Levels of serum paraprotein and FLC at presentation, maximum response, and relapse for patients grouped according to type of relapse. Whisker box plots showing the median, 25th, and 75th centiles for (A) paraprotein and (B) absolute levels of the involved light chain at presentation, maximum response, and relapse; tails represent 5th and 95th centiles (IgG PO, n = 186; IgG PLC, n = 138; IgG LCO, n = 24; IgA PO, n = 72; IgA PLC, n = 45; and IgA LCO, n = 30). Mann-Whitney U tests were performed to assess the statistical significance of the differences between the groups. *P < .05 when compared with PO at the same time point; **P < .01 when compared with PO at the same time point; X, P < .05 LCO vs PLC at the same time point; XX, P < .01 LCO vs PLC at the same time point. Shaded column represents normal range for sFLC. PO, paraprotein only; PLC, paraprotein plus FLC; LCO, FLC only.