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(Stroke. 1995;26:995-999.)
© 1995 American Heart Association, Inc.

Articles

Platelet Size in Stroke Patients

T. O'Malley, MRCP(UK); P. Langhorne, PhD, MRCP(UK); R.A. Elton, PhD C. Stewart, MD, FRCP(UK)

From the Department of Medicine for the Elderly, Royal Infirmary of Edinburgh and Liberton Hospital (T.O'M., P.L., C.S.), and the Department of Medical Statistics, University of Edinburgh (R.A.E.), Edinburgh, Scotland.

Correspondence to Dr T. O'Malley, Cardiovascular Research Unit, Hugh Robson Bldg, George Sq, Edinburgh EH8 9XF, Scotland.

Background and Purpose Large platelets are more reactive, produce more prothrombotic factors, and aggregate more easily. Platelet size can be readily estimated using automated analyzers, although accurate estimation depends on precise methodology. The disparate results from previous studies of mean platelet volume in cerebral ischemia may be explained by varying methodology. We have studied these variables using a precise methodology in an unselected group of stroke patients and compared them with data from age- and sex-matched control subjects.

Methods We studied 58 stroke patients consecutively admitted to a geriatric medical unit. Platelet variables were measured in the acute (<48 hours after stroke) and chronic (>6 months) phases of cerebral ischemia and compared with control variables. Control patients, admitted to the same unit, were of similar age and sex and without evidence of acute vascular events.

Results Mean platelet volume was higher in acute stroke (11.3 compared with 10.1 fL in control subjects; P<.001, Student's t test). In addition, platelet count was reduced in stroke patients (255x10⁹/L) compared with control subjects (299x10⁹/L; P<.01). Repeated measurements of mean platelet volume and platelet count in available survivors showed no significant change from the acute phase. Platelet changes did not relate to outcome measured at 6 months.

Conclusions With the use of more precise methodology, these findings show that an increase in mean platelet volume and a reduction in platelet count are features of both the acute and nonacute phases of cerebral ischemia. It is possible that these changes precede the vascular event, and further studies are warranted.

Key Words: cerebral ischemia • platelets • risk factors • thrombosis

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