PO046 | BLEEDING PHENOTYPE AND PLATELET FUNCTION TESTS IN BERNARD-SOULIER SYNDROME: A CORRELATION STUDY

L. Onorati, S. Ferrari, D. Regazzo, A. Galbiati, A. Cerbo, L. Gianesello, C. Samà, A. Bertomoro, L. Spiezia, P. Simioni | Dipartimento di Medicina, Azienda Osp. Università di Padova, Italy

Background and Aims. Bernard–Soulier Syndrome (BSS) is a rare autosomal recessive platelet disorder caused by defects of the GPIb-IX-V complex and characterized by a bleeding phenotype that does not always correlate with conventional laboratory findings. The ISTH-BAT provides a standardized method for assessing bleeding; however, its relationship with platelet function in patients with BSS, particularly when evaluated using whole-blood assays, is still not well defined. This study aims to investigate the association between bleeding severity, as measured by the ISTH-BAT score, and platelet function in a cohort of patients with BSS, including individuals with both bleeding and non-bleeding phenotypes.
Methods. Eighteen patients from seven unrelated families with clinical and genetic diagnosis of BSS underwent comprehensive laboratory evaluation. Bleeding tendency was assessed using the ISTH-BAT score. Data on platelet count, size, morphology were acquired. In addition, surface markers expression (CD41A, CD42A, CD42B, CD49B, PAC1, CD62P activated by ADP) were evaluated by platelet immunophenotyping on flow cytometer. Platelet function was assessed in platelet-rich plasma by light transmission aggregometry and in whole blood by using impedance aggregometry (Multiplate®). Whole-blood coagulation was additionally evaluated by rotational thromboelastometry (ROTEM®). Genetic variants were identified by Sanger sequencing.
Results. All patients with BSS (mean age 45 ± 20 years; 9M/9F) had low platelet averaging at 87 ± 45 ×10⁹/L. 13/18 patients manifested haemorrhagic episodes (bleeders group) while 5/18 not having haemorrhagic events were defined as non-bleeders. The ISTH-BAT score was 0 in non-bleeders and >1 in bleeders, with overall values ranging from 0 to 8 and a mean of 3 among bleeders. A significant difference in LTA aggregation between bleeders and non-bleeders was observed in response to collagen (64±24 vs. 81±7%, respectively; p = 0.04) and to Ristocetin (48±28 vs. 73±13%, respectively; p = 0.03). No association was found between the ISTH-BAT score and aggregation assessed by Multiplate®, nor with ROTEM® profiles. Multiplate® and ROTEM® parameters were in the normal range in both groups, except ASPI test, that was reduced in bleeders and non-bleeders (see Table 1). In the PFA-200 test, closure time was prolonged in both COL/EPI and COL/ADP cartridges in both groups; the increase was less pronounced in non-bleeders, although this difference did not reach statistical significance.
Conclusions. Platelet aggregation responses to collagen and Ristocetin are associated with bleeding severity in BSS, whereas platelet count is not. These findings support the variability of laboratory phenotypes in BSS and suggest that platelet function testing may better reflect bleeding risk than platelet count alone. Larger studies are needed to confirm these preliminary observations.