Assessment of immunoglobulins free light chains in serum and urine of
patients with system sclerosis: novel biomarkers for activity disease
Abstract
Free light chains (FLC), considered a biomarker of B cell activity, are
frequently elevated in different systemic inflammatory-autoimmune
diseases. As systemic sclerosis (SSc) clinical course may be variable,
this study aimed to assess FLCs levels in serum and urine of affected
individuals, as biomarkers of disease activity. We assessed FLC levels
in serum and urine of 72 SSc patients and 30 healthy controls (HC).
Results were analyzed in comparison with overall clinical and laboratory
findings, disease activity index (DAI) and disease severity scale (DSS).
SSc patients displayed increased levels of k and λ FLC in serum,
significantly higher than HC (p=0.0001) alongside with the mean levels
of free k/λ ratio and of the k+λ sum (p=0.0001). In addition, SSc
patients had significant higher levels in the urine of free k and of k/λ
ratio than HC (p=0.0001). SSc patients with increased k+λ sum in serum
showed a statistically higher levels of erythro-sedimentation rate
(p=0.034), C-reactive protein (p=0.003), higher DAI (p=0.024) and DSS
(p=0.015) than SSc patients with normal levels of FLC. A positive linear
correlation was found between serum levels of free k and DAI (r=0.29,
p=0.014). SSc patients with increased free k in urine had statistically
higher DAI (p=0.048) than SSc patients with normal level of free k. The
significant increased levels of FLC correlated with disease activity in
SSc patients. Our results strengthen the role of FLC as useful
biomarkers in clinical practice to early diagnosis and monitor disease
activity with an improvement of SSc patients’ management.