analysis to reveal conformity of both methods. The HAs, studied, produced no valid results with DGKL CSF controls, because P/B regression revealed no conformity with the reference values due to:—blank problems with impedance analysis,—leukocyte loss with preanalytical erythrocyte lysis procedures, especially of monocytes,—inaccurate results with ADVIA cell sphering and cell differentiation with algorithms and enzyme activities (e.g., peroxidase). HA techniques have to be improved, e.g., using no erythrocyte lysis and CSF adequate techniques, to examine CSF samples precise and accurate.

Interlaboratory Surveys of the Determination of Tumour Markers Scatter and Repeatability of the Results

Data collected between 1983 and 1991 in interlaboratory surveys of the determination of tumour markers are used to show the magnitude of the scatter of results from different laboratories for the analysis of a single quantity in a given matrix. These data also show that the varying specificity of different reagent combinations appears to make a considerable contribution to this scatter, and that the used reagent combinations were not of uniform quality over a relatively extended period. The results for the following tumour markers were studied: alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), human chorionic gonadotropin (hCG), human chorionic gonadotropin+beta-subunit (hCG+beta-hCG), tissue polypeptide antigen (TPA), carbohydrate antigen 19-9 (CA 19-9), cancer antigen 15-3 (CA 15-3), cancer antigen 125 (CA 125), prostatic acid phosphatase (PAP) and prostate-specific antigen (PSA).

Evaluation of cell counting and leukocyte differentiation in cerebrospinal fluid controls using hematology analyzers by the German Society for Clinical Chemistry and Laboratory Medicine.

Abstract Background: Manual cell counting in cerebrospinal fluid (CSF) is technique-dependent, time-consuming, and thus costly and prone to inter-operator variability and low precision. Flow cytometry (FCM) with fast hematology analyzers (HAs) appears to improve accuracy and precision of CSF cell analysis; rapid CSF cell analysis is especially needed in emergency laboratories. Ten external trials of the German Society for Clinical Chemistry and Laboratory Medicine evaluated FCM with Coulter (LH750, 755), Abbott CD3200™, CD3500™, CD3700™, CD4000™, Sapphire™, ADVIA120® CSF assay, and Sysmex® XE-2100 single platform analyzers. Methods: CSF controls were produced using native blood leukocytes and erythrocytes, resembling CSF and thus rendering the trials feasible and allowing comparison with native manual counting in a Fuchs-Rosenthal chamber and FACScan-CD45-CD14 dual platform analysis, which was used as the reference method. Statistical evaluation was performed using Passing/Bablok regression analysis. Results: Our evaluation revealed significant differences with respect to target values in leukocyte and erythrocyte counts, as well as leukocyte differentiation. These differences were attributed to inaccuracies produced by the HAs, due to blank correction in connection with impedance analysis, leukocyte loss, especially through monocyte injury due to the erythrocyte lysing agent, incomplete erythrocyte lysis, ADVIA cell sphering, cell differentiation using algorithms and peroxidase activity. Erythrocyte counting in the CSF controls was inaccurate with the Coulter and ADVIA analyzers. Conclusions: Evaluation of HAs by means of the CSF controls revealed inaccuracies in cell counting and leukocyte differentiation. Analyzer techniques, used for CSF cell assays, therefore need to be improved. Clin Chem Lab Med 2010;48:839–48.

External Quality Control in the Determination of Neonatal Bilirubin An Approach to the Improvement of Results

The reliability of bilirubin analyses is especially important in cases of neonatal hyperbilirubinaemia. However, when the means of the results of external quality control surveys and the method-dependent stated values for control sera were compared with reference method values, differences of up to 10% were found. Further inaccuracy arose from interlaboratory imprecision, which showed coefficients of variation of at least 7%, and from greater or lesser interference from contamination of samples with haemoglobin. The present work investigates whether the current situation can be improved by available means.

