Introduction: Mild bleeding symptoms are commonly encountered in the general population & amongst individuals with platelet disorders. One of the possible causes is due to reduced number of dense granules synthesis in platelets and defective release of its contents. This study was aimed to evaluate platelets mepacrine-labelled dense granules storage and release using flow cytometry in healthy individuals and those presenting with mild bleeding symptoms. Methods: This study was conducted at the National Blood Centre (NBC) and Faculty of Medicine and Health Sciences, Universiti Putra Malaysia (UPM). Thirty- four individuals were recruited as controls (n=24) and patients (n=10). ADP-activated platelets and mepacrine-labelled dense granules was detected using flow cytometry. Results were expressed as mean fluorescent intensity (MFI) of mepacrine in resting and activated platelets; representing dense granules storage and release, respectively. Statistical analysis was considered significant if p ≤0.05. Results: There was a significant difference of mean MFI between resting (1284.3 ± 91.8) and activated platelets (1233.8 ± 107.8) of overall respondents with mean difference of 50.5 (p<0.01). However, there was no significant difference of mean MFI in resting and activated platelets between controls and patients was observed. Conclusion: Results indicated there is no secretion defects in platelet dense granules among patients in comparison with controls. Flow cytometry provides alternative way of dense granule assessment in patients presented with mild bleeding symptoms.
Platelet disorders

Introduction: Platelet aggregation test using light transmission aggregometry (LTA) is considered as the gold standard for evaluation of platelet function. Variations of platelet aggregation had been reported in apparently healthy individuals whereby a normal cut–off value established locally is highly recommended. This study aims to determine the platelet aggregation pattern and the preliminary findings on reference values for multiple agonists–induced platelet aggregation among Malaysian healthy individuals in a single centre. Method: A total number of 63 informed consented healthy individuals consisted of Malay, Chinese and Indian were recruited among staff and blood donors at National Blood Centre, Kuala Lumpur. Platelet aggregation was measured using LTA against adenosine diphosphate 10 µM (ADP10), collagen 0.19 mg/mL (COL), ristocetin 1.5 mg/mL (RIS), arachidonic acid 1 mM (AA) and epinephrine 10 µM (EPI). Results were expressed as percent final aggregation (%FA). Reference values were calculated from mean±2SD. Results: Age, gender and ethnic groups had no significant effect on platelet aggregation. A variability of platelet aggregation response to EPI was observed among the healthy individuals. Ten of 33 respondents (30%) had impaired aggregation with <20% FA in response to EPI. The local population showed a slightly higher aggregation pattern in response to COL, RIS, AA and EPI (excluding non-responders) compared to manufacturer’s reference values. Conclusion: This study has provided a glimpse of the aggregation pattern of the local nationality showing considerable differences in the reference values from manufacturer’s; thus highlighting the need of establishing local reference values.