Platelet size has diagnostic predictive value in patients with thrombocytopenia.

We studied 473 unselected patients with thrombocytopenia. The mean platelet volume (MPV) was 8.1 fl in patients with marrow disease and 9.8 fl in patients without marrow disease (P < 0.001). A total of 5% of patients with an MPV >or=10.5 fl have marrow disease (odds ratio 0.05, 95% CI 0.02-0.13). Conversely over three quarters of patients with an MPV of <8.0 fl have marrow disease (odds ratio 8.1, 95% CI 5.0-13.0). Therefore the MPV can strongly guide the clinician as to the likely presence or absence of bone marrow disease in thrombocytopenic patients.