Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Influence of mechanical trauma of blood and hemolysis on PFA-100 testing Giuseppe Lippi a , Rossana Fontana a , Paola Avanzini a , Rosalia Aloe a , Luigi Ippolito a , Franca Sandei a and Emmanuel J. Favaloro b Although the appropriate quality of samples is essential for platelet function testing, information is lacking on interference from mechanical trauma of blood and hemolysis on PFA-100 analyzer. Citrated blood collected from nine healthy volunteers was divided into three aliquots. The first aliquot (‘A’) was processed without further manipulation, whereas the second and third were subjected to mechanical trauma by two (‘aliquot B’) or four passages (‘aliquot C’) through a very fine needle (30 gauge) to produce hemolysis and cell trauma mimicking poor sample collection. Samples were tested on PFA-100 and Advia 2120, and plasma then separated and tested for lactate dehydrogenase (LDH) and hemolysis index. Negligible hemolysis was present in aliquot A (hemolysis index 0.2 W 0.1, cell-free hemoglobin 0–0.5 g/l), whereas an increasing amount was present in aliquots B (hemolysis index of 13.1 W 1.8, cell-free hemoglobin 6.0–6.5 g/l) and C (hemolysis index 24.0 W 1.1, cell-free hemoglobin 11.5–12.0 g/l). Increases in LDH, and concomitant reductions in platelet and red blood cell counts were observed in aliquots B and C. In hemolyzed aliquots B, four out of nine samples yielded ‘flow obstruction’ with both PFA-100 agonist cartridges, whereas the closure times were dramatically prolonged in the remaining five samples. In hemolyzed aliquots C, flow obstruction was recorded in six of nine samples for collagen and ADP and all samples for collagen and epinephrine, whereas closure times of collagen and ADP in the remaining three samples were dramatically prolonged. Mechanical trauma of blood causing hemolysis makes PFA-100 testing unreliable. When flow obstructions are observed, the potential presence of hemolysis should be investigated. Blood Coagul Fibrinolysis 23:82–86 ß 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins. Blood Coagulation and Fibrinolysis 2012, 23:82–86 Keywords: hemolysis, hemolyzed specimens, interference, PFA-100 testing, preanalytical variability a U.O. Diagnostica Ematochimica, Dipartimento di Patologia e Medicina di Laboratorio, Azienda Ospedaliero-Universitaria di Parma, Parma, Italy and b Department of Haematology, Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, New South Wales, Australia Correspondence to Professor Giuseppe Lippi, U.O. Diagnostica Ematochimica, Azienda Ospedaliero-Universitaria di Parma, Via Gramsci 14, 43126 Parma, Italy Tel: +39 0521 703050; fax: +39 0521 703197; e-mail: glippi@ao.pr.it, ulippi@tin.it Received 2 July 2011 Revised 15 August 2011 Accepted 27 August 2011 Introduction The preanalytical phase is important, mandatory within the total testing process, because it includes all the manually intensive steps necessary to obtain samples that are suitable for testing [1]. Nevertheless, flawed or mishandled activities during the prelaboratory collection, handling, and transportation of blood, as well as in the laboratory preparation of test specimens might dramatic- ally influence the reliability of a wide range of clinical chemistry, immunochemistry as well as hematology test results [1]. The quality of the blood sample is also essential in the coagulation or hemostasis laboratory, including that for platelet function testing, since unreli- able results, potentially arising from ‘poor’-quality speci- mens might lead to misdiagnosis of platelet function disorders and von Willebrand disease (VWD), as well as inappropriate perceptions and clinical responses related to antiplatelet therapy [2–11]. Among the various preanalytical problems, spurious hemolysis is known to reflect the most frequently encountered preanalytical problem in specimens referred for both clinical chemistry [12,13] and coagulation testing [14]. In these settings, serum or plasma are the reference sample matrixes, which are obtained after centrifugation of whole anticoagulated blood. As such, the potential presence of hemolysis can be reliably ascertained and the degree of interference established. However, platelet function testing is often performed on whole anticoagu- lated blood [6,11,15], and it is thereby virtually imposs- ible to establish whether a certain degree of hemolysis has occurred or to what extent the poor quality of the specimen might affect test results. The PFA-100 analyzer is a reliable tool for screening platelet dysfunction and/or VWD, which is also charac- terized by acceptable sensitivity to different types of antiplatelet drugs [7,16–18]. According to manufacturer’s specifications, the leading quality requirements for pro- cessing a specimen for platelet function on this compact analyzer currently includes a visual assessment to ensure adequate filling of the primary tube and the lack of visible clots or aggregates. As such, hemolysis is not currently listed among the potential ‘interferences’, nor has its influence been assessed in the current scientific litera- ture. Therefore, the aim of this study was to investigate 82 Technical report 0957-5235 ß 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI:10.1097/MBC.0b013e32834c6cb5