FABP4 and chronic obstructive pulmonary disease: Airway FABP4 levels were lower in COPD patients with airway infection vs. those without it, reaching statistical significant differences in sputum [0.73 (0.35–15.3) vs. 15.6 (2.0–29.4) ng/ml, p = 0.02] but not in BALF [181.5 (28.7–395.5) vs. 228.5 (106.3–319.1) (pg/ml)/protein, p = 0.7) (Fig. 1B, D).