Vitamin D deficiency is common in patients with RA and linked to disease activity, but circulating levels are unaffected by TNFα blockade: results from a prospective cohort study. Issue 6 (3rd November 2010) - Welsh, Paul; Peters, Mike J L; McInnes, Iain B; Lems, Willem F; Lips, Paul T; McKellar, Gayle; Knox, Susan; Michael Wallace, A; Dijkmans, Ben A C; Nurmohamed, Michael T; Sattar, Naveed