Rheumatoid arthritis seropositive for the rheumatoid factor is linked to the protein tyrosine phosphatase nonreceptor 22-620W allele

Table 5 PTPN22-1858C/T genotypes frequencies in the affected sib-pair (ASP) rheumatoid arthritis (RA) sample

	PTPN22-1858C/T genotype frequencies [% (n)]				P ^a
	C/C	C/T	T/T	C/T or T/T
ASP RA index cases RF⁺ (n = 74) versus controls^b (n = 200)	66 (49)	31 (23)	3 (2)	34 (25)	0.15
ASP RA index cases RF⁺ and IBD1 or IBD2 at the PTPN22 locus with their RF⁺-concordant RA sib (n = 42) versus controls^b (n = 200)	71 (30)	26 (11)	3 (1)	29 (12)	0.63
All ASP RA index cases (n = 88) versus controls^b (n = 200)	69 (61)	29 (25)	2 (2)	31 (27)	0.32

RF⁺, seropositive for rheumatoid factor; IBD1 or IBD2, index sharing 1 or 2 identical by descent allele with the RA sib.
^aFollowing data previously reported in RA and because of the infrequency of the PTPN22-1858T/T genotype, it was combined with the 1858C/T genotype for the analysis.
^bControls derived from all non transmitted parental chromosomes.

ISSN: 1478-6362