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Table 2 Characteristics at the time of blood draw according to pre-RA ACPA results for RA cases and their matched controls in the Nurses’ Health Studies (n = 1133)

From: Asthma and elevation of anti-citrullinated protein antibodies prior to the onset of rheumatoid arthritis

 Pre-RA ACPA+ casesb
(n = 96)
Matched controls
(n = 286)
p valuePre-RA ACPA− cases
(n = 188)
Matched controls
(n = 563)
p value
Mean age, years (SD)a51.3 (7.3)50.8 (7.7)0.6751.6 (8.2)51.9 (8.0)0.65
Mean time to RA diagnosis or matched index date for controls, years (SD)a8.1 (5.8)8.1 (5.8)0.9610.5 (5.6)10.5 (5.6)0.99
CCP+ at diagnosis by medical record review, %58.3N/A9.4N/A
RF+ at diagnosis by medical record review, %70.8N/A52.7N/A
CCP+ or RF+ at diagnosis by medical record review, %79.2N/A53.7N/A
White, %96.996.50.8692.696.80.01
Mean body mass index, kg/m2 (SD)26.1 (5.2)24.9 (4.2)0.0525.6 (4.6)25.0 (4.7)0.08
Mean pack-years (SD)13.3 (17.6)11.1 (17.2)0.1811.1 (14.7)8.6 (14.8)0.02
Mean pack-years among smokers (SD)22.4 (17.9)21.0 (18.8)0.4521.4 (14.1)19.0 (17.0)0.02
Smoking pack-year category, %
 >0 to 1017.720.613.819.2
Parent(s) smoked at home during childhood, %68.866.10.6362.863.40.87
Ever lived with a smoker, %64.653.90.0758.057.90.99
Asthma, %
  1. ACPA anti-citrullinated protein antibodies, CCP cyclic citrullinated peptide (clinically tested), RA rheumatoid arthritis, RF rheumatoid factor, SD standard deviation
  2. aAge at index date and time from blood collection to index date were matching factors
  3. bPre-RA ACPA by sensitive definition: any research ACPA+ or CCP2 >3 units/mL