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Table 1 Basic characteristics of cases and controls

From: Infections and antibiotics during fetal life and childhood and their relationship to juvenile idiopathic arthritis: a prospective cohort study

  Controls JIA  
  n (%) n (%) p
No. of subjects 16,369 102  
Sex
 Boys 8453 (52%) 33 (32%) < 0.001
 Girls 7814 (48%) 69 (68%)
Gestational age, weeks (SD) 39.7 (2.4) 39.6 (2.0) 0.511
Season of birth
 Winter (December–February) 3840 (24%) 18 (18%) 0.155
 Spring (March–May) 4607 (28%) 34 (33%) 0.268
 Summer (June–August) 4270 (26%) 26 (25%) 0.854
 Autumn (September–November) 3523 (22%) 24 (24%) 0.654
Category at Onset (ILAR) (n)
Systemic Arthritis   7 (7%)  
Oligoarthritis   25 (25%)  
  Persistent oligoarthritis   19 (19%)  
  Extended oligoarthritis   6 (6%)  
Polyarthritis (Rheumatoid Factor Negative)   16 (16%)  
Polyarthritis (Rheumatoid Factor Positive)   4 (4%)  
Psoriatic Arthritis   11 (11%)  
Enthesitis Related Arthritis   16 (16%)  
Undifferentiated Arthritis   23 (23%)  
  1. JIA = juvenile idiopathic arthritis; ILAR = International League of Associations for Rheumatology
  2. P-value from chi-square test. Bold shows results reaching statistical significance (p-value below 0.05)