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Table 1 Summary of cohort characteristics

From: Investigation of Caucasian rheumatoid arthritis susceptibility loci in African patients with the same disease

  Cohort
Characteristics UKRAG Cameroon YRI HapMapa
Health status 1987 ACR RAb Controls 1987 ACR RAb Controls Controlsc
Number 5,024 4,281 43 44 119
Females, percentage 72 66 95 68 50
Age (IQR), yearsd 50 (39-61) - 44 (29-57)e - -
CCP-positive, percentagef 67 - 84 - -
Erosive patients, percentage 65 - 51 - -
  1. aUnrelated individuals from the Yoruba in Ibadan, Nigeria (YRI) population, from the International HapMap Project. bSatisfying the 1987 American College of Rheumatology classification criteria for rheumatoid arthritis (RA). cSince no phenotypic information was collected by the HapMap Consortium, medical conditions of the YRI individuals are unknown; based on the assumed low prevalence of RA in Nigeria, 'controls' means that YRI individuals are unlikely to have RA and were considered to be controls. dMedian patient age at disease onset, with interquartile range (IQR). eThe median age (IQR) at inclusion is 52 (37-61) and therefore does not differ from the age reported for the 56 patients in the original paper [29]. fPositive for anti-cyclic citrullinated peptide antibody (anti-CCP). For samples tested on several occasions over time, anti-CCP status was defined as positive if at least one of the tests was positive ('ever positivity'). Disease duration at the time of the last x-ray differs between patients and cohorts. The anti-CCP status was available for only 2,842 United Kingdom Rheumatoid Arthritis Genetics Consortium (UKRAG) patients, the rheumatoid factor status was available for 4,709 patients, and x-ray data were available for 2,851 patients, whereas there was almost no missing information in the Cameroonian cohort.