Bedeutung freier Leichtketten im Urin bei Patienten mit chronisch entzündlicher rheumatischer Erkrankung
Meaning of urinay free light chains in patients with chronic inflammatory rheumatic disease
by Britta Frölich
Date of Examination:2018-06-21
Date of issue:2018-06-21
Advisor:PD Dr. Carsten Bramlage
Referee:PD Dr. Carsten Bramlage
Referee:PD Dr. Friederike Braulke
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Abstract
English
The meaning of urinary free light chains (FLC) in patients with chronic inflammatory rheumatic disease has been analysed in different studies, mostly in serum and with low numbers of cases. Aim of this study was to analyse the meaning of urinary FLCs in the diag-nostic, activity index and therapy of rheumatic diseases. Additionally, we wanted to find out if FLCs were useful to identify infection in this group. 1500 patients with detected urinary FLCs were analysed in a retrospec-tive, monocentric study. These patients were divided in different groups: patients with chronic inflammatory rheumatic disease (N=382), one with “healthy” patients (N=140) and one with patients with infection (N=219). Patients with chronic inflammatory rheumatic disease had significantly higher FLC levels in urine than those of the healthy reference group (κ-FLC elevated in 84.0 %; λ-FLC in 60.5 %). The subgroups of the rheu-matic disease group also hat significantly higher levels of urinary FLCs, having the highest in patients with connective tissue disease, followed by those with vasculitis, spondyloyarthritis and chronic polyarthritis. Since there are many parameters – like organ involvement or infection – influencing the level of FLCs, they cannot be reliable markers in the diag-nosis of rheumatic disease. However, they can be seen as an additional parameter. Patients with rheumatoid arthritis had a good correlation between FLCs and systemic inflammation parameters CRP and ESR. Vasculitis patients also showed a good correlation with CRP. In addition, FLCs could be used as a therapy control in patients receiving Rituximab, although in this study the number of patients treated with Rituximab was too low to be sure. Urinary FLCs are also useful in identifying infection. Elevated levels of urinary FLCs indicated infection in patients with rheumatic disease. FLCs may be useful for distinguishing inflammation due to rheumatic disease activity from that due to the additional presence of infection (optimal cut-off point: κ: 32.2 mg/l; λ: 9.5 mg/l) and seen as an additional diagnostic tool. Since of the simplicity of a urine test (non-invasive) these results should be followed by further studies. In this connection the focus should be lain on urinary FLCs in patients with rheumatoid arthritis with regard to dis-ease activity, therapy control and dissociation from infection.
Keywords: rheumatic disease; free light chains