Thomas Streichert

Criteria for assigning laboratory measurands to models for analytical performance specifications defined in the 1st EFLM Strategic Conference.

Abstract This paper, prepared by the EFLM Task and Finish Group on Allocation of laboratory tests to different models for performance specifications (TFG-DM), is dealing with criteria for allocating measurands to the different models for analytical performance specifications (APS) recognized in the 1st EFLM Strategic Conference Consensus Statement. Model 1, based on the effect of APS on clinical outcome, is the model of choice for measurands that have a central role in the decision-making of a specific disease or clinical situation and where cut-off/decision limits are established for either diagnosing, screening or monitoring. Total cholesterol, glucose, HbA1c, serum albumin and cardiac troponins represent practical examples. Model 2 is based on components of biological variation and should be applied to measurands that do not have a central role in a specific disease or clinical situation, but where the concentration of the measurand is in a steady state. This is best achieved for measurands under strict homeostatic control in order to preserve their concentrations in the body fluid of interest, but it can also be applied to other measurands that are in a steady state in biological fluids. In this case, it is expected that the “noise” produced by the measurement procedure will not significantly alter the signal provided by the concentration of the measurand. This model especially applies to electrolytes and minerals in blood plasma (sodium, potassium, chloride, bicarbonate, calcium, magnesium, inorganic phosphate) and to creatinine, cystatin C, uric acid and total protein in plasma. Model 3, based on state-of-the-art of the measurement, should be used for all the measurands that cannot be included in models 1 or 2.

Suppression of Early Hematogenous Dissemination of Human Breast Cancer Cells to Bone Marrow by Retinoic Acid–Induced 2

UNLABELLEDnRegulatory pathways that drive early hematogenous dissemination of tumor cells are insufficiently defined. Here, we used the presence of disseminated tumor cells (DTC) in the bone marrow to define patients with early disseminated breast cancer and identified low retinoic acid-induced 2 (RAI2) expression to be significantly associated with DTC status. Low RAI2 expression was also shown to be an independent poor prognostic factor in 10 different cancer datasets. Depletion of RAI2 protein in luminal breast cancer cell lines resulted in dedifferentiation marked by downregulation of ERα, FOXA1, and GATA3, together with increased invasiveness and activation of AKT signaling. Functional analysis of the previously uncharacterized RAI2 protein revealed molecular interaction with CtBP transcriptional regulators and an overlapping function in controlling the expression of a number of key target genes involved in breast cancer. These results suggest that RAI2 is a new metastasis-associated protein that sustains differentiation of luminal breast epithelial cells.nnnSIGNIFICANCEnWe identified downregulation of RAI2 as a novel metastasis-associated genetic alteration especially associated with early occurring bone metastasis in ERα-positive breast tumors. We specified the role of the RAI2 protein to function as a transcriptional regulator that controls the expression of several key regulators of breast epithelial integrity and cancer.

Up-regulation of the T cell quiescence factor KLF2 in a leukaemic T-cell line after expression of the inositol 5'-phosphatase SHIP-1.

Inositol 5′‐phosphatase SHIP‐1 (SHIP) is a negative regulator of signal transduction in haematopoietic cells. SHIP inactivation may be involved in the pathogenesis of leukaemia. An inducible expression system was combined with microarray analysis to identify target genes regulated by SHIP in the human T‐cell leukaemia cell line Jurkat. One gene identified was Krüppel‐like factor 2 (KLF2), which was up‐regulated two to threefold at the RNA and protein level after the induced expression of SHIP. KLF2, a negative regulator of T cell proliferation, has been implicated in T cell quiescence. KLF2 or SHIP expression in Jurkat cells caused 45% or 60% reduction of proliferation, respectively. SHIP can up‐regulate KLF2 expression, implicating KLF2 in the SHIP‐mediated growth inhibition of a human leukaemic T‐cell line.

Critical comments to a recent EFLM recommendation for the review of reference intervals.

Abstract In a recent EFLM recommendation on reference intervals by Henny et al., the direct approach for determining reference intervals was proposed as the only presently accepted “gold” standard. Some essential drawbacks of the direct approach were not sufficiently emphasized, such as unacceptably wide confidence limits due to the limited number of observations claimed and the practical usability for only a limited age range. Indirect procedures avoid these disadvantages of the direct approach. Furthermore, indirect approaches are well suited for reference limits with large variations during lifetime and for common reference limits.

