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

Table 1 Summary of cohort characteristics

	Cohort
Characteristics	UKRAG		Cameroon		YRI HapMap^a
Health status	1987 ACR RA^b	Controls	1987 ACR RA^b	Controls	Controls^c
Number	5,024	4,281	43	44	119
Females, percentage	72	66	95	68	50
Age (IQR), years^d	50 (39-61)	-	44 (29-57)^e	-	-
CCP-positive, percentage^f	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.

ISSN: 1478-6362