Chapter 32

FLC proteinuria occurs in up to 70% of WM patients. However, the amounts excreted are usually low and do not relate particularly well to changes in tumour burden [712]. In contrast, the sFLC assay is informative in the majority of patients (Figure 32.2) [710]. Importantly, sFLCs do not cryoprecipitate and are not affected by other factors that can make IgM measurements difficult [711].

Itzykson et al. [669] assessed sFLCs in 42 WM patients prior to treatment. The median involved FLC (iFLC) concentration was 48.6 mg/L (range 11.3 - 19400 mg/L), and was elevated above the normal range in 83% of patients. The iFLC and IgM monoclonal protein concentration were not related to each other (p=0.89), similar to findings in multiple myeloma patients (Sections 11.2.5 and 17.2). Whilst guidelines state that sFLC analysis is not essential for the routine assessment of WM patients [707][710][703], in practice, it is routinely used by many clinicians in this context [706]. A recent survey of haematologists and oncologists in the Netherlands revealed that 43.4% currently measure sFLCs in the diagnostic work-up of patients with suspected WM [713].