Andrew Grant

Assessment of platelet activation in several different anticoagulants by the Advia 120 Hematology System, fluorescence flow cytometry, and electron microscopy

In vivo platelet activation results are often confounded by activation induced in vitro during the preparative procedures. We measured ex vivo (basal) and in vitro (thrombin-induced) platelet activation in sodium citrate, ethylenediaminetetraacetic acid (EDTA), and Citrate Theophylline Dipyridamole Adenosine (CTAD) whole blood specimens. Determinations were made by measurements of platelet density (mean platelet component: MPC concentration) on the Advia 120 Hematology System. The MPC has been previously shown to correlate with a fluorescence flow cytometric method, also determined in this study, using the surface expression of CD62P. Moreover, platelet shape and structure changes in EDTA and CTAD anticoagulated whole blood specimens were characterized by transmission electron microscopy (TEM). Observations made using the Advia 120 Hematology System platelet density parameter, MPC, in the absence of thrombin were 25.7 +/- 0.9 g/dl, 27.9 +/- 0.9 g/dl and 24.8 +/- 1.2 g/dl in sodium citrate, EDTA and CTAD whole blood specimens, respectively. Addition of thrombin induced a significant change in platelet MPC for sodium citrate (21.9 +/- 1.9 g/dl; p<0.0001) and EDTA (23.2 +/- 0.9 g/dl; p<0.0001) whole blood specimens. In contrast, thrombin had no effect on MPC measured in whole blood taken into CTAD tubes. In vitro fluorescence flow cytometric platelet activation experiments measuring the percentage of platelets expressing anti-CD62P showed increase in sodium citrate specimens from 9.2 +/- 7.0 to 55.5 +/- 23.1 % (p<0.0001) and in EDTA specimens from 1.9 +/- 1.7 to 64.6 +/- 12.4 % (p<0.0001) after addition of thrombin. However, in blood taken into CTAD tubes, there was no significant change. Studies on platelets isolated from whole blood in CTAD showed activation by thrombin indicating that platelets in CTAD, while protected in its presence remained functional upon its removal. When observed by TEM over time, platelets in EDTA appear more activated and contain fewer granules than platelets in CTAD. We conclude that CTAD demonstrates in vitro platelet activation inhibition and may be useful in stabilizing ex vivo platelet activation. The novel platelet activation parameter, MPC, measured by an automated routine hematology system, using customized proprietary software, may be used in conjunction with CTAD, a stabilizing anticoagulant, to measure the ex vivo platelet activation state in whole blood specimens. TEM studies verify shape modifications and simultaneous retention of intracellular granules at early post-venipuncture time periods in CTAD specimens.

Integrating feedback from a clinical data warehouse into practice organisation.

A patient oriented hospital information system (ARIANE) was inaugurated at the Sherbrooke University hospital (CHUS) in 1990 and a clinical data warehouse (CDW) completed 2004. The CDW is updated from ARIANE every 24h and includes ICD discharge diagnosis data, visit DRG and SNOMED encoding. The data is encrypted on storage. Data is accessed according to institutional approval. To facilitate data access two levels of tool have been made accessible using a web-browser. The first level consists of a dashboard that has a defined design and enables a set of pre-determined dynamic queries about a patient population. This level can be operated with minimal training. The second level uses a convivial database query tool, which requires some prior training. Two prototype dashboards have been designed and evaluated for acceptability. The first for the emergency department enables analysis of patient occupancy. The second for the biochemistry department enables quality assurance evaluation. In most cases worldwide the clinical data warehouse is only beginning to be exploited, often impeded by lack of connection between different enterprise databases. Our CDW is expected rapidly to create a culture change so that clinical practice can be continuously evaluated using compiled data readily available from the electronic health record/hospital information system.

The TEAM methodology for the evaluation of information systems in biomedicine.

