GDF15 and chronic obstructive pulmonary disease: However, the GDF15 level (approx. 300 pg/mL) of patients with COPD in this study was lower than the healthy control (approximately 400–500 pg/mL) in previous studies from the Caucasian population (22, 45), Chinese population (57, 58), etc. A previous study (59) indicated a clear dose–response association between serum GDF-15 concentrations and dietary patterns.