Platelets and Blood Cells A prospective cohort study of light transmission platelet aggregometry for bleeding disorders: Is testing native platelet-rich plasma non-inferior to testing platelet count adjusted samples? Jean Francois Castilloux 1 ; Karen A. Moffat 2,3 ; Yang Liu 2 ; Jodi Seecharan 3 ; Menaka Pai 2,3 ; Catherine P. M. Hayward 1–3 1 Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada; 2 Department of Medicine, McMaster University, McMaster University, Hamilton, Ontario, Canada; 3 The Hamilton Regional Laboratory Medicine Program, McMaster University, Hamilton, Ontario, Canada Summary Light transmission platelet aggregometry (LTA) is important to diag- nose bleeding disorders. Experts recommend testing LTA with native (N) rather than platelet count adjusted (A) platelet-rich plasma (PRP), al- though it is unclear if this provides non-inferior, or superior, detection of bleeding disorders. Our goal was to determine if LTA with NPRP is non- inferior to LTA with APRP for bleeding disorder assessments. A prospec- tive cohort of patients, referred for bleeding disorder testing, and healthy controls, were evaluated by LTA using common agonists, NPRP and APRP (adjusted to 250 x 10 9 platelets/l). Recruitment continued until 40 controls and 40 patients with definite bleeding disorders were tested. Maximal aggregation (MA) data were assessed for the detec- tion of abnormalities from bleeding disorders (all causes combined to limit bias), using sample-type specific reference intervals. Areas under receiver-operator curves (AUROC) were evaluated using pre-defined Correspondence to: Catherine P. M. Hayward, MD, PhD Professor of Pathology and Molecular Medicine Room 2N29, Health Sciences Center, McMaster University 1280 Main St. West, Hamilton, Ontario L8S 4K1, Canada Tel.: +1 905 521 2100 ext. 76274, Fax: +1 905 521 2338 E-mail: haywrdc@mcmaster.ca criteria (area differences: <0.15 for non-inferiority, >0 for superiority). Forty-four controls and 209 patients were evaluated. Chart reviews for 169 patients indicated 67 had bleeding disorders, 28 from inherited pla- telet secretion defects. Mean MA differences between NPRP and APRP were small for most agonists (ranges, controls: –3.3 to 5.8; patients: –3.0 to 13.7). With both samples, reduced MA with two or more agon- ists was associated with a bleeding disorder. AUROC differences be- tween NPRP and APRP were small and indicated that NPRP were non- inferior to APRP for detecting bleeding disorders by LTA, whereas APRP met superiority criteria. Our study validates using either NPRP or APRP for LTA assessments of bleeding disorders. Keywords Clinical studies, platelet disorders, platelet pathology, inherited, ac- quired Financial support: The research was supported by the Hamilton Regional Laboratory Medicine Program and a Canada Research Chair from the Government of Canada (C.P.M.H.). Received: June 3, 2011 Accepted: June 15, 2011 Prepublished online: July 28, 2011 doi:10.1160/TH11-06-0378 Thromb Haemost 2011; 106: 675–682 675 © Schattauer 2011 Thrombosis and Haemostasis 106.4/2011 Introduction Platelet function disorders are common bleeding disorders that often impair platelet function by light transmission aggregometry (LTA) (1–4). Most laboratories perform LTA to evaluate bleeding disorders, as recommended (5–8), but the procedures used vary, including whether native (N) or platelet count adjusted (A) pla- telet-rich plasma (PRP) samples are tested (4, 5). When LTA is per- formed using APRP with valid reference intervals (RI), it has im- portant diagnostic utility for platelet function disorders (2). How- ever, similar information has not been published on the diagnostic utility of LTA performed with NPRP. Recent expert consensus, from a working group of the Platelet Physiology Subcommittee of the International Society on Throm- bosis and Haemostasis (ISTH) recommends using NPRP for LTA (personal communication, Marco Cattaneo, Milan, Italy). This avoids diminutions in maximal aggregation (MA) that occur with some weak agonists when platelet-poor plasma (PPP) is added to adjust PRP to a standardised platelet count, particularly with ade- nosine diphosphate (ADP), epinephrine and collagen (7, 9–13). However, most published studies comparing NPRP and APRP evaluated LTA responses to a small number of agonists (9–11, 13), although one study (of 11 cases) assessed more agonists and ris- tocetin-induced platelet aggregation (RIPA) (12). Although differ- ences in NPRP and APRP findings with weak agonists have been noted (9–13), none of the published studies used non-inferiority or superiority analysis to compare NPRP and APRP detection of LTA abnormalities from bleeding disorders. The limited informa- tion on the suitability of NPRP for LTA detection of bleeding dis- orders has led some groups to recommend testing APRP (7) until NPRP are validated for bleeding disorder assessments. To test the hypothesis that performing LTA with NPRP is ac- ceptable for bleeding disorder assessments, we conducted a pros- pective cohort study. The primary objective was to determine if using NPRP is non-inferior to using APRP to detect LTA abnor- malities from definite bleeding disorders (all causes combined to For personal or educational use only. No other uses without permission. All rights reserved. Downloaded from www.thrombosis-online.com on 2018-05-06 | ID: 1001066444 | IP: 54.70.40.11