The TEAM evaluation methodology for information systems in biomedicine (Total Evaluation and Acceptance Methodology) is a unifying methodology for any computer-based information system based on a three dimensional framework; these dimensions being Role, Time and Structure. The theory is derived from how the information system relates to the general system where it should operate, the properties of information flow within a general system and the relation between a system and its models. As a system can in theory be modelled from many perspectives, a perspective to be modelled is built up by formulating criteria relevant to that perspective which can be evaluated by quantitative and qualitative assessment methods. Key characteristics of the methodology include the insistence on a global rather than partial approach to the evaluation of information systems, also the dynamic nature of an information system which is continually in modification as it more successfully deals with the inherent complexity of the environment in which it is operating. The role dimension identifies four main categories, designer, specialist user, end user and stakeholder from which several sub-categories may be identified. The time dimension has four main phases towards relative stability of the information system. The structural dimension distinguishes strategic, tactical or organisational and operational levels that often are confused together with risk of dilution in current approaches. It is believed that this framework and methodology can provide a basis for future standardisation of evaluation methodologies.

Comparative multicentre study of a panel of thyroid tests using different automated immunoassay platforms and specimens at high risk of antibody interference

Abstract The introduction of automation for immunoassays in recent years has brought about important and evident improvements in assay precision. Increasing standardization and comparability between platforms should enable the development of clinical guidelines and diagnostic algorithms for appropriate clinical decision making. A continuing source of variation between different automated immunoassay platforms is the sporadic effect of interfering antibodies or substances, thus causing aberrant results not supporting the patients clinical status. The aim of this study was to describe current thyroid panel variation between automated immunoassay platforms including population specimens at risk of antibody interference. A multisite design with laboratories in three different countries using four different automated immunoassay platforms (Roche-Boehringer Mannheim Elecsys® (Italy), Roche-Boehringer Mannheim ES300® (Wales), Bayer Immuno 1® and the Bayer ACS:180® evaluated the thyroid panel of thyrotropin (TSH), triiodothyromine (T3), free thryroxine (FT4) and free triiodothyronine (FT3). A common set of 158 randomly selected patient samples of non-thyroid and thyroid disorders, with and without treatment, was tested. Included were 62 patient samples at risk for endogenous antibody interference with high antimicrosomal antibody, anti-TSH receptor antibody and increased rheumatoid factor sub-populations. Across all controls and between platforms, precision measurements were comparable and varied between 0.7% and 12.8% for TSH, 2.8% and 13% for FT4, 1.8% and 10.5% for FT3 and 3.1% and 16% for T3 assay. Acceptable correlation and reproducibility were found between the three Bayer Immuno 1 platforms at each countrys site with all four thyroid panel assays demonstrating r-values of 0.989 to 1.000 and slopes of 0.915 to 1.078. Comparisons between the different platforms showed acceptable correlation for all thyroid panel assays. Specimens containing rheumatoid factor were associated with a significantly increased variation between systems for the FT4 and FT3 assays (p < 0.01). This effect did not appear to be selective for a given platform. For specimens with raised autoimmune antibodies and therefore at risk of assay antibody interference, no variation could be observed between the platforms.

Comparison of two methods to assess variability of platelet response to anti-platelet therapies in patients with acute coronary syndrome undergoing angioplasty.

The study investigated the clinical usefulness of a new method to evaluate platelet activation and the variability of platelet response to anti-platelet therapy in patients undergoing percutaneous transluminal coronary angioplasty (PTCA). Platelet activation was assessed in parallel by a new method for platelet density measurements (MPC, Mean Platelet Component Concentration), on the automated ADVIA 120 Hematology System and by the classic measurement of P-selectin (CD62P) expression, on a fluorescence flow cytometer. Patients received a loading dose of clopidogrel (300 mg; n = 29) or a bolus of abciximab (0.25 mg/kg; n = 15). Blood samples were collected before (baseline) and at different times after PTCA and antiplatelet drugs administration. Our data showed a close inverse correlation between the change in MPC and the CD62P fluorescence surface marker expression (r = -0.776, P<0.0001). Individual platelet activation determinations in patients receiving either clopidogrel or abciximab showed a variation in platelet activation as assayed by MPC and CD62P expression. Patients were characterized as having either high platelet activity upon admission and positive response to treatment or no detectable platelet activation before or after treatment. This study demonstrates the heterogeneity of platelet activation states in ACS patients undergoing coronary angioplasty. The present work also illustrates the potential use of the MPC parameter, generated on an automated hematology system, to define high risk patients and to monitor the variability of platelet response to anti-platelet therapies.

