Contamination of peripheral blood by monoclonal B cells following treatment of multiple myeloma by high-dose chemotherapy.

Peripheral blood samples obtained from five patients with multiple myeloma, after high-dose chemotherapy, were studied for monoclonal B plasma cell contamination. We used the technique of immunoglobulin heavy chain gene 'fingerprinting' at the time of diagnosis and during apheresis. The level of sensitivity of this technique is between 0.01% and 0.001% in two patients in whom a monoclonal population was detected in peripheral blood.