This study aims to improve platelet function testing during bleeding investigations. To this end, the study will evaluate the diagnostic accuracy of novel platelet function tests in patients with confirmed or suspected platelet function disorders. Study participants will be recruited from patients that are referred to or treated at the Coagulation Unit, Karolinska University Hospital, and Pediatric Coagulation Unit, Astrid Lingren Children's Hospital.

Inclusion Criteria, known defects:

• Known platelet function disorder under follow-up at Karolinska University Hospital (genetic or functional assay)
• High likelihood of platelet function disorder (aberrant screening test with inheritance)
• Family investigation for platelet disorder

Exclusion Criteria, known defects::

• Antiplatelet or anticoagulant drugs
• vWF:GPIb below 0.40 IU/mL
• Hematocrit below 0.35 or above 0.50
• Other coagulation disorder

Inclusion Criteria, suspected platelet function disorder:

• Bleeding investigation at Karolinska University Hospital

Exclusion Criteria, suspected platelet function disorder::

• Antiplatelet or anticoagulant drugs
• vWF:GPIb below 0.40 IU/mL
• Hematocrit below 0.35 or above 0.50
• Other coagulation disorder

Patients recruited at Karolinska University Hospital