Flow cytometric analysis of megakaryocytes from patients with abnormal platelet counts

Megakaryocytes (MKs) from 40 patients with quantitative platelet disorders and 19 normal volunteers were analyzed by flow cytometry for size, fine cell internal structure and granularity, membrane expression of the glycoprotein (GP) IIb/IIIa complex, and for ploidy distribution. Analysis was performed on unfractionated minimally manipulated marrows obtained from routine bone marrow aspirates. MKs were labeled with a fluorescent lineage-specific monoclonal antibody to the GPIIb/IIIa complex followed by DNA staining with propidium iodide. Eight hundred to 3,000 MKs were analyzed in each sample. The modal ploidy distribution in normals was 16N, comprising about half of the megakaryocytic population, with 22.6% of the cells ≤ 8N and 22.0% ≥ 32N. Twelve thrombocytopenic patients with decreased marrow MKs on biopsy (mean platelet count [MPC] 44,600/μl) showed an increase in low ploidy cells with 53.2% ≤ 8N (P < .01); cell size was reduced in three patients when compared to normal cells of identical ploidy (P < .05). Eight thrombocytopenic patients with enhanced platelet destruction (with normal or increased MKs on biopsy and shortened platelet survival; MPC 41,400/μl) showed an increased proportion of high ploidy cells ≥ 32N to 39.2% (P < .01). Incresed cell size and granularity were found in four of these patients (P < .05). Six patients with thrombocytopenia secondary to multiple mechanisms affecting both platelet production and destruction (MPC 66,700/μl) showed no shift in ploidy. Four patients with primary thrombocytosis (two with thrombocythemia and two with polycythemia vera; MPC 822,500/μl) showed a marked shift toward high ploidy cells with 42.3% ≥ 32N and 7.6% ≥ 64N cells (P < .01). The shift was accompanied by a marked increase in cell size and granularity in the patients with thrombocythemia. Ten patients with thrombocytosis secondary to chronic blood loss, malignant or inflammatory disorders (MPC 714,000/μl), showed variable distributions with four patients exhibiting a shift in ploidy to the right similar to that found in the patients with increased platelet destruction. Based upon the present data, flow cytometric ploidy distribution may be diagnostically useful in thrombocytopenic patients by discriminating between disorders of platelet production and destruction. Additional data are required to determine the usefulness of flow cytometric ploidy measurements in thrombocytosis patients. We conclude that flow cytometry is a clinically useful method for quantitative analysis of MKs obtained from routine marrow aspirates.