Consistency in platelet morphology in whole blood

The morphology of instantaneously fixed platelets in whole blood was assessed for intra-subject consistency in 24 subjects; 10 were healthy and 14 had metastatic carcinoma. In both groups two samples were obtained from each subject. The time between samples varied for the normal group from 1 to 17 months (average of 6 months) and for the cancer group from 13 to 39 days (average of 14 days). Analysis of variance pertaining to unactivated discs (i.e., discs without pseudopods) revealed that a factor that differs among individuals rather than any uncontrolled artifact probably accounts for the large range of values obtained. Additionally, it appears that, in a given individual, platelet morphology in whole blood, expressed as % discs, remains fairly constant over a period of weeks or months. These findings suggest that characteristic levels of unactivated platelet forms exist in whole blood and that these levels reflect in vivo conditions.