Paramagnetic micro-particles as a tool for rapid quantification of apixaban, dabigatran, edoxaban and rivaroxaban in human plasma by UHPLC-MS/MS

Abstract Background: Assessment of the anticoagulant activity of direct oral anticoagulants (DOACs) is justified in special clinical situations. Here, we evaluated two independent extraction methods and developed a multi-analyte ultra-high performance liquid chromatography tandem mass (UHPLC-MS/MS) method for the quantification of apixaban, dabigatran, edoxaban and rivaroxaban in human plasma. Methods: Routine extraction based on protein precipitation with acetonitrile and subsequent centrifugation was compared to sample clean-up using commercial paramagnetic micro-particles and subsequent magnetic depletion. Stable isotope-labeled analogs of all analytes were employed as internal standards. The method was validated according to international guidelines in terms of linearity, precision, trueness, sensitivity, recovery and matrix effects. The performances of both extraction methods were assessed in clinical samples obtained from patients treated with either apixaban or rivaroxaban. Additionally, we report on a patient with nonadherence to rivaroxaban treatment and fulminant pulmonary embolism. Results: The method was linear from 2 to 500 ng/mL for all analytes, and quantification of DOACs was established within a run time of 2.0 min. Based on MS/MS analyte responses, relative matrix effects were better controlled for dabigatran after extraction with paramagnetic micro-particles. Internal standards fully compensated for recovery and matrix effects in all assays, yielding equivalent results for both methods. Apixaban and rivaroxaban concentrations determined in clinical samples after extraction with both methods were in good agreement (R2=0.990). Conclusions: A rapid and accurate multi-component UHPLC-MS/MS method for the quantification of four DOACs in human plasma was established. Paramagnetic micro-particles appear suitable for clean-up of plasma samples for LC-MS/MS-based therapeutic drug monitoring purposes.

Optimizing the use of the “state-of-the-art” performance criteria

Abstract The organizers of the first EFLM Strategic Conference “Defining analytical performance goals” identified three models for defining analytical performance goals in laboratory medicine. Whereas the highest level of model 1 (outcome studies) is difficult to implement, the other levels are more or less based on subjective opinions of experts, with models 2 (based on biological variation) and 3 (defined by the state-of-the-art) being more objective. A working group of the German Society of Clinical Chemistry and Laboratory Medicine (DGKL) proposes a combination of models 2 and 3 to overcome some disadvantages inherent to both models. In the new model, the permissible imprecision is not defined as a constant proportion of biological variation but by a non-linear relationship between permissible analytical and biological variation. Furthermore, the permissible imprecision is referred to the target quantity value. The biological variation is derived from the reference interval, if appropriate, after logarithmic transformation of the reference limits.

Detection of multiple annexin autoantibodies in a patient with recurrent miscarriages, fulminant stroke and seronegative antiphospholipid syndrome

Anti-phospholipid syndrome (APS) is one of the main causes for recurrent miscarriages. The diagnosis of APS is based on the occurrence of clinical symptoms such as thrombotic events or obstetric complications as well as the detection of antiphospholipid antibodies directed against β2-glycoprotein I and cardiolipin, or a positive lupus anticoagulant assay. However, there is a subpopulation of patients with clinical symptoms of APS, but the lack of serological markers (seronegative APS). In addition, a large proportion of patients with unexplained recurrent miscarriages exist. These cases may be attributed, at least in part, to a seronegative APS.u2028The presence of autoantibodies against annexins is potentially associated with APS. Here we used immunoassays and immunoblots to detect autoantibodies directed against annexin A1-5, and A8, respectively, in a patient with a seronegative APS and a history of six recurrent pregnancy losses and fulminant stroke. We found strong IgM isotype antibody reactivity directed against annexin A2 and annexin A8, and moderate to weak IgM isotype antibody reactivity directed against annexin A1, A3, and A5. Further studies will evaluate the diagnostic value of IgM isotype antibodies against annexin A1-A5, and A8 for seronegative APS and recurrent miscarriages.

