A number of studies have investigated the correlation of sFLCs and other markers of B-cell activity with disease activity (as assessed by the EULAR Sjögren’s Syndrome Disease Activity Index, ESSDAI) . sFLC levels were associated with ESSDAI score in all four studies, and James et al.  found that sFLC levels were associated with the cutaneous, biological and renal domains of the ESSDAI in particular.
pSS is associated with an increased risk of non-Hodgkin lymphoma (particularly mucosa-associated lymphoid tissue (MALT) lymphoma) with an odds ratio of 12.9 . In a cohort of 395 patients enrolled into a 5-year prospective study (the ASSESS biobank), Gottenberg et al.  sought to discover whether sFLC measurements could identify pSS patients at increased risk of lymphoma. At enrolment, a total of 16/395 patients had a history of lymphoma; median serum concentrations of BAFF and β2-microglobulin were significantly higher in these patients but sFLC concentrations and ratios were normal. This finding was confirmed in their later publication . In a different study , an abnormal κ/λ sFLC ratio was found in 11% (5/45) pSS patients at diagnosis, but 50% (6/12) of patients with established salivary gland MALT lymphoma without recent B-cell depletion therapy. Therefore, an abnormal κ/λ sFLC ratio was proposed as a potential biomarker of MALT lymphoma.
There has been increasing interest in the role of BAFF as a marker of disease activity and as a potential therapeutic target in pSS. In a phase 2 trial of belimumab (a monoclonal antibody against BAFF), in which sFLC measurements were included as part of the haematological assessment, significant reductions in sFLC concentrations were observed following treatment .