Analytical Evaluation of the Testosterone Assay on the Bayer Immuno 1™ System

OBJECTIVESnTo evaluate the analytical performance of the testosterone assay performed on the Bayer immuno 1 system from Bayer Corporation.nnnDESIGN AND METHODSnThe precision was measured using three Bayer TESTpoint Ligand controls, three Medical Decision Pools and the Bayer SETpoint Testosterone calibrators. The linearity was verified by diluting two serum samples containing high testosterone concentrations with the zero calibrator and the minimum detectable concentration determined by repetitive analysis of the zero calibrator. The assay was correlated with the Diagnostic Products Corporation (DPC) Total Testosterone assay using 342 serum samples. The reference values were determined using serum samples from 75 women and 60 men.nnnRESULTSnThe assay showed within-run coefficients of variation (CVs) varying from 1.1-8.4% and between-day CVs from 1.5-4.9% for testosterone concentrations varying from 1.77 to 66.96 nmol/L. The minimum detectable concentration was estimated at 0.11 nmol/L. The assay linearity proved excellent. A good correlation between the Bayer Immuno 1 and the DPC assays was observed with different categories of serum samples (Immuno 1 = 1.11 x DPC-0.32, r = 0.989, Sy[symbol: see text]x = 2.07 nmol/L). The reference values were estimated at 0.3-3.2 nmol/L for females and 9.3-35.6 nmol/L for males.nnnCONCLUSIONSnThe Bayer Immuno 1 Testosterone assay demonstrates the analytical characteristics required for its utilization in the clinical laboratory.

Analytical evaluation of the CK-MB mass assay on the Technicon Immuno 1® system

OBJECTIVESnTo evaluate the performance of the Technicon Immuno 1 CK-MB mass assay.nnnDESIGN AND METHODSnThe precision was measured using the BioRad Liquichek CK-MB controls and the Technicon Immuno 1 SETpoint CK-MB calibrators. The linearity was verified by diluting 9 patient serum samples containing high CK-MB concentrations, and the minimum detectable concentration determined by repetitive analysis of the zero calibrator. The assay was compared with the Johnson & Johnson Vitros CK-MB activity assay using 111 patient serum samples. The reference range was determined using serum samples from 100 healthy adult volunteers.nnnRESULTSnThe assay shows within-run CVs varying from 1.5 to 7.5% and between-day CVs from 1.5 to 4.8% for CK-MB concentrations ranging from 3.9 to 99.0 micrograms/L. The linearity study gave correlation coefficients greater than 0.9961. There was a very good correlation between mass and activity assays (r = 0.985). The reference values were estimated at 0.0-4.2 micrograms/L and the minimum detectable concentration at 0.5 micrograms/L.nnnCONCLUSIONSnThe evaluation shows that the Technicon Immuno 1 CK-MB mass assay has the analytical characteristics suitable for its inclusion in the modern clinical repertoire.

Système d’aide à la décision clinique interactif: Les facteurs de réussite

The experience to date in the provision of informatics tools for clinical decision support has been promising but few succeed in being integrated into clinician’s workflows. Therefore in designing a decision support aid for primary care that can be triggered by data patterns from the electronic health record, it was decided to first undertake a detailed review of factors influencing content and implementation of such tools. This paper reports on the literature review and the consequence for the policy for knowledge management and representation to be incorporated in the prototype. Results: The literature review highlighted 4 main categories for attention: cognitive, work-flow, information quality, and interface design. Of central importance is pertinence hence triggering knowledge access must provide interpretable and useful information. It was decided to distribute the knowledge management between data pattern analysis and information sheets, the latter supporting contextual interpretation and easier knowledge maintenance compared to rule based systems. The design content of an information sheet is discussed.