Haematologica 2003 - Supplements

plasmids carrying the clonotypic insert were normalized by
parallel detection of β-actin copy numbers in the corresponding
sample.
Results: Sensitivity was 10E-4 to 10E-5 with linear correlation
coefficients of r≥0.98 for all standard curves and r=0.93 and
r=0.99 for inter- and intraassay variability. Accuracy was
confirmed by spiking experiments with dilutions of U266
myeloma cell line in normal mononuclear cells. For clinical
validation we used the method to monitor residual disease in
peripheral blood (PB) and bone marrow (BM) of 11 MM patients
following autologous and/or allogeneic peripheral blood stem cell
transplantation (PBSCT). The intraindividual quantification of
myeloma cells in BM and PB samples obtained at the same time
showed a median 58-fold higher tumor load in samples from BM
in comparison with PB as reflected by an IgH/β-actin ratio of
0.4% and 0.002% (p