Is interleukin-18 useful for monitoring rheumatoid arthritis?
OBJECTIVE
Interleukin-18 (IL-18) is a proinflammatory regulator of immune responses. Its similarities to IL-1beta and ability to induce tumour necrosis factor-alpha (TNF-alpha) make it potentially important in the pathogenesis of rheumatoid arthritis (RA).


METHODS
The level of IL-18 was assessed in matched pairs of blood and synovial fluid samples from 90 RA patients (47 erosive, 43 non-erosive) by an enzyme-linked immunosorbent assay (ELISA), and the results compared to 40 healthy controls.


RESULTS
In RA patients with erosive joint disease, the IL-18 level was higher than that in non-erosive RA [(median+/-QR) blood: 385+/-200 vs. 235+/-183 pg/mL, p = 0.02; synovial fluid: 392+/-392 vs. 224+/-324 pg/mL, p = 0.05]. IL-18 levels in blood of RA patients were similar and closely related to the local, intra-articular level (r = 0.96). The IL-18 level was not related to other markers of inflammation, to the duration of RA, or to the treatment modality. The IL-18 level in RA patients was similar to that of the controls (278+/-234 vs. 344+/-179 pg/mL, not significant).


CONCLUSIONS
An increased IL-18 level is associated with erosive joint disease, but the measurement of IL-18 does not help to distinguish between RA patients and healthy controls.
Bokarewa
M
M
Department of Rheumatology, Göteborg University, Sweden. maria.bokarewa@rheuma.gu.se
Hultgren
O
O
D001172:Arthritis, Rheumatoid / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D020382:Interleukin-18 / Q000097:blood*; D008297:Male; D008875:Middle Aged; D015166:Monitoring, Immunologic / Q000379:methods; D013582:Synovial Fluid / Q000378:metabolism*
D015415:Biomarkers; D020382:Interleukin-18