Interleukin 6 Levels and Disease Activity in Takayasu Arteritis

BackgroundVarious studies have suggested interleukin 6 (IL-6) as a potential biomarker for detecting disease activity in Takayasu arteritis.MethodsA systematic review and meta-analysis was performed to assess differences in IL-6 levels in patients with active (aTA) and inactive Takayasu arteritis (iTA), as well as healthy controls (HCs), using validated activity scores. Study quality and the risk of bias were assessed using STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) and the Newcastle-Ottawa and Joanna Briggs checklist, respectively. For the meta-analysis, we pooled the raw mean IL-6 levels in each group and then estimated and pooled the crude mean differences between the groups. We applied a random-effects model in all analyses.ResultsOf the 93 eligible articles, 10 were included after removing duplicates and studies that met the exclusion criteria. Overall, 1825 patients with a mean age ranging from 24 to 40.6 years were included. The pooled levels of IL-6 increased depending on disease activity as follows: HCs: 3.08 (95% confidence interval [CI], 0.88-5.28), iTA: 7.21 (3.61-10.82), and aTA: 22.67 (12.44-32.91) pg/mL. Patients with aTA had higher IL-6 levels than HCs (21.52 [95% CI, -0.43 to 43.47]) and those with iTA (16.69 [95% CI, 5.32-28.06]), whereas IL-6 levels were not different between HCs and patients with iTA (3.62 [95% CI, -13.18 to 20.42]).ConclusionsInterleukin 6 levels are significantly increased in patients with aTA compared with those with iTA and HCs but not in patients with iTA compared with HCs. More studies are needed to establish the IL-6 cutoff value for assessing disease activity.