In a model including only immunoassay measurements, five of 88 baseline serum protein measurements were predictive of pneumonia, including growth differentiation factor 15 (GDF-15; SHR, 1.65; 95% CI, 1.29–2.12), insulin-like growth factor binding protein 2 (IGFBP-2; SHR, 1.27; 95% CI, 1.00–1.60), matrix metallopeptidase 8 (MMP-8; SHR, 1.20; 95% CI, 1.06–1.37), C-reactive protein (CRP; SHR, 1.15; 95% CI, 1.04–1.27) and N-terminal prohormone of brain natriuretic peptide (NT-proBNP; SHR, 1.15; 95% CI, 1.04–1.28) (Fig 2B). Here, GDF15 is linked to susceptibility to pneumonia measurement.