Comparisons between Bone Marrow Differentials Prepared from Particles and from Random Samples of Aspirate and Determinations of the Dilution of Aspirate with Peripheral Blood Utilizing Radioactive Phosphorus (P³²)

Estimates of bone marrow cellularity based upon gross appearances and upon total nucleated counts of the aspirates were compared in 50 cases. These comparisons revealed some correlation between the gross appearances and the averages of the total nucleated counts. That this correlation did not always exist in individual cases was demonstrated by the wide range in total nucleated counts and by incorrect gross appearance estimates in two cases of acute leukemia.

Differential counts as obtained from particle smears and random sample smears of the same aspirates were compared in 50 cases. Such comparisons revealed certain consistent differences in cellular elements. These differences and their significance were discussed.

The dilution of aspirate fluid and aspirate particles with peripheral blood was determined in 10 cases. Appreciable and unpredictble dilution of aspirate fluid was demonstrated, but none was demonstrated in aspirate particles. This dilution of aspirate fluid with peripheral blood is implicated as the cause of the inaccurate estimations of bone marrow cellularity based upon gross appearances and total nucleated counts. It is also suggested as one of the factors underlying the observed differences in the cellular elements of particle smear and random sample smear differentials.