HP and diabetes mellitus: High haptoglobin expression (≥30.8% positive cells) was associated with advanced disease (Hurley stage III: 80% versus 41.7%, p = 0.01), active smoking (80% versus 50%, p = 0.039), increased pain (visual analogue scale: 5 versus 1.5, p = 0.03), and a higher prevalence of diabetes (35% versus 8.3%, p = 0.029) and hypertension (55% versus 25%, p = 0.042).