Circulating reticulated platelets in the early and late phases after ischaemic stroke and transient ischaemic attack.

The percentage of reticulated platelets (% RP) could be a useful marker of increased platelet production and/or turnover in patients with increased platelet activation, but few flow cytometric studies have measured the % RP in patients with ischaemic cerebrovascular disease (CVD). Whole blood flow cytometry using thiazole orange was performed to compare the % RP in patients in the early (1-27 d, n = 79) and late phases (79-725 d, n = 70) after ischaemic stroke or transient ischaemic attack (TIA) with controls without CVD (n = 27). The impact of aspirin dose escalation (75-300 mg/d) on the % RP was investigated in 10 patients in the late phase after stroke/TIA. The platelet count and mean platelet volume (MPV) were similar in CVD patients and controls. Compared with controls, the unadjusted % RP was not significantly higher in early or late phase CVD patients (P < or = 0.3). However, having adjusted for age, the % RP was higher in early (P = 0.047) and late phase CVD patients (P = 0.01). There was a positive correlation between % RP and MPV in EDTA- and citrate-anticoagulated blood in both early and late phase CVD patients (P< or = 0.01). The % RP was not significantly influenced by aspirin dose. These data do not convincingly support an excessive stimulus to platelet production in the early or late phases after ischaemic stroke/TIA, but are consistent with the hypothesis that reticulated platelets are larger than more mature 'non-reticulated' platelets in ischaemic CVD.