SFTPD and rheumatoid arthritis: SPD (21.91±2.17 vs. 15.76±1.34 ng/mL, p = 0.017) CCL18 (102±13 vs. 78±5 ng/mL, p = 0.026) and KL-6 (961±128 vs. 376±26 U/mL, p<0.001) concentrations (Fig 1A–1C) were significantly higher in patients with RA-ILD vs. unaffected RA patients.