BERNARD-SOULIER SYNDROME: WHOLE BLOOD DIAGNOSTIC ASSAYS OF PLATELETS

Diagnosis of Bernard-Soulier syndrome (BSS) is complicated by the difficulty of separating the giant platelets from other blood cells to pursue analyses of platelet function and structure. We report on the utility of three whole blood assay techniques for diagnosis of a patient with BSS. To our knowledge, these three techniques have not been simultaneously applied or compared for efficacy in laboratory diagnosis of BSS. (1) Whole blood platelet aggregation responses, studied with an electrical impedence aggregometer, were equivalent to those more laboriously obtained using platelet-rich plasma prepared by unit gravity sedimentation, studied with an optical light transmittance aggregometer. Platelet aggregation responses were normal with ADP or collagen stimulation, and absent with Ristocetin or bovine plasma stimulation. (2) Whole blood radioimmunoassay of platelet glycoprotein (GP) expression was performed using iodinated murine monoclonal antibodies HP1-1D (anti-GP IIb/IIIa) and 6D1 (anti-GPlb, kindly supplied by Dr. Barry Coller, Stony Brook, NY). After incubation with citrated whole blood, centrifugation was used to separate cell-bound antibody which was quantitated with a gamma counter. The patient’s whole blood had a normal level of cell-bound GP Ilb/IIIa, but a markedly reduced level of cell-bound GP lb (5% of normal mean; n = 20). (3) Whole blood smear immunocytochemical staining with the monoclonals (indirect immuno-alkaline phosphatase technique), and qualitative analysis by light microscopy, revealed a marked reduction of GP lb expression by the patient’s giant platelets, whereas GP Ilb/IIIa expression was normal. This latter technique might be especially valuable as a screening technique when the patient is not directly available for laboratory study. Together with the patient’s life-long history of thrombocytopenia and moderate bleeding diathesis, and other laboratory observations including markedly prolonged bleeding times and reduced whole blood prothrombin consumption, these data established diagnosis of BSS. We conclude that these three relatively simple assays of platelets in whole blood should be of particular value in the laboratory differential diagnosis of patients with congenital thrombocytopenias and giant platelet syndromes.