Table 7

PTPN22 genotype and HLA-SE interactions according to RF status in NHS/NHSII pooled samples

PTPN22

HLA-SE

All cases^a

RF-positive cases^b,c

RF-negative cases^b,d

CC

None

1.00 (ref.)

1.00 (ref.)

1.00 (ref.)

CC

Any

1.97 (1.39–2.78)

2.37 (1.62–3.46)

1.33 (0.89–1.99)

T carrier

None

1.41 (0.87–2.27)

1.76 (0.99–3.13)

1.40 (0.78–2.51)

T carrier

Any

2.73 (1.55–4.81)

3.58 (2.02–6.35)

1.47 (0.74–2.92)

Additive interaction

AP = 0.13 (95% CI -0.40 to +0.66); P_add^e = 0.62

AP = 0.13 (95% CI -0.41 to +0.67); P_add^e = 0.64^e

AP = -0.18^f

Multiplicative interaction

P_multi^g = 0.97^g

P_multi^g = 0.72

P_multi^g = 0.60

Values are expressed as odds ratio (95% confidence interval). ^aConditional logistic regression, adjusting for parity, pack-year smoking, breast-feeding, menstrual irregularity, and age at menarche, menopausal status and postmenopausal hormone use. ^bUnconditional logistic regression adjusting for year of birth, parity, pack-year smoking, breast-feeding, menstrual irregularity, and age at menarche, menopausal status and postmenopausal hormone use. ^cRF-positive RA cases and all controls. ^dRF-negative RA cases and all controls. ^eP for AP, one of the indices of additive interactions between binary PTPN22 genotype and binary HLA-SE genotype. ^f95% confidence interval and P value for AP not applicable because of the negative estimate (antagonistic rather than synergistic). ^gP for multiplicative interaction term between binary PTPN22 genotype and binary HLA-SE genotype with one degree of freedom. AP, attributable proportion; NHS, Nurses' Health Study; RA, rheumatoid arthritis; RF, rheumatoid factor.

Costenbader et al. Arthritis Research & Therapy 2008 10:R52   doi:10.1186/ar2421