Measurement of reticulated platelets following peripheral blood progenitor cell and bone marrow transplantation: implications for marrow reconstitution and the use of thrombopoietin.

Neutrophil and platelet engraftment times are significantly shorter in patients undergoing PBPCT compared with ABMT. The explanation for this is unclear. The reticulated platelet percentage (RP%) has been established as a measure of bone marrow platelet production. Using this measurement we have followed thrombopoiesis over the transplant period in 10 patients undergoing PBPCT, eight ABMT and four alloBMT. Neutrophil and platelet engraftment times were significantly shorter in patients undergoing PBPCT than either ABMT or alloBMT. The RP% fell to a nadir in parallel with the platelet count in all patients following conditioning therapy consistent with an aplastic state and rose before platelet recovery as young platelets were released. The peak rise in the RP% was significantly greater and occurred earlier in PBPCT compared with BMT. The total number of reticulated platelets released during the time of engraftment was significantly greater in PBPCT than BMT. The potential role of the RP% in the timing of thrombopoietin therapy is explored. Finally the diagnostic use of the RP% in post-transplant thrombocytopenia is illustrated by a case in which a persistently high RP% accurately predicted a consumptive aetiology.