Table 1

General characteristics at stool collection (133 participants)

CharacteristicsFDR controls n=50Pre-clinical RA stages† n=83
Age (years), median (IQR)55 (47–62)58 (50–66)
Female sex, n (%)39 (78)74 (89)
Current smoking, n (%)11 (22)16 (19)
Past smoking, n (%)26 (55)29 (41)
Pack years smoked, median (IQR)0.4 (0.4–0.7)0.4 (0.4–0.7)
Current alcohol, n (%)22 (47)29 (41)
Body mass index, median (IQR)24 (22–27)24 (22–27)
Swollen joints on examination, median (IQR)· 0 (0–1)1 (0–3)*
Tender joints at examination, median (IQR)0 (0–1)1 (0–2)*
ACPA positivity, n (%)0 (0)38 (46)*
RF positivity, n (%)0 (0)28 (34)*
Shared epitope (one or two copies), n (%)32 (65)42 (53)
  • *P value<0.05, Kruskal-Wallis test for continuous variables and Fisher’s exact test for categorical variables.

  • †Pre-RA group includes individuals with ‘systemic autoimmunity associated with RA’ and with ‘symptoms and signs associated with possible RA’. An isolated asymptomatic swollen joint was not sufficient to be classified as being in a ‘pre-clinical stage of RA’.

  • ACPA, anti-citrullinated protein autoantibody; FDR, first-degree relative; RA, rheumatoid arthritis; RF, rheumatoid factor.