ADA and adult-onset Still disease: The results showed that the serum ADA activity in AOSD patients was significantly higher than that of healthy controls (40.17 ± 25.88 vs 10.79 ± 3.40, p < 0.0001), SLE (40.17 ± 25.88 vs 18.73 ± 1.44, p < 0.0001), RA (40.17 ± 25.88 vs 17.32 ± 9.04, p < 0.0001) and SS patients (40.17 ± 25.88 vs 14.28 ± 7.96, p < 0.0001) (Fig. 1a).