RESUMO
Light transmission aggregometry (LTA) is the most common method used to assess platelet function. However, there is no universal standard for its performance. The Platelet Physiology Subcommittee of the Scientific and Standardization Committee (SSC) of the International Society on Thrombosis and Haemostasis formed a working party of experts with the aim of producing a series of consensus recommendations for standardizing LTA. Due to a lack of investigations that directly compared different methodologies to perform LTA studies, there were insufficient data to develop evidence-based guidelines. Therefore, the RAND method was used, which obtains a formal consensus among experts about the appropriateness of health care interventions, particularly when scientific evidence is absent, scarce and/or heterogeneous. Using this approach, each expert scored as "appropriate", "uncertain" or "inappropriate" a series of statements about the practice of LTA, which included pre-analytical variables, blood collection, blood processing, methodological details, choice of agonists and the evaluation and reporting of results. After presentation and public discussion at SSC meetings, the assessments were further refined to produce final consensus recommendations. Before delivering the recommendations, a formal literature review was performed using a series of defined search terms about LTA. Of the 1830 potentially relevant studies identified, only 14 publications were considered to be actually relevant for review. Based upon the additional information, 6 consensus statements were slightly modified. The final statements were presented and discussed at the SSC Meeting in Cairo (2010) and formed the basis of a consensus document, which is the subject of the present report. This article is protected by copyright. All rights reserved.
RESUMO
BACKGROUND: Light transmission aggregometry (LTA) is the most common method used in clinical and research laboratories to assess platelet function. However, the method has never been standardized. OBJECTIVES: As the first step towards development of methodological guidelines, the Platelet Physiology Subcommittee of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis (ISTH) undertook a large, detailed, global survey of LTA practices. METHODS: Members of ISTH and of External Quality Assurance in Thrombosis and Haemostasis organizations were invited to complete a 129 item, online questionnaire. Results were analyzed anonymously to participant identities. RESULTS: The online supplement for this article (http://www.isth.org/Publications/OfficialCommunications/PlateletPhysiology/LightTransmissionAggregometry/tabid/201/Default.aspx) contains the full details of the study findings. 359 (244 clinical, 115 research) laboratories from 48 countries participated in the survey. LTA was widely used to assess inherited or acquired bleeding disorders. Common practices were identified in sample collection, processing and analysis and although some are generally considered acceptable, others are not ideal. The agonist concentrations used for LTA varied, and many laboratories used ADP, collagen, epinephrine and Ristocetin, at more than one concentration, in addition to arachidonic acid. The parameters commonly used to assess LTA responses were maximal amplitude or % aggregation, which was considered particularly important, in addition to the presence of a 'secondary wave', deaggregation, shape change and a measure of the lag phase. However, many laboratories did not have appropriate reference intervals. CONCLUSIONS: This is the largest and most detailed survey of LTA practices ever undertaken. It shows a very high variability in LTA practices worldwide, and, as a consequence, methodological standardization is necessary. The information gathered in this survey will be helpful in the development of ISTH methodological guidelines for LTA.