Furthermore, multivariate regression analysis adjusted for sex and age indicated that the ALT level (adjusted OR [aOR] = 1.001, 95% CI: 1.001–1.002), EBV infection (aOR = 8.486, 95% CI: 6.753–10.663), inflammatory disease (aOR = 3.915, 95% CI: 3.198–4.794), autoimmune disease (aOR = 2.307, 95% CI: 1.823–2.920), and malignant disease (aOR = 1.381, 95% CI: 1.101–1.734) were risk factors for an elevated ADA level; of them, EBV infection was the strongest risk factor. Here, ADA is linked to Epstein-Barr virus infection.