An Glanzmann’s thrombasthenia and Bernard-Soulier syndrome”. This underestimation probably reflects the incomplete diffusion of platelet testing, required to identify PSD. In this study, focusing the investigation on all patients with any 94361-06-5 bleeding symptoms and BSS of 4 and above yielded a prevalence of approximately 19 . Our study shows that the prevalence of these defects is considerable also in patients with an 
important history of bleeding, indicating the importance of PSD as a cause of clinically relevant bleeding at the 76932-56-4 site population level. These results warrant interventions to make the diagnosis of PSD more widely available. This entails the development and diffusion of assays that can be more easily and rapidly performed. In consideration of the fact that many patients with PSD bleed during surgery or other invasive medical procedures, the detection of the defect at an early age could prevent unnecessary bleeding episodes. Screening for ADP-deficiency might be a sensitive strategy, given that ADP deficiency was herein present in all investigated PSD patients, butFigure 1. Flow-chart of the study of the prevalence of PSD. doi:10.1371/journal.pone.0060396.gmaximal agonist stimulation (pattern vs BSS, P = 0.342; pattern vs age-normalized BSS, P = 0.585; pattern vs age at first bleeding requiring medical attention, P = 0.132; all P-values calculated by Kruskal-Wallis test). No association was found also whenTable 2. Diagnosis and bleeding severity score values in 207 patients.Diagnosis Coagulation factor deficiency von Willebrand disease Primary secretion defects Other platelet defect Defect in fibrinolysis Secondaryc b aN ( ) 27 (13) 25 (12) 27 (13) 7 (3) 2 (1) 8 (4)Age at diagnosis, median (IQR) 37 (15?5) 36 (22?) 35 (20?4) 43 (32?4) 29, 38d 56 (35?4)BSS, median (IQR) 6 (4?) 9 (6?2) 6 (5?0) 10 (4?5) 9, 10d 7 (5?0)Negative screening Including platelet functional testing Not tested for platelet function 49 
(24) 62 (30) 41 (26?0) 41 (26?0) 6 (5?) 5 (4?)Patients with clinical bleeding or coagulation abnormalities and bleeding severity score of 4 or more are presented. Including hemophilia A and B or rare bleeding disorders. b Includes d-storage pool deficiency and Glanzmanns thrombasthenia. c Secondary to drugs or to underlying medical conditions. d Individual values are reported. BSS, bleeding severity score. doi:10.1371/journal.pone.0060396.taPrevalence and Characteristics of PSDFigure 2. Relationships between measures of bleeding severity and pattern of platelet defect. The Figure shows the distribution of bleeding severity score (top), age-normalized bleeding severity score (middle) and age of first bleeding requiring medical attention (bottom) in patients with different patterns of platelet defect. The asterisk (*) indicates a patient with age-normalized bleeding severity score of 1.89. P-values were calculated by Kruskal-Wallis test. doi:10.1371/journal.pone.0060396.gspecificity of the finding of PSD exclusive to stimulation with ADP might be a concern. Patients without associated medical conditions had earlier age of first bleeding and different platelet functional defect pattern compared to patients with PSD and accompanying medical conditions. This suggests a possible different etiologic and pathogenic mechanisms in the two groups of patients. The early age of onset in patients without associated conditions indicates congenital defects that may be amenable to genetic mapping. There was no association, in patients with or withou.An Glanzmann’s thrombasthenia and Bernard-Soulier syndrome”. This underestimation probably reflects the incomplete diffusion of platelet testing, required to identify PSD. In this study, focusing the investigation on all patients with any bleeding symptoms and BSS of 4 and above yielded a prevalence of approximately 19 . Our study shows that the prevalence of these defects is considerable also in patients with an important history of bleeding, indicating the importance of PSD as a cause of clinically relevant bleeding at the population level. These results warrant interventions to make the diagnosis of PSD more widely available. This entails the development and diffusion of assays that can be more easily and rapidly performed. In consideration of the fact that many patients with PSD bleed during surgery or other invasive medical procedures, the detection of the defect at an early age could prevent unnecessary bleeding episodes. Screening for ADP-deficiency might be a sensitive strategy, given that ADP deficiency was herein present in all investigated PSD patients, butFigure 1. Flow-chart of the study of the prevalence of PSD. doi:10.1371/journal.pone.0060396.gmaximal agonist stimulation (pattern vs BSS, P = 0.342; pattern vs age-normalized BSS, P = 0.585; pattern vs age at first bleeding requiring medical attention, P = 0.132; all P-values calculated by Kruskal-Wallis test). No association was found also whenTable 2. Diagnosis and bleeding severity score values in 207 patients.Diagnosis Coagulation factor deficiency von Willebrand disease Primary secretion defects Other platelet defect Defect in fibrinolysis Secondaryc b aN ( ) 27 (13) 25 (12) 27 (13) 7 (3) 2 (1) 8 (4)Age at diagnosis, median (IQR) 37 (15?5) 36 (22?) 35 (20?4) 43 (32?4) 29, 38d 56 (35?4)BSS, median (IQR) 6 (4?) 9 (6?2) 6 (5?0) 10 (4?5) 9, 10d 7 (5?0)Negative screening Including platelet functional testing Not tested for platelet function 49 (24) 62 (30) 41 (26?0) 41 (26?0) 6 (5?) 5 (4?)Patients with clinical bleeding or coagulation abnormalities and bleeding severity score of 4 or more are presented. Including hemophilia A and B or rare bleeding disorders. b Includes d-storage pool deficiency and Glanzmanns thrombasthenia. c Secondary to drugs or to underlying medical conditions. d Individual values are reported. BSS, bleeding severity score. doi:10.1371/journal.pone.0060396.taPrevalence and Characteristics of PSDFigure 2. Relationships between measures of bleeding severity and pattern of platelet defect. The Figure shows the distribution of bleeding severity score (top), age-normalized bleeding severity score (middle) and age of first bleeding requiring medical attention (bottom) in patients with different patterns of platelet defect. The asterisk (*) indicates a patient with age-normalized bleeding severity score of 1.89. P-values were calculated by Kruskal-Wallis test. doi:10.1371/journal.pone.0060396.gspecificity of the finding of PSD exclusive to stimulation with ADP might be a concern. Patients without associated medical conditions had earlier age of first bleeding and different platelet functional defect pattern compared to patients with PSD and accompanying medical conditions. This suggests a possible different etiologic and pathogenic mechanisms in the two groups of patients. The early age of onset in patients without associated conditions indicates congenital defects that may be amenable to genetic mapping. There was no association, in patients with or withou.