Table 1

Summary of cohort characteristics

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

-

-


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.

Viatte et al. Arthritis Research & Therapy 2012 14:R239   doi:10.1186/ar4082

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