Quantitative mass spectrometry in clinical chemistry

AbstractAs has been demonstrated, mass spectrometry provides a powerful analytical tool for the accurate measurement of small amounts of substances in a complex biological matrix. In our laboratory this technique is used as a reference method for measuring the routine clinical chemical parameters creatinine, uric acid, cholesterol, total glycerol and the hormones cortisol, testosterone, oestradiol-17β, oestriol, progesterone, aldosterone and thyroxine in human serum.In general, the analytical procedure for measuring a substance by isotope dilution mass spectrometry (IDMS) consists of the following steps:(a)Addition of a certain amount of the isotopically labeled analyte to the serum sample.(b)Isolation and purification of the labeled and the non-labeled endogenous analyte from the biological matrix.(c)Derivative formation of the isolated and purified labeled and non-labeled compound.(d)Selected ion recording of characteristicm/z values of the labeled and non-labeled analyte using combined gas chromatography-mass spectrometry (GCMS).(e)Calculation of the concentration of the analyte from the isotope ratio measured by GCMS. The methods described here are now routinely in use for the quality control scheme of the Deutsche Gesellschaft für Klinische Chemie for assessing target values in external quality control sera. The reference method values obtained by IDMS provide a reliable basis for evaluating and comparing the results of collaborative surveys.

External Quality Assessment of Absorbance Measurements on Spectral and Spectral-Line Photometers

From 1984-1987, 12 quality control surveys on photometric measurements were carried out in 600-800 laboratories. The participants measured the photometric absorbance of the control samples at 4 wavelengths of the mercury spectrum: 334.1 nm, 365.4 nm, 404.7 nm and 546.1 nm. The medians of the results were without exception lower than the target values, but only very few of them deviated more than 1%. The dispersion of the values did not follow a normal distribution. Two thirds of the values were concentrated within a very small range, while about 10% lay outside the 2- to 3-fold range. It was found that longer wavelengths resulted in a smaller dispersion of readings than shorter ones. Furthermore, precision showed a significant dependency on the absorbance readings of the samples, on the one hand, and on the different photometers, on the other.

The new RiliBAEK- Remarks by the “Referenzinstitut für Bioanalytik” (RfB)

With the latest version of the “Rili-BAEK” guideline, an important objective has been achieved, if we consider that it now provides comprehensive regulation of the entire field of quality control in medical laboratories. From the perspective of an organiser of external quality assurance, we think that the following aspects also deserve mentioning: The data collected in external quality controls not only provide immeasurable information about the current state of analytic technology. If one compares today’s external quality assurance results with those of 20 years ago, one discovers that analytical technology has made significant progress. External quality control has surely played an important role in this, and especially along with the concept of reference method values, has considerably improved the accuracy of analytical results. In several surveys of its participants with respect to internal quality control, the RfB has for a long time accompanied the process of deriving adequate limits for quantitative laboratory analyses, and validated these limits prior to their use, based on old external quality assurance data. With the current practical limits, the system has gained overall acceptance and should not present any major problems for any laboratory. The current guideline now for the first time also governs the area of quantitative classifications with respect to external quality control. Through the external quality assurance studies now also conducted in this field, we now anticipate an improvement in analytics that had not yet attained the desired standards in certain areas. The currently available English-language edition of the Rili-BAEK guideline is now enabling interested parties from the non-German speaking countries and the RfB’s international cooperation partners to gain insights in the German quality assurance system.

Report on a Joint European Quality Control Survey for Neonatal Thyrotropin Determinations (1986)

This paper presents the results of a joint European external quality control survey for thyrotropin determinations in blood dried on filter paper, carried out in 1986 in cooperation with several national quality control organizations. For the evaluation, 124 participants presented their individual diagnostic classifications in addition to their analytical results. Although, in relation to earlier studies of this kind, there was a significant improvement in interlaboratory precision the results still showed variance which depended on the analytical method and, possibly on the country in which it was performed. Regional differences were also evident in the diagnostic classifications.