Clinical studies
Autoantibodies against platelet glycoproteins in critically ill patients with thrombocytopenia

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Abstract

PURPOSE: The aim of the study was to investigate immunologic causes of thrombocytopenia in critically ill patients, especially causes that were related to platelet-associated IgG antibodies.

SUBJECTS AND METHODS: All patients admitted to two intensive care units between May 1 and October 30, 1997, who developed thrombocytopenia (less than 100 × 109 platelets/L) were studied prospectively. We measured platelet-associated IgG with a radioimmunoassay using I125-labeled polyclonal antihuman IgG. Characterization of platelet-associated IgG was assessed with a monoclonal antibody immobilization of platelet antigen. Circulating immune complexes were also assayed.

RESULTS: Of the 61 patients with thrombocytopenia, elevated platelet-associated IgG was found in 18 (30%). Associated antiplatelet autoantibodies (glycoprotein IIb/IIIa) were detected in 4 patients, circulating autoantibodies (glycoprotein Ib/IX) were detected in sera from 2 patients, and circulating immune complexes were detected in 3 patients. The nature of the platelet-associated IgG could not be determined in 10 patients. Elevated platelet-associated IgG was associated with sepsis and previous cardiopulmonary bypass. Thrombocytopenic patients with elevated platelet-associated IgG had a lower nadir platelet count (58 ± 27 × 109/L vs 74 ± 24 × 109/L, P = 0.03).

CONCLUSION: Elevated platelet-associated IgG, some of which are platelet autoantibodies, is frequent in thrombocytopenic patients with sepsis or after cardiopulmonary bypass.

Section snippets

Subjects

The study was conducted between May 1 and October 30, 1997, in a medical (Broussais hospital) and a surgical (Tenon hospital) intensive care unit. Patients who developed thrombocytopenia (less than 100 × 109 platelets/L) were identified prospectively. Platelet counts were performed daily for all patients. Because the patient characteristics were similar in the two institutions, the results were pooled.

Patients with a history of platelet disorders, hematologic malignancies or chemotherapy, and

Results

During a 6-month period, 132 patients were admitted to the intensive care unit at Broussais hospital, and 161 were admitted at Tenon hospital. They had mean age of 61 ± 17 years, and 65% were men. Their mean first-day APACHE II score was 19 ± 10, their median length of stay in the intensive care unit was 4 (1 to 10) days, 54% came from other medical departments or the emergency department, 31% had scheduled or unscheduled surgery (mainly abdominal, orthopedic, and thoracic surgery), 9% had a

Discussion

We found that 30% of intensive care unit patients with thrombocytopenia had elevated platelet-associated IgG values, approximately 30% of whom had autoantibodies directed against platelet glycoproteins. None of the 15 control patients or 43 thrombocytopenic patients without platelet-associated IgG had these autoantibodies. Thrombocytopenic patients with elevated platelet-associated IgG were less likely to have normalization of their platelet counts but did not require more blood products,

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