Platelet Function Testing: Quality Assurance

Abstract

Platelet function tests are widely used for the diagnosis of platelet disorders. In recent years there has been increasing interest in the use of platelet function tests to monitor antiplatelet drug therapy. Quality assurance is important to optimize the performance of laboratory assays but it has not been widely applied to platelet function tests. This deficiency likely reflects the need to use freshly collected blood samples for platelet function tests, and the complex, time-consuming nature of some assays such as aggregation studies. Platelet function testing lacks guidelines, is poorly standardized between laboratories, and rarely is evaluated by internal and external quality assurance exercises. The sensitivity, specificity, and diagnostic utility of some newer, simplified assays of platelet function have been evaluated in a range of clinical settings but corresponding quality assurance data for many established as well as emerging platelet function assays are lacking. Quality assurance issues relevant to testing platelet function are reviewed in this article, with a focus on their application to established and to new and emerging tests.

Diagnostic utility of light transmission platelet aggregometry: results from a prospective study of individuals referred for bleeding disorder assessments

“…Platelet function disorders are commonly evaluated by light transmission aggregometry (LTA), using ADP, collagen, epinephrine, arachidonic acid, ristocetin, and sometimes additional agonists [2,[5][6][7]. The diagnostic utility of LTA is uncertain as laboratory practises are inconsistent [2,[5][6][7].…”

“…Platelet function disorders are commonly evaluated by light transmission aggregometry (LTA), using ADP, collagen, epinephrine, arachidonic acid, ristocetin, and sometimes additional agonists [2,[5][6][7]. The diagnostic utility of LTA is uncertain as laboratory practises are inconsistent [2,[5][6][7]. Many laboratories evaluate LTA using platelet-rich plasma (PRP) without validated reference intervals (RI) [2,[5][6][7], which can differ for undiluted and platelet count adjusted PRP samples, tested by some instrument/reagent combinations [8][9][10].…”

Investigating people with mucocutaneous bleeding suggestive of primary hemostatic defects: a low likelihood of a definitive diagnosis?

“…flow cytometry procedures, overall hemostatic potential, thrombin generation). 24,25 Despite this, a previous study by Quiroga et al 12 did not find any significant findings in patients with hereditary mucocutaneous hemorrhages with respect to thrombin generation using platelet-poor plasma. Studies using plateletrich plasma in such patients remain unpublished, but as thrombin generation is generally considered a predominant part of the pathway of secondary hemostasis, perhaps we should not expect too much within the context of currently 'unexplained mucocutaneous bleeding'?…”

“…21,24 It is reassuring that a wide panel of appropriate tests and methodologies, as currently available, were employed in the study by Quiroga et al;…”

“…for investigation of VWD and PFD) will improve the overall clinical diagnosis of primary hemostatic disorders. 20,21,24 Moreover, additional tests considered new, or emerging technologies may also improve such diagnoses (e.g. flow cytometry procedures, overall hemostatic potential, thrombin generation).…”