TABLE 1

Baseline characteristics of the study sample

VariableAll subjectsRA-UIPRA-NSIP
Subjects n13710829
Age years64.7±10.666.0±9.160.1±14.3
Female n (%)68 (50)52 (48)16 (55)
Smoking history
 Available n13510629
 Ever smokers n (%)87 (64)73 (69)14 (48)
  Pack-years31.8±23.133.6±24.1 (n=67)20.0±11.5 (n=12)
 Never smokers n (%)48 (36)33 (31)15 (52)
Family history of RA
 Available n1239429
 Family history of RA n (%)29 (24)23 (24)6 (21)
Duration of RA preceding ILD years12.9±12.211.9±11.316.6±14.4
RA medications
 Methotrexate ever n (%)89 (65)67 (63)22 (71)
 Biologic agent ever n (%)87 (64)64 (60)23 (74)
FVC
 Available n13510728
 % pred69.3±19.269.7±18.567.8±21.9
FEV1
 Available n13410628
 % pred72.7±20.173.5±19.569.4±22.1
DLCO
 Available n1088424
 % pred48.9±17.849.1±16.948.3±20.7
CPI
 Available n1068323
 % pred47.2±14.747.0±13.947.6±17.6
Anti-CCP antibodies
 Available n806119
 CCP >20 n (%)66 (83)50 (82)16 (84)
 CCP titre for CCP positive140.5±87.1143.6±85.1130.5±95.0
RF
 Available n937419
 RF > 20 n (%)78 (84)64 (86)14 (74)
 RF titre for RF positive907.1±1754.71054.0±1914.0336.8±462.3
Died n (%)54 (39)47 (43.5)7 (24)
Median (IQR) follow-up years4.8 (2.5–7.8)4.6 (2.4–7.7)6.9 (4.1–8.1)
  • Data are presented as mean±sd, unless otherwise stated. RA: rheumatoid arthritis; UIP: usual interstitial pneumonia; NSIP: nonspecific interstitial pneumonia; ILD: interstitial lung disease; FVC: forced vital capacity; FEV1: forced expiratory volume in 1 s; DLCO: diffusing capacity of the lung for carbon monoxide; CPI: composite physiologic index; CCP: cyclic citrullinated peptide; RF: rheumatoid factor; IQR: interquartile range.