Variability in platelet dense granule adenosine triphosphate release findings amongst patients tested multiple times as part of an assessment for a bleeding disorder

Abstract

The variability in platelet dense granule ATP release findings amongst patients assessed for diagnostic purposes suggests that the test has limited value for diagnosing platelet disorders.

Electron microscopy examination of platelet whole mount preparations to quantitate platelet dense granule numbers: Implications for diagnosing suspected platelet function disorders due to dense granule deficiency

“…We found DGD in 6.5% of patient samples tested between 2006 and 2017 (excluding samples collected for NASCOLA EQA) and, not surprising, in a higher proportion (34%) of individuals that were recruited to a research study that had confirmed DGD as an inclusion criterion. Like our recent studies, we observed that the majority of patients referred for PFD testing were female, likely due to their increased burden of hemostatic challenges from menstruation and childbirth. Importantly, confirmed DGD by whole mount EM was associated with increased bleeding symptoms and a higher likelihood of having a bleeding disorder, which provides important evidence on clinical associations for reduced DG counts.…”

“…Our estimates of the respective sensitivities of LTA and DG ATP release (estimated by lumi‐aggregometry), for detecting abnormalities due to DGD, were only ~52% and 70%, which is inadequate to screen for DGD. Although impaired DG ATP release with multiple agonists was present in some participants with DGD, the assessment of DG ATP release has questionable diagnostic usefulness as the findings show considerable variability, and even if ATP release is consistently impaired, the finding does not show a significant relationship to elevated bleeding scores or the clinical diagnosis of a bleeding disorder . Laboratories should be cautious when interpreting data for DG ATP release as we noted that only 30% of individuals with confirmed DGD had impaired ATP release with all agonists.…”

“…Data collected for cohorts I and II included gender, age (inconsistently recorded for cohort I controls), date of testing, and the DG count for each unique sample. For cohort II, data were also collected on: whether the participant had a bleeding disorder (based on the hematologist's opinion, obtained by chart review, as described); ISTH‐BAT scores; the most recent HRLMP platelet count, mean platelet volume (MPV), DG ATP release findings (determined by lumi‐aggregometry as described, using an agonist panel that included: 1 U/mL thrombin, 5.0 μg/mL Horm collagen, 6 μmol/L epinephrine, 1 μmol/L thromboxane analogue U46619, and 1.6 mmol/L arachidonic acid [AA]) and MA responses (evaluated by LTA, as described, with the agonists: 1.25 and 5.0 μg/mL Horm collagen, 2.5 and 5.0 μmol/L ADP, 6 μmol/L epinephrine, 1 μmol/L thromboxane analogue U46619, 1.6 mmol/L AA, and 0.5, and 1.25 mg/mL ristocetin).…”

“…The causes of DGD include both nonsyndromic and syndromic platelet function disorders (PFD), including Hermansky‐Pudlak syndrome and Wiskott‐Aldrich syndrome . Tests for DGD are considered helpful for diagnosing PFD as about one‐third of persons with DGD have normal maximal aggregation (MA) responses to agonists by light transmission aggregometry (LTA) and some have normal findings in lumi‐aggregometry assessments of platelet DG ATP release . Furthermore, the International Society on Thrombosis and Haemostasis (ISTH) has recommended that assays for DGD be performed as part of the workup for a PFD …”

Update on diagnostic testing for platelet function disorders: What is practical and useful?

“…For LTA, MA findings provide important quantitative information for the test interpretation and the pattern of abnormalities can be readily interpreted using the North American guidelines . With both LTA and release assays, single agonist abnormalities are usually a false positive and are much less predictive of a bleeding disorder than multiple agonist abnormalities . Some laboratories perform LTA on automated coagulation analyzers, which appears to provide comparable findings to traditional LTA .…”