CRP and diabetes mellitus: Additionally, DM patients with high serum Kyn/Trp ratio had higher levels of inflammatory markers than those with low serum Kyn/Trp ratio, including NLR (3.2 (2.5–5.5) vs. 2.1 (1.4–3.2), P = 0.019), CRP (1.0 (0.3–3.6) vs. 0.3 (0.2–0.4), P = 0.041), and β2-MG (3022 ± 823 vs. 2247 ± 667, P = 0.019).