For patients with IgG kappa multiple myeloma receiving an IgG kappa mAb (i.e., daratumumab), how important is it clinically to use an interference assay if they're in a VGPR to see if their M-spike might actually be 0?

I always try to perform an assay to distinguish an IgG kappa monoclonal protein from the therapeutic antibody of interest. For daratumumab, the ‘hydra shift’ assay has been used for a while. Now, with Mass spectrometry available, it is the perfect way to assess very sensitively for a residual protei...