Poor reproducibility of IGT and IFG classification suggests caution should be exercised when interpreting a single test result.

The purpose of this multicenter study was to evaluate the technical performance of the automated Elecsys proBNP (brain natriuretic peptide) assay, which is indicated as an aid in the diagnosis of individuals suspected of having congestive heart failure. The Elecsys proBNP assay is an electrochemiluminescent immunoassay employing two polyclonal NT-proBNP-specific antibodies in a sandwich test format. The study was performed on the three Elecsys analyzers (E 1010, E 2010, and E 170) at eight different sites world-wide. Within- and total precision were < or = 3%, with total precision slightly higher on the Elecsys E 170 instrument with multiple modules. Reproducibility among sites and platforms was < 5%. Precision at particularly low NT-proBNP concentrations was assessed down to approximately 25 pg/ml with CVs of 12.6% at 29.2 pg/ml and 9.6% at 38.5 pg/ml for the Elecsys 1010/2010 and E 170, respectively. Linearity was evaluated up to 25,000 pg/ml with a sample-based non-linear response observed with recoveries of < 90% for proBNP concentrations < 10,000 pg/ml. Slopes ranged between 0.92 and 1.02 and intercepts from -5.3 to 10.4 pg/ml (r > or = 0.998) among the three types of analyzers. Slopes were 4.95 and 4.53 in comparison to the Biosite Triage and Shionogi BNP assays. There was no assay interference, and no effect of barrier gels, tube composition, or freeze-thaw. NT-proBNP concentrations in EDTA plasma were up to 10% lower than in serum or heparinized plasma and the analyte was stable at 4 degrees C for up to 72 hours (the maximum time tested). There was no circadian rhythm in normal subjects or congestive heart failure patients and there was no effect of drawing position. In summary, the Elecsys proBNP assay exhibits good technical performance and is suitable for use in routine clinical laboratories to aid in the diagnosis of congestive heart failure.

This international multicenter study was designed to evaluate the technical performance of the new doublemonoclonal, single-step Elecsys neuron-specific enolase (NSE) enzyme immunoassay (EIA) and to assess its utility as a sensitive and specific test for the diagnosis of small-cell lung cancer (SCLC). Intra-and interassay coefficients of variation, determined in five control or serum specimens in six laboratories, ranged from 0.7 to 5.3 (inter-laboratory median: 1.3%) and from 1.3 to 8.5 (inter-laboratory median: 3.4%), respectively. Laboratory-to-laboratory comparability was excellent with respect to recovery and inter-assay coefficients of variation. The test was linear between 0.0 and 320 ng/ml (highest measured concentration). There was a significant correlation between NSE concentrations measured using the Elecsys NSE and the established Cobas Core NSE EIA II in all subjects (n = 723) and in patients with lung cancer (n = 333). However, NSE concentrations were systematically lower (approximately 9%) with the Elecsys NSE than with the comparison test. Based on a specificity of 95% in comparison with the group suffering from benign lung diseases (n = 183), the cut-off value for the discrimination between malignant and benign conditions was set at 21.6 ng/ml. NSE was raised in 73.4% of SCLC patients (n = 188) and was significantly higher (p < 0.01) in extensive (87.8%) as opposed to limited disease (56.7%). NSE was also elevated in 16.0% of the cases with nonsmall cell lung cancer (NSCLC, n = 374). It is concluded that the Elecsys NSE EIA is a reliable and accurate di-

Abstract:The DGKL Working Group Guide Limits (Arbeitsgruppe Richtwerte) has published a proposal for deriving permissible analytical uncertainty limits related to biological variation data. Reference intervals were used to estimate biological variation. Biological variation data as basis for permissible uncertainty limits are generally accepted. These concepts usually apply a fixed factor leading to unrealistic stringent limits for quantities with a relatively small biological variation and to very permissive limits for quantities with relatively large biological variation. The working group has suggested a non-linear relation between biological variation and permissible uncertainty limits. The new approach has been exemplified with 84 quantities listed in the RiliBÄK (official German guidelines). The algorithms published allowed to derive permissible limits for all quantitative measurands in laboratory medicine. After its publication, three supplements appear necessary: 1. additional specifications of standard uncertainty, 2. a discussion on permissible limits for diagnosis and monitoring purposes, and 3. a discussion on circular reasoning in our approach.

Abstract Laboratory measurement values require interpretative assistance e.g. so-called guide limits (GL), as an interpretative aid. Legal and normative requirements for medical laboratories do not provide specific information for their implementation and verification. A German Society for Clinical Chemistry and Laboratory Medicine (DGKL) Working Group GL (WG-GL) has, therefore, developed recommendations to support medical laboratories in the management of GL. A specific objective was to create a framework that mainly takes into account those aspects that can be realistically implemented by routine laboratories and that should improve the management of GL of frequently requested quantitative measurement procedures in clinical chemistry. Thus, the focus of these recommendations is on the distinction between reference interval limits and clinical decision limits as well as the determination and verification of reference interval limits. Indirect approaches are highlighted, as they enable routine laboratories with a broad analytical spectrum but limited resources to evaluate or to establish reference limits.