Bone marrow aspiration technique may have an impact on therapy stratification in children with acute lymphoblastic...

Morphological evaluation of early response to chemotherapy and measurement of minimal residual disease by flow cytometry or PCR are being used for evaluation of prognosis and treatment stratification in children with acute lymphoblastic leukaemia (ALL).

In a series of 14 consecutive bone marrow investigations from children with precursor B-cell ALL, morphological evaluations of smears and flow cytometric measurements of minimal residual disease in sequentially aspirated small (2 ml) and large (5-10 ml) volumes of bone marrow were compared, at various time points during therapy.

The density of nucleated cells was markedly reduced in the large volume aspirate. The percentage of erythroblasts measured by flow cytometry was smaller, indicating dilution with peripheral cells. Similarly, the blast percentage was reduced with 54% in large aspirates, and in four instances with minimal residual disease of >0.1% in the small volume, the level of blasts in the large aspirate was below this limit.

The amount of minimal residual disease should be measured in the first 2.5 ml of bone marrow aspirated from one puncture site. The procedure should be performed by experienced and carefully instructed doctors. In large aspirates, minimal residual disease will be underestimated, which may lead to failure to undertake a required intensification of therapy and a lower fraction of high risk patients in the trial.