Abstract
Peripheral blood smears from seven patients with Bernard-Soulier syndrome were examined by an immunocytochemical staining procedure using a monoclonal antibody specific for platelet glycoprotein Ib. No platelet staining was observed except for very slight staining of the large sized platelets from one of the patients. Application of the assay to blood smears from 12 patients with immune thrombocytopenia showed that their peripheral platelets stained normally, so the assay can be used to differentiate between immune thrombocytopenia and Bernard-Soulier syndrome and to confirm a diagnosis of the syndrome.