Circulating microparticles and procoagulant activity in elderly patients.

BACKGROUND Microparticles (MP) are shed membrane vesicles released from activation or apoptosis of several cell types and carry a procoagulant activity. Age is associated with a procoagulant state, but the role of MP in this setting is unknown, as the relationship of MP to aging in humans. We tested the hypotheses that elderly persons compared with young persons may have different patterns of expression of MP and procoagulant activity in stable or septic conditions. METHODS Patients from Emergency and Geriatric Departments were divided into four groups according to their age (< 50 or > or = 75 years old) and the presence of systemic infection (yes or no). The diagnosis of infection was reached when it was classified as certain or possible by an expert panel. Circulating MP were isolated from venous citrated blood. Cytofluorometry using specific antibodies was performed to determine the origins of MP (endothelial microparticles [EMP], red blood cell microparticles, or platelet microparticles). Procoagulant activity was determined using annexin V (prothrombinase activity) and tissue factor (TF) assays. RESULTS One hundred and eleven patients were included. Elderly patients expressed a decrease in EMP in stable conditions, associated with a decrease in procoagulant annexin V MP in septic conditions (p < .05), and higher EMP levels were found in elderly infected patients who died during hospital stay than in survivors (p = .04). Compared with young patients, response to sepsis was altered in elders concerning EMP, annexin V MP, and TF-bearing MP. CONCLUSION Elderly patients expressed a different pattern of MP in stable conditions, with a different response to sepsis in procoagulant activity modification.