Can the Platelet Function Analyzer (PFA)-100 test substitute for the template bleeding time in routine clinical practice?

Abstract

The bleeding time (BT) is widely used in clinical medicine as a screening test of platelet function, although its deficiencies in such a role are well recognized. The Platelet Function Analyzer (PFA)-100 measures the ability of platelets activated in a high-shear environment to occlude an aperture in a membrane treated with collagen and epinephrine (CEPI) or collagen and ADP (CADP). The time taken for flow across the membrane to stop (closure time) is recorded. This study compared the PFA-100 with the BT as a screening test of platelet dysfunction in 113 hospital inpatients. The PFA-100 test was performed initially using the CEPI cartridge; CADP tests were performed on those with abnormal (> 163 s) CEPI closure times. Whole blood platelet aggregation studies and chart review were performed on patients in whom the BT and PFA-100 results did not agree.Abnormal bleeding times and PFA-100 results were obtained in 20.4% and 35.4% of patients, respectively. The results of BT and PFA-100 agreed in 74.3% of patients. Of the 29 patients in whom the BT and PFA-100 results were discordant, whole blood platelet aggregation studies supported the PFA-100 result in 25 (86.2%). The PFA-100 was more sensitive to aspirin-induced platelet dysfunction and was more rapidly and cheaply performed than the BT. Since the PFA-100 test reflects platelet function better than the BT, we conclude that this test could replace the BT as a first-line screening test for platelet dysfunction in clinical practice.

Clinical Utility of the PFA-100

“…The PFA-100 appears to be marginally more sensitive to Hermansky-Pudlak syndrome (HPS), giving abnormal CTs with C/ADP or with C/Epi in around 80% and 50% of cases, respectively. In contrast to the situation with VWD, the sensitivity of the PFA-100 to platelet function disorders is considered overall to be fairly similar to that of the SBT, 63,64,[66][67][68]72,89 although it should be recognized that the latter is a more invasive test procedure. In any case, given the relative insensitivity of the PFA-100 and the SBT to mild platelet function disorders, neither can be recommended to screen for these cases.…”

Desmopressin Improves Platelet Dysfunction Measured by in vitro Closure Time in Uremic Patients

“…This system has been shown to be efficacious in evaluating abnormalities of primary hemostasis. A comparison of in vitro CT with SBT showed that CT was not only more sensitive in detecting von Willebrand disease, including that of type 1 [7], it was more sensitive in detecting platelet defects in an unselected hospital inpatient population [8] as well as being useful in detecting many platelet defects encountered in routine laboratory testing [9]. Moreover, CT is rapid, cost-effective and simple to perform, providing further evidence that CT could replace BT measurement as a primary hemostasis screening tool.…”

Desmopressin improves platelet function in uremic patients taking antiplatelet agents who require emergent invasive procedures

“…Recent studies have shown the utility of CEPI-CT in patients with uremia or taking antiplatelet agents [7,18,19]. Moreover, CEPI-CT is significantly associated with the severity of bleeding [17], and its prolongation was observed in patients with aspirin ingestion despite a normal BT [6].…”

“…However, the usefulness of BT is questionable because it is invasive and highly operator-dependent [6,17]. CEPI-CT measured by a PFA-100 machine is an in vitro test that could substitute for BT in the diagnosis of primary hemostasis defects [17].…”

“…Previously, skin bleeding time was the best predictor of clinical bleeding [4], but this estimate is highly operatordependent and poorly reproducible, indicating disadvantageous characteristics for screening primary hemostasis [5,6]. In vitro closure time (IVCT) using a platelet function analyzer (PFA-100) is an alternative test that has shown utility in assessing abnormal primary hemostasis and monitoring antiplatelet therapy, both of which were also proven in dialysis patients [7].…”