Multicenter method evaluation of the ARK™ Methotrexate Immunoassay

*Corresponding author: Veronique Stove, Department of Laboratory Medicine, Ghent University Hospital, De Pintelaan 185 (2P8), 9000 Ghent, Belgium, Phone: +32 9 332 58 71, Fax: +32 332 49 85, E-mail: veronique.stove@ugent.be Maaike J. G. Godefroid and Alain G. Verstraete: Department of Laboratory Medicine, Ghent University Hospital, Ghent, Belgium; and Department of Clinical Chemistry, Microbiology and Immunology, Ghent University, Ghent, Belgium Alexander von Meyer: Städtisches Klinikum München GmbH, Department Klinische Chemie, Munich, Germany Hans Parsch: Central Laboratory, University Hospital Erlangen, Erlangen, Germany Thomas Streichert: Institut für Klinische Chemie, Zentrallaboratorien Universitätsklinikum Eppendorf, Hamburg, Germany

Residual rivaroxaban exposure after discontinuation of anticoagulant therapy in patients undergoing cardiac catheterization

PurposePatients treated with direct oral anticoagulants (DOACs) frequently undergo interventional procedures requiring temporary discontinuation of anticoagulant therapy. Little is known about remaining peri-procedural exposure to rivaroxaban in real-world patients.MethodsFifty-six patients with rivaroxaban treatment and scheduled cardiac catheterization were included in this prospective, observational, and single-center study. Rivaroxaban concentrations were determined by LC-MS/MS and a chromogenic anti-Xa assay. Population pharmacokinetic modeling was carried out on LC-MS/MS concentration data using NONMEM software, and results were applied to Monte Carlo simulations to predict appropriate rivaroxaban discontinuation intervals.ResultsRivaroxaban concentrations ranged from <LLOQ to 300.6xa0ng/ml at the time of admission to hospital and from <LLOQ to 55.5xa0ng/ml at the beginning of the procedure. Times since last rivaroxaban intake were (mean ± SD) 51.0u2009±u200931.7xa0h (admission) and 85.5u2009±u200936.8xa0h (start catheterization). LC-MS/MS and anti-Xa assay results were in good agreement (ru2009=u20090.958); however, the anti-Xa assay may underestimate low rivaroxaban concentrations and overestimate rivaroxaban exposure when performed on plasma samples contaminated with heparins. Pharmacokinetics of rivaroxaban were adequately described, and simulations predicted that 95% of patients will have rivaroxaban concentrations ≤u200928.4xa0ng/ml (15xa0mg dose group) and ≤u200931.9xa0ng/ml (20xa0mg dose group) after 48xa0h of discontinuation.ConclusionsIn the majority of patients, rivaroxaban plasma concentrations dropped below 30xa0ng/ml after 48xa0h of treatment discontinuation which is considered hemostatically safe before surgery with high bleeding risk. For accurate determination of low rivaroxaban concentrations, LC-MS/MS is the preferred choice.

Indirect methods for reference interval determination – review and recommendations

Abstract Reference intervals are a vital part of the information supplied by clinical laboratories to support interpretation of numerical pathology results such as are produced in clinical chemistry and hematology laboratories. The traditional method for establishing reference intervals, known as the direct approach, is based on collecting samples from members of a preselected reference population, making the measurements and then determining the intervals. An alternative approach is to perform analysis of results generated as part of routine pathology testing and using appropriate statistical techniques to determine reference intervals. This is known as the indirect approach. This paper from a working group of the International Federation of Clinical Chemistry (IFCC) Committee on Reference Intervals and Decision Limits (C-RIDL) aims to summarize current thinking on indirect approaches to reference intervals. The indirect approach has some major potential advantages compared with direct methods. The processes are faster, cheaper and do not involve patient inconvenience, discomfort or the risks associated with generating new patient health information. Indirect methods also use the same preanalytical and analytical techniques used for patient management and can provide very large numbers for assessment. Limitations to the indirect methods include possible effects of diseased subpopulations on the derived interval. The IFCC C-RIDL aims to encourage the use of indirect methods to establish and verify reference intervals, to promote publication of such intervals with clear explanation of the process used and also to support the development of improved statistical techniques for these studies.